Pure &App/, Chem., VOI. 61, No. 8, pp. 1483-1504, 1989.
Printed in Great Britain.
@ 1989 IUPAC
INTERNATIONAL UNION OF PURE
AND APPLIED CHEMISTRY
ANALYTICAL CHEMISTRY DIVISION
COMMISSION ON RADIOCHEMISTRY AND NUCLEAR TECHNIQUES*
TOTAL AND SPONTANEOUS FISSION
HALF-LIVES FOR URANIUM, PLUTONIUM,
AMERICIUM AND CURIUM NUCLIDES
Prepared for publication by
NORMAN E. HOLDEN
Brookhaven National Laboratory, Upton, New York 11973, USA
* Membership of the Commission during the period (1985-89) this report was prepared was
as follows:
Chairman: 1985-87 J. C. White (USA); 1987-89 D. C. Hoffman (USA); Secretary: 1985-87
D. C. Hoffman (USA); 1987-89 H. R. von Gunten (Switzerland); Titular Members: J.-P.
Adloff (France; 1987-89); J. Foos (France); K. S. Kasprzak (USA); Y.-F. Liu (China;
1987-89); M. Sakanoue (Japan; 1985-87); I. Zv6ra (USSR); Associate Members: H. J.
Ache (FRG); J.-P. Adloff [France; 1985-87); H. A. Das (Netherlands); H. R. von Gunten
(Switzerland; 1985-87); R. J. Ch. Hagemann (France; 1987-89); G. Herrman (FRG; 198789); P. Karol (USA); Y.-F. Liu (China; 1985-87); S. G. Luxon (UK); W. Maenhaut
(Belgium; 1986-89); M. Sakanoue (Japan; 1987-89); H. Sano (Japan; 1987-89); National
Representatives: G. B. Bar0 (Argentina); E. Roth (France); K. Burger (Hungary; 1987-89);
M. Sankar Das (India; 1987-89); E. Yellin (Israel); T. Shiokawa (Japan; 1986-89); E.
Steinnes (Norway); M. Peisach (RSA); N. K. Aras (Turkey; 1987-89); B. F. Myasoedov
(USSR); N. E. Holden (USA).
Republication of this report is permitted without the need for formal IUPAC permission on condition that an
acknowledgement, with full reference together with IUPAC copyright symbol (0
1989 IUPAC), is printed.
Publication of a translation into another language is subject to the additional condition of prior approval from the
relevant IUPAC National Adhering Organization.
CONTENTS
Introduction
1485
Uranium Isotopes
Plutonium Isotopes
1486
Americium Isotopes
1487
Curium Isotopes
1487
Discussion of Results
1487
Tabulated Results
Table
Table
Table
Table
Table
Table
Table
Table
Table
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43.
44.
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46.
47.
48.
49.
Spontaneous fission half-life of 232U
Total half-life of 232U
Spontaneous fission half-life of 233U
Total half-life of 233U
Spontaneous fission half-life of 234U
Total half-life of 234U
Spontaneous fission half-life of 235U
Total half-life of 235U
Spontaneous fission half-life of 236U
Total half-life of 236U
Total half-life of 238U
Spontaneous fission half-life of 2%
Spontaneous fission half-life of 236Pu
Total half-life of 236Pu
Alpha half-life of 238Pu
Spontaneous fission half-life of 238Pu
Spontaneous fission half-life of 239Pu
Total half-life of 239Pu
Spontaneous fission half-life of 240Pu
Total half-life of 240Pu
Spontaneous fission half-life of 241Pu
Alpha half-life of 241Pu
Total half-life of 241Pu
Spontaneous fission half-life of 242Pu
Total half-life of 242Pu
Spontaneous fission half-life of 244Pu
Total half-life of 244Pu
Spontaneous fission half-life of 241Am
Total half-life of 241Am
Spontaneous fission half-life of 242mAm
Partial half-lives of 242mAm
Total half-life of 243Am
Spontaneous fission half-life of 243Am
Spontaneous fission half-life of 242Cm
Total half-life of 242Cm
Spontaneous fission half-life of 243Cm
Total half-life of 243Cm
Spontaneous fission half-life of 244Cm
Total half-life of 244Cm
Spontaneous fission half-life of 245Cm
Total half-life of 245Cm
Total half-life of 246Cm
Spontaneous fission half-life of 246Cm
Total half-life of 247Cm
Spontaneous fission half-life of 248Cm
Total half-life of 248Cm
Spontaneous fission half-life of 250Cm
Total half-life of 250Cm
Recommended half-lives and uncertainties
1488
1488
1488
1489
1489
1489
1489
1490
1490
1490
1490
1491
1491
1491
1492
1492
1492
1492
1493
1493
1493
1493
1494
1494
1494
1495
1495
1495
1495
1496
1496
1496
1496
1497
1497
1497
1497
1498
1498
1498
1498
1499
1499
1499
1499
1500
1500
1500
1500
Acknowledgement
1501
References
1501
1484
Total and spontaneous fission half-lives for
uranium, plutonium, americium and curium
nuclides
A b s t r a c t - M e a s u r e m e n t s of t h e h a l f - l i v e s of s o m e l o n g - l i v e d
n u c l i d e s of e l e m e n t s Z = 98, 9 4 , 95 a n d 9 6 h a v e b e e n c o m p i l e d a n d
e v a l u a t e d . R e c o m m e n d e d v a l u e s a r e p r e s e n t e d f o r 232-236,238U,
for
236,238-242.244pu, f o r 2 4 1 . 2 4 2 m , 2 4 3 ~ ~a n, d f o r 2 4 2 - 2 4 6 , 2 5 0 ~ ~v, a l u e s
a r e presented for both spontaneous fission half-life a n d t o t a l
half-life. Problems with reported u n c e r t a i n t i e s a r e also discussed
INTRODUCTION
The long-lived n u c l i d e s of t h e u r a n i u m , p l u t o n i u m , a m e r l c i u m a n d c u r i u m e l e m e n t s a r e
of i n t e r e s t f o r t h e i r u s e i n n u c l e a r r e a c t o r s , f o r n u c l e a r r e a c t o r b u r n u p s t u d i e s
in waste m a n a g e m e n t , a n d in c e r t a i n safeguard applications, e g . , a counting is
o f t e n u s e d t o d e t e r m i n e t h e a m o u n t of m a t e r i a l p r e s e n t . The t o t a l h a l f - l i f e , w h i c h
f o r h e a v y e l e m e n t s is o f t e n s y n o n o m o u s w i t h t h e half-life f o r a d e c a y , a n d t h e
half-life for s p o n t a n e o u s fisslon a r e evaluated for these various long-lived nuclides
of i n t e r e s t F o r m a n y of t h e s e n u c l i d e s , t h e r e i s a l s o a d e c a y m o d e of h e a v y f r a g m e n t
r a d i o a c t i v i t y ( r e f 1 ) H o w e v e r i n t e r m s of t h e c o n t r i b u t i o n t o t h e t o t a l h a l f - l i f e
v a l u e t o be r e c o m m e n d e d , t h i s h e a v y f r a g m e n t r a d i o a c t i v i t y d e c a y m o d e is u s u a l l y m u c h
s m a l l e r t h a n t h a t of t h e s p o n t a n e o u s f i s s i o n d e c a y m o d e , a l t h o u g h t h i s is n o t t r u e in
a l l c a s e s ( r e f . 8 ) . S i n c e t h e s p o n t a n e o u s f i s s i o n d e c a y m o d e h a l f - l i f e is u s u a l l y o n l y
a s m a l l p e r t u r b a t i o n o n t h e v a l u e of t h e h a l f - l i f e of t h e a l p h a d e c a y m o d e , h e a v y
f r a g m e n t r a d i o a c t i v i t y d e c a y w i l l n o t be c o n s i d e r e d i n t h i s p a p e r .
A l l of t h e v a r i o u s e x p e r i m e n t s h a v e b e e n r e a n a l y z e d a n d r e c o m m e n d e d h a l f - l l f e v a l u e s
a r e p r e s e n t e d f o r 2 3 2 - 2 3 6 , 2 3 6 ~ 236,238-242,244pu, 2 4 1 . 2 4 2 m . 2 4 3 A m , a n d f o r 2 4 2 - 2 4 8 , 2 5 0 C m ,
These r e c o m m e n d e d half-life v a l u e s s u p e r s e d e p r e l i m i n a r y e s t i m a t e s p r e v i o u s l y p r e s e n t e d ,
in particular with respect to their reported uncertainties.
T o t a l h a l f - l i v e s f o r t h e u r a n i u m n u c l i d e s w e r e r e v i e w e d s o m e y e a r s a g o ( r e f . 3 ) . At t h a t
t i m e , 2 3 6 U was t h e o n l y n u c l l d e f o r w h i c h a s p o n t a n e o u s f i s s i o n v a l u e w a s e v a l u a t e d
More r e c e n t l y , t h e u r a n i u m a n d p l u t o n i u m nuclides ( r e f . 4 ) , a n d t h e a m e r i c i u m a n d c u r i u m
nuclides (ref 5 ) were s e p a r a t e l y reviewed a n d v a l u e s were r e c o m m e n d e d f o r b o t h t o t a l a n d
spontaneous fission half-lives.
It w i l l be n o t e d t h a t m a n y of t h e u n c e r t a i n t i e s r e c o m m e n d e d h e r e c o n s i d e r a b l y exceed, by
u p t o a n o r d e r of m a g n i t u d e , u n c e r t a i n t i e s q u o t e d by t h e i n d i v i d u a l a u t h o r s i n t h e i r
publication; e , g . t h e total half-life
of 2 3 8 , 2 4 0 “ ‘ P u ,
2 4 4 , 2 4 a C ma n d t h e
s p o n t a n e o u s f i s s i o n h a l f - l i f e of ‘44Cm.
The g e n e r a l p r o c e d u r e followed i n t h i s p a p e r h a s been t o r e v i e w e a c h e x p e r i m e n t a n d t o
r e v i s e t h e p u b l i s h e d v a l u e s f o r t h e l a t e s t e s t i m a t e s of v a r i o u s p a r a m e t e r s o r i g i n a l l y
r e p o r t e d by t h e a u t h o r s ; e . g . i m p r o v e d d a t a o n b r a n c h i n g r a t i o s a s s u m e d , o n t h e
h a l f - l i v e s of o t h e r n u c l i d e s i n v o l v e d , e t c . W h e n d e t a i l e d i n f o r m a t i o n o n t h e
u n c e r t a i n t i e s was a v a i l a b l e i n e a c h o f t h e s e e x p e r i m e n t s , t h e s t a n d a r d d e v i a t i o n f o r
t h e e x p e r i m e n t w a s c o m b i n e d w i t h o n e t h i r d of t h e s y s t e m a t i c e r r o r t o p r o v i d e t h e
u n c e r t a i n t y q u o t e d i n t h e t a b l e f o r e a c h e x p e r i m e n t . The r e s u l t of t h i s p r o c e d u r e
s h o u l d b e t h a t t h e l i m i t of e r r o r of t h e h a l f - l i f e would be o b t a i n e d f r o m t h e s u m of
t h e s y s t e m a t i c e r r o r p l u s t h r e e s t a n d a r d d e v i a t i o n s ; i . e . 3 0 Where t h e r e w a s n o
a d e q u a t e d i s c u s s i o n of t h e s y s t e m a t i c e r r o r a n d t h e t o t a l e r r o r q u o t e d w a s e x t r e m e l y
s m a l l ; e . g . 0 . 1 p e r c e n t o r l e s s , a s y s t e m a t i c e r r o r of 0 . 1 p e r c e n t w a s e s t i m a t e d .
O n e - t h i r d of t h i s a m o u n t , a b o u t 350 p a r t s p e r m i l l i o n ( p p m ) , w a s a d d e d t o t h e
p u b l i s h e d e r r o r t o o b t a i n t h e f i g u r e t a b u l a t e d i n t h e v a r i o u s t a b l e s . The u n c e r t a i n t y
listed for t h e recommended value in each t a b l e was calculated f r o m a weighted
a v e r a g e of t h e l i s t e d m e a s u r e m e n t s u s i n g a v a r i a n c e w e i g h t i n g t e c h n i q u e ; e i t h e r t h e
r e c i p r o c a l s q u a r e of t h e a u t h o r ’ s r e p o r t e d u n c e r t a i n t y , o r a s r e v i s e d a c c o r d i n g t o
t h e above scheme. Exceptions t o t h e weighted average r u l e had t o be m a d e for some
n u c l i d e s a n d w i l l be discussed u n d e r t h e a p p r o p r i a t e s e c t i o n f o r t h o s e nuclides.
In s u c h c a s e s , r e c o m m e n d a t i o n s w e r e m a d e u s i n g e i t h e r a s e l e c t e d v a l u e c o n s i d e r e d
s u p e r i o r to o t h e r listed m e a s u r e m e n t s , o r a weighted average was calculated for
e a c h of t h e d i f f e r e n t e x p e r i m e n t a l t e c h n i q u e s u s e d a n d a n u n w e i g h t e d a v e r a g e of
t h e s e h a l f - l i v e s w a s r e c o m m e n d e d . All of t h e t a b l e s i n d i c a t e t h e p a r t i c u l a r
method chosen.
1485
1486
COMMISSION ON RADIOCHEMISTRY AND NUCLEAR TECHNIQUES
U R A N I U M ISOTOPES
In g e n e r a l , t h e r e c o m m e n d e d v a l u e s f o r t h e h a l f - l i v e s of t h e v a r i o u s n u c l i d e s a r e
o b t a i n e d by w e i g h t i n g e a c h r e p o r t e d v a l u e by t h e v a r i a n c e r e p o r t e d by t h e a u t h o r
f o r t h e e x p e r i m e n t . In a few c a s e s , v a l u e s h a v e b e e n r e v i s e d w h e n t h e e x p e r i m e n t
w a s e v a l u a t e d . I n t h e c a s e of 2 3 3 U , d e t a i l s w e r e m i s s i n g f r o m G e i d e l ' m a n ' s
p a p e r ( r e f . 6 ) s u c h a s t h e m e a s u r e d s p e c i f i c a c t i v i t y , t h e m a s s of 233U a s s u m e d
a n d t h e m a s s s p e c t r o m e t r i c analysis. A s a r e s u l t , t h e e x p e r i m e n t could n o t be
e v a l u a t e d on t h e s a m e basis a s o t h e r m e a s u r e m e n t s . The f i n a l u n c e r t a i n t y was
i n c r e a s e d by 50%. t o a c c o u n t f o r t h e m i s s i n g i n f o r m a t i o n
In t h e c a s e of 2 3 4 U , t h e m e a s u r e m e n t by DeBievre ( r e f . 7 ) u s e d a v a r i e t y of m e t h o d s
o n 8 3 s o u r c e s . Upon q u e s t i o n i n g s o m e of t h e d a t a , t h e a u t h o r s a g r e e d t o r e v i s e t h e
f i n a l v a l u e of t h e h a l f - l i f e a s i n d i c a t e d i n T a b l e 6 . T h i s is o n e of t h e f e w
experiments where multiple sources were prepared and measured Lounsbury's
r e s u l t s ( r e f . 8 ) h a v e b e e n r e v i s e d f o r t h e s p e c i f i c a c t i v i t y of t h e o t h e r u r a n i u m
n u c l i d e s d u e t o b e t t e r e s t i m a t e s of t h e r e s p e c t i v e h a l f - l i v e s . T h e p r o b l e m of 232U
c o n t a m i n a t i o n w a s n o t d i s c u s s e d a n d t h e u n c e r t a i n t y was i n c r e a s e d by 50% t o a c c o u n t
f o r t h i s p o t e n t i a l e r r o r i n a s o u r c e w h i c h is o n l y 1% e n r i c h e d i n 2 3 4 U .
F o r t h e t o t a l h a l f - l i f e of '"U , o n l y o n e v a l u e i s l i s t e d i n t h e t a b l e . E a r l i e r
d e t e r m i n a t i o n s w e r e b a s e d o n m e a s u r e m e n t s of t h e s p e c i f i c a c t i v i t y of n a t u r a l u r a n i u m
s a m p l e s a n d t h e a s s u m p t i o n of s e c u l a r e q u i l i b r i u m b e t w e e n 2 3 4 U a n d 2 3 a U i n t h o s e
s a m p l e s . In a r a d i o a c t i v e d e c a y c h a i n , w h e n a d a u g h t e r n u c l i d e h a s a m u c h s m a l l e r
half-life t h a n i t s p a r e n t nuclide, a t a t i m e i n t e r v a l very long compared t o t h e
d a u g h t e r ' s l i f e t i m e , t h e g r o w t h a n d d e c a y of t h e d a u g h t e r is c o n t r o l l e d by t h e p a r e n t
a n d t h e two nuclides a r e in secular equilibrium i.e., t h e i r specific activities, N h ,
a r e e q u a l , w h e r e N i s t h e n u m b e r of a t o m s a n d X is t h e d e c a y c o n s t a n t ( h = n a t u r a l
l o g a r i t h m 2 / h a l f - l i f e ) . S i n c e t h e h a l f - l i f e of 2 3 4 U is o n l y lo5 y e a r s a n d t h e
a g e of t h e e a r t h i s o r d e r s of m a g n i t u d e g r e a t e r , 10' y e a r s , a l l of t h e 2 3 4 U
o r i g i n a l l y f o r m e d i n n a t u r a l u r a n i u m h a s long s i n c e d e c a y e d . The 234U now p r e s e n t
i n u r a n i u m i s d u e t o t h e 238U d e c a y s e r i e s , i . e . ,
238U(a)-+ 234Th(,5)+ 234Pa(,5)-* 2 3 4 U
In a c l o s e d s y s t e m , t h e 2 3 a U a n d t h e 234U s h o u l d b e i n s e c u l a r e q u i l i b r i u m . T h i s
i m p l i e s t h a t a m e a s u r e m e n t of t h e s p e c i f i c a c t i v i t y of a n a t u r a l u r a n i u m s a m p l e , w h e n
c o r r e c t e d f o r t h e s m a l l a m o u n t of 2 3 5 U a c t i v i t y ( ~ 2 . 2 % )w o u l d p r o v i d e a v a l i d
d e t e r m i n a t i o n of t h e e q u a l a m o u n t s of a c t i v i t y of 2 3 a U a n d 2 3 4 U p r e s e n t . H o w e v e r ,
Holden ( r e f . 3 ) h a s s h o w n t h a t t h i s a s s u m p t i o n of s e c u l a r e q u i l i b r i u m is n o t v a l i d .
T h e r e is a d i s e q u i l i b r i u m i n u r a n i u m s o u r c e s f o u n d i n v a r i o u s p a r t s of t h e w o r l d . The
s p e c i f i c a c t i v i t y of n a t u r a l u r a n i u m c a n v a r y by u p t o a f a c t o r of t w o i n d i f f e r e n t
s o u r c e s . A s a r e s u l t , o n l y t h e m e a s u r e m e n t by J a f f e y (ref 9 ) i s g i v e n i n t h e t a b l e a n d
is t h e r e c o m m e n d e d v a l u e .
In t h e c a s e of t h e s p o n t a n e o u s f i s s i o n h a l f - l i f e f o r 2 3 8 U , r e s u l t s a r e p r e s e n t e d f o r
t h e s p e c i f i c a c t i v i t y a s r e p o r t e d . M e a s u r e m e n t s u s i n g f i s s i o n t r a c k d e t e c t i o n i n 2.ir
geometry; e , g . mica-uranium, or lexan-uranium sandwiches have a problem with partial
f i s s i o n t r a c k f a d i n g i n t h e geological m a t e r i a l s ( r e f . 10). Fission t r a c k f a d i n g would
u n d e r e s t i m a t e t h e specific a c t i v i t y a n d lead t o o v e r e s t i m a t i n g t h e half-life. These
m e a s u r e m e n t s d o h a v e h a l f - l i v e s w h i c h a r e f r o m 10% t o 3 0 % t o o l a r g e c o m p a r e d t o a l l
o t h e r t e c h n i q u e s . These e x p e r i m e n t s h a v e n o t b e e n i n c l u d e d i n t h e a v e r a g i n g b e c a u s e
of t h i s s y s t e m a t i c e r r o r . O t h e r t e c h n i q u e s u s e d i n t h e m e a s u r e m e n t of 2 3 8 U h a v e
been separately weighted a n d t h e r e s u l t s averaged a n d converted i n t o a half-life
recommendation.
P L U T O N I U M ISOTOPES
In t h e m e a s u r e m e n t s of t h e p l u t o n i u m n u c l i d e s , w e i g h t e d a v e r a g e s h a v e u s u a l l y been
recommended, except for cases where a u t h o r s report exceedingly small absolute values
f o r t h e o v e r a l l u n c e r t a i n t y . I n a l a t e r s e c t i o n , t h e p r o b l e m of t r e a t i n g g o o d
m e a s u r e m e n t s w h i c h a r e m u t u a l l y e x c l u s i v e w i l l be a d d r e s s e d . I f o n e a p p l i e s w e i g h t e d
a v e r a g e s t o d e t e r m i n e t h e a h a l f - l i f e of 2 4 0 P u , t h r e e of t h e f i v e m o s t r e c e n t
measurements fall some t e n s t a n d a r d deviations away from t h e recommended value. A
h a l f - l i f e h a s b e e n r e c o m m e n d e d o n t h e b a s i s of t h e u n w e i g h t e d a v e r a g e of t h e v a r i o u s
techniques o r m e t h o d s utilized t o m e a s u r e t h i s half-life.
I f o n e u s e d w e i g h t e d a v e r a g e s f o r t h e t o t a l h a l f - l i f e of 2 4 1 P u . a l l of t h e r e c e n t
m e a s u r e m e n t s t h a t w e r e p e r f o r m e d a t t h e a c c u r a c y level of t e n t h s of o n e p e r c e n t would
c a r r y n o w e i g h t i n t h e e v a l u a t i o n of t h i s h a l f - l i f e . S i n c e S t r o h m ( r e f . 11) q u o t e s a n
Total and spontaneous fission half-lives
1487
a b s o l u t e a c c u r a c y f o r t h e 2 4 1 P u h a l f - l i f e of 488 p a r t s p e r m i l l i o n , w h i l e e x a m i n i n g
only one s a m p l e , his r e s u l t would e l i m i n a t e all o t h e r c a r e f u l m e a s u r e m e n t s f r o m
c o n s i d e r a t i o n . An u n w e i g h t e d a v e r a g e of t h e v a r i o u s t e c h n i q u e s was a g a i n r e c o m m e n d e d .
a s i n g l e s o u r c e w a s m e a s u r e d by a l a r g e
In t h e c a s e of t h e a h a l f - l i f e of “‘Pu,
n u m b e r of l a b o r a t o r i e s u s i n g v a r i o u s t e c h n i q u e s . The h i g h l y p r e c i s e v a l u e s r e p o r t e d
h a d a r a n g e of r e s u l t s f r o m t h e v a r i o u s l a b o r a t o r i e s w h i c h was a n o r d e r of m a g n i t u d e
g r e a t e r t h a n t h e u s u a l s t a n d a r d d e v i a t i o n q u o t e d i n m o s t of t h e s e e x p e r i m e n t s . An
u n w e i p h t e d a v e r a g e of t h e h a l f - l i f e f o r t h e v a r i o u s t e c h n i q u e s w a s r e c o m m e n d e d .
F o r t h e a h a l f - l i f e of 2 4 2 P u , t h e r a n g e of r e s u l t s w a s t e n t o f i f t e e n t i m e s
l a r g e r t h a n t h e t y p i c a l u n c e r t a i n t y q u o t e d by t h e a u t h o r s . A w e i g h t e d a v e r a g e of
t h e helf-life was recommended, w i t h t h e u n c e r t a i n t y calculated f r o m t h e e x t e r n a l
error.
A M E R I C I U M ISOTOPES
Most of t h e r e c o m m e n d e d v a l u e s f o r t h e a m e r i c i u m h a l f - l i v e s a r e b a s e d o n a w e i g h t e d
a v e r a g e of t h e r e p o r t e d r e s u l t s . I n t h e c a s e of 2 4 1 A m . t h e r e p o r t e d u n c e r t a i n t i e s
were revised t o i n s u r e t h a t c o m p a r a b l e e x p e r i m e n t s were t r e a t e d w i t h c o m p a r a b l e weights.
F o r t h e s p o n t a n e o u s f i s s i o n h a l f - l i f e of 241Am, t h e r a n g e of r e p o r t e d r e s u l t s w a s
l a r g e r t h a n q u o t e d u n c e r t a i n t i e s by m o r e t h a n a n o r d e r of m a g n i t u d e . A v a l u e was
s e l e c t e d u s i n g t h e b e t t e r m e a s u r e m e n t s a n d t h e u n c e r t a i n t y was c h o s e n so a s t o o v e r l a p
t h e r a n g e of t h e m o s t r e c e n t m e a s u r e m e n t .
C U R I U M ISOTOPES
F o r s p o n t a n e o u s f i s s i o n of 2 4 2 C m . t h e m e a s u r e m e n t w h i c h s h o u l d c a r r y m o s t of
t h e weight i n t h e evaluation completely disagrees with all o t h e r recent m e a s u r e m e n t s
by f i v e t o t e n u . A s e l e c t e d v a l u e was c h o s e n w i t h a n u n c e r t a i n t y t o e n c o m p a s s t h e
r a n g e of r e c e n t m e a s u r e m e n t s .
F o r t h e c a s e of 2 4 4 C m , t h e m o s t a c c u r a t e m e a s u r e m e n t s , a c c o r d i n g t o t h e p u b l i s h e d
e r r o r s , d i s a g r e e by s i x t e e n u . A w e i g h t e d a v e r a g e was r e c o m m e n d e d w i t h t h e u n c e r t a i n t y
b e i n g c o n t r o l l e d by t h e e x t e r n a l e r r o r . S i m i l a r p r o b l e m s f o r t o t a l h a l f - l i v e s of 244,246Cm
were t r e a t e d i n t h e s a m e m a n n e r .
D ISC U SSI O N OF RESULTS
In m o s t c a s e s , t h e r e c o m m e n d e d v a l u e s a n d u n c e r t a i n t i e s i n t h e t a b l e s a r e b a s e d o n
variance weighted averages. Other recommendations a r e based on selecting t h e one
g o o d r e c e n t m e a s u r e m e n t of t h e p a r t i c u l a r h a l f - l i f e . I n a f e w c a s e s , t h e
d i s c r e p a n c i e s i n v a l u e s a n d u n c e r t a i n t i e s q u o t e d r e q u i r e d t h e a v e r a g i n g of
techniques t o produce a reasonable recommendation. The recommended values listed
i n t h e f o l l o w i n g t a b l e s a r e g i v e n i n u n i t s of e i t h e r d a y ( d ) o r y e a r ( a ) . B e f o r e
c o n c l u d i n g , a few w o r d s a r e i n o r d e r o n t h e p r o b l e m of e r r o r e s t i m a t i o n .
It h a s b e e n n o t e d a b o v e t h a t v a r i o u s m e a s u r e m e n t s i n t h e t a b l e s q u o t e u n c e r t a i n t i e s
by a u t h o r s s u c h t h a t t h e y b o t h d i s a g r e e w i t h a n d e x c l u d e m a n y o t h e r good r e c e n t
m e a s u r e m e n t s f r o m c o n s i d e r a t i o n . Undoubtedly, s y s t e m a t i c e r r o r s h a v e n o t been
c a r e f u l l y c o n s i d e r e d i n t h e s e p u b l i c a t i o n s . When e x p e r i m e n t s a r e p e r f o r m e d a t t h e
l e v e l of f i v e t o t e n p e r c e n t a c c u r a c y , r e c o r d i n g t h e n u m b e r of c o u n t s i s a n
i m p o r t a n t c o n s i d e r a t i o n . I n P o i s s o n s t a t i s t i c s , i n c r e a s i n g t h e n u m b e r of c o u n t s
c a n i m p r o v e t h e o v e r a l l a c c u r a c y , w h i c h v a r i e s i n v e r s e l y w i t h t h e t o t a l n u m b e r of
c o u n t s . H o w e v e r , b y t h e t i m e t h a t t h e o v e r a l l a c c u r a c y r e a c h e s t h e l e v e l of
o n e - h a l f p e r c e n t o r b e t t e r , t h e e s t i m a t e of a l l s y s t e m a t i c e r r o r s b e g i n s t o
control t h e t o t a l accuracy. The effort t o continue t o improve t h e s t a t i s t i c a l
precision, by c o n t i n u i n g t o collect raw d a t a points, does n o t significantly
i m p r o v e t h e t o t a l e r r o r , e x c e p t s u p e r f i c i a l l y , i n t h e a b s e n c e of a n y e f f o r t t o
estimate t h e systematic error. If one uses variance weighting indiscriminately
i n s u c h c a s e s , o n e p e n a l i z e s t h e a u t h o r s w h o a t t e m p t t h e d i f f i c u l t t a s k of
e s t i m a t i n g t h e s y s t e m a t i c e r r o r , while b e n e f i t i n g t h e a u t h o r s who m a k e no s u c h
a t t e m p t t o d e t e r m i n e a l l of t h e i r s o u r c e s of e r r o r , ( a n a d m i t t e d l y d i f f i c u l t t a s k ) .
In t h e r e v i e w of n u c l e a r d a t a by t h e I n t e r n a t i o n a l A t o m i c E n e r g y Agency ( r e f . 12),
their general comment on uncertainties included a s t a t e m e n t questioning t h e
v a l i d i t y of a n y p r e s e n t l y s t a t e d u n c e r t a i n t i e s of l e s s t h a n 0 . 1 % f o r h a l f - l i v e s .
COMMISSION ON RADIOCHEMISTRY AND NUCLEAR TECHNIQUES
i488
T h e s a m e c r i t e r i a h a s a l s o b e e n a p p l i e d h e r e i n a f e w c a s e s . No h a l f - l i f e h a s
b e e n r e c o m m e n d e d w i t h a n a c c u r a c y of b e t t e r t h a n 0.1%; s e e t h e t o t a l h a l f - l i f e
of 2 3 3 U a s a n e x a m p l e . T h e r a t i o n a l e f o r t h i s r u l e i s t h a t s y s t e m a t i c e r r o r s
u p t o t e n t i m e s smaller t h a n t h e t o t a l statistical u n c e r t a i n t y quoted could have
a n a p p r e c i a b l e e f f e c t o n t h a t t o t a l u n c e r t a i n t y , i f t h e r e w e r e a n u m b e r of s u c h
e r r o r s . R e c o m m e n d i n g v a l u e s a t a c c u r a c y l e v e l s of a few h u n d r e d p p m would i m p l y
t h a t a l l p o t e n t i a l e r r o r s i n t h e e x p e r i m e n t a t t h e l e v e l of t e n p p m h a d b e e n
investigated, documented, and their effect on t h e result taken into account.
An e x p e r i m e n t , i n w h i c h s u c h a t h o r o u g h s t u d y h a s b e e n b o t h p e r f o r m e d a n d
documented, h a s yet t o be reported t o m y knowledge.
If one had a choice in designing t h e ideal experiment t o measure t h e half-life,
o n e w o u l d c h o o s e t o d e t e r m i n e m a n y s a m p l e s , u s i n g a n u m b e r of d u p l i c a t e
i n s t r u m e n t s a n d u t i l i z i n g a v a r i e t y of d i f f e r e n t m e t h o d s o r t e c h n i q u e s . T h i s
should provide the necessary information to correctly estimate t h e systematic
e r r o r . Some effort toward t h i s goal has been made in t h e last decade in t h e
m e a s u r e m e n t s o n t h e h a l f - l i f e of 2 3 9 P u a n d 2 4 0 P u b y t h e U S H a l f - l i f e
Evaluation Committee. However, t h i s effort usually involved only one sample
a n d f o r 2 3 9 P u , o n e of t h e m e a s u r e m e n t s w a s d i s c a r d e d b e c a u s e i t w a s l o w e r
t h a n t h e o t h e r r e s u l t s ( r e f . 13). It s h o u l d be e m p h a s i z e d t h a t t h i s is n e v e r
a s u f f i c i e n t r e a s o n of a n d by i t s e l f t o d i s c a r d d a t a
TABULATED RESULTS
Table 1. Spontaneous fission half-life of 232U
Reference
Author (Year)
As R e p o r t e d
~ 4 / 1 0 la~
J a f f e y i 4 (1951)
8.
Segrel' (1952)
> 0.8
i
Comments
5.5
Not u s e d ; I o n i z a t i o n C h a m b e r
R e c o m m e n d e d V a l u e = 8 i 6 x 1013 a ;
Selected V a l u e
Table 2. Total half-life of 232U
Reference
Author (Year)
As Revised
T4/a
Comments
James"
70.
Not u s e d ; I n g r o w t h w i t h p u l s e a n a l y s i s
(1949)
Sellars"
(1954)
73.6
i
10
2 n a c o u n t i n g ; Mass s p e c t r o m e t r y ;
Revised p r o b a b l e e r r o r t o
Standard deviation
Chiiton"
(1964)
72.1
i
0.5
71.4
i
06
99.2% e n r i c h e d s a m p l e , 2 n a c o u n t i n g ,
Coulometry
99.2% e n r i c h e d s a m p l e ; C a l o r i m e t r y
Aggarwal"
(1979)
Weaghted Average
=
70.
*
68.90 i 0 3 9
Specific a c t i v i t y ;
R e l a t i v e a c t i v i t y t o 233U
1 a;
Recommended Value
Table 3. Spontaneous fission half-life of 233U
Reference
Author (Year)
Segre''
As R e p o r t e d
T'i/10'~ a
(1952)
Aleksandrov"
von Gunten"
> 2 7
(1966)
(1981)
1 2 T 0 3
> 2.7
R e c o m m e n d e d V a l u e = > 2.7 x 1017 a ;
Comments
Ionization Chamber
m e n t i o n of c o r r e c t i o n f o r 2 3 2 ~
J u s t 0 03% of 232U c o u l d a c c o u n t f o r
discrepancy with o t h e r measurements
NO
97.11% e n r i c h e d ;
Rotating Bubble Chamber;
Corrected for (a,n,f) reaction
Selected V a l u e
Total and spontaneous fission half-lives
1489
Table 4. Total half-life of 233U
Reference
Author (Year)
A s Revised
m/105 a
Jaffey"
1.5910 i 0.0015
99.477% e n r i c h e d ;
Intermediate geometry a counting
V a n i n b r o ~ k x ' (1976)
~
1.5925 i 0.0013
99.762% e n r i c h e d ; Low g e o m e t r y c t g
99.9986% e n r i c h e d ; l i q u i d s c i n t . c t g .
Geidel'man' (1979)
1.5937 i 0.0017
98.112% e n r i c h e d ; 471 a-x c o i n c i d e n c e ;
U n c e r t a i n t y x 1.5 f o r m i s s i n g d e t a i l s
AggarwalZ4 (1980)
1.5865
(1974)
+
0.0026
R e c o m m e n d e d V a l u e = 1.592 i 0.002 x lo5 a ;
Comments
99.703% e n r i c h e d ; a c o u n t i n g a n d
liquid scintillation counting
Weighted Average u s i n g u n c e r t a i n t y r u l e
Table 5. Spontaneous fission half-life of 234U
As Revised
T%/IO" a
Reference
Author (Year)
Segre"
> 0.6
(1952)
Comments
Not u s e d ; I o n i z a t i o n C h a m b e r
+
0.7
Not u s e d ; Revised; I o n i z a t i o n c h a m b e r
Ghiorsoz5 (1952)
1.6
von G u n t e n "
1.42 i 0.08
99.36% enriched; Rotating Bubble Chamber;
Corrected for (a,n,f) reaction
+
99.64% enriched; Phosphate glass d e t e c t o r ;
232U Corrected for; Increased u n c e r t a i n t y
by 50% t o a c c o u n t f o r o v e r e s t i m a t e of
t h e z e n i t h a n g l e of fission f r a g m e n t s
Wang"
(1961)
1.9
(1967)
Weighted Average
=
0.15
1.5 i 0 . 2 x 10l6 a ;
Recommended Value
Table 6. Total half-life of 234U
Reference
Author (Year)
As Revised
7-4/105 a
Comments
F l e m i n g z 7 (1952)
2.475 i 0.049
Not u s e d ; Medium g e o m e t r y a c o u n t i n g
Whitez8 (1965)
2.47
Not u s e d ; a c o u n t i n g
Meadows"
2.439 f 0.036
(1970)
i 0.06
f 0.009
Not u s e d ; a l % e n r i c h e d ; A u t h o r
w i t h d r e w d a t a ; 50% i n c r e a s e in
Uncertainty for missing details
E n r i c h e d t o 99.873%;Revised v a l u e ,
see t e x t f o r a d e t a i l e d d i s c u s s i o n
DeBievre7 (1972)
2.450
L o u n s b u r y ' (1972)
2.458 f 0.013
1.08% e n r i c h e d ; Revised v a l u e ;
Low g e o m e t r y a c o u n t i n g
Geidel'man3' (1960)
2.4604 + 0.009
93.437% e n r i c h e d ; 471a-x Coincidence;
Revised u n c e r t a i n t y
93.437% e n r i c h e d ; l i q u i d s c i n t i l l a t o r ;
Revised u n c e r t a i n t y
2.4570 i 0.009
Poenitz31 (1983)
Weighted Average
2.457 i 0.006
=
2.455
+
0.006 x l o 5 a ;
Not u s e d ; Mass i n t e r c o m p a r i s o n ;
Confirms direct measurements
Recommended Value
Table 7. Spontaneous fission half-life of 235U
Reference
Author (Year)
Segre"
A s Reported
T%/~o"a
(1952)
Aleksandrov''
0.18
(1966)
G r u e t t e r 3 ' (1973)
von G u n t e n "
(1981)
Not u s e d ; I o n i z a t i o n c h a m b e r
0.35 i 0.09
> 1.8
9.8
Comments
Not u s e d ; Fission t r a c k d e t e c t o r s
Not u s e d ; No c o r r e c t i o n s
Rotating bubble chamber;
i
2.8
R e c o r n m e n d e d V a l u e = 1.0 i 0.3 x 10lg a ;
99.76% enriched; Rotating bubble c h a m b e r
Corrected for (a,n,f) reaction
Selected V a l u e
COMMISSION ON RADIOCHEMISTRY AND NUCLEAR TECHNIQUES
1490
Table 8. Total half-life of 235U
Reference
Author (Year)
A s Reported
T%/IO' a
Comments
N i e r 3 3 (1939)
7.04
f
207Pb/206Pb Rat i o
S a ~ a (1951)
g ~ ~
6.94
f 0.40
a counting
Fleming"
7.12
f 0.31
a counting; medium geometry
K n i g h t 3 5 (1950)
7.10
f
Wurger3' (1957)
6.93
i 0.27
a counting
White"
7.12
i 0.18
a counting
(1952)
(1965)
0.31
0.32
a c o u n t i n g ; 50% g e o m e t r y
B a n k s 3 7 (1966)
7 . 0 2 (+ 0.14 - 0.06)
2O7Pb/2O6Pb
D e r u y t t e r 3 ' (1965)
6.97
a counting; silicon detector
J a f f e y ' (1971)
7 . 0 3 7 f 0.011
f 0.19
W e i g h t e d A v e r a g e = 7 . 0 4 i 0.01 x 10' a ;
Ratio
a counting; intermediate geometry
Recommended Value
Table 9. Spontaneous fission half-life of 236U
Reference
Author (Year)
As R e p o r t e d
T%/IO" a
Jaffey3' (1949)
2.
f 1.6
Conde4' (1971)
2.7
f 0.3
yon Gunten''
(1981)
B e l e n k v 4 ' (1983)
Comments
238U/236U = 0 3 0 f 0 . 0 3
2 . 4 3 f 0.13
99.68% e n r i c h e d ; R o t a t i n g b u b b l e c h a m b e r ;
Corrected for (a,n,f) reaction
2.7
Multiple n e u t r o n coincidence
f 0.4
W e i g h t e d A v e r a g e = 2.5 i 0.1 x 10''
a;
Recommended Value
Table 10. Total half-life of 236U
Reference
Author (Year)
As R e v i s e d
m/107 a
J a f f e y 4 ' (1951)
2 46
f 0.14
a counting, Increased u n c e r t a i n t y
b y 50% f o r m i s s i n g d e t a i l s
F l e m i n g z 7 (1952)
2.391
f 0.057
a counting, Increased u n c e r t a i n t y
b y 50% f o r m i s s i n g d e t a i l s
F l ~ n (1972)
n ~ ~
2.3422 f 0.0039
Weighted A v er a g e = 2.342 i 0.004 x lo 7 a ;
Comments
Revised u n c e r t a i n t y ;
Intermediate geometry a counting
Recommended Value
Table 11. Total half-life of 238U
Reference
Author (Year)
A s Reported
~ % / 1 a0 ~
Comments
J a f f e y ' (1971)
4 . 4 6 8 f 0.022
Intermediate geometry a counting
R e c o m m e n d e d V a l u e = 4 . 4 7 i 0.02 x 10' a ;
Selected Value
1491
Total and SDontaneous fission half-lives
Table 12. Spontaneous fission half-life of 23*U
Reference
Author (Year)
A s Reported/(1O-l7 a - ' )
Specific Activity
Comments
W h i t e h ~ u s e(1950)
~~
838 f 052
Ionization Chamber
Segre''
860 i 029
Ionization Chamber
(1952)
+
F l e i ~ c h e r(1964)
~~
685
020
Not u s e d ; M i c a - u r a n i u m S a n d w i c h
R o b e r t s 4 ' (1968)
7 0 3 i 011
Not u s e d ; M i c a - u r a n i u m S a n d w i c h
S p a d a ~ e c c h i a(1967)
~~
8 4 2 f 0 10
Rotating Bubble Chamber
von G ~ n t e n
(1969)
~ ~
866 i 022
F i s s i o n P r o d u c t s f r o m 238U
G a l l i k e r 4 ' (1970)
846
f
006
Rotating Bubble Chamber
Storzer"
849
+
076
F i s s i o n T r a c k s i n Dated U r a n i u m C l a s s
68
i 0 6
(1970)
Kleeman"
(1971)
Not u s e d ; L e x a n - u r a n i u m
Sandwich
T h u r y 5 ' (1971)
866 f 043
Third Order Coincidence
Leme53 (1971)
7 3 0 f 016
Not u s e d ; M i c a - u r a n i u m S a n d w i c h
K h a n 5 4 (1973)
6 82 i 0 55
Not u s e d ; M i c a - u r a n i u m S a n d w i c h
I ~ a n o v(1975)
~ ~
7 12
*
E m m a 5 6 (1975)
72
Wagner57 (1975)
8 7
ThieI5' (1976)
857
Kase5' (1978)
822 f 020
Ionization Chamber
Popeko"
79
i 0 4
Multiple Neutron Coincidence
926
+
Not u s e d ; M i c a - u r a n i u m S a n d w i c h
66
1 0 2
Not u s e d ; M i c a - u r a n i u m
Sandwich
86
f 0 4
Not u s e d ; M i c a - u r a n i u m
Sandwich
118
i 07
Not u s e d ; Fission T r a c k s ( O r d i n a r y Glass)
(1980)
Spaggiari"
Baptista"
(1980)
(1981)
H a d l e r B 3 (1981)
d e C a r v a l h o a 4 (1982)
Not u s e d ; M i c a - u r a n i u m
Sandwich
1 0 2
Not u s e d ; M i c a - u r a n i u m
Sandwich
+ 0 6
F i s s i o n T r a c k s i n Dated U r a n i u m Glass
+
F i s s i o n T r a c k s i n Dated U r a n i u m Glass
032
042
017
+
835
V a r t a n i a r ~ ' ~(1984)
823 f 043
Not u s e d ; F i s s i o n T r a c k s i n P l a s t i c .
U r a n i u m Foils
I v a n o v B 6 (1985)
8.29 i 0.27
Double I o n i z a t i o n C h a m b e r
Recommended Half-life
040
Multiple Neutron Coincidence
B e l e n k y 4 ' (1963)
V a l u e = 8.2 f 0.1 x lOI5 a ; U n w e i g h t e d A v e r a g e o f
Techniques
Table 13. Spontaneous fission half-life of 23sPu
~~
Reference
Author (Year)
As Revised
T%/~o'a
Comments
~~
G h i o r s o Z 5 (1952)
3.4
S e l i c k i j B 7 (1988)
2.09 i 0.06
R e c o m m e n d e d V a l u e = 2.1
*
f
1.2
0.1 x l o g a ;
Not u s e d ; Revised v a l u e
Ionization chamber
Two s o u r c e s ; F r a g m e n t d e t e c t i o n
i n 27r g e o m e t r y
Selected Value
Table 14. Total half-life of 23sPu
Reference
Author (Year)
James"
(1949)
Hoffman"
Nakanishi"
(1957)
(1984)
A s Reported
T%/a
Comments
+
a counting
2.7
0.3
2.85 f 0.10
a counting
2.87 f 0.01
Activity Ratios;
Silicon Surface Barrier Detector
W e i g h t e d A v e r a g e = 2 8 7 f 0.01 a ,
Recommended Value
COMMISSION ON RADIOCHEMISTRY AND NUCLEAR TECHNIQUES
1492
Table 15. Alpha half-life of 238Pu
Reference
Author (Year)
As R e v i s e d
T%/a
Comments
J a f f e y 7 ' (1950)
89.59i 0.44
271 a c o u n t e r : R e v i s e d u n c e r t a i n t y
Mech71 (1956)
86
R e l a t i v e a c t i v i t y t o 240Pu
H o f f m a n 7 z (1957)
86.41i 0.32
a c o u n t i n g ; Revised u n c e r t a i n t y
S t o h m " (1974)
87.77i 0.053
C a l o r i m e t r y : Revised u n c e r t a i n t y
P o l y ~ k o v(1976)
~ ~
86.98i 0.23
47r,low g e o m e t r y a c o u n t i n g
D i a m o n d 7 4 (1977)
87.71 f 0.06
a c o u n t i n g ; Revised u n c e r t a i n t y
~ e v o s t i j a n o v(1981)
~~
86.54f 0.33
a c o u n t i n g ; Revised u n c e r t a i n t y
Aggarwa17' (1981)
87.98i 0.25
R e l a t i v e a c t i v i t y t o 239Pu
Revised u n c e r t a i n t y
i
3.5
Revised u n c e r t a i n t y
W e i g h t e d A v e r a g e = 87.7 i 0.1a ;
Recommended Value
Table 16. SDontaneousfission half-life of 2 3 8 P ~
As R e v i s e d
T%/IO'O
a
Reference
Author (Year)
Comments
~~~~~
Segre"
(1952)
3.8
Not u s e d ; R e v i s e d ; I o n i z a t i o n C h a m b e r
J a f f e ~(1949)
~ ~
4.7
i
0.6
f
0.6
Revised Value;
D r ~ i (1961)
n ~ ~
5.1
H a s t i n g s 7 ' (1972)
4.77f 0.14
a/fission Ratio
Silicon S u r f a c e B a r r i e r Detectors
G a y a o (1975)
4.63i 0.12
F i s s i o n F r a g m e n t C o i n c i d e n c e s i n Mica
S e l i c k i j a 7 (1988)
5.01 i 0.21
4 sources; Fragment Detection i n
Revised: Nuclear P h o t o g r a p h i c E m u l s i o n s
27r G e o m e t r y
W e i g h t e d A v e r a g e = 4.75 i 0.09x 10" a ;
Recommended Value
Table 17. Spontaneous fission half-life of 239Pu
Reference
Author (Year)
Segre"
(1952)
(1985)
Druzhinin"
A s Reported
~ % / 1 0 al ~
Comments
5.5
Not u s e d ; I o n i z a t i o n C h a m b e r
7.8 f 1.6
a/fission activity
R e c o m m e n d e d V a l u e = 8. i 2. x 1015 a :
Selected Value
Table 18. Total half-life of 239Pu
Reference
Author (Year)
As R e v i s e d
7-%/104 a
Comments
47r a - x c o i n c i d e n c e ; R e v i s e d u n c e r t a i n t y
2 4060
f
0.0019
G l o v e r e 3 (1975)
2 4115
i
0.0080
Not u s e d * ; Low g e o m e t r y a c o u n t i n g
J a f f e y e 4 (1977)
2 4124
2 4139
i
i
0.0014
0.0013
Intermediate geometry a counting;
Isotope dilution mass s p e c t r o m e t r y
L u c a s a 5 (1978)
2 4112
+
0.0033
a c o u n t i n g ; Revised u n c e r t a i n t y
G u n n e e (1 978)
2 4102 i 0.0010
M a r s h e 7 (1978)
2 4164
*
0.0017
Mass s p e c t r o m e t r y ; R e v i s e d u n c e r t a i n t y
2 4101
f
0.0010
C a l o r i m e t r y ; Revised u n c e r t a i n t y
2 4089
2 4019
f
f
0.0019
0.0015
Mass s p e c t r o m e t r y ; R e v i s e d u n c e r t a i n t y
a c o u n t i n g ; Revised u n c e r t a i n t y
2 4085
2 4114
f
f
0.0014
0.0013
Not u s e d * ; Low g e o m e t r y a c o u n t i n g
Not u s e d * ; L i q u i d s c i n t i l l a t o r
2 4088
f
0.0025
Low g e o m e t r y a c o u n t i n g ;
Revised u n c e r t a i n t y
Aleksandrov"
Seabaugh"
(1975)
(1978)
P r i n d l e a g (1978)
Vaninbroukx"
B r o w n g 1 (1981)
(1978)
C a l o r i m e t r y ; Revised u n c e r t a i n t y
* Experiments considered preliminary.
R e c o m m e n d e d V a l u e = 2.410f 0.003 x
lo4 a ;
U n w e i g h t e d a v e r a g e of t e c h n i q u e s
w i t h u n c e r t a i n t y r u l e invoked
1493
Total and spontaneous fission half-lives
Table 19. Spontaneous fission half-life of 240Pu
Reference
Author (Year)
As Revised
T'l/loil a
Comments
Kindermann"
1314 f 0 0 2 6
Not u s e d , Low g e o m e t r y a c o u n t i n g
B a r c l a y g 3 (1954)
1225 i 0030
Not u s e d , Low g e o m e t r y a c o u n t i n g
C h a m b e r l a i n g 4 (1954)
120
Not u s e d , Low g e o m e t r y a c o u n t i n g
Mikheev"
120
Not u s e d , a c o u n t i n g ; g a s s c i n t i l l a t o r
(1953)
(1959)
W a t t g e (1962)
134
f
0015
Not u s e d , Low g e o m e t r y a c o u n t i n g
Malking7 (1963)
145
*
002
Not u s e d , a c o u n t i n g , g a s s c i n t i l l a t o r
Whitege (1967)
127
i 005
F i e l d h o u s e g 9 (1967)
1176 i 0 0 2 5
Budtz-Jorgensen'"
Androsenko"'
(1980)
(1984)
S e l i c k i j B 7 (1988)
Not u s e d , No d e t a i l s a v a i l a b l e
Not u s e d , Revised; S p o n t a n e o u s
Fission n e u t r o n e m i s s i o n r a t e s
1.15
*
0.03
Fragment spectra; ionization chamber
1.15
i
0.03
Spontaneous fission n e u t r o n
Emission r a t e s
1.17
+
0.03
Two S o u r c e s ; F r a g m e n t d e t e c t i o n i n
8n geometry
Weighted A v e r a g e = 1.16 i 0.02 x 10" a ;
Recommended Value
Table 20. Total half-life of 240Pu
Reference
Author (Year)
A s Revised
~ ' 1 1 1 0 ~a
Comments
Inghram"'
6.505 i 0 . 0 4 5
Not u s e d ; Mass s p e c t r o m e t r y
(1951)
B u t l e r 1 0 3 (1956)
6.600
+
0.100
Not u s e d ; a c o u n t i n g
D o k u ~ h a e v '(1959)
~~
6.610
i
0.055
Not u s e d ; Low g e o m e t r y a c o u n t i n g
Oetting'"
6 . 5 3 3 i 0 010
Not u s e d ; C a l o r i m e t r y ; Revised v a l u e
6.569
-t
0006
Intermediate geometry a counting
6.5524
+
0.0017
Calorimetry
(1967)
Jaffey"'
(1978)
(1984)
Lucas'"
(1984)
Steinkruger"'
Beckman"'
_
_
_
_
(1984)
(1984)
6.5522 i 0.0052
a counting
6.571
i 0.007
Low g e o m e t r y a c o u n t i n g
6.574
*
~
Recommended Value = 6 5 6
*
0.0062
0 0 1 x lo3 a ,
Mass s p e c t r o m e t r y ; r e v i s e d u n c e r t a i n t y
U n w e a g h t e d A v e r a g e of T e c h n a q u e s
Wath U n c e r t a z n t y R a n g e E z t e n d e d
Table 21. Spontaneous fission half-life of 241 Pu
Reference
Author (Year)
As R e p o r t e d
T%/lO" a
Comments
D r u z h i n i n e i (1985)
< 6
a/f activity measured
Recommended Value < 6 x loi6 a
Selected Value
Table 22. Alpha half-life of 241Pu
Reference
Author (Year)
As Revised
~ % / 1 a0 ~
Comments
Bigham"'
6.35 i 0.32
a s p e c t r o m e t r y r e l a t i v e t o 239
(1958)
+
2 4 0 ~ ~
(1960)
5.84
*
0.12
Revised v a l u e ;
a spectrometry/total Pu a emission
S m i t h 1 I 3 (1961)
597
*
020
Revised v a l u e ;
a / @ branching, a spectrometry
B e r t ~ l i n i " (1966)
~
5.98
Ahmad"'
5.88
Brown"'
Gunnink"'
(1968)
(1976)
Van i n b r o u kx1I7 (1978)
*
*
0.10
Revised, G r o w t h m e t h o d ; Ge(Li) d e t e c t o r s
0.21
a / y coincidence
5.85 i 0.075
y e m i s s i o n p r o b a b i l i t i e s , Ge(Li) d e t e c t o r s
6.04 i 0.06
a spectrometry; ingrowth method
Solid s t a t e d e t e c t o r s
W e i g h t e d A v e r a g e = 5.96 i 0.04 x lo'
a;
Recommended Value
COMMISSION ON RADIOCHEMISTRY AND NUCLEAR TECHNIQUES
1494
Table 23. Total half-life of 24'Pu
Reference
Author (Year)
A s Revised
T%/a
Comments
Strohm"
14.355 i 0.007
Calorimetry
14.56 i 0.15
I n g r o w t h of 241Am Y r a y
(1974)
Whitehead"'
(1977)
14.38
G a r n e r i i g (1979)
Vaninbroukx"'
Aggarwal'"
Marsh"'
(1978)
(1980)
(1980)
*
0.07
Mass s p e c t r o m e t r y
14.60 i 0 10
I n g r o w t h of 241Am Y r a y
14.42 f 0.09
a spectrometry
14.38
Mass s p e c t r o m e t r y
-t
0.06
A g g a r ~ a l " (1981)
~
14.52 f 0 . 0 8
a spectrometry
Aggar~al''~
(1981)
14.44 f 0.06
a spectrometry, a proportional counting
Aggar~al"~
(1982)
14.32 f 0.06
Mass s p e c t r o m e t r y ; Revised u n c e r t a i n t y
DeBievre"'
1 4 . 3 3 f 0.02
Mass s p e c t r o m e t r y
H i y a m a I z 7 (1984)
14.29 f 0.15
Mass s p e c t r o m e t r y
Aggarwal"'
(1985)
14.38 f 0.02
Mass s p e c t r o m e t r y
T i m ~ f e e v " (1986)
~
14.57 f 0.10
Mass s p e c t r o m e t r y
(1983)
R e c o m m e n d e d V a l u e = 14.4 i 0.1 a ;
Unweighted Average of T e c h n i q u e s
Table 24. Spontaneous fission half-life of 242Pu
~~
Reference
Author (Year)
A s Revised
T4/101' a
Comments
Studier"
6.7
Quoted by Mech71
(1956)
0.7
a/fission ratio
B u t l e r i 3 ' (1956)
6 . 6 5 i 0.10
Mech7' (1956)
6.79 i 0.19
Revised Value f o r 2 4 2 P u a T %
Druin7' (1961)
6.6
Gas s c i n t . ; R e l a t i v e t o 238Pu a T b
Malking7 (1963)
7 . 4 5 f 0.17
Gas s c i n t i l l a t o r ; S p e c i f i c a c t i v i t y
Meadows131 (1977)
6.74 f 0.05
a/fission ratio
KhanI3' (1980)
7.43
Not u s e d ; Mica f i s s i o n t r a c k d e t e c t o r
S e l i c k i j a 7 (1988)
6.86 i 0.26
f 0.7
Fission f r a g m e n t detection i n
2.rr g e o m e t r y
A e i g h t e d A v e r a g e = 6.77 i 0.07 x 10''
a;
Recommended Value
Table 25. Total half-life of 242Pu
Reference
Author (Year)
As Reported
~ 4 1 1 0a ~
Comments
~~
ButlerI3' (1956)
3649 f 005
Not u s e d ; R e l a t i v e a a c t i v i t y t o 238Pu
B u t l e r 1 0 3 (1956)
3 790 f 0 05
Not u s e d ; Ion C h a m b e r e n e r g y a n a l y s i s
Mech7' (1956)
3 8 5 5 f 0100
Not u s e d ; R e l a t i v e a a c t i v i t y t o 2 4 0 P u
be mi^'^^ (1969)
3 8 2 3 i 0016
R e l a t i v e a a c t i v i t y t o 239Pu
D u r h a m 1 3 4 (1970)
3674 i 007
R e l a t i v e a a c t i v i t y t o 238Pu
O ~ b o r n e '(1976)
~~
3763 i 0009
Calorimetry
B ~ l y a n i t s a '(1976)
~~
3 7 0 2 f 0014
4na-x c o i n c i d e n c e
Meadows131 (1977)
3708 f 0024
R e l a t i v e a a c t i v i t y t o 239Pu
A g g a r ~ a l '(1979)
~~
3754 i 0025
R e l a t i v e a a c t i v i t y t o 239Pu a n d 238Pu
Aezghted Average = 3 7 5 f 0 0 2 x lo5 a ,
Recommended Value
Total and spontaneous fission half-lives
1495
Table 26. Spontaneous fission half-life of 244Pu
Reference
Author (Year)
As Revised
T4/10" a
*
6.67 *
6.8 *
Fields'38 (1955)
2.5
Fields'39 (1966)
G o k h b e r g i 4 ' (1977)
Comments
0.8
Not u s e d ; I o n i z a t i o n c h a m b e r
0.32
Revised v a l u e
0.8
No d e t a i l s
Khani3' (1980)
7.32
Not u s e d ; Fission t r a c k d e t e c t o r
Moorei4' (1982)
6.56 i 0.30
Ion c h a m b e r ; a c o u n t i n g ;
a spectrometry
Weighted Average =
6.6 i 0.2 x 10"
a;
Recommended Value
Table 27. Total half-life of *"Pu
Reference
Author (Year)
A s Revised
~ 4 1 1 0
a ~
Comments
Butleri3' (1956)
6.65 f 0.10
Not u s e d ; R e l a t i v e a a c t i v i t y t o 238Pu
Diamond14' (1956)
7.3
*
2.
Revised; a n t i - c o i n c i d e n c e p r o p . c o u n t e r
Butler'03 (1956)
7.6
f
2.
a counting
Fields139 (1966)
8.12 i 0.26
be mi^'^^
(1969)
Weighted A v e r a g e = 8.00
7.99
*
i 0.09
Revised v a l u e
0.10
Revised; R e l a t i v e a c t i v i t y t o 239Pu
x lo7 a ;
Recommended Value
Table 28. Spontaneous fission half-life of 24rAm
Reference
Author (Year)
A s Reported
~ 4 / 1 0 'a~
Comments
Segre"
> 0.14
Not u s e d ; I o n i z a t i o n c h a m b e r
> 2.
Not u s e d ; Gas s c i n t i l l a t o r
(1952)
Mikheev"
(1960)
D r ~ i n (1961)
' ~ ~
2.3
Galliker4' (1970)
0.90
~ 0 ~ 1 4(1970)
4
1.147 i 0.024
Mica fission t r a c k d e t e c t o r
1.8
Mica fission t r a c k d e t e c t o r
(1986)
Moodyi4' (1987)
0.8
f 0.04
f 0.4
0.64
Gas s c i n t i l l a t o r
Rotating bubble chamber
Phosphate glass t r a c k detector
R e c o m m e n d e d V a l u e = 1.0 f 0.4 x 1014 a ;
Selected V a l u e ; U n c e r t a i n t y o v e r l a p s r a n g e
Table 29. Total half-life of 24rAm
Reference
Author (Year)
As Revised
T%/a
Comments
~ ~ 1 1 1 4(1958)
7
458 1 i 0.5
Not u s e d ; Low g e o m e t r y a c o u n t i n g
wall mar^'^^
457.7
(1958)
Oetting14' (1967)
Stone'"
(1968)
*
432.7
1.8
Not u s e d ; Low g e o m e t r y a c o u n t i n g
0.7
Calorimetry
436.6 i 3.0
Low g e o m e t r y a c o u n t i n g
Brownis1 (1988)
433.
434.4
*
*
7.
3.6
Coulometric a counting
R e l a t i v e Activity t o 243Am
Jove15' (1972)
426.3
+
2.1
Calorimetry
St r o h m "
432.5
*
1.0
435.0
*
1.0
Calorimetry (power decay);
Revised u n c e r t a i n t y
Calorimetry (specific power);
Revised u n c e r t a i n t y
P o l y ~ k h o v '(1974)
~~
432.8
*
1.6
R a m t h ~ n '(1975)
~ ~
432.0 i 0.7
C a l o r i m e t r y ; Revised U n c e r t a i n t v
W e i g h t e d A v e r a g e = 432.7
+
Recommended Value
(1974)
0.6 a ;
4 n a c o u n t i n g ; Revised u n c e r t a i n t y
COMMISSION ON RADIOCHEMISTRY AND NUCLEAR TECHNIQUES
1496
Table 30. Spontaneous fission half-life of 242mAm
Reference
Author (Year)
C a l d ~ e l l (1967)
'~~
Z e l e n k ~ v '(1986)
~~
R e c o m m e n d e d Value =
A s Revised
T4/10" a
Comments
1.0 f 0.4
Not used; Revised; FissionFragment - Neutron coincidence
> 3.0
a/fission;
Silicon s u r f a c e b a r r i e r d e t e c t o r s
> 3. x 10" a ;
Selected Value
Table 31. Partial half-lives of 242mAm
Reference
Author (Year)
A s Revised
Th/a
Comments
S t r e e t ' 5 7 (1950)
10000
a decay branch
H ~ f f (1955)
' ~ ~
Barnes'59 (1959)
Henderson'59 (1959)
Zelenkov'"
(1980)
Electron capt. decay branch
850.
29000. i 1450.
50.
960. i
152
f
7.
182.
Revised Value; a d e c a y b r a n c h
Electron capt. branch
Total h a l f - l i f e
p d e c a y b r a n c h ; q u o t e d by Barnes159
i
8.
171. f
31200. r
140.8 i
2.
@ decay branch
500.
1.7
a decay branch
Weighted A v e r a g e = 141. i 2. a ;
Total h a l f - l i f e
Recommended Value
Table 32. Total half-life of 243Am
Reference
Author (Year)
As Revised
7-4/103 a
Street15' (1950)
10.
Comments
Not u s e d ; D a u g h t e r g r o w t h
Diamondi6' (1953)
8.1
i 0.6
wall mar^'^^ (1958)
7.95
*
Barnes'5g (1959)
7.29
i 0.16
Not u s e d ; R e l a t i v e a c t i v i t y t o z4lAm
Beadle'"
(1960)
7.22
i 0.05
Not u s e d ; Revised v a l u e ;
R e l a t i v e a c t i v i t y t o 241Am
Brown"'
(1968)
7.34
7.39
i 0.065
*
0.05
R e l a t i v e a c t i v i t y t o 241Am
Coulometric a counting
P o l y u k h ~ v '(1974)
~~
7.38
i.
0.034
AggarwaliB4 (1980)
7.36
i 0.042
0.05
Weighted A v e r a g e = 7.37 i 0.02 x l o 3 a ;
Not u s e d ; Revised v a l u e ;
R e l a t i v e a c t i v i t y t o 241Am
Not u s e d ; Low g e o m e t r y a c o u n t i n g
a counting;
R e l a t i v e a c t i v i t y t o 241Am
Revised; r e l a t i v e a c t i v i t y t o 241Am
R e c o m m e n d e d Value
Table 33. Spontaneous fission half-life of '"Am
Reference
Author (Year)
As R e p o r t e d
~ 4 / 1 0 'a~
A l e k ~ a n d r o v " ~(1966)
> 033
Grozdev'06 (1966)
2
*
003
* 0 5
R e c o m m e n d e d V a l u e = 2.0 i 0.5 x 1014 a ;
Comments
Glass fission t r a c k d e t e c t o r
Glass fission t r a c k d e t e c t o r
S e l e c t e d Value
Total and spontaneous fission half-lives
Table 34. Spontaneous fission half-life of 242Cm
A s Revised
T~/10'a
Reference
Author (Year)
H a n n a I e 7 (1951)
7.2
+
Armani'"
6.82
f 0.18
(1967)
0.2
Comments
Fission f r a g m e n t c o u n t i n g ,
Ion c h a m b e r
Revised v a l u e ;
L i - I fission n e u t r o n c o u n t i n g
Zhang'Ov (1979)
7.46 i 0.06
Mica fission t r a c k d e t e c t o r
R a g h ~ r a m a n ' ~(1982)
'
7.15
i 0.15
Solid s t a t e t r a c k d e t e c t o r
U r n e ~ a w a ' ~(1982)
'
6.89
*
0.17
Mica fission t r a c k d e t e c t o r
Z e l e n k ~ v ' ~(1986)
'
6.98
f
0.33
Revised v a l u e ; a / f i s s i o n
Silicon s u r f a c e b a r r i e r d e t e c t o r s
R e c o m m e n d e d V a l u e = 7.0 i 0.2 x 10' a ;
Selected Value; U n c e r t a i n t y c o v e r s
t h e r a n g e of r e c e n t m e a s u r e m e n t s
Table 35. Total half-life of "'Cm
Reference
Author (Year)
As Revised
TC/d
HannaI7' (1950)
162.5
*
G 1 0 v e r - l ~(1954)
~
162 4 6
f 0.33
H ~ t c h i n s o n '(1954)
~~
163.0
*
F l ~ n n " (1965)
~
163.1
i 0.4
Revised v a l u e ; 2n a c o u n t i n g
K e r r i g a r ~ '(1975)
~~
163.2
*
0.2
Calorimetry
Diamond'77 (1977)
162.76
f
0.10
Revised u n c e r t a i n t y ;
Intermediate geometry a counting
Zhang'"
163.02
*
0.17
Revised u n c e r t a i n t y ;
Low g e o m e t r y a c o u n t i n g
(1979)
1.
1.8
JadhavI7' (1980)
162.13 i 2.25
U ~ u d a ' ~(1981)
'
161.35
Aggarwal'"
162.82 f 0.27
(1982)
i 0.16
i 0.12
163.17
Wiltshine'"
(1984)
163.03 i 0.22
Weighted A v e r a g e = 162.8 i 0.2 d ;
Comments
Low g e o m e t r y a s p e c t r o m e t r y
Revised u n c e r t a i n t y ;
Low g e o m e t r y a c o u n t i n g
Calorimetry
a s p e c t r o m e t r y , solid s t a t e d e t e c t o r
2rr a c o u n t i n g ; Revised u n c e r t a i n t y
R e l a t i v e a c t i v i t y t o 244Cm;
Revised u n c e r t a i n t y
a c o u n t i n g ; Revised u n c e r t a i n t y
Low g e o m e t r y a c o u n t i n g ;
Revised u n c e r t a i n t y
Recommended Value
Table 36. Spontaneous fission half-life of '"Cm
Reference
Author (Year)
As R e p o r t e d
TC/IO" a
Polynov'82 (1987)
5.5
R e c o m m e n d e d V a l u e = 5.5
*
*
0.9
0.9 x 10" a ;
Comments
Mica fission t r a c k d e t e c t o r
Selected V a l u e
Table 37. Total half-life of '"Cm
Reference
Author (Year)
A s Revised
TC/a
Asarola3 (1953)
35.
ChoppinIa4 (1958)
28.4
T i r n ~ f e e v " (1986)
~
29.13 f 0.10
Weighted A v e r a g e = 29.1 f 0.1 a ;
Comments
Not u s e d ; No d e t a i l s
*
0.8
Revised v a l u e f o r t h e 244Cm T %
R e l a t i v e a c t i v i t y t o 244Cm
Recommended Value
1497
COMMISSION ON RADIOCHEMISTRY AND NUCLEAR TECHNIQUES
1498
Table 38. Spontaneous fission half-life of 244Cm
Reference
Author (Year)
A s Revised
m/107 a
C h i o r s o Z 5 (1952)
139
Ma I k i nlss (19 63)
1.46
*
*
Revised v a l u e , I o n i z a t i o n c h a m b e r
0.05
Gas s c i n t i l l a t o r
M e t t a i s 7 (1965)
1.346 f 0.006
Armani'"
1.33
B a r t o nl"
(1967)
(1970)
H a s t i n g s l B g(1972)
Comments
0.20
f 0.03
a / s p o n t a n e o u s fission r a t i o
Li-I
fission n e u t r o n c o u n t e r
1.250 f 0.007
L o w g e o m e t r y fission f r a g m e n t c o u n t i n g
1.343 f 0.006
a/fission ratio;
Silicon s u r f a c e b a r r i e r d e t e c t o r
0 0 2 x lo7 a ,
R e c o m m e n d e d Value
~~
Wezghted A v e r a g e = 1 3 2
+
Table 39. Total half-life of 244Cm
Reference
Author (Year)
As Revised
T%/a
S t e v e n s i g o (1954)
19.2
*
0.6
Not u s e d ; R e l a t i v e a c t i v i t y t o z42Cm
F r i e d m a n l g l (1954)
17.9
f
0.5
Not used; R e l a t i v e a c t i v i t y t o 242Cm
Carnall'"
17.59
0.067
Specific a c t i v i t y ; Revised u n c e r t a i n t y
(1961)
Comments
B e n t l e y i g 3 (1968)
18.099
*
0.032
2n and l o w geometry a counting;
Revised u n c e r t a i n t y
K e r r i g a n i g 4 (1972)
18.13
*
0.037
C a l o r i m e t r y ; Revised u n c e r t a i n t y
P o l y ~ k h o v ' ' ~(1982)
18.24 f 0.247
Specific a c t i v i t y ; Revised u n c e r t a i n t y
R e c o m m e n d e d Value
Weighted A v e r a g e = 18.1 i 0.1 a ;
Table 40. Spontaneous fission half-life of 245Crn
Reference
Author (Year)
As R e p o r t e d
T % / I O ' ~a
Druzhinin"'
1.4
(1985)
+
0.2
Comments
a/fission ratio
R e c o m m e n d e d V a l u e = 1.4 f 0.2 x 10" a ;
Selected Value
Table 41. Total half-life of 245Cm
Reference
Author (Year)
As Revised
~ % / 1 a0 ~
Comments
H u l e t i g 7 (1954)
20.
Not u s e d ; D a u g h t e r x - r a y s m e a s u r e d
F r i e d m a n ' g l (1954)
11.3
f 5
Browneigs (1955)
14.3
f
2.9
Not u s e d ; a c o u n t i n g
H u i z e n g a i g 9 (1957)
7.5
*
1.9
Not u s e d ; No d e t a i l s
H.Diamond. p r i v a t e c o m m u n i c a t i o n
C a r n a l l l g z (1961)
9.32
0.28
Not u s e d ; R e l a t i v e a c t i v i t y t o 244Cm
M e t t a Z o 0(1969)
8.265 i. 0.180
R e l a t i v e a c t i v i t y t o 244Cm
MacMurdo"'
8.538 f 0.071
Revised u n c e r t a i n t y ;
R e l a t i v e a c t i v i t y t o 244Cm
8.445
R e l a t i v e a c t i v i t y t o 244Cm
(1971)
P o l v u k h o v i g 5 (1982)
0.100
Weighted Average = 8.48 i 0.06 x l o 3 a ;
Not u s e d ; Revised v a l u e ;
R e l a t i v e a c t i v i t y t o 244Cm
R e c o m m e n d e d Value
Total and spontaneous fission half-lives
Table 42. Total half-life of "%m
Reference
Author (Year)
As Revised
~ 4 / 1 0a ~
Friedman'"
3.9
f
0.6
Not u s e d ; Revised v a l u e ;
R e l a t i v e a c t i v i t y t o 244Cm
Browneigs (1955)
2.3
f
0.46
Not u s e d ; a c o u n t i n g
(1954)
Comments
Butlerz0' (1956)
6.62
i 0.32
Not u s e d ; R e l a t i v e a c t i v i t y
Carna11'Q2 (1961)
5.48
*
Not u s e d ; R e l a t i v e a c t i v i t y t o 244Cm
Metta'"
4.711 i 0.022
R e l a t i v e a c t i v i t y t o 244Cm
4.82
R e l a t i v e a c t i v i t y t o 244Cm
(1969)
MacMurdo'"
(1971)
0.17
i 0.02
McCrackenzo3 (1971)
4.654 f 0.04
Specific a c t i v i t y
P o l y u k h ~ v(1976)
~ ~ ~
4.852 i 0.076
Relative a c t i v i t y t o 244Cm
Weighted A v e r a g e = 4.76 i 0.04 x l o 3 a ;
R e c o m m e n d e d Value
Table 43. Spontaneous fission half-life of '%m
Reference
Author (Year)
A s Reported
7%/107 a
Fieldszo5 (1956)
> 1.24
Comments
Not u s e d ; E s t i m a t e d v a l u e
from t h e a/fission ratio
*
Not used; Fission c o u n t i n g ;
Estimated t h e mass
Fried'"
(1956)
2.0
Metta'"
(1969)
1.60 f 0.01
a/fission ratio;
27r c h a m b e r , s e m i - c o n d u c t o r
1.85 i 0.02
a/fission ratio
MacMurdo'"
(1971)
0.8
Weighted A v e r a g e = 1.61 f 0.02 x lo7 a ;
R e c o m m e n d e d Value
Table 44. Total half-life of 247Cm
Reference
Author (Year)
As R e p o r t e d
~ 4 1 1 0 a~
Comments
D i a m o n d z o 7 (1957)
> 4.
Not u s e d ; D a u g h t e r g r o w t h m e t h o d
Fields"'
(1963)
Fieldszog (1971)
1.64
*
0.24
1.56 i 0.05
Weighted A v e r a g e = 1.56 f 0.05 x lo7 a ;
Daughter growth method
Relative a activity
Recommended Value
Table 45. Spontaneous fission half-life of '%n
Reference
Author (Year)
As R e p o r t e d
T ~ / I Oa ~
Comments
B u t l e r z 0 ' (1956)
4.6
f 0.5
Not u s e d ; Specific fission a c t i v i t y
Metta'"
4.22
f 0.12
a/fission ratio;
27r c h a m b e r , s e m i - c o n d u c t o r
4.20
i 0.05
(1969)
MacMurdo'"
(1971)
McCrackenZo3(1971)
4.115 i 0.034
Weighted A v e r a g e = 4.15 f 0.03 x lo6 a ;
R e l a t i v e a c t i v i t y t o 244Cm
Specific fission a c t i v i t y ; Ion c h a m b e r
Recommended Value
1499
COMMISSION ON RADIOCHEMISTRY AND NUCLEAR TECHNIQUES
1500
Table 46. Total half-life of 248Cm
Reference
Author (Year)
As R e p o r t e d
7'4/105 a
Comments
Schuman'l'
4.0
i 0.3
Not u s e d ; a h a l f - l i f e
(1968)
*
MettaZo0 (1969)
3.52
*
0.04
a half-life
r e p o r t e d = 3.84
MacMurdo"'
3.60
-I.
0.04
a half-life
r e p o r t e d = 3.94 f 0 . 0 4
3.40 i 0.03
a half-life
r e p o r t e d = 3.703 f 0.032
(1971)
McCrackenZo3(1971)
Weighted A v e r a g e = 3 . 4 8
+
0.06 x l o 5 a ;
0.04
R e c o m m e n d e d Value
Table 47. Spontaneous fission half-life of 250Cm
Reference
Author (Year)
A s Reported
~ 4 1 1 0a ~
Comments
Huizenga'"
2.3
Not used; E s t i m a t e d v a l u e
1.74 f 0.24
Not u s e d ; P r e l i m i n a r y
PAR b o m b s h o t r e s u l t s
1.13 i 0.05
Ion c h a m b e r ; PAR b o m b s h o t r e s u l t s
CRG2"
(1957)
(1966)
Metta212 (1967)
R e c o m m e n d e d V a l u e = 1.13 i 0.05 x l o 4 a ;
Selected Value
Table 48. Total half-life of 250Cm
As Reported
Reference
Author (Year)
7-4/104 a
This work (1987)
6
Comments
S p o n t a n e o u s fission h a l f - l i f e
1.13 i 0.05
systematics
a systematics
a 10.
E s t i m a t e d p a r t i a l half-life f o r 6 d e c a y
Q p = 3 7 13 keV ( s e e Wapstra213)
z
Estimated partial half-life for a decay
Q a = 5.197 i 0.021 MeV ( s e e Wapstra213)
R e c o m m e n d e d Value a 9.7
*
20
x lo3 a ;
Value calculated f r o m p a r t i a l h a l f - l i v e s
Table 49. Recommended half-lives and uncertainties
~
Referenct
Nuclide
T4 ( t o =
(Years)
T k ( s p o n t fiss )
70. i 1.
8
(Years)
+
6 x 1013
z
7
2.455 f 0.006 x l o 5 1 5
*
1.592 5 0.002 x l o 5 >
7.04 f 0.01 x l o 8
1017
0 2 x 1018
1 0 f 0 3 x 1010
2.342 k 0.004 x l o 7 2 5 i 0 1 x 1016
4.47
*
0.02 x 108
2.410
*
$:
0.1
+
o1
4 75
*
103
0.1
3.75 i 0.02
1015
105
0 09 x 101
T C (spont.fiss.)
(Years)
8.00 i 0.09 x 107
6.6 i 0.2 x 10'"
432.7
* 0.6
* 2.
7.37 * 0.02
1o
141.
> 3. x 10"
103
162.8 i 0.2 Days
+
2.0
0 . 4 x 1014
+
0 . 5 x 1014
7.0 i 0 . 2 x l o 8
29.1
+
0.1
5.5 i 0.9 x 10"
18.1
*
0.1
1.32
8.48
+
0.06 x l o 3
*
0.02
x lo7
1.4 k 0.2 x 10"
4 . 7 6 i 0.04 x l o 3
1.81 i 0.02 x 107
1 1 6 i 0 02 x 10"
1.56 i 0.05 x l o 7
--- - - - - -
< 6 x 10l6
3.48
0.003 x l o 4 8 A 2
6.56 i 0.01
14.4
*
2 1 i 0 1 x log
2.87 i 0.01
87.7
8 2
:eferencf 7'4 ( t o t a l )
luclide
(Years)
677
1015
0 0 7 x 10'
*
a 9.7
0.06
lo3
105
4.15
+
0.03 x lo6
1.13 f 0.05 x l o 4
Total and spontaneous fission half-lives
1501
-
Acknowledaement T h i s w o r k w a s c a r r i e d o u t u n d e r t h e a u s p i c e s of t h e U S D e p a r t m e n t
of
E n e r g y u n d e r c o n t r a c t No. DE-AC02-76CH00016.
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