THESE TERMS GOVERN YOUR USE OF THIS DOCUMENT
Your use of this Ontario Geological Survey document (the “Content”) is governed by the
terms set out on this page (“Terms of Use”). By downloading this Content, you (the
“User”) have accepted, and have agreed to be bound by, the Terms of Use.
Content: This Content is offered by the Province of Ontario’s Ministry of Northern Development and
Mines (MNDM) as a public service, on an “as-is” basis. Recommendations and statements of opinion
expressed in the Content are those of the author or authors and are not to be construed as statement of
government policy. You are solely responsible for your use of the Content. You should not rely on the
Content for legal advice nor as authoritative in your particular circumstances. Users should verify the
accuracy and applicability of any Content before acting on it. MNDM does not guarantee, or make any
warranty express or implied, that the Content is current, accurate, complete or reliable. MNDM is not
responsible for any damage however caused, which results, directly or indirectly, from your use of the
Content. MNDM assumes no legal liability or responsibility for the Content whatsoever.
Links to Other Web Sites: This Content may contain links, to Web sites that are not operated by MNDM.
Linked Web sites may not be available in French. MNDM neither endorses nor assumes any
responsibility for the safety, accuracy or availability of linked Web sites or the information contained on
them. The linked Web sites, their operation and content are the responsibility of the person or entity for
which they were created or maintained (the “Owner”). Both your use of a linked Web site, and your right
to use or reproduce information or materials from a linked Web site, are subject to the terms of use
governing that particular Web site. Any comments or inquiries regarding a linked Web site must be
directed to its Owner.
Copyright: Canadian and international intellectual property laws protect the Content. Unless otherwise
indicated, copyright is held by the Queen’s Printer for Ontario.
It is recommended that reference to the Content be made in the following form: <Author’s last name>,
<Initials> <year of publication>. <Content title>; Ontario Geological Survey, <Content publication series
and number>, <total number of pages>p.
Use and Reproduction of Content: The Content may be used and reproduced only in accordance with
applicable intellectual property laws. Non-commercial use of unsubstantial excerpts of the Content is
permitted provided that appropriate credit is given and Crown copyright is acknowledged. Any substantial
reproduction of the Content or any commercial use of all or part of the Content is prohibited without the
prior written permission of MNDM. Substantial reproduction includes the reproduction of any illustration or
figure, such as, but not limited to graphs, charts and maps. Commercial use includes commercial
distribution of the Content, the reproduction of multiple copies of the Content for any purpose whether or
not commercial, use of the Content in commercial publications, and the creation of value-added products
using the Content.
Contact:
FOR FURTHER
INFORMATION ON
PLEASE CONTACT:
The Reproduction of
Content
MNDM Publication
Services
The Purchase of
MNDM Publications
MNDM Publication
Sales
Crown Copyright
Queen’s Printer
BY TELEPHONE:
Local: (705) 670-5691
Toll Free: 1-888-415-9845, ext.
5691 (inside Canada,
United States)
Local: (705) 670-5691
Toll Free: 1-888-415-9845, ext.
5691 (inside Canada,
United States)
Local: (416) 326-2678
Toll Free: 1-800-668-9938
(inside Canada,
United States)
BY E-MAIL:
[email protected]
[email protected]
[email protected]
LES CONDITIONS CI-DESSOUS RÉGISSENT L'UTILISATION DU PRÉSENT DOCUMENT.
Votre utilisation de ce document de la Commission géologique de l'Ontario (le « contenu »)
est régie par les conditions décrites sur cette page (« conditions d'utilisation »). En
téléchargeant ce contenu, vous (l'« utilisateur ») signifiez que vous avez accepté d'être lié
par les présentes conditions d'utilisation.
Contenu : Ce contenu est offert en l'état comme service public par le ministère du Développement du Nord
et des Mines (MDNM) de la province de l'Ontario. Les recommandations et les opinions exprimées dans le
contenu sont celles de l'auteur ou des auteurs et ne doivent pas être interprétées comme des énoncés
officiels de politique gouvernementale. Vous êtes entièrement responsable de l'utilisation que vous en faites.
Le contenu ne constitue pas une source fiable de conseils juridiques et ne peut en aucun cas faire autorité
dans votre situation particulière. Les utilisateurs sont tenus de vérifier l'exactitude et l'applicabilité de tout
contenu avant de l'utiliser. Le MDNM n'offre aucune garantie expresse ou implicite relativement à la mise à
jour, à l'exactitude, à l'intégralité ou à la fiabilité du contenu. Le MDNM ne peut être tenu responsable de tout
dommage, quelle qu'en soit la cause, résultant directement ou indirectement de l'utilisation du contenu. Le
MDNM n'assume aucune responsabilité légale de quelque nature que ce soit en ce qui a trait au contenu.
Liens vers d'autres sites Web : Ce contenu peut comporter des liens vers des sites Web qui ne sont pas
exploités par le MDNM. Certains de ces sites pourraient ne pas être offerts en français. Le MDNM se
dégage de toute responsabilité quant à la sûreté, à l'exactitude ou à la disponibilité des sites Web ainsi reliés
ou à l'information qu'ils contiennent. La responsabilité des sites Web ainsi reliés, de leur exploitation et de
leur contenu incombe à la personne ou à l'entité pour lesquelles ils ont été créés ou sont entretenus (le
« propriétaire »). Votre utilisation de ces sites Web ainsi que votre droit d'utiliser ou de reproduire leur
contenu sont assujettis aux conditions d'utilisation propres à chacun de ces sites. Tout commentaire ou toute
question concernant l'un de ces sites doivent être adressés au propriétaire du site.
Droits d'auteur : Le contenu est protégé par les lois canadiennes et internationales sur la propriété
intellectuelle. Sauf indication contraire, les droits d'auteurs appartiennent à l'Imprimeur de la Reine pour
l'Ontario.
Nous recommandons de faire paraître ainsi toute référence au contenu : nom de famille de l'auteur, initiales,
année de publication, titre du document, Commission géologique de l'Ontario, série et numéro de
publication, nombre de pages.
Utilisation et reproduction du contenu : Le contenu ne peut être utilisé et reproduit qu'en conformité avec
les lois sur la propriété intellectuelle applicables. L'utilisation de courts extraits du contenu à des fins non
commerciales est autorisé, à condition de faire une mention de source appropriée reconnaissant les droits
d'auteurs de la Couronne. Toute reproduction importante du contenu ou toute utilisation, en tout ou en partie,
du contenu à des fins commerciales est interdite sans l'autorisation écrite préalable du MDNM. Une
reproduction jugée importante comprend la reproduction de toute illustration ou figure comme les
graphiques, les diagrammes, les cartes, etc. L'utilisation commerciale comprend la distribution du contenu à
des fins commerciales, la reproduction de copies multiples du contenu à des fins commerciales ou non,
l'utilisation du contenu dans des publications commerciales et la création de produits à valeur ajoutée à l'aide
du contenu.
Renseignements :
POUR PLUS DE
RENSEIGNEMENTS SUR
VEUILLEZ VOUS
ADRESSER À :
la reproduction du
contenu
Services de
publication du MDNM
l'achat des
publications du MDNM
Vente de publications
du MDNM
les droits d'auteurs de
la Couronne
Imprimeur de la
Reine
PAR TÉLÉPHONE :
Local : (705) 670-5691
Numéro sans frais : 1 888 415-9845,
poste 5691 (au Canada et aux
États-Unis)
Local : (705) 670-5691
Numéro sans frais : 1 888 415-9845,
poste 5691 (au Canada et aux
États-Unis)
Local : 416 326-2678
Numéro sans frais : 1 800 668-9938
(au Canada et aux
États-Unis)
PAR COURRIEL :
[email protected]
[email protected]
[email protected]
cjOMNR-OGS
1981
Ministry of
Natural
^te^lan w- Pope
W.T Foster
Deputy Minister
Ontario
ONTARIO GEOLOGICAL SURVEY
Open File Report 5368
Grant #38
Radon Decay Products - U Exploration
by
Keith Bell and J.W. Card
1981
Parts of this publication may be quoted
if credit is given. It is recommended
that reference to this report be made
in the following form:
Bell, Keith, and Card, J.W.
1981:
Radon Decay Products - U Exploration,
Ontario Geological Survey OFR 5368,
16 p.
Ontario Geological Survey
OPEN FILE REPORT
Open file reports are made available to the public subject to the following conditions:
This report is unedited. Discrepancies may occur for which the Ontario Geological Survey does
not assume liability. Recommendations and statements of opinion expressed are those of the author or
authors and are not to be construed as statements of government policy.
Open file copies may be read at the following locations:
Mines Library
Ontario Ministy of Natural Resources
8th Floor, 77 Grenville Street, Toronto
The office of the Regional or Resident Geologist in whose district the area covered by
this report is located.
Handwritten notes and sketches may be made from this report. Check with the Library or Region
al or Resident Geologist's office as to whether there is a copy of this report that may be borrowed.
The Library or Regional or Resident Geologist's office will also give you information on copying ar
rangements. A copy of this report is available for Inter-Library Loan.
This report is on file in the Regional or Resident Geologists' office(s) located at:
All Regional and
Resident Geologists
The right to reproduce this report is reserved by the Ontario Ministry of Natural Resources.
Permission for other reproductions must be obtained in writing from the Director, Ontario Geological
Survey.
E.G. Pye, Director
Ontario Geological Survey
ONTARIO GEOSCIENCE RESEARCH GRANT PROGRAM
Final Research Reports, 1981
Preface
This publication includes one final report on a research
project that terminated March 31, 1981 and was funded
under the Ontario Geoscience Research Grant Program.
A requirement of the Program is that recipients of grants
are to submit final reports within six months after
termination of funding. Many of the research projects
supported in 1978-79 (the first year of the Grant Program)
were planned for three years. As a result, an unusually
large number (19) of final reports were received this
year. Unlike previous years, each report has been put
on a separate Open File.
A final report is defined as a comprehensive summary
stating the findings obtained during the tenure of the
grant, together with supporting data. It may consist,
in part, of reprints or preprints of publications and
copies of addresses given at scientific meetings.
It is not the intent of the Ontario Geological Survey to
formally publish the final reports for wide distribution
but rather to encourage the recipients of grants to seek
publication in appropriate scientific journals whenever
possible. The Survey, however, also has an obligation
to ensure that the results of the research are made
available to the public at an early date. Although final
reports are the property of the applicants and the
sponsoring agencies, they may also be placed on an open
file. This report is intended to meet this obligation.
E.G. Pye
Director
Ontario Geological Survey
December 1981
11
GRANT 38
RADON DECAY PRODUCTS - U EXPLORATION
Keith Bell and J.W. Card
Geology Department, Carleton University, Ottawa.
ABSTRACT
The spontaneous deposition of short-lived radon decay
products onto solid surfaces ("collectors") provides the
basis for a simple and efficient way of prospecting for
uranium.
The alpha-activity of two of the decay products,
218p o an(3 214p Of can fce measured by conventional counting
techniques following the exposure of a collector to a radon
source.
Laboratory studies have shown:
(i) radon decay
products can be collected on a wide variety of materials,
(ii) the number of radon decay products increases with the
surface area of the collectors, (iii) the number of decay
products collected is greater when the collectors are
negatively charged, (iv) the shape of the collectors is
relatively unimportant, and (v) reproducibility is about
5%
of the measured values.
Field tests, carried out on known uranium anomalies,
involved the suspension of collectors into holes in the
soil.
After an overnight exposure, the collectors were
removed and their alpha-activity counted.
The data readily
delineated radon anomalies at three different sites.
In
addition, some of the anomalies were outlined using activity
measurements from collectors suspended above soil aliquots
in sealed containers.
The activity of the radon decay products deposited onto
collectors provides an effective method for delineating
radon anomalies in uranium exploration.
The field
techniques are simple to apply, and results are available
after short exposure times (about 18 hours) and after short
counting intervals (5 minutes).
1.
INTRODUCTION
Radon, because of its inert and gaseous nature, has
already been used extensively as a geochemical tracer for
buried uranium deposits.
Among the methods available are
soil-gas sampling (Dyck, 1969a; 1969b; Bowie et al., 1971;
Morse, 1976), alpha-particle track counting (Gingrich, 1975;
Gingrich and Fisher, 1976; Beck and Gingrich, 1976),
solid-state alpha-particle detection (Gaucher, 1976; Warren,
1977), and the collection of radon on activated charcoal.
222 Rn (ti s 3.824 days), a member of the 238 U decay
series, is produced by the decay of 22 ^Ra (ti s 1599 years),
and in turn yields a series of four short-lived decay
products, 218 Po (t! ^ 3.05 minutes, 214 Pb (ti = 26.8
minutes), 214 Bi (ti = 19.7 minutes), and 214 Po (ti - 1.64 x
10~4 seconds).
Of these, 2 l 8 Po and 2 ^ 4 Po can be detected
using alpha particle counting techniques.
It has only
recently been realized that the collection of these
short-lived decay products may be useful in uranium
exploration.
Our earlier results have been published
elsewhere (Card and Bell, 1979).
Here our most recent
findings are summarized.
LABORATORY STUDIES
The collection of radon decay products was initially
studied under controlled laboratory conditions.
Each test
involved the exposure of a "collector" (any solid surface
that collects radon decay products) to a radon-bearing
2.
atmosphere, followed by the counting of the alpha activity
from the collected decay products, 218p o an ^ 214p Of
Each
collector was inserted into a ZnS(Ag)-coated scintillation
chamber and counted for a 5 minute interval.
Our earlier
work had shown that radon itself does not become attached to
the collectors and that approximately steady-state activity
is reached after an exposure of about 3 hours.
Key problems
that remained involved the determination of the optimum
material and shape for the collectors, and an evaluation of
the effect of surface area on collecting efficiency.
The most significant findings are summarized below:
(1)
Metal, plastic, and cardboard plates of similar size
and shape resulted in similar activities.
(2)
Collectors exposed in 226 mL containers with 10 g
aliquots of CANMET Standard BL-3 (a crushed ore bearing
1.02^^ U) yielded excellent reproducibility with a
standard deviation of iS'fc.
(3)
The amount of activity was substantially greater on
those collectors with greater surface areas.
(4)
Collectors in the form of discs and open-ended hollow
cylinders showed no advantages over simple rectangular
plates.
(5)
Activity on the collectors showed an almost linear
relationship with sample mass, although for a given
soil aliquot the activity is greater for a smaller
container.
3.
(6)
The activity on the collectors corresponds to the
theoretical growth curve for 222^n . equilibrium
conditions are approached after 15 days.
(7)
The radon decay products seem to be firmly attached to
the collectors; attempts to remove them by rinsing in
water were unsuccessful.
(8)
Activity on copper plates was significantly increased
by negatively charging the collectors during the last
few hours of the exposure.
a factor of about 2.7.
Sensitivity was enhanced by
Surface area of the collector
is less important for the charged plates; very small
plates provided almost as much activity as the larger
ones.
Although the activity reached a plateau at about
-60 V, sensitivity was greatly increased by applying a
potential as low as -10 V.
Tests with positively
charged plates showed that only a small number of decay
products were collected.
On the basis of these laboratory observations a series of
field tests were undertaken to evaluate the collector method
for uranium exploration.
FIELD TESTS
Initial field tests were carried out at a radon anomaly
associated with a small uranium occurrence in Palaeozoic
sedimentary rocks at South March, 20 km west of Ottawa,
Ontario (see Card and Bell, 1979).
Collectors suspended in
covered holes (20 cm in diameter and roughly 35 cm deep)
4.
collected a sufficient number of decay products to readily
delineate the anomaly.
Related tests, involving the
suspension of collectors above soil aliquots in sealed
containers, showed also that there was sufficient radium in
the soil to allow a successful delineation of the anomaly.
In-situ measurements were obtained from soil-covered
areas overlying uranium-bearing pegmatites in Grenville
Province rocks; the pegmatites take the form of concordant,
tabular bodies in gneisses and marbles.
At one of the test
sites, in Palmerston Township, Ontario (Lat. 44 0 54' 15" N,
Long. 76 0 44' 45" W), the suspension of collectors in
inverted flower pots resulted in a higher activity than
recorded using the covered holes.
Readings taken at regular
intervals across the strike of the regional structural trend
are shown in Figure l(b), along with a cross-section of the
geology (Figure l(a)).
anomalous zones.
The radon profile indicates three
The most significant occurs immediately to
the west of the main pegmatite, and probably reflects either
the extension of the pegmatite under the overburden, or
radium-bearing detritus from the pegmatitic source.
Four
stations yielded anomalous values; one, at over 1300 cpm,
represents the highest number of counts yet documented by
the collector method.
Analyses of the soils from the
Palmerston occurrence also clearly delineated the main
anomaly (Figure l(c)).
At another test site, in Blithfield Township, Ontario
(Lat. 45 0 16' 25" N, Long. 76 0 48' 20" W), a pegmatite in
5.
high grade Grenville gneisses and marbles is exposed in
cross section at a road cut.
Although only about l m wide
the pegmatite produced a radon anomaly that was readily
detected.
Assessment of the overall reproducibility of the
activity measurements under in-situ conditions involved
monitoring a single hole at the Palmerston site eight times
during a 30 day period.
The reproducibility was of the
order of ±15* of the mean number of the counts.
At South
March three holes were monitored every hour for a period of
six hours and the reproducibility was better than
2(^.
Data from one of these holes yielded a reproducibility of
5%.
These measurements are in surprisingly good agreement
with one another, in spite of the fact that many workers
(i.e., Kraner et al., 1964) have reported large secular
variations in radon concentrations in soil gas.
THE THORON PROBLEM
In thorium-enriched terrains decay products from 22 ^Rn
(radon produced from the 232-pn d ecay series, normally
referred to as thoron) may be collected and counted along
with the 2 38u-produced radon decay products.
Such results
could well produce anomalously high readings that bear no
relationship to the distribution of 238|j series nuclides.
Although the half-life of thoron is only 55.6 seconds, the
half-lives of two of the thoron decay products, 2 ^ 2 Pb (ti 10.64 hours) and 212 Bi (ti - 60.60 minutes), are much longer
6.
than those of the
^n d ec ay products and this feature can
be used to apply a correction to the collector readings.
Tests using 2 g of Th(C03)2 show that the thoron decay
products, like those of radon, can be collected but their
subsequent behaviour differs in the following ways:
(1)
The decay curve for an assemblage of collected thoron
decay products is quite different from that for the
radon decay products.
The thoron decay products decay
much more slowly than those of radon.
(2)
Exposures longer than 48 hours are required before
equilibrium is reached between thoron and its decay
products.
In contrast an exposure of only 3 hours
produces a steady-state radon decay product activity.
(3)
Removal of the collector after a short exposure (up to
a few hours) results in an increase in activity for the
first few hours.
This is probably due to the
collection of 212pjDf a beta emitter.
The subsequent
decay of 212pb to 212gi an ^ 212p Of both alpha emitters,
increases the amount of activity observed on the
collectors.
The observed thoron decay product curves are consistent with
the shapes expected from the equations for successive
transformations.
Thoron decay product activity can thus be simply
checked by counting the collector a second time, about 5 to
6 hours after the initial reading.
During this time the
activity of the radon (222^n ) decay products decays to
7.
negligible levels.
The decay rate of the thoron decay
products is, however, dominated by the longer half-lives of
212pb an(3 212gi^ an(3 the count rate after 5 hours changes
only slightly.
Counting a second time thus yields data
which can be used to estimate the thoron contribution to the
initial measurements.
Thoron corrections applied at the Palmerston Township
test site showed that only negligible amounts of thoron
decay products were present on the collectors.
The extent
to which thoron migrates is limited by its short half-life
(55.6 seconds) and it may well be that only relatively small
amounts were able to migrate to the collector.
COMPARATIVE STUDIES
We have also used the South March site for evaluating
different uranium exploration techniques, and these results
will form the basis of a future paper.
Included are data
for in-situ radon surveys using alphameters (Gratton, 1980)
and the soil-gas suction method (Christie, 1980).
Analyses
of soils for radium, both by total digestion, (Wilson, 1979)
and immersion methods, (Bradley, 1979), and uranium by
fluorimetry and delayed neutron analysis were also
obtained.
The results from the collector method for in-situ
measurements and soil sample analyses compared favourably
with the results obtained from these conventional
techniques.
8.
CONCLUSIONS
The field and laboratory results reported here provide
some interesting insights into the application of the
collector method to radon measurement.
The successful
testing at three different sites shows that the collectors
can be used to locate radon anomalies in a variety of
geological environments.
A commercially-available
instrument package (the Alphacard system) based on the
collector method has recently been designed by Alpha Nuclear
Company of Mississauga, Ontario.
The simplicity of the collector method and its ease of
use are factors that are much in its favour as a uranium
exploration tool.
ACKNOWLEDGEMENTS
The geology of the Palmerston area was kindly shown by
K.L. Ford of the Geological Survey of Canada, and A.J.M.
Limited allowed access to the property.
REFERENCES
Beck, L.S. and Gingrich, J.E.
1976: Track-Etch Orientation Survey in the Cluff Lake
Area, Northern Saskatchewan; Canadian Inst. Min. and
Met. Bull., 69, No. 769, p 104-109.
Bowie, S.H.U., Ball, T.K. and Ostle, D.
1971: Geochemical Methods in the Detection of Hidden
Uranium Deposits; p. 103-111 in Canadian Inst. Min. and
Met., Spec. Vol. 11.
Bradley, C.J.
1979: Delineation of a Soil Radium Anomaly; An Evaluation
of a Soil-Immersion Technique; unpubl. B. Se. Thesis,
Carleton University, Ottawa, Ontario, 43 p.
Card, J.W., and Bell, K.
1979: Radon Decay Products and their Application to Uranium
Exploration; Canadian Inst. Min. and Met. Bull., 72,
No. 812, p 81-87.
Christie, D.S.
1980: Radon-Thoron Survey of a Known Uranium-Copper
Occurrence: An Evaluation of a Soil-Gas-Suction
Emanometry Technique; unpubl. B.Se. Thesis, Carleton
University, Ottawa, Ontario, 37 p.
Dyck, W.
1969a: Field and Laboratory Methods Used by The Geological
Survey of Canada in Geological Surveys, No. 10; Radon
Determination Apparatus for Geochemical Prospecting for
Uranium; Geol. Surv. Canada, Pap. No. 68-21, 30 p.
1969b: Development of Uranium Exploration Methods Using
Radon; Geol. Surv. Canada, Pap. No. 69-46, 25 p.
Gaucher, E.
1976: Alphameters: Uranium Prospecting by Radon Detection;
Canadian Min. J., 97, April, 1976, p. 28-34.
Gingrich, J.E.
1975; Results from a new Uranium Exploration Method; Soc.
of Min. Eng. of AIME, Trans., 258, p 61-64.
Gingrich, J.E. and Fisher, J.C.
1976: Uranium Exploration Using the Track-Etch Method; p.
213-227 in Exploration for Uranium Ore Deposits,
I.A.E.A. Proc.
Gratton, F.J.
1980: Radon Variations in Soil Gas at the South March
Uranium-Copper Occurrence; unpubl. B.Se. Thesis,
Carleton University, Ottawa, Ontario, 45 p.
lo.
Kraner, H.W., Schroeder, G.L., and Evans, R.D.
1964: Measurements of the Effects of Atmospheric Variables
on Radon-222 Flux and Soil-Gas Concentrations; p.
191-215 in The Natural Radiation Environment,
University of Chicago Press.
Morse, R.H.
1976: Radon Counters in Uranium Exploration; p. 229-239 in
Exploration for Uranium Ore Deposits, I.A.E.A. Proc.
Warren, R.K.
1977: Recent Advances in Uranium Exploration with
Electronic Alpha Cups; Geophysics, 42, p. 982-989.
Wilson, J.S.
1979: Soil-Radium Geochemistry of a Uranium-Copper
Occurrence, South March, Ontario; unpubl. B.Se. Thesis,
Carleton University, Ottawa, Ontario, 26 p.
UJ
'o
o
CN
•o
-
o
"c
o
O
"S
O ——
l/)
c
3
ULJ
O
O
c
o
0)
J
o
o.
0)
u
CO
E
-C
a
ok.
D) S
JD
*-fc-
a
k.
a
M!
o
o
ok.
a
k.
o
u
c
o
x
0
u
U
O
0)
O)
0)
JD
o
*-
"O
c
o
E
o
k.
D)
O
C
c
o
o
u
o
Q.
X
o
O)
JO
Q.
J^
"o
o
-C
u
o
u
•n
-f
•o
l
o
T
o
o
•o
o
o
CM
o
o
00
o
o
(ajnujuj jed S4unoD)
o
o
CN
CO
o
o
CM
o
U
(94nujai jsd
(D
"O
UO
kD
O)