The physical science of
“Fukushima”
1.
Binding energy and masses
a) The mass lost when p + e-  H is
13.6 ev.
b) The mass lost when n + 120Sn  121Sn is 8,000,000 eV.
2. The nuclear processes
a) Fission (controllable)
b) Beta decay (not controllable)
3. Boiling-Water reactors
a) How these reactors are supposed to work
b) Fuel rods, Zircalloy, and the Spent-Fuel Ponds (SFP)
4. Fukushima
a) The sites
b) What failed
c) Status
LGS May 28, 2011 - 1WU
1a: Binding energies
Atomic
vs
Nuclear
P + e-  H + 13.6 ev
120Sn
+ n 121Sn + 8*106 ev
120
p
+
e-
r (pm)
Change in mass of 1 part in 108
Electromagnetic  WEAK
Sn
+
n
r (fm)
Change in mass of almost 0.8 parts in 100
“Strong”  Strong, this is why it is called
“Strong”, i.e. binding E large fraction of mass
2
1a: Nuclear Binding energy
MASS
120 bound Nucleons < 120 free Nucleons
120 Bound
=
119 free
Take 120 “nucleons” and put them together to make a nucleus and the mass is reduced
By the equivalent of an whole nucleon.
Like IF when you walked into a crowded room your “weight” dropped by ~ 1%.
3
1b: The Chart of the Nuclides
The VALLEY of Stability
At bottom ~ 1 : 1 n/p
At end
~1.4 : 1 n/p
Cut Across valley
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1b. The nuclear energy landscape
 DM ~ 1% 
U
Fission
In going from one large nucleus, with weak binding, to two
smaller nuclei, with stronger binding,
the mass goes down.
As overall energy must be conserved…..
Mass  kinetic energy
5
2a: 1St nuclear process: Fission
allure and hazard
235U + n  2 ~ ½-sized fragments + 2-3 neutrons + energy ~ 180 MeV
~ x 107 more E than an
energetic chemical reaction
ALL THERMALIZED
YOU can control the fission (turn it off)
IF you can absorb the neutrons.
The energy comes from the fact that, on a per particle basis, the
products of fission are more “bound” (less massive) than the parent.
Overall energy is conserved, so the difference in mass is released as
energy.
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2a: Nuclear Fission (the first, controllable, step)
Energy from REDUCTION in mass
(increase in nuclear binding)
And E = mc2
n’s from one step initiate another reaction.
Stop by: absorbing n’s in nonfissile material.
Neutron Absorbers (i.e. Fission STOPPERS)
(19.9%) 
(12.2%) 
149Sm (13.8%) 
157Gd (15.8%)

135Xe( 0%, 9 hr) 
10B
113Cd
s=
3,800 b ADDED TO WATER
s = 20,600 b IN (during SCRAM)
s = 40,000 b
s = 255,000 b
s = 2,600,000 b Initially kept reactors in shut down initially.
This safety gone after a few days.
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2b: The Second (uncontrollable) step decay of nuclear “ash”
Beta decay (“n”  “p” + e- + n_ ) follows fission
1. The products of fission have too many neutrons
2. The beta decay has an order of magnitude less energy than
fission BUT Nature is in complete control. You have NO “knobs”
to use to “dial down” process.
# of P’s 
Important Detail:
a fraction of 1 % of the neutrons
come after b – decay.
Fission Product
# of N’s 
STEP # 2 Radioactive “beta” decay
One example:
137Cs  137Ba* + e- + n_ + Energy (~~ MeV)
 gamma rays
Cs acts like K – both alkali metals
Sr acts like Ca – both alkaline earths
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2b: Beta decay Heat AFTER SCRAM*/shut down
% of running power
When running Beta decay
provides ~ 8% of the
heat/energy.
~ 25 MW ~ 1 WU
For a 2500 MW plant
~ 5 MW ~ 1S-40
After “shutting down” a reactor,
the heat from b decay remains!
This dies off like

For a 2500 MW plant
1 min
1 week
After one year, typical spent nuclear fuel generates about 10 kW of decay heat
per tonne, decreasing to about 1 kW/t after ten years.[4]
Hence effective active or passive cooling for spent nuclear fuel is required for
a number of years.
* Safety Control Rod Axe Man
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 ~ 1 MCi
2b: Beta Decay activity (long time)
- the nuclear waste as a function of time
Takes ~ 3000 y to get down to
level of natural U ore.
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3a: Boiling-Water Reactors – BWR
Logical diagram
235U
239,xPu
Turbine
generator
Condenser
PUMP
PUMP
efficiency = 1/3 = electrical/thermal
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3a: BWR
GE MARK-I
Outside containment
Not part of containment system
Top level
“refueling bay”
A debris zone
Units 1,3, & 4
Lower levels 
Flooded 1,2,3
Containments
1. Zr rods
2. Reactor vessel
3. Primary containment
Outer bld.
Part of primary
None active for SFP
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Vent tube
Moved by overhead crane
Ponds normally below 50 C = 120F
at ~ 1000 C the Zr rapidly oxidizes.
Typically SFP hold more radioactivity
than reactor core.
~ 40 feet deep.
4 – 5 feet thick reinforced concrete with
SS liner.
Rods in Pond 4 removed from reactor in
Dec 2010
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3b: Fuel rods (1st containment) and assembly
~ 100/assembly several hundred/reactor
Zircalloy
“MP” ~ 2200 oC
Fuel rods of “Zircalloy” (~ 95% Zr + Sn, Nb, ...)
~ 100 fuel rods per assembly
x Several hundred assemblies/reactor
UO2
MP ~ 3000 oC
Zr + 2H2O → ZrO2 + 2 H2 + Q (= heat)
highly exothermic
1. Loss of inner containment
2. Reaction exothermic (makes heating problem worse.)
3. Hydrogen > few percent in air is explosive
4. 5-20% of the hydrogen diffuses into the Zr
10 -15 tonnes Zr/core
Loss of hardness, thermal conductivity, STRENGTH
~~100 X103 moles
..... due to Hydrogen embrittlement.
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H = E + PV
3b: The Zr reaction, order of magnitude numbers
0 --
Reactants  Products
Chemical association energy
But overall energy is conserved
Q out is the consequence.
Zr + 2H2O(g)  ZrO2 + 2H2(g) + Q
Dhfo [kJ/mole] = 0
2(-241.8)
-1097.5
2(0)
= - 613.9 [kJ/mole]
The heat released Q = 613.9 [kJ/mole] = [6.7 kJ/g of Zr]
Reaction does not occur (rapidly) unless T > 1000 C.
Rods
~ 1 cm OD, ~366 cm long, ~ 0.05 (?) cm wall  57 [cm3/rod] ~ 370 [g/rod]
~ 100 rods/assembly ~ 400 assemblies ~ 40,000 rods 15 x 106 [g/reactor] ~ 15 tonnes
The total potential chemical energy is ~ ~ 60-100 GJ
If ½ burned in a day [~ 86 x103 s]  ~ ~ 1/2 MW
The potential Chemical energy << b-decay energy but not insignificant.
Difference : b-decay energy is inevitable, chemical energy  only if Zr oxidizes.
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4a: Fukushima quake and tsunami of Friday March 11, 2011
POWER STATION 1 (Dai-ich)
6 reactors + 6 storage ponds
LOST GRID POWER
 Diesel fuel floated away
 pumps ran on battery few hrs
 pumps stopped  partial melt downS
Power Station 2 (Dai-ni)
4 reactors + 4 storage ponds
Stayed on grid/Successful conversion to diesel pumps
Pumps worked…. No serious issues.
Inside exclusion zone  not running.
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3. Fukushima
W
60 Hz
50 Hz
E
Note:
Power generated on W
incompatible with need on
the E.
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What happened in a nutshell
1. Earth quake (9.0 R) hit
2. The reactors SCRAMED, i.e. Emergency shut down. All
reactors shut down normally.
3. Tsunami (~ 40 ft)
Lost Grid Power, Lost secondary Diesel fuel, …..
Lost all cooling.
4. Reactors 1,2,3  ~ total melt down within hrs due to
beta decay heat.
5. Operators did NOT vent H2  explosions.
They did not follow some procedures, some valves may not
have operated properly and other actions were impeded by
lack of communication.
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Status – dynamic story, information sometimes conflicting.
Issues Site 1 - Daiich
1
2
3
4
5
6
type
BWR-3
BWR-4
BWR-4
BWR-4
BWR-4
BWR-5
GE design, made by
GE
GE
Toshiba
Hatachi
Toshiba
GE
Before Quake status Running
Running
Running
Shut-dn
Shut-dn
Shut-dn
Fuel Integrity (1st )
TOTAL
~ TOTAL
OK
OK
OK
Melt-dn
Melt-dn
~TOTAL Melt-dn
 MOX 
Primary Containment
BREACHED
BREACHED BREACHED OK
OK
OK
Build. Integrity
(SFP)
Damaged
Damaged
upper
Damaged
upper
OK
OK
upper/lower?
Damaged
lower
Spent Fuel ponds
?
?
?
Problem OK
OK
1,2,3 Fresh water flowing through reactor core tertiary system.
Will have to do this until closed loop system is constructed.
(This might take years.)
Not sure where all the water (from the present open loop system) is going !!
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4b:
5 and 6
Cold shut down
Along with 4, not
Running before quake
4
0
1479
3
548 (MOX)
512 (MOX)
2
548
587
1 UNIT
400 ASSEMBLIES reactor
292  ASSEMBLIES SFP
Chemical explosions! From H2 from Zr oxidation. (Operators did NOT follow procedures to vent gas!)
What was blown away was NOT part of the containment system

BUT it did contain the SFP management apparatus !
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The upper floors have been blown (out) by the H2 explosion.
This makes working on the SFP very difficult.
Must clear up debris and make some sort of overhead mechanism operable.
This task will take months/years during which the pools must be keep cool.
Keeping the SFP cool and the Zr in reduced form (i.e. as the metal)
Must be a very high priority.
There is 10x more radioactivity in the SFP as there is in the
(mostly) contained reactor cores.
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BWR MARK 1 containments in the US
Browns Ferry 1,2,3
Brunswick 1,2
Cooper
Dresden 2,3
Duane Arnold
Edwin I. Hatch 1,2
Fermi 2
Hope Creek 1
James A Fitzpatrick
Monticello
Nine Mile Point 1
Oyster Creek 1
Peach Bottom 2,3
Pilgrim 1
Quad Cities 1,2
Vermont Yankee 1
Alabama
North Carolina
Nebraska
Illinois
Iowa
Georgia
Michigan
New Jersey
New York
Minnesota
New York
New Jersey
Pennsylvania
Massachusetts
Illinois
Vermont
HOWEVER, NRC reviews in
1970
1980’s
( short and long term upgrades)
1999 Blayais France
& 2001 (after 9/11)
Several additional safety measures
were implemented.
A few of these, if they had been
implemented in Japan, would have, at
the very least, reduced the number of
problems at Fukushima.
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Summary
Must keep cores 1,2,3 cool for months to years – with a closed inner loop.
Until the core can (safely) be removed “bit by bit”.
QUESTION: where has all the (pumped in/once through) water gone?
Must keep SPF 1,2,3,4,(5,6) cool for months to years - ...
Until they clean up debris zone and reconstruct the overhead
assembly management system and can remove assemblies
one by one.
Those who argue for “entombment” think they cannot do this.
Those who think they many not be able to do this well, argue that the
Fukushima site should itself become a long-term rad. waste repository.
This effort is well beyond TEPCO, i.e. it is a national scale effort.
TMI
-------------------------------------- Fukushima --
Chernobly
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4a: Fukushima
W
60 Hz
50 Hz
E
Note:
Power generated on W
incompatible with need on
the E.
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