WASH- 1400
(NUREG 751014)
REACTOR SAFETY STUDY
AN ASSESSMENT
OF ACCIDENT RISKS
in
U.S. COMMERClAL NUCLEAR POWER PLANTS
U.S. NUCLEAR REGULATORY COMMISSION
OCTOBER 1975
Foreword
This i s t h e f i n a l r e p o r t o f t h e R e a c t o r S a f e t y Study "An
Assessment o f A c c i d e n t Risks i n U.S. Commercial Nuclear Power
P l a n t s , " p r e p a r e d under t h e d i r e c t i o n o f P r o f e s s o r Norman C.
Rasmussen o f t h e M a s s a c h u s e t t s I n s t i t u t e of Technology.
The
work, o r i g i n a l l y s p o n s o r e d by t h e U.S. Atomic Energy C o m i s s i o n ,
was completed under t h e s p o n s o r s h i p o f t h e U.S. Nuclear Regulator y Commission which came i n t o b e i n g on J a n u a r y 1 9 , 1975.
A d r a f t r e p o r t was p u b l i s h e d i n August o f 1974 and was c i r c u l a t e d
t o o b t a i n comments from a wide v a r i e t y o f p e o p l e and o r g a n i z a tions.
Comments were r e q u e s t e d from o t h e r a g e n c i e s o f t h e f e d e r a l government, e n v i r o n m e n t a l g r o u p s , g r o u p s c r i t i c a l o f n u c l e a r
Dower.
l a w v e r s r e ~ r e s e n t i n s e n v i r o n m e n t a l QrouDs
- . and i n d u s t r v .
and industrial organizations r e p r e s e n t i n y r e a c c o r m a n u f a c t u r e r s ,
a r c h i c e c c c n y i n c c r i n y f l r l r s and e l e c t r i c utilities. In a d d i c i o n
t o t h i s d i s t r i b u t i o n , many r e q u e s t s f o r t h e r e p o r t were r e c e i v e d
from o t h e r i n d i v i d u a l s and o r g a n i z a t i o n s . A t o t a l o f a b o u t 90
l e t t e r s o f c o m n t were r e c e i v e d which were v e r y h e l p f u l i n t h e
p r e p a r a t i o n of t h i s f i n a l r e p o r t .
A new Appendix X I h a s been
added t o t h e r e p o r t t o i n d i c a t e t h e s t u d y ' s
responses t o t h e
comments r e c e i v e d and t h e r e s u l t i n g changes made i n t h e f i n a l
report.
> .
The R e a c t o r S a f e t y Study was performed, a s d e s c r i b e d i n Chapter
1, by an a d hoc group o f p e o p l e i n i t i a l l y assemhled by t h e Atomic
Energy Commission t o do an i n d e p e n d e n t a s s e s s m e n t o f p o t e n t i a l
a c c i d e n t r i s k s i n U.S. c o m e r c i a l n u c l e a r power p l a n t s .
When t h e
U.S. N u c l e a r R e g u l a t o r y Commission was c r e a t e d i n January o f 1975
t h e work c o n t i n u e d under i t s a u s p i c e s w i t h renewed re-emphasis on
t h e i n d e p e n d e n t n a t u r e o f t h e s t u d y group.
The s t u d y group w i s h e s t o thank a l l t h o s e who c o n t r i b u t e d t o t h e
s u p p o r t o f t h e e f f o r t and t h e t e c h n i c a l work a s w e l l a s t h o s e who
commented on t h e d r a f t r e p o r t t o h e l p improve t h e q u a l i t y o f t h e
f i n a l version.
Main Report
Table of Contents
Page No
Chapter
FOREWORD
................................................................
1.1
1.2
1.3
1.4
1.5
1.6
1.7
1.8
1.9
1.10
2
THE BASIC
2.1
2.2
2.3
...............................................
.....................
...................
.................................
.......................................
............................
......................................................
...........................
...................................
..............................................
CONCEPTS OF RISK .......................................
Introduction
O b j e c t i v e s of t h e R e a c t o r S a f e t y S t u d y
Organization o f t h e Reactor Safety Study
Organization o f t h e Report
Technical Appendices
R e a c t o r S a f e t y S t u d y Flow C h a r t
Factors That Contributed S i g n i f i c a n t l y i n Performing t h e
Study
I n s i g h t s Gained During t h e S t u d y
Limitations i n t h e Study
F i n a l Remarks
2.3.1
2.3.2
2.4
REFERENCES
........................................
......................................
.........................................
H i g h P r o b a b i l i t y E v e n t s .............................
Low P r o b a b i l i t y E v e n t s ..............................
Measurement o f R i s k
A t t i t u d e s Toward R i s k
Risk Determination
Presentation of Risk Estimates
.............................
.....................
......................
3.1
I n t r o d u c t i o n ...............................................
3.2
L o c a t i o n a n d M a g n i t u d e of R a d i o a c t i v i t y ....................
3.3
L o s s o f C o o l a n t A c c i d e n t s ..................................
3.3.1
LOCA I n i t i a t i n g E v e n t s ..............................
E f f e c t s o f E n g i n e e r e d S a f e t y F e a t u r e s ...............
3.3.2
3.3.3
M o l t e n F u e l I n t e r a c t i o n s ............................
3.4
R e a c t o r T r a n s i e n t s .........................................
3.5
A c c i d e n t s I n v o l v i n g the S p e n t F u e l S t o r a g e P o o l ............
REFERENCES ..............................................................
4
RISK ASSESSMENT METHODOLOGY ......................................
4 -1
I n t r o d u c t i o n ...............................................
4.2
Q u a n t i f i c a t i o n o f R a d i o a c t i v e R e l e a s e s .....................
4.2.1
D e f i n i t i o n o f A c c i d e n t S e q u e n c e s .E v e n t T r e e s ......
4.2.2
P r o b a b i l i t y o f R e l e a s e s .............................
4.2.2.1
F a u l t T r e e s ................................
4.2.2.2
F a i l u r e R a t e D a t a ..........................
4.2.2.3
Common Mode F a i l u r e s .......................
4.2.3
M a g n i t u d e of R e l e a s e s ...............................
3
THE NATURE OF NUCLEAR POWER PLANT ACCIDENTS
.
Table of Contents (Continued)
Chapter
P a g e No
4.3
4.4
REFERENCES
5
........................
4.3.1
A t m o s p h e r i c D i s p e r s i o n Model ........................
4.3.2
P o p u l a t i o n Model ....................................
4.3.3
H e a l t h E f f e c t s and P r o p e r t y Damage Model ............
O v e r a l l R i s k A s s e s s m e n t ....................................
C o n s e q u e n c e s of R a d i o a c t i v e R e l e a s e
..............................................................
............................................
I n t r o d u c t i o n a n d Summary ...................................
R a d i o a c t i v e R e l e a s e C a t e g o r i e s .............................
5.2.1
PWR R e l e a s e C a t e q o r i e s ..............................
5.2.2
BWR R e l e a s e C a t e g o r i e s ..............................
P r o b a b i l i t y of R e l e a s e .....................................
5.3.1
PWR R e l e a s e P r o b a b i l i t y .............................
5.3.2
PWR D o m i n a n t A c c i d e n t S e q u e n c e s .....................
5.3.2.1
L a r g e LOCA (A) .............................
5.3.2.2
S m a l l LOCA ( S 1 ) ............................
5.3.2.3
S m a l l LOCA ( S 2 ) ............................
5.3.2.4
R e a c t o r V e s s e l R u p t u r e (R) .................
5.3.2.5
I n t e r f a c i n g S y s t e m s LOCA (V) ...............
5.3.2.6
PWR T r a n s i e n t E v e n t s ( T ) ...................
5.3.3
BWR R e l e a s e P r o b a b i l i t y .............................
5.3.4
BWR D o m i n a n t A c c i d e n t S e q u e n c e s .....................
5.3.4.1
LOCA E v e n t s ................................
5.3.4.2
R e a c t o r V e s s e l R u p t u r e (R) .................
5.3.4.3
T r a n s i e n t E v e n t s (T).......................
REACTOR ACCIDENT RISK
5.1
5.2
5.3
5.3.5
5.4
Risks
5.5.1
5.5.2
5.5.3
5.5.4
5.5.5
5.6
...............................
...............
E a r t h q u a k e R i s k .....................................
T o r n a d o e s ...........................................
F l o o d s ..............................................
A i r c r a f t I m p a c t s ....................................
T u r b i n e Missiles ....................................
O t h e r E x t e r n a l C a u s e s ...............................
f r o m A c c i d e n t a l R e l e a s e s .............................
E a r l y F a t a l i t i e s ....................................
T a b u l a r Summary o f R e s u l t s ..
E a r l y I l l n e s s e s .....................................
Long-Term H e a l t h E f f e c t s ............................
5.5.4.1
l a t e n t C a n c e r s F a r a l i t i e s ..................
5.5.4.2
T h y r o i d N o d u l e s ............................
5.5.4.3
G e n e t i c E f f e c t s ............................
P r o b a b i l i t y of Releases from E x t e r n a l Causes
5.4.1
5.4.2
5.4.3
5.4.4
5.4.5
5.4.6
5.5
Other I n t e r n a l Causes
P r o p e r t y Damage
A c c i d e n t R i s k s Due t o
.....................................
1 0 0 N u c l e a r Power P l a n t s .............
49
50
50
51
51
52
.
Table of Contents (Continued)
P a g e No
Chapter
REFERENCES
6
..............................................................
..............
I n t r o d u c t i o n a n d Summary ...................................
I n d i v i d u a l R i s k o f F a t a l i t y a n d I n j u r y .....................
6.2.1
F a t a l i t i e s ..........................................
6.2.2
I n j u r i e s ............................................
S o c i e t a l R i s k ..............................................
6.3.1
F a t a l i t i e s a n d I n j u r i e s .............................
6.3.2
Economic L o s s e s .....................................
R i s k s From L a r g e C o n s e q u e n c e E v e n t s ........................
6.4.1
H u r r i c a n e s ..........................................
6.4.2
T o r n a d o e s ...........................................
6.4.3
E a r t h q u a k e s .........................................
6.4.4
M e t e o r s .............................................
6.4.5
A i r p l a n e C r a s h e s ....................................
6.4.6
E x p l o s i o n s ..........................................
6.4.7
Dam F a i l u r e s ........................................
6.4.8
F i r e s ...............................................
6.4.9
H a z a r d o u s C h e m i c a l R e l e a s e s .........................
COMPARISON OF NUCLEAR RISKS TO OTHER SOCIETAL RISKS
6.1
6.2
6.3
6.4
..............................................................
CONCLUSIONS AND RECOMMENDATIONS ..............
7.1
O v e r v i e w ...................................................
7.2
R e s u l t s of t h e R i s k A s s e s s m e n t .............................
7.3
F a c t o r s A f f e c t i n g t h e R i s k .................................
REFERENCES
7
7.3.1
7.3.2
7.4
Other
7.4.1
7.4.2
7.4.3
7.5
ADDENDUM
Final
............................
.........................
S t u d y O b j e c t i v e s ..................................
R e a l i s m V e r s u s C o n s e r v a t i s m .........................
M e t h o d o l o g i c a l D e v e l o p m e n t s .........................
R e s e a r c h S u g g e s t i o n s ................................
O b s e r v a t i o n s .........................................
P r o b a b i l i t y o f Core M e l t
Large Consequence A c c i d e n t s
An O v e r v i e w of E v e n t T r e e a n d F a u l t T r e e M e t h o d o l o g y a n d
t h e H a n d l i n g o f Common Mode F a i l u r e
..........................
EXECUTIVE SUMMARY
APPENDIX I
Accident D e f i n i t i o n and U s e of Event Trees
APPENDIX I1
APPENDIX I11
APPENDIX IV
Fault Trees
F a i l u r e Data
Common Mode F a i l u r e s
.
Table of Contents (Continued)
APPENDIX V
Quantitative Results of Accident Sequences
APPENDIX VI
Calculation of Reactor Accident Consequences
APPENDIX VII
Release of Radioactivity in Reactor Accidents
APPENDIX VIII
APPENDIX IX
APPENDIX X
APPENDIX XI
Physical Processes in Reactor Meltdown Accidents
Safety Design Rationale for Nuclear Power Plants
Design Adequacy
Analysis of Comments on the Draft WASH-1400 Report
List of Tables
Page No
S o r e U.S.
A c c i d e n t Death Statistics-.1967-1970
Some U.S.
A c c i d e n t Death S t a t i s t i c s - - 1 9 6 7 - 1 9 6 8
1967 F a l l i n g Deaths..
by Age
...................
...................
Group ................................
T y p i c a l R a d i o a c t i v i t y I n v e n t o r y f o r a 1000 MWe N u c l e a r Power
Reactor
..........................................................
Summary o f A c c i d e n t s I n v o l v i n g Core ..............................
PWR Dominant A c c i d e n t Sequences v s . R e l e a s e C a t e g o r i e s ...........
BWR Dominant Accident Sequences o f Each Event T r e e v s . R e l e a s e
C a t e g o r y .........................................................
Consequences of R e a c t o r A c c i d e n t s f o r V a r i o u s P r o b a b i l i t i e s
f o r One R e a c t o r
..................................................
Consequences of R e a c t o r A c c i d e n t s f o r V a r i o u s P r o b a b i l i t i e s
f o r One R e a c t o r ..................................................
Approximate Average S o c i e t a l and I n d i v i d u a l Risk P r o b a b i l i t i e s
p e r Year from P o t e n t i a l Nuclear P l a n t A c c i d e n t s
..................
Consequences of R e a c t o r A c c i d e n t s f o r V a r i o u s P r o b a b i l i t i e s
f o r 100 R e a c t o r s .................................................
Consequences of R e a c t o r A c c i d e n t s f o r V a r i o u s P r o b a b i l i t i e s
f o r 100 R e a c t o r s .................................................
Risk o f E a r l y F a t a l i t i e s from N u c l e a r and Non-Nuclear
Accidents
U.S.
........................................................
Fatalities..
by Major C a t e g o r i e s (1969) ..........
I n d i v i d u a l R i s k of E a r l y F a t a l i t y by V a r i o u s Causes
.
I n d i v i d u a l R i s k of E a r l y F a t a l i t y from Nuclear and Non-Nuclear
Accidents
........................................................
E s t i m a t e d Average Annual R i s k o f I l l n e s s from V a r i o u s A c c i d e n t s
i n t h e U.S
.......................................................
Annual A c c i d e n t F a t a l i t i e s and I n j u r i e s i n t h e U.S ......
U.S. Economic Losses from V a r i o u s Causes ....................
Consequences o f Major U . S. H u r r i c a n e s 11900-1972) ................
Consequences o f Major U.S. E a r t h q u a k e s (1900-1972) ....
16
16
16
.
List of Tables (Continued)
Table
-
Page No
6-10
F a t a l i t i e s i n Major A i r p l a n e C r a s h e s Throughout t h e World
(1960-1973)
6-11
E a r l y F a t a l i t i e s i n Major E x p l o s i o n s Throughout t h e World
(1925-1971)
6-12
6-13
7-1
7-2
.
..............................................
......................................................
Dam and Levee F a i l u r e s i n t h e U.S. (1889-1972) ...................
Annual R a t e s o f F i r e s w i t h Large Economic L o s s e s .................
117
118
118
Approximate V a l u e s o f E a r l y I l l n e s s and L a t e n t E f f e c t s f o r
100 R e a c t o r s
141
Land Area A f f e c t e d by P o t e n t i a l N u c l e a r Power P l a n t A c c i d e n t s
f o r 100 R e a c t o r s
141
.....................................................
.................................................
List of Figures
Figure
Page No
..................................
P a t t e r n ...........................................
i n C o m e r c i a l A i r T r a v e l ..........................
1-1
R e a c t o r S a f e t y Study Flow C h a r t
2-1
A Benefit-Risk
2-2
F a t a l i t y Rates
2-3
F a t a l A c c i d e n t s P e r O p e r a t i o n (Landing o r T a k e o f f ) a s a
F u n c t i o n o f Time f o r t h e U.S. A i r C a r r i e r F l e e t
..................
F a t a l i t y R a t e s i n Motor V e h i c l e T r a v e l
8
17
17
18
...........................
Uranium Dioxide P e l l e t s Used f o r C o m e r c i a l Water Cooled N u c l e a r
Power P l a n t s
.....................................................
Cutaway o f F u e l Rod Used f o r C o m e r c i a l Water Cooled N u c l e a r
Power P l a n t s .....................................................
Schematic o f R e a c t o r C o o l a n t System f o r PWR ......................
Schematic o f BWR R e a c t o r C o o l a n t System..........................
Schematic o f R e a c t o r C o o l a n t System f o r BWR.
Primary Containment
Inside of the
..............................................
BWR R e a c t o r B u i l d i n g Showing Primary Containment System
Enclosed .........................................................
T y p i c a l PWR Containment ..........................................
Power Water R e a c t o r Loss o f C o o l a n t A c c i d e n t (LOCA) E n g i n e e r e d
S a f e t y F e a t u r e (ESF) F u n c t i o n s ...................................
Major Tasks o f Study .............................................
4-2
4-3
I l l u s t r a t i v e R e l e a s e P r o b a b i l i t y Versus R e l e a s e Magnitude
Histogram
........................................................
S u b t a s k s i n t h e Q u a n t i f i c a t i o n o f R a d i o a c t i v e R e l e a s e s ...........
53
54
.
List of Figures (Continued)
Page No.
Figure
..........................
Development. ..........................
4-4
S i m p l i f i e d Event T r e e s f o r a Large LOCA
55
4-5
I l l u s t r a t i o n o f F a u l t Tree
56
4-6
S u b t a s k s i n t h e D e t e r m i n a t i o n o f t h e Consequences o f R a d i o a c t i v e
Releases.
........................................................
H i s t o g r m of PWR R a d i o a c t i v e R e l e a s e P r o b a b i l i t i e s ...............
Histogram o f BWR R a d i o a c t i v e R e l e a s e P r o b a b i l i t i e s ...............
P r o b a b i l i t y D i s t r i b u t i o n f o r E a r l y F a t a l i t i e s p e r Reactor
Year
.............................................................
P r o b a b i l i t y D i s t r i b u t i o n f o r E a r l y I l l n e s s p e r R e a c t o r Year......
P r o b a b i l i t y D i s t r i b u t i o n f o r L a t e n t Cancer F a t a l i t y
I n c i d e n c e p e r R e a c t o r Year
.......................................
P r o b a b i l i t y D i s t r i b u t i o n f o r Thyroid Nodule I n c i d e n c e
p e r R e a c t o r Year .................................................
P r o b a b i l i t y D i s t r i b u t i o n f o r I n c i d e n c e of G e n e t i c E f f e c t s
p e r Reactor Year .................................................
P r o b a b i l i t y D i s t r i b u t i o n f o r P r o p e r t y Damage p e r R e a c t o r
Year .............................................................
P r o b a b i l i t y D i s t r i b u t i o n f o r R e l o c a t i o n and Decontamination
Area p e r Reactor Year ............................................
P r o b a b i l i t y D i s t r i b u t i o n o f E a r l y F a t a l i t i e s p e r Year
f o r 100 R e a c t o r s .................................................
P r o b a b i l i t y D i s t r i b u t i o n of E a r l y I l l n e s s p e r Year
f o r 100 R e a c t o r s .................................................
P r o b a b i l i t y D i s t r i b u t i o n f o r L a t e n t Cancer F a t a l i t y
I n c i d e n c e p e r Year f o r 100 R e a c t o r s ..............................
P r o b a b i l i t y D i s t r i b u t i o n f o r Incidence of Genetic E f f e c t s
p e r Year f o r 1 0 0 R e a c t o r s ........................................
P r o b a b i l i t y D i s t r i b u t i o n f o r Thyroid Nodule I n c i d e n c e
p e r Year f o r 100 R e a c t o r s ........................................
P r o b a b i l i t y D i s t r i b u t i o n f o r P r o p e r t y Damage p e r Year
f o r 100 R e a c t o r s .....................................
P r o b a b i l i t y D i s t r i b u t i o n f o r R e l o c a t i o n and Decontamination
Area p e r Year f o r 100 R e a c t o r s .............................
Frequency of Man-Caused Events I n v o l v i n g F a t a l i t i e s ...........
Frequency o f N a t u r a l E v e n t s I n v o l v i n g F a t a l i t i e s
.................
Frequency of A c c i d e n t s I n v o l v i n g P r o p e r t y Damage.
Frequency of H u r r i c a n e Consequences
..............................
List of Figures (Continued)
Page No
Figure
.
6-5
Frequency
6-6
Frequency
6-7
Frequency
6-8
Frequency
6-9
Frequency
6-10
Frequency
6-11
Frequency
6-12
Frequency
................................
Earthquake Consequences .............................
Meteorite Consequences ..............................
Airplane Crash Consequences .........................
Explosion Consequences ..............................
Dam Failure Consequences ............................
Fire Consequences ...................................
Chlorine Accidents Involving Fatalities .............
Tornado Consequences
123
124
125
126
127
128
129
130
.
Chapter 1
Objectives and Organization of the Reactor Safety Study
1.1 INTRODUCTION
systems had n o t been w e l l developed.
Clearly,
even
if
the
reliability
t e c h n i q u e s needed f o r r i s k a s s e s s m e n t
h a d been a v a i l a b l e ,
the
engineering
i n f o r m a t i o n needed t o draw meaningful
conclusions about t h e p r o b a b i l i t y o f
accidents
i n future plants did not
exist.
Although n u c l e a r powex
plants
have
a d v a n t a g e s o v e r f o s s i l p l a n t s i n most
a r e a s o f e n v i r o n m e n t a l e f f e c t s and i n
t h e c o s t o f e l e c t r i c i t y , t h e y have some
p o t e n t i a l f o r accidents with
larger
p u b l i c consequences than f o s s i l - f u e l e d
- p l a n t s . While t h e s a f e t y o f n u c l e a r
plants
has
been much d i s c u s s e d i n
n u c l e a r c i r c l e s f o r more t h a n twenty
years,
it has o n l y r e c e n t l y a t t r a c t e d
w i d e r i n t e r e s t . Much c o n f u s i o n e x i s t s
i n t h i s a r e a p r i n c i p a l l y because t h e
p u b l i s h e d r e s u l t s o f e a r l y s t u d i e s 1 have
been w i d e l y misunderstood and b e c a u s e no
r e c e n t assessment of r e a c t o r r i s k s has
been made.
The p r i n c i p a l p u r p o s e o f
t h i s study is t o assess the risks t o t h e
p u b l i c from p o t e n t i a l a c c i d e n t s i n nuc l e a r power p l a n t s o f t h e t y p e b e i n g
b u i l t i n t h e United S t a t e s today.
It i s
intended t h a t t h e present study w i l l
produce a more r e a l i s t i c assessment o f
t h e s e r i s k s t h a n h a s been p r o v i d e d i n
e a r l i e r work; i t may a l s o h e l p t o d i s p e l
some o f t h e e x i s t i n g c o n f u s i o n .
For
t h e s e reasons,
t h e 1957 e f f o r t
d e v o t e d l i t t l e a t t e n t i o n t o t h e probab i l i t y o f occurrence of accidents.
In
t h e p a s t 10 y e a r s t h e development o f
r e l i a b i l i t y techniques has progressed
considerably.
Further, a s a result of
t h e i n c r e a s e d use o f commercial n u c l e a r
power p l a n t s i n t h e l a s t decade, a w e l l developed approach t o t h e s a f e t y d e s i g n
o f water-cooled
r e a c t o r s and s p e c i f i c
e n g i n e e r i n g d e s i g n s needed t o implement
a
quantitative
approach
to
risk
assessment now e x i s t s .
1.2 OBJECTIVES OF THE REACTORSAFETY
STUDY
a
A t t h e s t a r t o f t h e R e a c t o r S a f e t y Study
I t is important t o understand t h a t t h e
e a r l i e r s t u d i e s o f n u c l e a r power p l a n t
a c c i d e n t s were performed w i t h o b j e c t i v e s
o t h e r t h a n r e a l i s t i c r i s k assessment i n
mind.
The A E C ' s major e a r l y s t u d y ,
p u b l i s h e d i n 1957, was performed by
Brookhaven N a t i o n a l L a b o r a t o r y (BNL) and
was e n t i t l e d " T h e o r e t i c a l P o s s i b i l i t i e s
and Consequences of Major A c c i d e n t s i n
Large Nuclear
Power
Plants."
Its
o b j e c t i v e was t o p r o v i d e a n e s t i m a t e o f
t h e upper l i m i t t o t h e consequences t h a t
might be i n v o l v e d i n s u c h a c c i d e n t s i n
o r d e r t o h e l p t h e Congress e n s m e t h a t
l e g i s l a t i o n being considered t o provide
government i n d e m n i f i c a t i o n o f t h e p u b l i c
would be adequate.
I t is of interest
t h a t , a t t h e time o f t h e BNL s t u d y , o n l y
a few v e r y s m a l l m i l i t a r y power p l a n t s
e x i s t e d and n o commercial n u c l e a r power
p l a n t s were i n o p e r a t i o n , a l t h o u g h some
were b e i n g d e s i g n e d and c o n s t r u c t e d .
Furthermore, techniques f o r p r e d i c t i n g
the likelihood o f f a i l u r e of engineered
'WASH 1250, C h a p t e r 6 ,
o f t h i s e a r l y work.
summarized
i n t h e summer o f 1972, t h e r e was conside r a b l e u n c e r t a i n t y about t h e a p p l i c a b i l i t y of r e l i a b i l i t y techniques t o quantit a t i v e r i s k a s s e s s m e n t and about t h e
a b i l i t y o f these techniques t o achieve
c r e d i b l e e s t i m a t e s o f t h e occurrence of
e v e n t s o f low p r o b a b i l i t y .
Experience
had i n d i c a t e d t h a t a p p l i c a t i o n o f t h e s e
techniques generally l e d t o estimates of
f a i l u r e o f e n g i n e e r e d s y s t e m s t h a t were
so
small
as
t o c o n t r a d i c t common
experience.
Much o f t h e u n c e r t a i n t y
is
exhibited i n the
that
existed
s t a t e m e n t o f o b j e c t i v e s given t o t h e
Ileactor
S a f e t y Study by t h e Atomic
Energy Commission on August 4 , 1972:
"The p r i n c i p a l o b j e c t i v e o f t h e s t u d y i s
t o t r y t o r e a c h some meaningful conclusions
about
the
r i s k s of nuclear
a c c i d e n t s u s i n g c u r r e n t technology.
It
i s r e c o g n i z e d , however, t h a t t h e p r e s e n t
s t a t e o f knowledge p r o b a b l y w i l l n o t
permit
a complete a n a l y s i s o f lowprobability accidents i n nuclear p l a n t s
w i t h t h e p r e c i s i o n t h a t would be d e s i r a ble.
Where t h i s i s t h e c a s e , t h e s t u d y
w i l l consider the uncertainty i n present
knowledge and t h e consequent r a n g e i n
the predictions, a s well a s delineating
o u t s t a n d i n g problems.
I n t h i s way,
any
some
-1-
-
uncertainties i n the results of t h i s
s t u d y can be p l a c e d i n p e r s p e c t i v e .
Thus, a l t h o u g h t h e r e s u l t s o f t h i s s t u d y
o f n e c e s s i t y w i l l be i m p r e c i s e i n some
aspects, t h e study nevertheless w i l l
provide an important f i r s t s t e p i n t h e
development o f q u a n t i t a t i v e r i s k a n a l y s i s methods."
A s c o n f i d e n c e w i t h i n t h e s t u d y group
grew i n t h e a b i l i t y t o a c h i e v e a meaningful
r i s k assessment,
t h e Reactor
S a f e t y S t u d y added t h e f o l l o w i n g more
s p e c i f i c o b j e c t i v e s under i t s o r i g i n a l ,
broadly s t a t e d c h a r t e r :
a s s i g n e d S a u l Levine a s P r o j e c t S t a f f
Director.
I n a d d i t i o n , one p a r t - t i m e
and seven f u l l - t i m e p a r t i c i p a n t s were
AEC employees.
One p a r t i c i p a n t was from
t h e o p e r a t i o n a l s i d e o f t h e AEC t o
a s s i s t i n m a t t e r s i n v o l v i n g d e s i g n and
t h e o t h e r s , on l o a n from t h e AEC's
r e g u l a t o r y s t a f f , were t e c h n i c a l s a f e t y
s p e c i a l i s t s w i t h d e t a i l e d knowledge o f
reactor plants.
Additional p a r t i c i p a n t s
were f u r n i s h e d
by
contractors
and
national laboratories t o f u l f i l l the
s p e c i a l i z e d t e c h n i c a l needs
of
the
study.
Some o f t h e o r g a n i z a t i o n s and
t h e i r f i e l d o f e x p e r t i s e were:
a.
a.
Boeing Company-Fault
b.
A e r o j e t Nuclear Cowany-Data c o l l e c tion,
f a u l t t r e e and e v e n t t r e e
analysis.
c.
Science
Applications,
analysis, quantification
t r e e s and e v e n t t r e e s .
d.
Lawrence Livermore
t r e e analysis.
e.
Sandia Laboratories-Data
analysis,
f a u l t t r e e a n a l y s i s and consequence
modeling.
f.
Oak
Ridge
National
LaboratorySystems e n g i n e e r i n g a n a l y s i s .
g.
Teknekron-Technical e d i t i n g .
h.
Hanford
Engineering
Development
Laboratory-Consequence modeling.
b.
c.
d.
e.
Perform a q u a n t i t a t i v e a s s e s s m e n t o f
t h e r i s k t o t h e p u b l i c from r e a c t o r
accidents.
This r e q u i r e s analyses
d i r e c t e d toward d e t e r m i n i n g b o t h t h e
p r o b a b i l i t i e s and t h e consequences
o f such accidents.
Perform a more r e a l i s t i c a s s e s s m e n t
a s opposed t o t h e " c o n s e r v a t i v e l y o r i e n t e d " s a f e t y approach t a k e n i n
p r e v i o u s s t u d i e s o f t h i s t y p e and
the l i c e n s i n g process f o r nuclear
power p l a n t s .
Develop
the
methodological
app r o a c h e s needed t o perform t h e s e
a s s e s s m e n t s and g a i n an u n d e r s t a n d ing o f t h e i r limitations.
Identify
areas
i n which f u t u r e
s a f e t y r e s e a r c h might be f r u i t f u l l y
directed.
P r o v i d e a n independent check o f t h e
effectiveness of the reactor safety
practices of
industry
and
the
government.
1.3 ORGANIZATION OF THE REACTOR
SAFETY STUDY
The s t u d y was o r g a n i z e d t o b e indepenAEC's
o p e r a t i n g and
dent
of
the
regulatory
organizations.
Professor
Norman C. Rasmussen o f MIT, a s D i r e c t o r
o f t h e Reactor S a f e t y Study, reported t o
t h e Commission.
While funds and s u c h
o t h e r a s s i s t a n c e a s were needed were
p r o v i d e d by t h e AEC, t h e s t u d y o p e r a t e d
under t h e g e n e r a l c h a r t e r p r o v i d e d by
t h e Commission, b u t r e c e i v e d no o t h e r
d i r e c t i o n from i t . l
tree analysis.
1nc.-Data
of
fault
Laboratory-Fault
C
The work by t h e above o r g a n i z a t i o n s was
performed a l m o s t e n t i r e l y a t AEC Headq u a r t e r s under t h e d i r e c t i o n o f D r .
Rasmussen and M r . Levine.
I n a d d i t i o n , work was c o n t r a c t e d t o
other
organizations
not located a t
Headquarters.
However, it w a s d i r e c t e d
i n c o n s i d e r a b l e d e t a i l by t h e R e a c t o r
S a f e t y Study.
I n c l u d e d were:
a.
Battelle
Columbus
LaboratoryR a d i o a c t i v i t y r e l e a s e and t r a n s p o r t ;
analysis
of
molten
fuel
interactions.
b.
B a t t e l l e P a c i f i c Northwest Laboratory-Radioactivity
release
and
transport.
c.
Oak
Ridge
National
LaboratoryR a d i o a c t i v i t y r e l e a s e and t r a n s p o r t ;
s a f e t y design r a t i o n a l e .
d.
A e r o j e t Nuclear Company-Radioactivit y r e l e a s e and t r a n s p o r t .
To a s s i s t D r . Rasmussen i n t h e t e c h n i c a l
t h e AEC
management
of
the
study,
''This same independence was p r e s e r v e d by
t h e U . S . N u c l e a r Regulatory Commission
when it assumed s p o n s o r s h i p o f t h e
s t u d y on J a n u a r y 1 9 , 1975.
C
*