ML19210B025
| ML19210B025 | |
| Person / Time | |
|---|---|
| Site: | Crane  |
| Issue date: | 03/22/1972 |
| From: | Grimes B US ATOMIC ENERGY COMMISSION (AEC) |
| To: | Dicker G US ATOMIC ENERGY COMMISSION (AEC) |
| References | |
| NUDOCS 7911010760 | |
| Download: ML19210B025 (8) | |
Text
.
Z. A) 0 2;4Vi.iv 4,..C 1 MAR 2 21972
[0ff G. Dicker, Chief, Project Branch No. 2. DREP TIC.23 MILE ISLAND REALISTIC ACCIDENT SECTION OF THE DRAFT ENVIRONMENTAL STATEMENT Enclosed is a mark-up of the realistic sceident section of the draft environmental statement for Three Mila Island. There have been some minor revisions to the dose table due to a refinement of the dose calculations performed by E. G. Adan===.
However, our opinion that the environmental risk remaina extremely low has not changed.
Brian Crimes. Chief Accident Analysis Branch Division of Reacter Licensing Enclosures (As Stated) g E!f[
ect W. H. Eagan (w/ enclosure) l H. E. Schier11ng (w/anelnaura) j L $b U uJ uLa D. Haller (w/o enclosure)
- 1. DeYoung (w/o enclosure)
H. R. Denton (w/o enclosure)
K. Eniel (w/o enclosure) bec: E. Adensam (w/ enclosure)
DISTRIBUTION D
- Rdg.
RL - Suppl.
S&RS - Rdg.
Acc. Anal - Rdg.
1564 263 OFFICr >
_R..............
R g
sunwr > EADENSWimj....
...EGRN5
&K*I
/.. 2 f..../.72..
. 3/..i.;.C./.22_.-..1dl 2.h om
.c.,..
..,n _
.s.
,,,, y,,
79
/93
.' j';
'l gry' j
D a-m l
D n ) 3\\ h., Dh i.
U.
s'O frhti2 *.h-ENVIRO:0! ENTAL IMPACT OF. ACCIDENTS n
A. Phddm;Uc A high degree of protection against the occurrence of postulated accidents in the Three Mile' Island Nuclear Station, Unit 1 and Unit 2, is provided through correct design, manufacture, and operation, and the quality assurance program used to establish the necessary high integrity of the reactor system as will be considered in the Coccission's Safety Evaluation for each unit.
Deviations that may occur are handled by protective systems to place and hold the plant in a safe condition.
Not-
. withstanding this, the conservative postulate is made that serious accidents might occur, in spite of the fact that they are extremely unlikely, and engineered safety features are installed to mitigate the consequences of these postulated events.
The probability of occurrence of accidents and the spectrum of their consequences to be considered from an environmental effects standpoint have been analyzed using best estinates of probabilities and realistic fission product release cad Mu S s ()
transport assumptions.
For site evaluation in ce safety review, extrenely conservative assumptions were used for the purpose of comparing calculated doses resulting fron a hypothetical release of fission products from the fuci, against the 10 CFR Part 100. siting guidelines.
The ccm-puted deses that would be received by the population and enviror.ent from actual accidents would be significantij lecs than these that will bc
,s.
w.
prescated in er Safety Evaluations.
The Cc-.ission issund guidance to 1564 264
i IJ 57 6L
-/-
JOU'
.m j
l applicante on September 1, 1971, requiring the consideration of a spectrum i
of accidents with assumptions as realistic as the state of knowledge permits.
The applicant's response is contained in " Environmental Report - Operating License Stage" for the Three Mile Island Nuclear S tation, Unit 1 and i
Unit 2,I' dated December 10, 1971.
The applicant's report has been evaluated usi'g the standard accident n
assumptions and guidance issued as a proposed Annex to Appendix D of 10 CF2 Par:~50 by the Conaission on December 1, 1971.
Nine classes of postulated accidents and occurrences ranging in severity from trivial to very serious were identified by the Commission.
In general, accidents in the. high consecuence end of the spectrum have a low occurrence rate, and those on the low consequence end have a higher occurrence rate.
The exanples 17 selected by the applicant for these classes are shown in Table,T.
The examples selected are reasonably homogeneous in terns of probability with h cur. G:,. & h-b two exceptions.
..'a e c-4 4 "or=4c to be more appropriate to classify (1) the failure of the waste gas decay tank as an accident in Class 3 (applicant uses Class 3) and (1) the s: car: generator tube rupture as an accident in Class 5 (applicant uses Class S).
The following assumptiens cade by :he applicant are cuestionable:
(1) no s:ccm generator tube leaks pric to h,. i r.e...S the steam generator tube rupture,, (2h/p"rinary coolant activity is based A
on 0.1% failed fuel, and (3) the consequences of various releases are evaluated based on release rates pplicable for specified times.
Hevever, the use of 21:ernative 'caun *'.cna 'ecc at si:mifi r s.ti. aff-;.
overall environ:2ntal risks.
1564 263 r
\\
s
\\
t
/ 0 3' 4
)
cc 3 -
1ol
~
f- - j t
eg au 1s u < a i
.I
$a-V '\\
Oer estimates of the dose which might be receiv,cd by an assumed individual Juve..r SO s.
standing at the site boundary in the t ee eerd direction, using the assump-e tions in the proposed Annex to Appendix D, are presented in Table lf.Ib j
e:7 estimates of the integrated exposure that night be delivered to the population within 50 miles of the site are also presented in Table II'.
The man-rem estimate was based on the projected population around the site for the year 2014.
The estimates presented.in Table II refer to a singic unit.
To rigourously establish a realistic annual risk, the calculated doses in
/f Tabic.4f would have to be multiplied by estimated probabilities.
The events in Classes 1 and 2 represent occurrences which are anticipated during plant operation and their consequences, which are very small, are considered within the framework of routine effluents from the plant.
Except for a limited amount of fuel failures and some steam generator leakage, the events in Classes 3 throu;;h 5 ce_not ant.ic'gred during plant operation but events of this type could occur sometime during the 40-year plant lifetime.
Accidents in Classes 6 and 7 and small accidents in Class S are of siuilar or lower probabil'ity than accicents in Classes 3 through 5 but are s till possible.
The probability of occurrence of large Class 8 accide:::s is very small.
Therefore, when the consequences indicated
/3 in Table,5{ are weighted by prebabilitics, the environment:1 risk is very low.
The postulated occurrences in Class 9 inrelve secucnces of successive failures more severe than ;3cse requ:-rcd to be ccncid;rei in the ri;r 1564 266
/d[0 h'
f D Y]
D
'Qij]ph r basis of protection systems and engineered safety features.
Their ennse-quences could be severe.
However, the probability of their occurrence is so small that their environmental risk is extremely low.
Defense in depth (multiple physical barriers), quality assurance for design, manufacture and operation, continued surveillance and testing, and conservative design are all applied to proki e and maintain the required high degree of assurance that potential accidents in this class are, and will remain sufficiently small in probability that the environmental risk is extreecly low.
9
/s Table pf indicates that the realistically esticated radiological conse-quences of the postulated accidents would result iri exposures of an assuced individual at the site boundary to concentrations of radioactive y< b w v.tw w y gjf?,
materials within the Maxinum Permissible Concentrations (EC) of Table,~f -:
of 10 CFR Part 00.
The tabic also shows that the estimated integrated exposure of the population uithin 50 niles of the. plant from each postulated accident would be orders of nagnitude smaller than that from naturally occuu :.ng radioac ti. it.,
iic.'
rresp<.c:.a to apprc:. irately 3?'.,000 man-remfyr C er.r u b se & J J L based on a natural background level of 130 nren/yr.
When m "'_.. -. the
\\
probability of occurrence, the annual potential radiation expcsure of the population from all the postulated accidents is an even smallcr fraction of the c::posure from aatural background radiation and, in f act, is well within naturally occurrine, variations in the n.'tural bac:q,round.
It is concluded W
- /
from the results of the re.lirrit"9-.1:si
- H: the firc;.:.tal ric...;
due to pos tulated radiological accidents are c::ccedingly small.
1564 267
~
f o[Y I
D~@D 9 ' a q r 1r b -
,l
'D ib d J L Cu ca a
I7 TABLE,f CLASSIFICATION OF POSTULATED ACCIDENTS AND OCCURRENCES Class AEC Descrintion Applicant's Er. amole (s)
! rivial Incidents
.L'e m4t:t-red / e r#,,
.1 T
l 2
!Small Releases Outside Spill in Sample Hood Containment 3
Radwaste System Failure Inadvertent Release of Waste Gas Decay Tank 4
Fission Products.co Primary Not applicable System (SWR) 5 Fission Products to Primary One day Operation with Primary System and Secondary Systems (PWR)
Leak to Reactor Building Normal Operation tith S:eam Generator Tube Leak and Release from Condenser 6
Refueling Accidents Drop of Fuel Assembly or Drop of Heavy Object on Fuel Assembly 7
Spent Fuel Handling Accident Drop of Fuel Assembly 8
Accident Initiation Events Uncompensated Operating Reactivity Considered in Design Basis Changes Evaluation in :he Safety Star:up Accident Analysis Report Rod Withdrawal Acciden Moderator Dilution Accident Cold Yater i:ciden:
Loss of Coolan: Flow Accident S tuck-Ou t, Stuck-In, or Dropped Control Rod Acciden:
Loss of Electric Load Accident Steam Line Failure Steam I.ine Lenkage Steam Generator Tube Failure Rod Ejec:len Acciden.
Loss of Ceelan: '. :iden:
Waste Gas Tank Rupture 9
- ypo th ::ica' S c:;uences :f
- a _ mait~;ri /<'e,:.,
Failures :.. : u Sevcre Than Class S 1564 268
s
/o C 2 I
f
/I TABLE K SU:' MARY OF RADIOLOGICAL CONSEQ'.'ESCES OF FOSTULATED ACCIDENTS '
"(Single Unit Only) l l
Esticated Dose Estimated Fraction of to Population 10 CFa.Part 20 Limit in 50 Mile Class Event at Site Eeundaryl/
Radius, nan-ren 1.0 Trivial incidents 2/
2/
2.0 Small releases outside 2/
2/
containnent 3.0 Radvaste system failures o.o73
/d 3.1 Equipment leakage or
.-026-0.0-54L calfunction 0, > f Ye 3.2 Release of waste gas
.ThNb 15=606 storage tank contents 0,003
- 4. % 7 3.3 Release of liquid waste Eng.
- Neg, storage tank contents 4.0' Fission prcdue:s to primary sys:en (3%R) 4.1 Fuel cladding defects N.A.
N.A.
4.2 Off-design transients that N.A.
N.A.
induce fue1 failures above those cnpcc:cd 5.0 F:ssion produc:: to primary Fd64 2b9 and secondary systems (PWR) 5.1 Fuel cladding def ects ar.d 2/
2/
stean genera:or icaks c.
t 5.2 off-design transients that
.002
- 253 induce fuc1 failure.. ce there a..cc;;;_ e s' s:ca generator ida';
c C. C7 f.
/3 5.3 S:can generator tube rupture
.lEzr
' ' ' ne
/O(*./.-
d Ie TABLE R~(cont'd)
I Estinated Dose Estinated Fraction of to Population i
10 CFR Par: 20 Limit in 50 Mile Class Event at Site Eoundcrvl_/
Rndius, mn-rem 6.0 Refueling accidents 0.0 /[
.:.. /
6.1 Fuel bundle drop,
M
.350
- p. 2 C JG 6.2 l
Heavy obj ect drop onto 4074 10+290-l fuel in core l
7.0
- Spent fuel handling accident O,o/
/, ",
7.1 Fuel assenbly drop in fuel (C04 35G:
storage pool 5,S87
,.C 3 7.2 Heavy object drop onto fuel
-MGZ 7
rack 7.3 Fuel cask drop N.A.
N.A.
8.0 Accident initiation events considered in design basis p ' n ' ' 1 ' i 'T i
~
i I
evaluation in the safety D {iU Jb g>" "f j g "
analysis report 8.1 Loss-of-coolant accidents 0./4 Snall 3reak cM)et-
.-0T3
/. L-
/000 Large Break M
f;0-620 8.1(a) 3rcak in instruncat line from N.A.
N.A.
prinary systen that penctrates
- hc nte'~.:en
- 0. I V
/00 8.2(a)
?.::i ejection accident ( ?'.iR)
.6@t-M 8.2(b)
Red drop accident (BliR)
N.A.
N.A.
8.3(a)
S:canline breaks (PtiR 's outside containnent) s.'.
Snell-3reak
<.001
,999-fC00 f,/3 Large Break d:fW
.690 1564 270
F \\
)
(
\\
6
\\ \\
TABLE J2- (cont 't" Esticated Dose Estimated Fraction of to Population 10 CFR Part 20 Limit in 50 Mile Class Event at Site Bourdary1/
Radius ran-ren 8.3(b)
Steamline breaks (BWR)
Small Ereak N.A.
N.A.
Large Break N.A.
N.A.
J_/ Represents the calculated fraction of a tehole body dose of 500 cr 'f or the equivalent dose to an organ.
k 2/ These releases will be comparable to the design objectives indicated in the proposed 1.ppendix I to 10 CFR Part 50 for routine effluents (i.e., 5 mrem /yr to an individual from all sources).
e 8
6
.f l-h J2k' lg,.0,rQ, " '
g 1564 271
.