ML20128C503
Text
5 56 f,.lz A
ha aggqt d
o UNITED STATES
[ '*,
,. g(,)
NUCLEAR REGULATORY COMMISSION
{) T _
g/ p WASHINGTON. D. C. 20555 g.,
- ..,((.
f Ib1
'^-
C AL 18 580
. w - f. M y n[ u -
we ad JGe TL MEMORANDUM FOR: Roger J. Mattson, Director k.md.s.u M Division of Systems Safety 0
NW A
Office of Nuclear Reactor Regulation rCClc ViR W N2AL c
FROM:
Robert M. Bernero, Director i
Probabilistic Analysis Staff WW t 4
U J
Office of Nuclear Regulatory Research Ik
SUBJECT:
INDIAN POINT RISK STUDIES N d
,a As you know the PAS staff has conducted a scoping risk study of the i
Indian Point 2'and 3 reactors. The results of this study were presented to the Commission in the Task Force Report, SECY-80-283, and by briefing
-on June 26, 1980.
The Task Force Report contains the results of the work which was done; time was not available to present the details behind that work. Conse-quently, we are preparing a more detailed report, which we will likely publish as a NUREG, to make such information readily available. The outline of that report is attached for your infomation (Enclosure 1).
We expect to put SECY-80-283 in the report as an appendix.
In addition to preparing this report on our own work, we are looking at the Indian Pointriskstudy.donebyOffshorePowerSystems(OPS),etal.
I will send you a report on our evaluation of that work along with the report whose outline is attached. This is a unique opportunity to compare two probabilistic risk analyses done by different groups using different methods.
In addressing the OPS work we expect to use the following outline:
1.
Comparison of Methodoloqy - There are some important differ-ences in the way we and OPS. handled accident sequence and consequence analysis. They will be described'and we'will address how they affect the completeness of the analysis.
2.
Dominant Sequences - Section II.A.(4) of our report will identify these from our work and previous work. Here we will try to compare against the OPS dominant sequences.
3.
Sequence Probability - The differences in our methodology makes sequence by sequence comparison difficult. We will compare probabilities of core melt and the dominant contri-butions to that probability.
h2 1 842015 p
SHOLLYS4-624 PDR
. il L
R ger J. Mattson
.. s 4
Individual Risk Chara tance from the plant frisk characteristics (c JUL I81990,
- We plant conditional probabilitywill compare t analys,isthe PAS analysis or the WASH-1400 analy ithe of Overall or Societthe Indian Point pla of of death vs. dis-ual S.
s s of nts, andthe Surry nts.
early fatalities (al Risk - We will the OPS analysi their CCDF) as they model. s of compare the We will..also accident sequen(ce inputOPS) analyzed it, to melt and the first fatali compare the The evaluation described ab with our our ty in the OPS andrelative probabilitiesconse serve as Indian Point.a basis for your ove, with some the PAS analysisof core and R. BlondIn addition to the ab safety evaluationoverall comentary, sho l of the OPS analysisud are also preparing a te hove reports, which being prepared by Gaccident sequ,ences for we of M. Ernst and S. Is. Edison nical report on dominantein use in regulatory revie c
'It wil.l. include (a)rael related systems,t sequences in LWRs,ication, et al., and is acciden w
or This latter identif to review f the Limerick risk ad on discuss o
the systems,of principal interacticomponents. and discussion of likely candidates for b) guides to the ide t with ssessment.
enable a actions in thesen ification of impthe dominant competent systemscomponents, and operato ons, dependencies, sequences, and (ortant experience to do an ff at least identify the pr rs.
analyst who hasWe believe thisand failure modes) e uncovered by a probabili ective first level revi c a.
no probabilistic analy ireport will esence S:ptember 5esently expect to stic analysis.of major design proble We pr ew of.a plant which will.
s s ms which would be possible use,s in r.
1980 I expect tocomplete the preparatio eactor wor n of regulation.k closely with yourthese reports by staff on their A,.
Robert M. Bernero w--
Probabilistic Analy i, Director
Enclosures:
Office As stated of Nuclear Regulatory R s s Staff-cc:
D.'Eisenhut esearch M. Ernst S. Israel D. Okrent T. MurleyG. Quittschreiber R. Blond M. Taylor L. 01shan E. Hanrahan J. Olshinski W. Vesely G. Edison F. Rowsome p
J-. -.
INDIAN POINT - SCOPING RISK STUDY I.
Introduction a.
Purpose of Report b.
Major Findings - Summary II.. Approach to Analysis of Design / Operations for I.P. II, III A. (1) Background /other risk studies (2)-Information/ summary other risk studies (3) Rebaselinging for purpose of IP comparisons (4) Results of Above - Dominant sequences (5) Envel' ope perspective - Individual Risk vs. Design
~
B. I.P. Results (1) LOCA Event tree (2) Transient Event tree (3) Sequence summary (a) Sequence probability
-(b) Containment failure modes assumptions (c) Dominant sequences and WASH.1400 comparison (d) System Unavailabilities (e) CRAC Inputs (1) Analogies with WASH 1400 PWR releases and rebaselined releases
'C.
Individual Risk vs. Distance
-(a) Acute Fatalities (b) Latent Fatalities (c) -Consequence dominating sequences D.
Societal Risk Comparisons (1) Site variations (2) Protective measure variations (3) Design variations III. Basic Conclusions
, - - - - -