ML19291C032
| ML19291C032 | |
| Person / Time | |
|---|---|
| Issue date: | 10/09/1979 |
| From: | Rowsome F NRC OFFICE OF NUCLEAR REGULATORY RESEARCH (RES) |
| To: | Baranowsky P, Edison G, Hanauer S Office of Nuclear Reactor Regulation, NRC OFFICE OF NUCLEAR REGULATORY RESEARCH (RES) |
| References | |
| REF-GTECI-A-44, REF-GTECI-EL, TASK-A-44, TASK-OR NUDOCS 8001110062 | |
| Download: ML19291C032 (4) | |
Text
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wt MEMORANDUM FOR: Stephen H. Hanauer, DSS, NRR Gordon E. Edison, PAS, RES Patrick W. Baranowsky, PAS, RES FROM:
Frank H. Rowsome, Acting Director Probabilistic Analysis Staff, RES
SUBJECT:
TAP A-44, STATION BLACK 0UT I think we all agree that there may be a few plants at which station blackout poses an unacceptable risk, but that at most plants there is time for a careful and thorough study of the problem before rushing into a licensing position.
This action plan is based on the following guidelines:
1.
Identify and draf t orders to address any plants having a high-risk susceptibility to blackout. This phase of the program will be modeled on (and depend upon) the AFWS study follcwed by B&OTF quick fixes.
2.
The resolution will be based on probabilistic safety analysis.
3.
Maximum use will be made of licensee--supplied analyses rather than drawn-out contractor studies.
4.
The quick fix approach is intended to:
buy time for a more careful approach to the ultimate regulatory resolution, a.
and b.
pioneer NRC/ industry collaboration on the development of reliability or performance based regulation.
5.
Where probabilistic studies are solicited of licensees, the scope, data, and procedures should be specified in great detail to shrink the window for lying with statistics, aid in unit-to-unit comparisons, and to serve as prototypes of acceptable reliability studies.
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6.
Plant specific analyses will be necessary to catch all the potentially high risk contributors that may lie hidden in design or procedural detail.
7.
Unacceptable accident outcome is defined as significant core damage.
8.
Event sequences entailing blackout and the failure to start of non-AC-dependent cooling systems will be tackled first in PWR's, then in BWR's.
Blackout out-lasting the point of no return for the restoration of AC power (with AFWS/RCIC starting properly) will be addressed later.
I.
Task Action Plan A.
Formulate Statement of the Problem and Flesh Out this Action Plan.
(NRR
& PAS)
B.
Preliminary Assessment of the Failure Rate for Core Cooling Due to Blackout Plus Failure to Start of Non-AC-Powered Cooling Systems.
(PAS) 1.
Collect in-house and published data on the site-specific frequency and duration of loss of offsite power.
Employ actuarial data wherever possible.
Use regional models where the statistics are thin.
Scope problem of estimating the long duration (d) tail on ALOOp (t>d) consider packaging this problem for EPRI or IEEE.
Initiate study.
2.
Collect in-house data on the plant-specific probability of failures to start and rua for diesel generators.
1734 27 A(core damage / blackout) = A(LOOP, t>t 3.
Calculate for each PWR:
x P(n DG failure) x P(AFWS/ Blackout) using the PAS /B&OTF survey of W&CE AFWS reliability, the comparable B&W study, and conservative estimates of t).
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C.
Prepare a "Short Term Lessons Learned" Report for PWR's.
(PAS Lead, NRR Collaborate and Follow-Up) 1.
Formulate generic and plant specific recommendations.
D.
Develop a Specification for Reliability Studies to be Performed by BWR Owners on Blackout Core Cooling Systems (RCIC and Turbine Driven HPSI if Any) - Follow Matrix Format of,AFWS Study.
E.
Draft and Issue Specifications for Longer Term Studies to be Required of Licensees.
Determine the critical times Maximum delay for starting non-AC-dependent shutdown coolinc a.
system (t]).
b.
Point of no return for restoration of AC power without cort damage (t ).
Develop a list of hypothetical limiting factors 2
to be considered, such as DC dependence and battery A-hr, instrument air dependence, room cooling, condensate storage tank capacity, and limitations of natural circulation with tech spec RCS leakage (PWR), etc.
2.
Studies of cul de sac's for repair / recovery of offsite power, diesel generators, non-AC-power and of the adequacy of procedures.
F.
Implementation of Short Term Lessons Learned for Very High Risk Cases (PWR).
(NRR Lead, PAS Collaboration) 73 G.
Review Industry-Supplied Frequency-Predictive Models of Blackout Outlasting the Capability of Non-AC-Dependent Cooling Systems to Cope and Site on Region Specific Estimates of the Frequency of Long-Duration Losses of Offsite Power.
H.
Review BWR Submittals and Draft Short Term Lessons Learned for BWR's.
(PAS, Follow with Implementation for High Risk NRR Cases.)
I.
Probabilistic Assessment for Blackouts Outlasting the Capability of Non-AC-Dependent Systems to Cope.
(PAS)
J.
Short Term " Lessons Learned:" Require Quick-Fixes at Plants with Design or Procedural Characteristics that Severely Limit the Tolerable Duration of Blackouts and Have Comparatively High Assessed Risk.
K.
Develop "Long Term Lessons Learned:"
1.
Where are the natural cliffs and clusterings in the risk picture emerging from the foregoing studies?
2.
Where is further research necessary to strengthen weak points in the risk picture?--perform the research. '
L.
Develop Long Term Regulatory Position on Station Blackout.
II.
Options for Quick Fixes A.
Implement Recommendations Eminating from the AFWS Study or Their Equivalent.
B.
Apply RG 1.108 (DG Testing) to Operating Plants.
Diesels of Poor Reliability will Force Shutdowns Due to Overlapping Diesel Repairs Under this Test Schedule.
It May Aggravate the Problem Briefly but Will Light a Fire Under Licensees to Make the DG's Work.
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C.
Mandate Peaking Units that are Designed to be Devoted to Hotel Loads Under Loss of Offsite Power for Sites With Precarious Grids.
Frank H. Rowsome, Acting Director Probabilistic Analysis Staff Office of Nuclear Regulatory Research