ML20126E333
| ML20126E333 | |
| Person / Time | |
|---|---|
| Issue date: | 01/04/1985 |
| From: | Palladino N NRC COMMISSION (OCM) |
| To: | Dircks W NRC OFFICE OF THE EXECUTIVE DIRECTOR FOR OPERATIONS (EDO) |
| Shared Package | |
| ML20126E298 | List: |
| References | |
| FOIA-85-124, REF-GTECI-A-47, REF-GTECI-A-49, REF-GTECI-RV, REF-GTECI-SY, TASK-A-47, TASK-A-49, TASK-OR NUDOCS 8506170049 | |
| Download: ML20126E333 (4) | |
Text
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January 4, 1985 MEMORANDUM FOR:
William J. Dircks Executive Director for Operations FROM:
Nunzio J. Palladino
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SUBJECT:
PRESSURIZED THERMAL SHOCK AND SAFETY IMPLICATIONS OF CONTROL SYSTEMS - USI A-47/49 In consonance with our Open Door Policy, on January 3, 1985 I met with Mr. D. Basdekas to discuss his concerns regarding the above subject.
The attached discussion notes were provided by Mr. Basdekas and these served as the basis for our discussion.
We understand that you have previously seen Mr. BasdeKas' concerns and have forwarded them to ACRS.
Please inform the Commission when the results of the ACRS review have been received.
Attachment:
As stated cc:
Commissioner Roberts Commissioner Asselstine Commissioner Bernthal Commissioner Zech OGC OPE SECY l
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MEYERS85-124 PDR
DISCUSSION NOTES ON PRESSURIZED THERMAL SH0CK AND OTHER SAFETI IMPLICATIONS OF CONTROL SISTD!S (UNRESOLVED SAFETI ISSUES A-47/49)
BI DDfETRIOS L. BASD1EAS
/. e PTS - A primary system probles with important secondary system initiators.
- An example of how control systems mayaffectsafety(A-47/49 relation-ship / interdependence).
- 1980-81 impetus for PTS resolution despite NRC' staff!s position that athis is not a new problem, we are working on it".
- A-47 and A-49 and the importance of lack of coordination between them.
- Design and operational information needs remain outstanding.
Large computer code modeling assumptions e.g. MFV overfeed transient analysis with RELAP-5.
A-47 lack of information resulting in substantial resource / time vaste.
A-47/A-49 ignoring common cause/ common mode failures (seismic,env., etc.)
7/ e PTS Fin,a1 Rule
- It abould not be issued as presently formulated because:
(a) the screening criterion is unrealistically high, and (b) it vill not accomplish anything because flux rodwtion measures already have been taken or are in progress.
-. V. German experience / example.
- The screening criterion (predecided) is too high because it does not take into account the following major concerns:
- 1. It was based on operational experience in this country only. It left out foreign operational experience. It was set at RTPTS Of 270 *F for axial veldsents, forgings and plate materials, and 300 *F for circumferential veldsents, even though at least one transient, at TMI-2, dropped Tf to 210 *F.
- 2. Assumption, as in Marshall report, that the QA/QC programa during the manufacture of the vessels were 100% effective in preventing gross manufacturing errors. Marriott and Beyers note'in M. I. Pres. Ves.
1~ Piping 12(1983)63-105 that = In this Marahall report the problem is reviewed in the introduttory chapter, but it is specifically excluded from further consideration on the grounds that it is the task of quality assurance (QA) to avoid such failures.' 'Ihey conclude i
that
- errors in QA procedure clearly contribute to the overall risk of tailure", ' making specif!: reference to data on nuclear plant power plant construction problems, as well as other advanced technology industries.
Figure 1, abovn on the next page abovs the relationship of failure probabilities to the strength and load functions.
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Fig.1. Failure probability diaframs for vanations la) muhin controlled limits and tb) outside controlled limits.
- 3. Assumption that in-situ inspection programs are effective in identifying faults important for PTS purposes (surface vs.
subsurface faults). Surface faults which are important for PTS are not detectable by curent monthods.
- 4. Ignoring insights from A-47/49 analyses indicating that more severe transients are likely that initially assumed. GDC-ll./15 are not met at least by some B&W plants (e.g. Three Oconee units and TMI-1 have 721 series ICS/NNI)
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- 5. Assumption of effectiveness of measures recommended by Bulletin 79/27. Eleven failures of ICS/NNI power supplies in last four and a half years.
- 6. Generic vs. plant specific differences in materials and systems design. Averaging does not bound, worst case might, based on present knowledge.
- 7. Sensitivity of probability of vessel failure vs. Tf and RTNDT*
- 8. Mixing in downconer analyses rely on opening of internals' vent valves designed to keep core from becoming uncovered. Analyses here are based on fractions of a psi (extremely small differences of very large numbers).
- 9. Earthquakes, environmental effects, and sabota6e "not within scope.
- 10. Bren n:2 der currest conditions 300 *F may have been exceeded because Simproved" data, including' their documentation, which became available recently may not be. properly supportable.
An interia screening critorion of RTPTS of 150 - 200'F would be more realistic and hopefully sufficiently conservative. Measures such as taken by the Germans for the primary pressute and temperature would be prudent nov for plants with advanced embrittlement conditions.
3e Appendix G, IV.B, ' thermal Annealing section abould not be deleted as provided under a separately proposed rule. A cost / benefit analysis would probably support its retention.
3-j, A47, safety Implications of control Systems cannot be resolved without e
considering and evaluating in a systematic analysis the seismic, environ-nantal and sabotage aspects of the safety implications of cod,rol systems and their support systems and their interactions with safety grade systems.
'lhis is not covered under any other work currently under way or planned, including A-49 and kl7.
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$e Schedules for USI's take inordinate importance over quality of resolution.
Note striking inconsistencies of tight schedules while refusing to require information needed to resolve these issues.
[* o Differing professional opinions and those who express them vis a vis the quality of work produced and submitted to the Consission by the NRC staff and the ACRS.
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