ML19253B799
| ML19253B799 | |
| Person / Time | |
|---|---|
| Issue date: | 09/18/1979 |
| From: | Ross D NRC - TMI-2 BULLETINS & ORDERS TASK FORCE |
| To: | Reed C WESTINGHOUSE OPERATING PLANTS OWNERS GROUP |
| Shared Package | |
| ML19253B800 | List: |
| References | |
| NUDOCS 7910220252 | |
| Download: ML19253B799 (5) | |
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NUCLEAR REGULATORY COMMisslON j ; '.
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SEP 1.5 El9 Cordell Reed, Chatman Westinghouse Operating Plants Owner's Group Comenwealth Edison P. O. Box 767 Chicago, Illinois 60690
Dear Mr. Reed:
In a recent telephone conversation Mr. D. 3. Waters, en behalf of the Analysis Subcennittee of the Westinghouse Cwner's Grcup, asked if NRC would recensider the need to analyze the Semiscale S-07-10B test with the small-break methods developed by Westinghcuse.
I agreed to such reconsideration, and asked for a written request, which was received (Reference 1). Fcr the reasons described belcw I still believe that the comparison should be made, and have ccmunicated this belief to Mr. Waters by telephone on September 14, 1979.
Although there have been differences of cpinicn between W and NRC for several years en the merit of Semiscale as a PWR si.aulator, the imediate history starts with Reference 2, which was a request by NRC to perfom analyses on s:nall breaks at Semiscale, Mcd-3. The W rejoinder, Reference 3, cited several claims of scaling atypicality, incliiding:
2 f) break flow behavior dependent en small break area (e.g., 0.2in );
ii) different two-phase characteristics due to pipe size scale; iii) steam generator atypicality; iv) metal heat loads in Semiscale vessel atypical; and, y) other.
The NRC replied to the Reference 3 letter in Reference 4.
We concluded that there is limited integral test data available for small breaks; that the proposed test will provide needed additionai infomation in this area; and that pretest predictions should be provided.
Westinghcuse responded in Reference 5 letter, stating:
"Regarding calculations of any small break experiments scheduled for the Semiscale Mod-3 facility, our prior correspondence with you (Ref. 3, 5, 6) has detailed our concerns regarding the usefulness and validity of such an effort. Therefore, as previously stated, Westingnouse has n: plans to participate in pre-test evaluation model analysis of this test".
7 91022 0 EP
Cordell Reed, Chairman SEP 181979 Reference 5 went on to propose two criteria for continual yerification of EM codes:
If new data, from technically yalid experiments showed either; il evidence of a new phenomena which. had not been postulated during a LCCA transient, or, it) test data showed that currently identified phenomena which contribute to reduced ECCS are more severe than originally anticipated in relation to LOCA behavior in a PWR, In its comentary on the NRC-RES budget the ACRS this year indicated a concern on technical limitations of Semiscale.
In order to better define scaling justification the Reference 6 letter was sent. This requires identification of known scaling atypicalities before the test, and an engineering estimate of the effects. The subject of scale was further discussed at a meeting of the ACRS-ECCS Subcomittee on August 27-28, 1979.
Six scaling deficiencies were identified and the remedies were noted, in a presentation at that meeting. Subsequently, in Reference 7, additional directio 1 on scaling was given to INEL.
With this background it mighc be useful to return to the original reason for requesting further small break verification. The only integral small-break test that has had any cSmparison is Semiscale S-02-6.
The pressure iomparison (Enclosure 1) shows considerable variation. However there were test deficiencies.
Hence it was desirable to do a better job of both running the test as well as modeling it. This is the basis for the Refarence 2 request.
'de believe the scaling atypicalities can be handled and that the benefits of Semiscale outweigh the drawbacks. Huever, we believe that the essence is integral verification.
If the judgment of the holders of operating licenses is that Semiscale is not worthwhile as an integral verification device, then some alternate must be proposed. My letter to you (Reference 8) reaffirmed the need for verification. Of potential interest for scaling with respect to the effect of pipe diameter is some recent Dartmouth data which tends to show that, for 2-10" pipe flooding data, the effect of diameter is minimal (Enclosure 3).
We have recently examined the effects of RCP trip time on small-break LOCA. is a comparison of the three vendor responses. Enclosure 6 is a parametric study of the 'd response.
I believe the modelino of the system,
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whether heterogeneous or hemogeneous (especially the break node) as well as the punp trip time, satisfies the two critaria expressed by Mr. Anderson in Reference 5.
Finally, I enclose some further thoughts on Semiscale scaling as expressed by EG&G in August 1979.
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- 1) there has been enough exchange of letters, and it is time to get on with the integral verification; 11) if licensees, who bear the burden of providing a verified Appendix K model, do not choose Semiscale then some other proposal for integral verification should be offered; and, iii) enough new questions and new information exist to require reconciliation of contrasting theories of small-break behavior by an appropriate integral test.
I understand from the telephone conversation that I had with Mr. Waters on September 14 that the _W Owner's Group is directing W to proceed.
Let me know if further infornation is needed.
Sincerely,
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Den h RoYs JY., Director Bulletins and Orders Task Force Office of Nuclear Reactor Regulation
Enclosures:
1.
Comparison of Upper Plenum Pressure for Semiscale Test S-02-6.
2.
Letter, L. S. Tong to R. E. Tiller; September 5, 1979.
3.
Dartmouth air-water flooding data graph for 2", 6" and 10" diameter pipes.
4 Addendum 7B to the EOS for Semiscale (March 1978) 5.
Comparison of vender responses to bulletins 79-OSC and 06C 6.
Effect of pump trip time on PCT for W 3-loop plant 7.
Semiscale scaling; a presentation to ACRS; August 27, 1979.
References :
1.
Letter, D. B. Waters to D. F. Ross, September 10, 1979: Recuirements to Perfonn Semiscale Mod-3 Analysis.
2.
Letter, D. F. Ross to T. M. Anderson on August 29, 1978.
3.
Letter, T. M. Anderson to R. J. Mattson, November 16,1978 (NS-TMA-1989).
4.
Letter, R. J.
Mattson to Tcm Anderson; January 9,1979.
5.
Letter, T. M. Anderson to R. J. Mattson, March 1,1979 (NS-TMA-2048).
6.
Letter, L. S. Tong (NRC) to R. E. Tiller (DOE-ID0) on Semiscale Testing; July 31,1979.
7.
Letter, L. S. Tong to R. E. Tiller of September 5,1979.
8.
Letter, D. F. Ross to Cordell Reed, Evaluation of Semiscale Small Break Experiment; July 9,1979.
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