ML19220B611
| ML19220B611 | |
| Person / Time | |
|---|---|
| Site: | Crane  |
| Issue date: | 03/16/1977 |
| From: | Tedesco R Office of Nuclear Reactor Regulation |
| To: | Vassallo D Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 7904270101 | |
| Download: ML19220B611 (4) | |
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! 3 077 CSB Reading PS Reading Dcchet No. 50-320 ME"0RAtlDUM FOR:
D. Vassallo, Assistant Director for Light Water Reactors, DPM FR04:
R. L. Tedesco, Assistant Director for Plant Systems, Division of Systems Safety
SUBJECT:
REVISION TO THE DRAFT SAFETY EVALUATION REPORT FOR THREE MILE ISLAND NUCLEAR STATIO?l, UNIT 2 Plant Name: Three Mile Island Nuclear Station, Unit 2 Docket number:
50-320 Milestone Number:
24-04 Licensing Stage: 0L NSSS Supplier: Babcock & Wilcox Architect Engineer: Burns a Roe Containment Type: Dry Responsible Branch & Profect Manager: LWR-2; H. Silver Requested Cocpletion Date: N/S Review Status:
Incomplete Enclosed is Revision 1 to the draft Safety Evaluation Report for the Three Mile Island Nuclear Station, Unit 2.
This report has been prepared by the Containment Systems Branch after having reviewed the apolicable portions of the FSAR through knendment 50 Additional information is necessary before we can conclude on the adequacy of the containment functional design.
The status of the outstanding items previously identified in the memorandum frcra R. Tedasco to D. Vassallo, dated December 17, 1976, is sumarized in the following paragraphs:
- 1. Teactor Cavity Analysis At the tt:e our draft SER was written, the applicant indicated his intention of using shield plugs to reduce the neutron streaming from the reactor cavity. Because of the uncertainties in the plug dynamtes
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- 0. Vassallo analysis, the staff recuested additional infor aticn frca t.ie applicant.
In respense to our concerns, the applicant decided to renove th2 shield clugs and orovide a neutron shield platfona about G-1/2 feet above the reactor vessel seal flance that vould be permanently fixed and restrained from movement. Due to anticipated constructicn difficulties, tne applicant has decided to replace the neutron shield Dlatform with hinged tanks filled with water that would swing out cf the way to provide the vertical vent area necessary to relieve the pressure build-up in the reactor cavity following a pioe break. We have completed our evaluation nf the applicant's analysis of the behavior of these water filled tanks under postulated accident conditions, and conclude that the analysis is reasonably conservative and, therefore, acceptable.
2.
Main Stern Line Break Accident Analysis In the draft SER, we reported that the apolicant had not analyzed the containment response for a spectrum of oostulated nain stean line breaks at different power levels, and that we wculd repuire furtner information to complete our review. We have received additional information regarding the main steam line break accident analysis in Amendment 50 to the FSAR. The applicant has identified the double-ended ruoture of a main steam line with a turbine stop valve failure as the accident resulting in the highest containment temperature (385'F). We calculate a peak containment ataosphere temperature that is 65*F higher than that calculated by the applicant, due to the fact that the CONTEMPT version' used by the applicant is not conservative for temoerature calculation for a main steam line break accident. To resolve this problen, the applicant has comitted to use the tamperature profile based on our confirmatory analysis for equicment qualification (see memorandum from R. Tedesco to D. Vassallo, dated Haren 10,1977).
It should be noted that the above memorandum contains a request for additicnal information concerning the applicant's equipgent qualification progrmn.
We have also requested the applicant to provide assurance that a sincie active failure sill not jeopardize the capability to tarminata feedwater flow to the affected steam generator following a main steam line break accident (see memorancuc from R. Tedesco to D. Vassallo, dated February 4,1977). As a result, the main steam line break accident analysis will remain an outstanding item until our concerns regarding single active failures are resolved.
3.
Containment Purgino During !!crmal Plant Oceration The applicant has indicated his intention of limiting containment purging durirg normal plant operation to 90 hours0.00104 days <br />0.025 hours <br />1.488095e-4 weeks <br />3.4245e-5 months <br /> cer year (about 1 percent of the time). We find this aporoach acceptable. The piant
+achnic6 nnardfications will reflect this limitation.
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4 Ccntainment Heat Renoval Systens In the draft SER, we reported that the tiSSS vendor reanalyzed the containment spray system arformance. The analysis indicated tnat the sodiua hydroxide tank (SHT), sodium thicsulfate tank (STT), and barated water storage tank (BSWT) would not draw down together as previously predicted. This would result in tne emptying of the SHT and STT up to twenty-two minutes before reaching the BUST level setpoint. We requested the applicant to evaluate the effect of uneven drawdown on system perfomance, includinq tne potential for spray pump cavitation. Since then, the applicant has changed tne spray system design to eliminate the potential for uneven drawdown.
Based on our review of the new design, we conclude that the heat removal system design is acceptable.
5.
Containment Sump Our draft SER does not identify any unresolved concerns with the containment sump. However, in recent discussions with the applicant regarding the model testing done on the Three Mile Island, Unit 2 sump design, we noted that the recirculation piping intakes are not physically separated.
We have discussed this matter with the applicant. The applicant has indicated that screening could enhance the femation of vortices.
It is our posicicn that the applicant should separate tne intakes either with a solid plate or w.ith screening, and verify that vortex femation will not occur.
All of the above matters have been discussed with the applicant. We will complete our review after receipt of further information.
Or!&.al si.~H b7 Rd.ert L TMesco Robert L. Tedesco, Assistant Director for Plant Systems Division of Systems Saf. ;
Enclosure:
As Stated cc: See Page 4
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