ML19308C919
| ML19308C919 | |
| 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 | |
| TASK-TF, TASK-TMR NUDOCS 8002110654 | |
| Download: ML19308C919 (4) | |
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MEMOPAflD!T4 FOR:
D. Vassallo, Assistant J.icector for Light Water Reactors, DPM FROM:
R. L. Tedesco, Assistant Director for Plant Systems.
Division of Systems Safety
SUBJECT:
REVISION TO THE DPAFT SAFETY EVALUATION REPORT FOR THREE MILE ISLAND NUCLEAR STATIO1, UNIT 2 Plant Name: Three Mile Island Nuclear Station, Unit 2 Docket htsber:
S0-320 Milestone Number:
24-04 Licensing Stage: OL NSSS Supplier: Babcock & Wilcox Architect Engineer: Burns & P.ce Containment Type: Dry Responsible Branch & Project Manager: LWR-2; H. Silver Requested Cocpletion Date: N/S Review Statas:
Incomplete Enclosed is Revision 1 to the draft Safety Evaluation Report fer 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 S0. 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 memorandu:n from R. Tedesco to D. Vassallo, dated December 17, 1976, is sumarized in the following paragraphs:
- 1. -Reactor Cavity Analysis At the time our draft SER was written, the applicant indicated his intention of.us,ing shield plugs to reduce the neutron streaming from the reactor cavity. Because of the uncertainties in the plug dynamics
Contact:
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analysis, the staff recuested additional inforaaticn from the applicant.
In response to our concerns, the applicant decided to remove the shield plugs and orovide a neutron shield platfom about G-1/2 feet above the reactor vessel seal flange that eld be permanently fixed and restrained from movement. Due to anticipated constructicn difficultias, the applicant has decided to replace the neutron shield platfonn with hinged tanks filled with water that would swing out of the way to provide the vertical vent area necessary to relieve the pressure build-up in the reactor cavity following a pipe break. We have completed our evaluation of 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 Steam Line Break Accident Analysis In the draft SER, we reported that the applicant had not analyzed the containment resconse for a spectrum of postulated nain steam line breaks at different power levels, and that we would require further infomation 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 rupture 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 atmosphere temperature that is 65*F higher than that calculated by the applicant, due to the fact that the C0HTetPT version' used by the applicant is not conservative for temperature calculation for a main steam line break accident. To resolve this problem, the applicant has comitted to use the tamperature profile based on our confirmatory analysis for equipment qualification (see cemorandum from R. Tedesco to D. Vassallo, dated March 10, 1977).
It should be noted that the above memorandum contains a request for additional infor: ration concerning the applicant's equipment qualification program.
We have also requested the applicant to provide assurance that a single active failure will not jeopardize the capability to tarminate feedwater flow to the affected steam generator following a main steam line break accident (see memorandum 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 Purnino Ouring flomal Plant Operation The applicant has indicated his intention of limiting containment purging during nomal plant operation to 90 hours0.00104 days <br />0.025 hours <br />1.488095e-4 weeks <br />3.4245e-5 months <br /> per year (about 1 percent of the ti ne). We find this approach acceptable. The plant eachnical enocifica-icns will reflect this limitation, opries
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Centainment Heat Reaoval Systens In the draft SER, we reported that the tiSSS vendor reanalyzed the containment spray system perfomance. The analysis indicated that the sodium hydroxide tank (SHT), sodium thiosulfate tank (STT), and borated water storage tank (BSWT) would net draw down together as i
previously predicted. This would result in the emptying of the SHT and STT up to twenty-two minutes before reaching the BUST level i
setDoint. We requested the applicant to evaluate the effect of uneven drawdown on system perfomance, including the 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.
Containcent Sumo Our draft SER does not identify any unresolved concerns with the containment sump. Hcwever, in recent discussions with the applicant regarding the model testing done on the Three '411e 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 fomation of vortices.
It is our position that the applicant should separate the intakes either with a solid plate or w.ith screening, and verify that vortex formation will not occur.
All of the above matters have been discussed with the applicant. We will complete our review after receipt of further information.
Orf&.21 siz.e! by Rctert L. Tefesco Robert L. Tedesco, Assistant Director for Plant Systems Division of Systems Safety
Enclosure:
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