ML20024E764
| ML20024E764 | |
| Person / Time | |
|---|---|
| Site: | Big Rock Point File:Consumers Energy icon.png |
| Issue date: | 08/31/1983 |
| From: | Toner K CAROLINA POWER & LIGHT CO. |
| To: | Crutchfield D Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML20024E765 | List: |
| References | |
| TASK-09-05, TASK-9-5, TASK-RR NUDOCS 8309070031 | |
| Download: ML20024E764 (2) | |
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p Consumers Power Company General Offices: 1946 West Parnell Road, Jackson. MI 49201 + (517) 788-o550 August 31, 1983 Dennis M Crutchfield, Chief Operating Reactors Branch No 5 Nuclear Reactor Regulation US Nuclear Regulatory Commission Washington, DC 20555 DOCKET 50-155 - LICENSE DPR BIG ROCK POINT PLANT - SEP TOPIC IX-5 " VENTILATION SYSTEMS" -
ADDITIONAL STUDIES AND REVISIONS TO SUPPORT THE JUNE 23, 1983 CONSUMERS POWER COMPANY PRA The Nuclear Regulatory Commission (NRC) transmitted, by letter dated October 12, 1982, a Safety Evaluation Report (SER) on SEP Topic IX-5
" Ventilation Systems." It was concluded that the ventilation systems at Big Rock Point are in conformance with current licensing criteria except for the following areas: the Shop and Uninterruptable Power Supply (UPS) Rooms, the Electrical Equipment Room, and the Emergency Diesel. Generator Room. During the SEP Integrated Assessment (IA) meeting held during the week of November 15, 1982 with the NRC's IA team, Consumers Power Company proposed certain actions that would be taken to address NRC concerns regarding these ventila-tion systems. Procedural changes have been implemented to allow adequate air flow if Electrical Equipment Room and UPS Room ventilation systems fail.
In addition, a thermostatically-controlled ventilation system (exhaust fan and supply air damper) in the diesel generator room will be installed by the end of 1983.
A copy of the Probabilistic Risk Assessment (PRA), which addressed the impact of the loss of ventilation in the aforementioned rooms was submitted to the NRC on March 31, 1983. We submitted an updated copy of our PRA on June 23, 1983. Further review of these submittals revealed that the rate of hydrogen generation from the charging of fully charged batteries was incorrectly calculated for the UPS Rooms. Using extremely conservative assumptions, the modified hydrogen generation rate for the UPS Rooms is below the value calculated in the previous submittals.
It is important to note that only fully charged batteries generate hydrogen due to the electrolysis of water, and that the charging of discharged batteries does not generate significant amounts of hydrogen. The revised calculations increase the time for reaching inflammable levels of hydrogen in the UPS Rooms from 2.7 to 6.1 hours1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br />. The revised operating procedures call for the opening of doors in the UPS Rooms 6035 oc0883-0242a142 8309070031 830831 r
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s D M Crutchfield, Chief 2
Big Rock Point Plant SEP Topic IX-5 August 31, 1983 and Electrical Equipment Room within approximately two hours if necessary after a loss of ventilation.
In a recent conference call with the NRC, the staff requested that Consumers Power Company evaluate _the extent to which hydrogen generation may reach combustible levels (4 volume percent) due to ventilation system failure and whether." pocketing" will occur within the Electrical Equipment Room. The attached revised PRA provides calculations of the hydrogen generation rate in the Electrical Equipment Room after a loss of ventilation cooling. The results of our analysis show that after a loss of ventilation, 4.0 days would have to elapse before inflammable levels of hydrogen would accumulate. As corroborated by the enclosed calculations, the high diffusion rate of hydrogen leads to rapid dispersion; thus, " pocketing" will not occur.
With the incorporation of the results of these studies in the attached revised PRA which supersedes our June 23, 1983 PRA, Consumers Power Company asserts that the NRC concerns have been adequately addressed and that SEP Topic IX-5 is completely resolved.
0 Kerry A Toner Senior Licensing Engineer CC Administrator, Region III, USNRC NRC Resident Inspector-Big Rock Point Attachment i
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