ML20141E243
| ML20141E243 | |
| Person / Time | |
|---|---|
| Site: | Nine Mile Point  |
| Issue date: | 04/04/1986 |
| From: | Mangan C NIAGARA MOHAWK POWER CORP. |
| To: | Starostecki R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I) |
| References | |
| (NMP2L-0678), (NMP2L-678), NUDOCS 8604210273 | |
| Download: ML20141E243 (2) | |
Text
fl
~
~'
M V NIAGARA
'RUMOHAWK NIAGAAA GAONAWK POWER CORPORAT90N/300 ERIE BOULEVARD WEST, SYRACUSE, N.Y.13202/ TELEPHONE (315) 4741511 April 4, 1986 (NMP2L 0678)
Mr..R. W. Starostecki, Director U.S. Nuclear Regulatory Comission Region I Division of Reactor Projects 631 Park Avenue King of Prussia, PA 19406 Re: Nine Mile Point - Unit 2 Docket No. 50-410
Dear Mr. Starostecki:
' Enclosed is a final report, in accordance with 10CFR50.55(e), for the problem concerning Secondary Containment. Pressure Drawdown Time following a loss of coolant accident.
This problem was reported via tel-con to L. Doerflein of
.your staff on March 3, 1986.
Very truly yours, b
C. V. Manga Senior Vice President CVM/GG/cla (1521H) xc: Director of Inspection and Enforcement U.S. Nuclear Regulatory Commission Washington, DC 20555 R. A. Gram, NRC Senior Resident Inspector NMPC Project File hk S
,\\\\
y:\\
a NIAGARA M0 HAWK POWER CORPORATION NINE MILE POINT - UNIT 2 DOCKET N0. 50-410 Final Report For a Problem Concerning Secondary Containment Pressure Drawdown Time Following a loss of Coolant Accident Description of the Problem The reactor water cleanup system incorporates some eauipment locatt! within secondary containment (heat exchangers,
- pump, vessels) which are not seismically supported.
Considering simultaneous loss of coolant accident and safe shutdown earthauake, a failure of reactor water cleanup system components within secondary containment could considerably increase the secondary containment pressure drawdown time and consecuently, the radiation dose outside the building could exceed 10CFR100 limits.
Analysis of Safety implications The secondary containment pressure drawdown time following a loss of coolant accident and seismic event is calculated as part of the plant loss of coolant accident analysis as described in Final Safety Analysis Report Section 6.2.3.
l This event does not consider a coincident high energy line break within the secondary containment boundary.
The secondary containment pressure drawdown time based on the above scenario is about 2 minutes.
The radiological conse-auences associated with 2 minutes of direct leakage from the secondary containment to the outside environment are a small fraction of the offsite dose limits of 10CFR100 and less than the control room guidelines set by 10CFR50, Appendix A, General Design Criteria 19.
With this design, if simultaneous loss of coolant accident and safe shutdown earthauake is considered, reactor water cleanup system eauipment nozzles may rupture within the reactor building resulting in secondary containment pressure drawdown time of about 23 to 26 minutes depending upon the reactor water cleanup system break location.
The radiological consecuences associated with this event could exceed the 10CFR100 limit at the exclusion area boundary and General Design Criteria 19 guideline for the control room, while remaining within the 10CFR100 limit at the low population zone.
Based on the above, if the described design had remained uncorrected, the safety of operations of the plant could have been adversely affected.
Corrective Action Stone & Webster has analyzed General Electric supplied reactor water cleanup system eauipment to determine if it will maintain pressure integrity under safe shutdown earthauake events.
As a result, the addition of lateral supports is reauired for each of the vessels (filter-demineralizers).
The regenerative heat exchanger reauired additional welding metal between the baseplate and floor embedment.
These changes are incorporated through Engineering and Design Coordination Report Nos. Z93,133 and 293,141.
_. - _