ML20148E045
| ML20148E045 | |
| Person / Time | |
|---|---|
| Site: | Big Rock Point File:Consumers Energy icon.png |
| Issue date: | 10/31/1978 |
| From: | Bixel D CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.) |
| To: | James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| References | |
| TASK-15-19, TASK-RR NUDOCS 7811060084 | |
| Download: ML20148E045 (2) | |
Text
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I October 31, 1978 I
Mr James G Keppler Office of Inspection & Enforcement Region III US Nuclear Regulatory Commission T99 Roosevelt Road Glen Ellyn, IL 60137 DOCKET 50-155 - LICENSE DPR-o -
BIG ROCK POINT PLANT - DEFICIENCIES FOUND IN ANALYSIS FOR VERY SMALL EREAK LOCA This letter is written to inform you of a possible deficiency which may exist in previous LOCA analyses for Big Rock Point.
This deficiency is not considered a reportable occurrence under Technical Specifications requirements.
Big Rock Point normally operates with the reactor containment ventilated. Pre-liminary evaluation has shown that this condition cay hinder detection and ini-tiation of action for a loss of coolant accident caused by a pipe break smaller than those previously analyzed.
The reactor feed-water system and the water inventory normally present in the steam drum could accommodate the reactor coolant lost during a very small break.
In this case, reactor trip might not occur due to lov steam drum level. Previous analyses have assumed that the reactor would trip as a result of increased pres-sure in the containment. Recent, preliminary evaluation has identified that very small breaks might exist for which the containment ventilation system could pre-vent, or significantly delay, an increase in containment pressure. Delay of reactor scram in this case vould result in the introduction of steam to the con-tainment atmosphere, thereby increasing containment temperature.
Subsequent initiation of the reactor depressurization systen. might result in containment temperature exceeding the design limit considered in the Final Hazards Summary report.
Several indicators exist by which the operator would know that a very small bresk had occurred. Principal indicators (alarmed in the control rocm) are containment temperature and dew point temperature monitors and low levels for both the conden-sate storage tank and condenser hot well. Additional indications include recircu-lating pump room temperature and steam leak detectors (not individually alarmed),
observed mismatch in steam flew and feed flow, and local alarms on continuous air monitors.
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At this time, it is not known whether the condition discussed above would result in development of an unsafe condition or exceeding analyzed temperatures.
Consumers Power Company is initiating a detailed analysis of this problem.
This type of analysis (considering the effect of varying containment ver:'!Lation con-ditions) has not been previously performed for Big Rock Point and nethods must be developed for performing the analysis. This analysis is currently expected to be ccepleted in late su==er of 1979 Consumers Power Company considers it prudent to initiate temporary corrective actions to alleviate any problem which may exist. A containment temperature or dev point temperature alarm vill be set to detect increases from normally observed conditions.
Procedural corrective action vill require the operator to immediately close the ventilation system intake and exhaust valves on receipt of this alarm.
This action vould lead to an increase in containment pressure in the event a very small break LOCA exists, thereby initiating reactor trip.
The discovery of this condition is not considered a reportable occurrence because of the uncertainty as to whether an unuafe condition could exist.
If the analysis discussed above determines that permanent corrective action is required to prevent development of an unsafe condition, a licensee event report vill be submitted.
David A Bixel (Signed)
David A Bixel Nuclear Licensing Administrator CC:
Director, Office of Nuclear Reactor Regulation Director, Office of Inspection and Enforcement l
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