ML18054B296

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Submits Addl Info Re Station Blackout Rule 10CFR50.63. Independent Makeup Sys Which Would Be Available to Maintain Reactor Coolant Inventory During Station Blackout Condition Not Required
ML18054B296
Person / Time
Site: Palisades Entergy icon.png
Issue date: 12/11/1989
From: Berry K
CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.)
To:
NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
TAC-68578, NUDOCS 8912150082
Download: ML18054B296 (2)


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consumers Power Kenneth W Berry Director POWERiNii Nuclear Licensing MICHlliAN'S PRDliRESS General Offices: 1945 West Parnall Road, Jackson, Ml 49201 * (517) 788-1636 December 11, 1989 Nuclear Regulatory Commission Document Control Desk Washington, DC 20555 DOCKET 50-255 - LICENSE DPR PALISADES PLANT -

ADDITIONAL INFORMATION RELATED TO STATION BLACKOUT RULE 10CFR50.63 (TAC No. 68578)

Consumers Power Company letter dated April 17, 1989 provided Palisades response to the Station Blackout Rule 10CFR50.63 (52FR23203). That letter noted Consumers Power Company was evaluating the potential for excess primary coolant system leakage via the control rod *drive mechanism (CRDM) seals. This letter provides the results of that evaluation.

The control rod drive mechanisms (CRDM) at Palisades are of a rack and pinion design. The rotating shaft which drives the pinion gear penetrates the primary coolant system pressure boundary. This penetration is closed by means of a face-type rotating seal which is cooled by component cooling water.

During a Station Blackout (SBO) event, component cooling water flow to the seals would be lost. The seal face could be exposed to a steam environment if the primary coolant system (PCS) inventory loss were sufficient to result in draining the pressurizer, thus allowing the formation of a steam bubble in the reactor vessel head.

During normal operation, total CRDM seal leakage is in the range of 0-400 ml/hr. This rate was considered to be insignificant when compared to the 100 gpm overall PCS leakage assumed in the SBO analysis. However, it was identified that no data existed regarding steam leakage past the CRDM seals at elevated temperatures and pressures.

  • To determine the performance of the CRDM seals during a postulated SBO, Consumers Power Company participated in a CRDM seal leakage testing program conducted by Combustion Engineering. The objective of the testing was to determine the CRDM seal leak rates for.saturated water and steam at pressures ranging between. 200 psig and 2200 psig. To simulate the loss of component cooling water to the seals and the loss of HVAC in the containment, the seal

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  • Nu-clear Regulatory Commission Palisades Plant Addtl Info Station Blackout Rule December 11, 1989
  • 2 housing was heated to various external ambient temperatures ranging from 200°F to 500°F. The results of this testing indicate that the maximum CRDM seal leak rate for either steam or water is bounded by 10 cc/min (0.00264 gpm) per seal. For Palisades, which has 45 CRDM seals, this results in a total maximum CRDM seal leakage rate of 0.119 gpm.

As described in our April 17, 1989 letter, the ability to maintain adequate reactor coolant inventory to ensure core cooling can be maintained has been assessed for a four-hour period assuming 100 gpm (25 gpm per pump) primary coolant pump seal leakage. The maximum expected CRDM seal leakage rate (0.119 gpm) is insignificant when_compared to the 100 gpm leak rate assumed for the primary coolant pump seals. Thus, our conclusion that the maximum expected rate of reactor coolant inventory loss under SBO conditions will not result in core uncovery during an SBO of four hours remains valid. Our April 17, 1989 letter concluded that an AC independent makeup system which would be available to maintain reactor coolant inventory during SBO condition was not required.

Based on the information presented, that conclusion remains valid.

Kenneth W Berry Director, Nuclear Licensing CC Administrator, Region III, USNRC NRC Resident Inspector - Palisades OC1289-013S-NL01