ML20137H640

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Advises That Ga Technologies,Inc Has Confirmed That Core Damage Estimate Obtained from Xe-133 Concentration Can Be Independently Confirmed by Use of Kr-88 in Primary Coolant. Procedure RERP-CORE Will Be Revised by 851231
ML20137H640
Person / Time
Site: Fort Saint Vrain Xcel Energy icon.png
Issue date: 11/25/1985
From: Gahm J
PUBLIC SERVICE CO. OF COLORADO
To: Berkow H
Office of Nuclear Reactor Regulation
References
TASK-2.B.3, TASK-TM P-85446, TAC-44443, NUDOCS 8512020438
Download: ML20137H640 (2)


Text

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z 16805 WCR 19 1/2, Platteville, Colorado 80651 November 25, 1985 Fort St. Vrain Unit No. 1 P-85446 Director of Nuclear Reactor Regulation U. S. Nuclear Regulatory Commission Washington, D.C. 20555 ATTENTION: Mr. H. N. Berkow, Project Director Special and Standardization Project Directorate Docket No. 50-267

SUBJECT:

POST ACCIDENT SAMPLING SYSTEM

REFERENCE:

(1) PSC Letter Dated September 20, 1985 Gahm to Hunter (P-85328)

Dear Mr. Berkow:

In a letter dated September 20, 1985, (Reference 1) Public Service Company stated that we were working with GA Technologies, Inc. to evaluate the possibility of implementing a backup method for evaluating core damage in addition to our existing procedure which utilizes Xe-133 concentration in the reactor coolant.

The analysis performed by GA Technologies, Inc. concluded that the concentration of water, carbon monoxide, carbon dioxide and other gaseous impurities in the primary coolant can only be used to provide an upper bound estimate of the total amount of graphite that has been oxidized. The distribut.on of oxidation within the core, reflector and core support structures, cannot t. discerned and the amount of oxidation would be expected to ury significantly among these graphite components due to variations in graphite types.

With regard to core temperature information, core temperatures during Loss of Forced Circulation (LOFC) at locations other then the core support blocks can only be inferred from core outlet thermocouple information and additional calculations. GA Technologies, Inc. (p0k i

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concluded that the core outlet thermocouples are primarily of value in indicating to the operators whether the LOFC transient is proceeding in a manner similar to that analyzed and described in the FSAR.

GA Technologies, Inc. and Public Service Cor.pany believe that fission product activity is the best indicator of core damage. To this end, procedure RERP-CORE is in place and contains procedural guidance for determining core damage based on Xe-133 concentration in primary coolant. GA Technologies, Inc. has confirmed that the core damage estimate obtained from the Xe-133 concentration can be independently confirmed by utilizing the Kr-88 concentration in primary coolant.

Procedure RERP-CORE will be revised by December 31, 1985, to incorporate the use of Kr-88 concentration in primary coolant to confirm the core damage estimate obtained from the Xe-133 concentration in primary coolant.

Should you have any questions concerning this matter, please contact Mr. M. H. Holmes at (303) 480-6960.

Sincerely,

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J . Gahm Manager, Nuclear Production Fort St. Vrain Nuclear Generating Station JWG: FJB/so