ML20084Q115

Ro:On 740223,following Repairs to tube-to-shell Side Gasket in RHR 1B Sys Hx,Rhr Svc Water Pump Started & Spike from 200-1000 Cps Immediately Received on Svc Water Process Monitor.Annunciator Response Procedure Will Be Reviewed

ML20084Q115
Person / Time
Site:	Quad Cities
Issue date:	03/25/1974
From:	Kalivianakis N COMMONWEALTH EDISON CO.
To:	Oleary J US ATOMIC ENERGY COMMISSION (AEC)
References
NJK-74-11, NUDOCS 8306130127
Download: ML20084Q115 (2)

Text

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March 25, 1974 Hr. John F. O ' Leary, Director Directorate of Licensing Regulation U. S. Atomic Energy Commission Washington, D. C. 20545 Subj ect: Quad-Cities Nuclear Power Station, Unit 1 Docket No. 50-254 DPR-29, Appendix A, Section 6.6.B.2.b

Dear Mr. O ' Leary:

The purpose of this letter is to recort a variance in the perfornance of the Residual Heat Removal (RHR) system from that innlied by the FSAR. Recent experience with a heat exchanger leak resulted in torus water leaking to the service water piping and being discharged to the river with the subsequent startun of the service water systen.

The FSAR states that reactor water leakage into the service water system is prevented by raintaining a higher pressure on the service water, or tube, side of the heat exchanger while the service water system is in operation. With the shell side of the heat exchanger constantly pressurized by the ECCS Fili System, the surnose of this design feature is defeated when a tube to shell side leak exists and the service water pumps are off.

DESCRIPTION OF EVENT On February 23, Ic74 repairs were completed to a tube-to-shell side gasket in the IB RHR system heat exchanger. When the heat exchanger was returned to service, an RHR service water pump was started and a spike from 200 to 1000 cps was immediately received on the service water process radiation monitor.

EVALUATION l

A calculation of the concentration in the discharge bay could not -)

be made with any degree of accuracy due to the transient nature of i the nonitor spike and flows involved. The duration of the spike '

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o O O Mr. J. F. O ' Leary March 25, 1974 was estimated to be only a few seconds since the monitor reading was decreasing to normal when the operator observed it after re-ceiving the alarm. A sarole of the water in the heat exchanger before the repair was analyzed and the most significant isotopes present were determined to be 1 -131 (2.39 x 10-5 ut/mi), cs-134 (5.00 X 10-4 ut/ml) and cs-137 (1.19 x 10-3 uc/mi) . However, the heat exchanger had been drained for maintenance after that sample was obtained. in summary, due to the small volume of water dis-charged and the short duration of the release, it was concluded that this should be classified as an unusual event to; report the design performance of the RHR system rather than an uncontrolled release. This conclusion has been discussed with the Directorate of Regulatory Operations-Region Ill .

Although in this case the cause of the Process Radiation Monitor alarn was readily apparent, the annunciator response procedure will be reviewed to insure that it leads to the early detection of heat exchanger leaks. The surveillance procedure for the RHR Service Water System will also be revised to include a check of the process radiation monitor recorder after each pump operation.

Any detectable increase in reading would then lead to a more thorough investigation and timely repair of the leak to minimize the frequency of releases of this nature.

Very truly yours, -

COMMONWEALTH EDISON COMPANY QUAD-clTI ES NUCLEAR POWER STATION bo , _

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N. . Kallvianakis Station Superintendent NJK/lk cc: Regional Director Directorate of Regulatory Operations - Region t il 4