ML19322B695

Ro:On 770418,routine Sample of Yard Drains Indicated a Ph Reading of 9.7.Caused by Partial Operation of Water Treatment Room Sump Pumps During Regeneration Cycle.Abnormal Change Will Be Reported to Duty Chemist

ML19322B695
Person / Time
Site:	Oconee
Issue date:	04/25/1977
From:	Parker W DUKE POWER CO.
To:
References
NUDOCS 7912050700
Download: ML19322B695 (2)

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w w u. o ma aa ra..sm. April 25, 1977 VsCE P8CSsDEnt TELE *=o%C: Asta 704 S'Ea= Peooweno= 373-4 c e 3 Mr. Norman C. Moseley, Director U. S. Nuclear Regulatory Commission Suite 818 230 Peachtree Street, Northwest Atlanta, Georgia 30303 Re: Oconee Nuclear Station Docket Nos. 50-269, -270, -287

Dear tir.' Moseley:

Oconee Nuclear Station Appendix B Technical Specification 1.2B requires that all water discharged from the plant site have a pH between 6.0 and 9.0. On April 18, 1977, a routine sampl.: of the yard drains indicated a pH reading of 9.7. The following is a description of the events lead-ing to this incident.

Since January 20, 1977, flow to the waste water collection basins (WCB) has been controlled to provide holb!p of radioactivity released to the WCB during a January 17, 1977 incident described in Reportable Occurrence Report R0-269/77-3. To reduce flow to the basins in order to eniunce holdup time, the two water treatment room (WTR) sump pumps have bem used only during the regeneration of a demineralizer or during acid or caustic additions to the WCB.

On April 18, 1977, a routine demineralizer regeneration was performed.

Part of the regener tion involves an acid / caustic injection followed by a demineralized water flush (approximately two hours in duration) to remove all traces of the addition from the system. The WrR sump pumps were placed in operation prior to the acid / caustic injection and were secured after one hour of flush water had been added. This method had been used successfully for several previous regenerations, and experience head indicated that essentially all the caustic was removed during the fir:,t hour of the flush. It is postulated that for this case, however, that all the caustic was not removed from the sump during the first hour of the flush. After the sump pumps were secured, the flush water over-flowed to the storm drains. The storm drains empty into the oil collec-tion pond which provides dilution before the water reached the yard drains and then entered the Keovee tailrace.

• Four and one-half hours after the sump pumps were secured, regeneration was completed. At this time, the pH at the yard drain was 6.4. Approxi-mately one-half hour later the'pH at the yard drain exceeded 9.0. The incident lasted approximately two and one-half hours, and the maxiaum pH recorded was 9.7. The pH of the water leaving the site was apprcximately 9.0 when the dilution factor resulting from mixing with the Kecwee tailrace j is considered. P.

7912050700 f #

. -v nr. Norman c. nocaley April 25, 1977 Page Two l

All other sources of highly alkaline materials on site were checked to assure that no other source could have caused this incident. The' procedure for regeneration of demineralizer resins has been revised to assure that the WTR sump pumps are operating for the entire regenera-tion cycle.

Our present policy of recording pH readings of the settling basins and yard drains every four hours and before and after completion of deminera-lizer regeneration will continue. Any abnormal change in pH will be reported to the duty chemist who will take appropriate measures. It is considered that implementation of the audible alarms on the yard drain pH monitors which will be completed by June 1, 1977 will prevent future occurrences of this incident.

Very truly yours, h.

Willir.m O. Parker, Jr. # A //

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