ML17037C144

Letter Reporting That the Nine Mile Point Reactor Was Scrammed from 25 Percent Power on November 20, 1969 and Advising That the Reactor Will Be Brought Critical and the Turbo-Generator Set Placed on the Line on December 8, 1969

ML17037C144
Person / Time
Site:	Nine Mile Point
Issue date:	12/06/1969
From:	Burt P Niagara Mohawk Power Corp
To:	Morris P US Atomic Energy Commission (AEC)
References
Download: ML17037C144 (4)

Text

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DOCKETED USAEC

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NIAGARA MOHAWK POWER CORPORATION NIAGARA "~ MOHAWK

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Nine Mile Point Nuclear Station P. 0. Box 32.

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DECB 1969 ~ -g Lycoming, New York 13093 REGUlATORY December 6, 1969 NlL SECTION DOCKET CLERK

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United States Atomic Energy Commission Division of Reactor Licensing Washington, D. C. 20545 Attention: Dr. Peter A. Morris, Director Gentlemen:

On Thursday,'ovember 20, 1969, the Nine Mile Point reactor was scrammed from 25 percent power. Thirty control rods, which were hooked up to a brush recorder, averaged 4.17 seconds for 90 percent insertion. The original 90 percent insertion time for ALL rods was 3.00 seconds.

During the approximate six-week time interval between the original and November 20th scrams, eight drives were continuously monitored for spurious. as well as planned scrams. Their times for 90 percent insertion increased approximately 40 percent during the monitoring period. During the November 20th scram, one rod was outside the Technical Specification limit of 5.3 seconds; Rod No. 24-23 scrammed in 5.32 seconds.

Inasmuch as excessive rod insertion time was experienced at Oyster Creek due to partially plugged 400 mesh inner rod drive strainers and the rate at which our tim-ing was increasing gave cause to suspect our next scram might be above the Technical Specification limi.t of 5 seconds average, it was decided to change out the strainers.

A screen having clear rectangular openings of 10 by 100 mils was installed in place of the original 400 United States standard .mesh. In this manner, the drive is protected while decreasing screen pluggage probability by an order of magnitude of approximately 400 times. The work was completed, including drive timing, on December 6, 1969. At this lime all rods have been scram tested under cold pressur-ized conditions with an average 90 percent insertion time of 2.7 seconds. IYhen the reactor reaches operating pressure and temperature and with approximately 5 percent bypass steam to the condenser, all rods will be individually scram tested.

Ne shall continue to honor commitments previously made of reporting rods whose 90 percent insertion time do not fall within the range of 1.9 to 3.6 seconds, also, if the average'f 129 rods is not within the range of 2.4 to 3.1 seconds.

The same eight drives as before will continue'to be constantly monitored and scram checked once every two weeks should a scram not occur in that period. In addition, they will be similarly tested before planned scrams from 50 percent power. Feed-water quality will be controlled at all times and especially monitored when impuri-ties might be added, such as when cutting in feedwater strings, new pumps, piping systems, and so on.

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United States Atomic Energy Commission Page 2 December 6, 1969 The following chemistry surveillance is performed and will continue to be in order to evaluate the crud introduced into the reactor water:

l. A 24-hour integrated crud sample is taken on the feedwater entering the reactor and analyzed daily. This sample tap is located so that it samples the feedwater just before the reactor regardless of feed-water path used.

2. A continuously recording turbidimeter is installed on the reactor feedwater to give assi. stance in evaluating trends.

3. A daily grab sample for crud is taken on the reactor water.

4. i&en either conductivity or the turbidimeter indicate that a con-densate demineralizer should be changed, the operating demineralizer outputs 'will be evaluated for both conductivity and crud to deter-mine which bed or beds should be switched.

5. Every effort will be made to keep feedwater crud levels low by frequent changing of demineralizers and by reduction of flow through the demineralizers where necessary.

6. i&en new parts of the feedwater cycle are being cut into service, every effort will be made to recirculate as much condensate back to the condenser, thereby polishing it through the demineralizers at a higher rate.

It is expected that the Nine Mile Point reactor will be brought critical and the turbo-generator set placed on the line on December 8, 1969. During the following week, additional feedwater heaters will be brought into service and power raised to the 50 percent level.

Very truly yours, P. Allister Burt Station Superintendent mjs cc: Mr. M. H. Pratt Mr. F. J. Schneider Mr. J. N. Ewart, Chairman, SR 5, A Board Mr. M. Hildr'eth, A.E.C. Compliance

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