ML20043F825

Special Rept:On 890425,gas Sample Drawn from PASS Indicated Reactor Gases Not Removed from Liquid Sample Rcs.Four RCS Liquid Samples Successfully Obtained & Two of 4 Samples Produced RCS Dissolved Gas Samples

ML20043F825
Person / Time
Site:	Millstone
Issue date:	06/08/1990
From:	Scace S NORTHEAST NUCLEAR ENERGY CO., NORTHEAST UTILITIES
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
MP-90-561, NUDOCS 9006180192
Download: ML20043F825 (2)

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June 8, 1990 MP-90-561 l Docket No. 50-423 Re: 10CFR50.36 I I

1 U.S. Nuclear Reculatory Commission Document Contr'ol Desli Washington, D.C. 20555 Gentlemen:

Millstone Nuclear Power Station, Unit No. 3 Post Accident Samnle System This Special Report is being submitted as an update to the Special Report submitted on May 3,1989.

On April 25,1989 at 1115 hours0.0129 days <br />0.31 hours <br />0.00184 weeks <br />4.242575e-4 months <br />, with the plant in Mode 1, at 100W power,2250 psia, and 586 degrees Fahrenheit, analysis of a gas sample drawn from the Post Accident Sample System,(PASS) indicated that reactor coolant gases were not being removed from the liquid. sample of the Reactor Coolant System (RCS).

The PASS can obtain liquid samples from the reactor coolant hot legs when RCS pres-sure is above 240 psig, or from the containment sump when the Containment Recircula-tion Spray System is operating. Pressurized reactor coolant liquid samples are isolated in the liquid sample loop. By then connecting the liquid sample loop to a gas sample loop through a four-way valve, the liquid sample expands and depressurizes. A small strip-ping pump acitates the sample, " stripping" the cases for collection in a gas sample chamber. The PASS can also obtain a sample of the containment atmosphere.

As directed by Regulatory Guide 1.97, Millstone 3 has a program to periodically verify PA!'S operabGo. The Millstone 3 program requires semi-annual surveillances be per-formed rc verify that samples can successfully be drawn from the containment atmo-sph% and the RCS, While not a surveillance requirement. the containment sump is sampled during the quarters between RCS samples.

From March 3,1988 to April 25,1989, several RCS liquid samples were successfully obtained, but attempts to separate reactor coolant gas samples from the liquid samples were unsuccessful. Throughout March and April 1989 corrective maintenance was per-formed on the system and successive RCS samples were drawn. Since April 1989 addi-tionhl actions have been accomplished including inspection of the liquid loop to gas loop four-way valve actuator and testing of the cas stripping pump. Root cause investigation of component failures was conducted with" General Dynamics Reactor Plant Services, surveillance procedures were reviewed and surveillances were performed more often than required by the program to enhance system reliability. Information has been shared with other plants with the same PASS design.

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From April 25,1989 to May 5,1990, four RCS liquid samples were successfully ob-tained, and two of the four samples produced RCS dissolved gas samples with accept-able gaseous activity. These samples were collected on February 23,1990 and May 5, 1990. Hydrogen and total gas were acceptable in the February 23,1990 sample. Howev.

er the total gas in the May 5,1990 sample was too hich, indicating a possible leak in the four-way valve between the liquid and gas loops. This possible leak will be investigated and appropriate corrective actions will be implemented. Improvements in collection of the dissolved RCS gas sample are due to changes in sampling techniques.

Additional design improvements are being evaluated with the intent of modifying the system to improve RCS dissolved gas collection reliability.

The licensee contact for this special report is Robert Conway, who may be contacted at (203) 444-5442.

Very truly yours, NORTHEAST NUCLEAR ENERGY COMPANY Steph n Director, Millstone Station ~

SES/RDC:tp cc: T. T. Martin, Recion I Administrator W. J.'Raymond,' Senior Resident inspector, Millstone Unit Nos.1, 2 and 3 D. H. Jaffe, NRC Project Manager, Millstone Unit No. 3