ML20149J519

Errata to NRC Info Notice 97-040, Potential Nitrogen Accumulation Resulting from Backleakage from Safety Injection Tanks. Last Paragraph Revised

ML20149J519
Person / Time
Issue date:	06/26/1997
From:	NRC (Affiliation Not Assigned)
To:	ARKANSAS POWER & LIGHT CO., BOSTON EDISON CO., CONSOLIDATED EDISON CO. OF NEW YORK, INC.
References
IEIN-97-040-ERR, IEIN-97-40-ERR, NUDOCS 9707280250
Download: ML20149J519 (1)

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UNITED STATES J NUCLEAR REGULATORY COMMISSION OFFICE OF NUCLEAR REACTOR REGULATION WASHINGTON, DC 20555-0001 June 26,1997 NRC INFORMATION NOTICE 97-4n: POTENTIAL NITROGEN ACCUMULATION RESULTING FROM BACKLEAKAGE FROM SAFETY INJECTION TAPMS Addressees All holders of operating licenses or construction permits for presturized-water reactors.

Purpose The U.S. Nuclear Regulatory Commission (NRC) is issuing this information notice to alert addressees to potential nitrogen accumulation in interfac ng systems resulting from backleakage from safety injection tanks (SITS). It is expected that recipients will review the information for applicability to their facilities and consider actions, as appropriate, to avoid similar problems. However, suggestions contained in this information notice are not NRC requirements; therefore, no specific action or written response is required.

Description of Circumstances Waterford On November 19 and 21,1996, Waterford Generating Station, Unit 3, experienced waterhammer events on the low-pressure safety injection (LPSI) B train. On November 19, 1996, the control room pressure gauge was observed to spike to approximately 3.55 MPa

[500 psig)(normal operating pressure is approximately 1.2 MPa [160 psig)). On November 21,1996, the train B piping was vented, and a strip chart recorder was installed to monitor pressure. A pressure of 4.65 MPa [660 psig) was observed following the start of the pump. Shortly thereafter, the LPSI train B flow control valve was found partially open because of a valve mispositioning error by the operations crew. The valve was closed, and the pump started without a pressure transient. Apparently no structural damage resulted from the waterhammer events. 1 On December 13,1996, LPSI train A experienced a waterhammer event. During a routine surveillance run of LPSI pump A, the pressure spiked to approximately 2.3 MPa [317 psig).

The licensee's investigation after this event utilized ultrasonic testing (UT) to inspect high points in the LPSI piping. The licensee identified gas voiding in the horizontal run of the two A train injection lines of 30.5 cm (12 inches] and 35.5 cm [14 inches) of arc. The injection lines are 20 cm [8 inches)in diameter. The gas was sampled and found to be approximately 97 percent nitrogen. The licensee canc'uded that nitrogen-saturated water from the SIT (the SIT has a 4.6-MPa [650-psig) nitrogen blanket) was leaking back to the LPSI system. At reduced pressures such as those found in the LPSI system piping, the nitrogen comes out of solution and forms the gas voids, l H' O W f p N =

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