ML20216J809

Informs That New Diaphragm Matl Has Corrected Sticking Problem Associated with Increased Control Rod Drive Scram Times.Augmented Testing of Valves at Monticello Has Been Discontinued

ML20216J809
Person / Time
Site:	Monticello
Issue date:	09/24/1999
From:	Day B NORTHERN STATES POWER CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
NUDOCS 9910060171
Download: ML20216J809 (2)

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i Northem states Power company Monticello Nuclear Generating Plant 2807 West County Road 75 Monticello, MN 55362 l

September 24,1999 l

U S Nuclear Regulatory Commission l Attn: Document Control Desk Washington, DC 20555 MONTICELLO NUCLEAR GENERATING PLANT Docket No. 50-263 License No. DPR-22 Closure of ASCO Scram Pilot Valve Diaphragm issue ,

l Ref.1 Letter from W J Hill, NSP, to NRC Document Control Desk, " Transmittal of Plan on Interim Recommendations of BWR Owners' Group Regulatory Response Group Regarding Viton CRD SSPV Response Time Delay", May 10,1996.

Ref. 2 Letter from W J Hill, NSP, to NRC Document Control Desk, " Update on Dual ASCO Scram Pilot Valve issue", June 19,1997 Ref. 3 Letter from M F Hammer, NSP, to NRC Document Control Desk, "1998 Update on ASCO Scram Pilot Valve Diaphragm Issue", May 6,1998 On February 16,1996, the BWROG Regulatory Response Group (RRG) provided guidance related to testing of dual type ASCO Scram Solenoid Pilot Valves (SSPVs) with Viton internals and testing of the Alternate Rod Insertion (ARI) system. By letter dated May 10,1996 (Ref.1), Northern States Power (NSP) notified the NRC of the intent to monitor Monticello's SSPV performance and made the following commitment:

CRD SSPV Viton diaphragm perfonnance willbe monitoredin accordance with U the BWROG recommendations until a long term solution is implemented.

In 1997, General Electric (GE) qualified a replacement material designated as Viton 515AB. As a test of the new material, Monticello then replaced four Viton A SSPV B\

Solenoid Valve-118 (SV-118) exhaust valve diaphragms with the new Viton 515AB 0 material. The NRC was informed of this installation (Ref. 2) and NSP's intent to continue monitoring SSPV performance.

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, USN,RC September 24,1999 Page 2 During Monticeho's 1998 refueling outage, all remaining SV-118 SSPV Viton A exhaust diaphragms were replaced with the new Viton 515AB material developed and qualified by GE. (Other SSPV Viton A components which did not contribute to the problem associated with increased control rod drive scram times caused by sticking diaphragms were not replaced. Note that NSP's May 6,1998 letter (Ref. 3) did not make this differentiation.) This action fulfilled the above 1996 commitment.

l To ensure the new material continued to function as intended, NSP continued testing the CRDs per the BWROG's recommendations until NSP was satisfied with the diaphragms' performance. Therefore, in NSP's May 6,1998 letter (Ref. 3), the following commitment was made:

NSP will continue to monitor the CRD scram times in accordance with the BWROG recommendations until satisfactory performance has been established.

The replacement diaphragms made from Viton 515AB have demonstrated satisfactory performance during qualification testing and post-installation augmented surveillance testing. Therefore, it is concluded the new diaphragm material has corrected the sticking problem associated with increased control rod drive scram times. Accordingly, the augmented testing of these valves at Monticello has been discontinued. Control rod drive operability will continue to be demonstrated in accordance with existing Monticello Technical Specification Section 3.2 requirements.

Please contact Marcus Voth at 612-271-5116 if you have any questions related to this submittal.

rh Byron D. Day Plant Manager Monticello Nuclear Generating Plant c: Regional Administrator-Ill, NRC NRR Project Mgr., NRC NRC Resident inspector State of Minnesota Attn: Steve Minn J E Silberg i

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