ML20129G221

Forwards Engineering Evaluation Rept AEOD/E506, Valve Stem Susceptibility to IGSCC Due to Improper Heat Treatment. Corrective Actions Suggested

ML20129G221
Person / Time
Site:	Brunswick
Issue date:	05/20/1985
From:	Ippolito T NRC OFFICE FOR ANALYSIS & EVALUATION OF OPERATIONAL DATA (AEOD)
To:	Jordan E, Ross D NRC OFFICE OF INSPECTION & ENFORCEMENT (IE), NRC OFFICE OF NUCLEAR REGULATORY RESEARCH (RES)
Shared Package
ML20129G226	List: ML20129G221 ML20129G270 ML20129G303
References
AEOD-E506, NUDOCS 8506070196
Download: ML20129G221 (2)

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MAY 2 0 tr i AE0D/E506 HEHORANDUM FOR: Denwood F. Ross, Deputy Director Office of Nuclear Regulatory Research Edward L. Jordan, Director Division of Emergency Preparedness and Engineering Response Office of Inspection and Enforcement FROM: Thomas A. Ippolito, Deputy Director Office for Analysis and Evaluation of Operational Data

SUBJECT:

VALVE STEM SUSCEPTIBILITY TO IGSCC DUE TO IMPROPER HEAT TREATMENT Enclosed is an Engineering Evaluation Report on the above subject recently completed by this office. Our evaluation indicates that valve stems made of 400 series stainless steel and heat treated to high hardness are highly susceptible to intergranular stress corrosion cracking (IGSCC). The excessive hardness can result from improper heat treatment. Since dis-crepancies in hardness between the actual measurement and the expected value based on heat treatment records existed in all four events evaluated, we conclude that excessive hardness may not be detected in either the licensee's or the supplier's QA programs. Also, the existing code require-ments regarding actual testing to verify the hardness for the stem material after heat treatment may not be adequate.

The stress corrosion cracking on valve stems described in this evaluation were discovered by close inspection after disassembly of the valves during refueling outages. None of the cracked stems were detected by the routine valve operability test programs for the identified plants. This indicates that the IGSCC on a valve stem could go undetected _ until failure occurs with a sudden shear of the stem upon actuation of the valve during system operation. Such failure can prevent the system from performing its safety function.

Therefore, we suggest the following:

1. RES should consider the adequacy of the existing code requirements with regard to assurance of proper hardness of martensitic stainless steel following the heat treatment process. If appropriate, RES should attempt to have such requirements included in the applicable code.

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2. IE should issue an IE Infonnation Notice to infona licensees of the potential generic problem concerning improper heat treatment of sten material made of 400 series stainless steel which could lead to IGSCC. This Information Notice should indicate that the gland packing section is the most likely location for the initiation of valve stem IGSCC.

Original signed by Thomas A. Ippolito Yhomas A. Ippolito, Deputy Director Office for Analysis and Evaluation of Operational Data

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