NUREG-0103, Safety Evaluation Supporting Relief from Inservice Insp Requirements of ASME Boiler & Pressure Vessel Code Requiring Quarterly Stroke Testing of RCS Valves & Denying Relief from Code Requirements for Valve RC-11 Testing

Safety Evaluation Supporting Relief from Inservice Insp Requirements of ASME Boiler & Pressure Vessel Code Requiring Quarterly Stroke Testing of RCS Valves & Denying Relief from Code Requirements for Valve RC-11 Testing

ML20202H374
Person / Time
Site:	Davis Besse
Issue date:	03/06/1986
From:	Office of Nuclear Reactor Regulation
To:
Shared Package
ML20202H361	List: NUREG-0103, Safety Evaluation Supporting Relief from Inservice Insp Requirements of ASME Boiler & Pressure Vessel Code Requiring Quarterly Stroke Testing of RCS Valves & Denying Relief from Code Requirements for Valve RC-11 Testing
References
RTR-NUREG-0103, RTR-NUREG-0737, RTR-NUREG-103, RTR-NUREG-737 GL-83-37, TAC-57291, NUDOCS 8604150240
Download: ML20202H374 (3)

Text

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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION REQUEST FOR RELIEF FROM CERTAIN RE0UIREMENTS OF SECTION XI 0F THE ASME BOILER AND PRESSURE VESSEL CODE T0i.ED0EDIS0NCOMPANY AND THE CLEVELAND ELECTRIC ILLUMINATING COMPANY DAVIS-BESSE NUCLEAR POWER STATION, UNIT NO. 1 1

j -DOCKET N0. 50-346

1. BACKGROUND The NRC staff has identified the reactor coolant system (RCS) vents as an extension of the reactor coolant pressure boundary and as such they must meet applicable inservice inspection requirements described in 10 CFR 50.55a(g). Further, ASME Boiler and Pressure Vessel Code,Section XI of the 1977 Edition through the Summer 1978 Addenda, requires quarterly stroke testing of the high point vent valves.

I By letter dated March 22, 1985 (Serial No. 1123), Toledo Edison Company  ;

(the licensee) requested relief from certain testing requirements  !

contained in Section XI of the ASME Boiler and Pressure Vessel Code, '

1977 Edition through Suniner 1978 Addenda (the Code), for pressurizer and I RCS high point vent valves. Alternative testing was proposed.

2. DESCRIPTION OF REQUESTED RELIEF AND PROPOSED ALTERNATIVE TESTING j l

Subsection IWV of the Code requires that RCS and pressurizer high point l vent valves be classified as Category B, active valves and specifies that such valves be stroked quarterly. The licensee seeks relief from quarterly stroke testing and proposes instead that the RCS and pressurizer high point vent valves be full stroke tested during each cold shutdown lasting more than 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />, but not more frequently than I once every three months.

3. EVALUATION The RCS.and pressurizer vent valves at Davis-Besse, RC-11, RC-200, RC-239A, SV4608A and B, and SV4610A and B, serve two active functipns:

1. The vents may be used to exhaust noncondensible gases and/or steam from the primary system that could inhibit natural circulation core cooling.

I 9604150240 860306 PDR ADOCK 05000346 i G PDR, l

2. The vents may also be used to enhance core cooling by reducing primary pressure and enhancing High Pressure Injection and/or Makeup Flow. i l

In addition, valve RC-11 functions as the Pressurizer Power Operated i Relief Valve (PORV) block valve.  ;

The RCS vent valves, SV4608A and B, and SV4610A and B, vent directly to containment atmosphere. As such, cycling these valves during other than cold plant conditions could result in the release of primary coolant at an excessive rate to the containment atmosphere. The pressurizer vent path through valves RC-200 and RC-239A vents to the Pressurizer Quench Tank (PQT). As such, cycling these valves during other than cold conditions could result in the release of primary s coolant at an excessive rate.to the PQT possibly causing the PQT

? rupture disk to fail and releasing primary coolant to the containment u atn.osphere. This fact is reflected in Generic Letter 83-37 dated November 1, 1983, and entitled, "NUREG-0737 TECHNICAL SPECIFICATIONS."

This document, sent to all pressurized water reactor licensees, provided RCS vents. guidanc.e on Technical This guidance suggests Specifications that RCS vent paths on, among(other including things, pressurizer vents) be demonstrated operable at least once every 18 months by cycling each vent valve in the vent path through at least one complete cycle of full travel during cold shutdown or refueling. The licensee's proposed alternate testing for RC-200, RC-239A, SV4608A and B and SV4610A and B, consisting of valve stroking during each cold shutdown of greater than 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />, but not more frequently than once every three months, is conservative with respect to the guidance provided in Generic letter 83-37 and is acceptable to the NRC staff.

As stated earlier, valve RC-11 functions as the PORV block valve and is open during normal plant operations. Cycling the valve would not increase the possibility for release of primary coolant under conditions when the PORV is operable. If the PORV is inoperable, the block valve would be closed and would remain closed. Further, the safety significance of the PORV block valves is considered important enough such that they are specifically included in Standard Technical Specifications for Babcock and Wilcox Pressurized Water Reactors l (NUREG-0103, Revision 4). The specification requires that the PORV block valve be demonstrated operable by operating it through one complete cycle of full travel once every 92 days in Modes 1, 2 and 3.

Based on the reasons cited above, we have determined that the block  ;

valve function takes precedence over the venting function; the l licensee's request for relief from quarterly stroke testing of RC-11 is '

denied.

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4. CONCLUSION We have concluded, based on the considerations discussed above, that 1

granting of relief is authorized by law and will not endanger life or property or the common defense and security and is otherwise in the public interest giving due consideration to the burden that could result if the requirements were imposed on the facility. The relief request denied by the NRC staff requires compliance with Code requirements.

Dated: March 6, 1986 Principal contributor: W. G. Guldemond

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