ML20151C997
| ML20151C997 | |
| Person / Time | |
|---|---|
| Site: | Calvert Cliffs  |
| Issue date: | 04/06/1988 |
| From: | Lemons J BALTIMORE GAS & ELECTRIC CO. |
| To: | NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM) |
| References | |
| NUDOCS 8804130325 | |
| Download: ML20151C997 (4) | |
Text
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s BALTI M ORE GAS AND ELECTRIC CHARLES CENTER + P. O. BOX 1475 BALTIMORE, MARYLAND 21203 J AMES R. LEMONS MANAGER NUCLE Am OPERAToNs DE PARTutNT April 6,1988 U. S. Nuclear Regulatory Commission Washington, DC 20555 ATTENTION:
Document Control Desk SUBJECf:
Calvert Cliffs Nuclear Power Plant Unit Nos.1 & 2; Docket Nos. 50-317 & $0-318 Request for Relief from Relief Valve Testing Requirements in Section XI of the ASME Boiler and Pressure Vessel Code. Article IWV-3500 Gentlemen:
Pursuant to 10 CFR 50 Ha(gX5Xiii),
we hereby request relief from certain requirements in the ASME Boiler and Pressure Vessel Code Section XI,1983 Edition with Addendum through Summer 1983.
COMPONENTE FOR WillCil RELIEF IS REOUESTED All ISI Class 2 and 3 relief valves with the exception of the main steam safety valves.
ASME REOUIREMEN T. FROM WillCII REl.lEF IS REOUF5TED 1
1 Article IWV-3500 states "relief valve setpoints shall be tested in accordance with ASME PTC 25.3-1976." The article also specifies when additional tests are required and what corrective actions are necessary when a valve fails to function properly, i
I l
As a result of our ASME Section XI repair / replacement program instituted on l
April 1,1987, we have determined that a number of our ISI Class 2 and 3 relief valves l
may have incorrectly calculated setpoints. Because some of our relief valve setpoints l
may be in error, we cannot conclude that we meet the testing requirements of Article l
IW V-3500 of ASME Section XI. Thus, we are requesting relief from ' 2e testing requirements of Article IWY-3500 until we can verify / establish the correct setpoints.
BASIS FOR REl.lEF The ANSI /ASME code states that the set pressure of at least one of the pressure relief l
devices connected to a system shall not be greater than the system design pressure.
Also, the set pressure determination shall take into account the effets,of constant backpressure in the relief valve discharge piping.
any
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8804130325 000406 PDR ADOCK 05000317 ql q
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Document Control Desk April 6,1988 Page 2 Some of the calculated relief valve setpoints at Calvert Cliffs may be in error due to one or both of the factors listed below.
1.
Relief valve setpoint testing allows the operator to set the relief valve setpoint to a higher pressure than system design pressure by allowing a positive tolerance on the band of acceptable setpoint values (e.g.,
2485 25 psig).
2.
The constant backpressure was added to the setpoint value for some relief valves.
The net result of the errors listed above is to cause some relief valves to have setpoints that are slightly higher than the system design pressure. We suspect that this error affects many ISI Class 2 and 3 relief valves.
We estimate it will take eight months to review all of the approximately 150 Class 2 and 3 relief valve setpoints and to verify and/or establish new setpoints in accordance with the original construction codes. After that, several more months may be required to make the necessary setpoint adjustments.
We have conducted a preliminary evaluation and have determined that the increase in overall system stress levels is insignificant. Therefore, the plant systems are fully capable of performing their design functions during the period for which relief is requested.
ACrlONS TAKEN IN LIEU OF SECTION XI REOUIREMENE Pending completion of the setpoint verification program, we will continue to test the valves based upon the existing setpoints in accordance with IWV-3500. As shown in the following bounding analysis, the existing setpoint values are sufficient to prevent system pressure from causing stresses in excess of code allowable stresses. The analy*is is based upon conservatively postulating the existence of a relief valve with a setpoint error caused by the coincident misapplication of constant backpressure and positive setpoint tolerance result;ng in a "worst case" valve setpoint. The values for constant backpressure and setpoint band tolerance are worst case values chosen from a review of the relief valve data sheets and setpoint testing procedures. These values are 20 psi backpressure and 25 psi positive tolerance on setpoint. Therefore, the theoretical "worst case" relief valve is assumed to have a set pressure that is 45 psi above the code allowable set pressure or system design pressure.
The ' worst case" relief valve is then assumed to exist in each of the following five systems; Safety injection System, Boric Acid System, Saltwater System, Service Water System and Component Cooling Water System. As a further added conservatism, the postulated "worst case" relief valve is assumed to be located at the highest stressed location for each system as identified in the stress analysis report for that system.
The analysis evaluates the additional stresses in each of the five plant systems caused by an overpressure condition of 45 psi above the system design pressure (i.e., the net effect of the relief valve setpoint being 45 psi high).
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Document Control Desk April 6,1988 Page 3 It is important to note that the analysis results as tabulated in Attachment (1) are conservative for the reasons listed below.
1.
A 20 psi constant backpressure does not exist for every relief valve. afany valves have a O psi backpressure or values less than 20 psi.
2.
A positive 25 psi above system design pressure is the limit per procedures that any relief valve setpoint can be adjusted. Many relief valves have setpoint band tolerances of less than 25 psi.
As can be seen from the stress analysis results in Attachment (1) for each of the piping systems, the additional stress due to the postulated "worst case" relief valve setpoint is negligible under any loading combination. The inaccurate setpoints do not preclude the system relief valves from performing their design safety function. The resultant stresses are within the code allowable values, and as such, the systems meet the requirements of the code.
Schedule for Actions Taken in Lieu of Reauirements Relief valve setpoint testing will continue in accordance with the established surveillance test schedule.
Schedule for Comoliance The relief we request is temporary. We estimate that we will have identified all relief valves whose setpoints are not in accordance with their construction code and will have determined the correct setpoints by November 1988. This effort is now underway.
We intend to adjust relief valves that do not require an outage expeditiously and we plan to make those adjustments that recuire an outage during the spring 1989 (Unit 2) refueling outage and spring 1989 (Unit 1) maintenance outage.
Pursuant to 10 CFR 170.21, we are including BG&E Check No. 1915929 in the amount of
$150.00 for the application fee for this request.
Should you have further questions regarding this matter, we will be pleased to discuss them with you.
Very truly yours, ff
" <>* W JRL/ WPM /KBC/SRC/dtm
l Document Control Desk April 6,1988 Page 4 cc-D. A. Brune, Esquire J. E.
Silberg, Esquire R. A.Capra, NRC S. A.McNeil,NRC W. T. Russell, NRC D. C. Trimble, NRC