ML20205G422
| ML20205G422 | |
| Person / Time | |
|---|---|
| Site: | Perry  |
| Issue date: | 03/31/1999 |
| From: | NRC (Affiliation Not Assigned) |
| To: | |
| Shared Package | |
| ML20205G394 | List: |
| References | |
| NUDOCS 9904070243 | |
| Download: ML20205G422 (9) | |
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\ UNITED STATE 8
-g j NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 308eN201 e
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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO THE SECOND TEN-YEAR INSERVICE TEST PROGRAM RELIEF REQUESTS PERRY NUCLEAR POWER PLANT q DOCKET NUMBER 50-440
1.0 INTRODUCTION
The Code of FederalRegulations,10 CFR 50.55a, requires that inservice testing (IST) of certain American Society of Mechanical Engineers (ASME) Code Class 1,2, and 3 pumps and valves be performed in accordance with Section XI of the ASME Boiler and Pressure Vessel Code (the Cooe) and app;icable addenda, except where alternatives have been authorized or relief has been requested by the licensee and granted by the U. S. Nuclear Regulatory Commission (Commission or NRC) pursuant to Sections (a)(3)(i), (a)(3)(ii), or (f)(6)(i) of 10 CFR 50.55a. In proposing attematives or requesting relief, the licensee must demonstrate that (1) the proposed altematives prodde an acceptable level of quality and safety; (2) compliance would result in hardchip or unusual difficulty without a compensating increase in the level of quality and safety; or (3) conformance is impractical for its facility. Section 50.55a authorizes the Commission to approve alternatives and to grant relief from ASME Code requirements upon making the necessary findings. NRC guidance contained in Generic Letter (GL) 89-04, " Guidance on Developing Acceptable Inservice Testing Programs," provides alt 9matives to the Code taquirements determ:ned to be acceptable tc the staff. Further guidance was given in GL 89-04, Supplement 1, ed NUREG-1482, " Guidelines for Inservice Testing at Nuclear Power Plants."
The IST program for the Perry Nuclear Power Plant, second 120-month interval was submitted in a letter dated July 22,1998. The second ten-year interval began on November 18,1998, and will end on November 17,2008. The IST program was developed in accordance with the 1989 Edition of the ASME Boiler and Pressure Vessel Code which references the Operations and Maintenance (OM) standards Part 1, Part 6, ud Part 10 (OM-1, OM-6, and OM-10), for IST of safety and relief devices, pumps, and valves, respectively. ,
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} NRC's findings with respect to authorizing attematives and granting or denying the IST program )
[ relief requests, VR 6, VR-8, PR-3, and PR-6 are given below. Due to the licensse's urgent need !
for relief from these Code requirements during its upcoming refueling outage, these four relief requests were evaluated separately. A forthcoming SE will include results of a review of the remaining relief requests and deferred test justifications contained in the licensce's submittal. )
l ENCLOSURE 9904070243 DR 990331 F p ADOCK 05000440 '
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2.0 VALVE RELIEF REQUESTS 2.1 Rsilef Reauest VR-6 -
The licensee has requested relief from the requirements of OMa-1988, Part 10, Paragraphs 4.3.1 and 4.3.4 which require safety and relief valves and rupture disks to meet the requirements of OM-1987, Part 1 for all Code class pressure relief devices. The licensee proposes to adopt ASME OM Code-1995 Appendix I as the mandatory Code for testing pressure relief devices.
2.1.1 Licensee's Basis for Requesting Relief The licensee states:
OM Part 1 has evolved over the past decade; such that it is now a Code (ASME OM Code-1995 Appendix I) at opposed to a Standard (ASME/ ANSI OM Part 1- 1987), and now provides guidance on establishing acceptance criteria, grouping of valves, and additional testing. ' Perry Nuclear Power Plant has evaluated the Standard OM Part 1-1987 versus OM Code 1995 Appendix l and determined that the requirements of ASME OM Code. Edition 1995 are preferred for performance of inservice testing of nuclear power plant pressure relief devices.
Therefore, PNPP is requesting the use of the mandatory appendix, ASME OM Code- l 1995 Appendix 1, inservice Testing of Pressure Relief Devices in Light-Water Reactor j Power Plants. l The use of this mandatory appendix is supported by the Proposed Rule Change to 10 CFR Part 50, dated December 3,1997. The proposed amendment for IST would require licensees to implement the 1995 Edition of the ASME Code for Operation and Maintenance of Nuclear Power Plants (CM Code) for Class 1, Class 2, and Class 3 pumps and valves prior to the start of a new 120 month interval.
2.1.2 Alternate Testing ,
l The licensee proposes:
Adopt the mandatory appendix, ASME OM Code - 1995 Appendix 1, inservice Testing of Pressure Relief Devices in Light-Water Reactor Power Plants as the mandatory Code for testing pressure relief devices.
2.1.3 Evaluation This relief request is generic to all pressure relief devices in the licensee's IST program. The pressure relief devices include s fety valves, relief valves, pilot operated pressure relief valves, power actuated pressure relief valves, nonrec' 'ing pressure relief devicea and vacuum relief devices. These devices provide pressure relie) ar overpressure protection in systems that are subject to IST.
l OMa-1988, Part 10, Paragraphs 4.3.1 and 4.3.4 require safety and relief valves and rupture disks to meet the requirements of Part 1. As discussed in NUREG-1482, Section 4.3.9, OM-1987. Part i has numerous editorial errors. The NUREG provides guidance on the use of clarifications provided in later editions and addenda of the OM Code. The licensee has requested to use Appendix i of the 1995 Edition of the OM Code in its entirety. This Edition includes clarifications, as well as technical changes, to the requirements of OMa-1988 Part 1.
The ASME OM Code-1995 is not currently referenced in 10CFR50.55a(b), but is included in the proposed rulemaking without any modification or limitation. As part of the rulemaking, the staff 1 reviewed the 1995 Edition of the OM Code and found thn the use of Appendix l provides an acceptable level of quality and safety.
2.1.4 Conclusion Use of Appendix l of the 1995 OM Code in its entirety for the testing of pressure relief devices is I authorized in accordance with 10 CFR 50.55a(a)(3)(i). This alternative provides an acceptable I level of quality and safety.
2.2 Relief Reauest VR-8 The licensee has requested relief from the requirements of OM Code-1995, Appendix 1, Paragraph 1.3.6 for the control rod drive hydraulic system rupture discs. The Code requires that all Class 2 and 3 non-reclosing pressure relief devices be replaced every 5 years, unless historical data indicates a requirement for more frequent replacement. It is proposed that replacement of these rupture discs will be at the owner's discretion but not to exceed 40 years of in-service life.
2.2.1 Licensee's Basis for Requesting Relief l
The licensee states: !
l The rupture units supplied with the Control Rod Drive (CRD), Hydraulic Control Unit l (HCU) Accumulator have an active safety function to provide overpressure protectioi. to I the HCU accumulator. The rupture units also have a passive safety function to rnaintain the nitrogen charge in the HCU accumulator, which in tum maintains the control rod scram (rapid insertion) capabilities. The rupture unit is designed to burst at 2000 to 2200 psig at 400 'F, or 2550 to 2900 psig at 72 'F, and has a normal operating pressure of )
1750 psig. j If the rupture unit were to burst during normal plant operation, a CRD HCU low pressure l alarm would annunciate in the control room. With a low pressure condition the l associated control rod would remain operable, but the control rod scram time would be declared " slow". The Perry Technical Specifiestions allow no more than 13 operable control rods to be declared " slow", and no opersble control rod that is " slow" shall be adjacent to another operable control rod that is " slow" or a withdrawn control rod that is stuck. Thus, the increase in control rod insertion time would have a negligible effect on the capability to safely shutdown the reactor. The affected rupture unit would then be replaced and the control rod returned to service.
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These rupture discs are not subjected to operating conditions that cause degradation, as they are in an inert environment (nitrogen blanketed) and remain at a relatively constant pressure. These devices also have a qualified life of 40-years as identified in the environmental qua!ification program. Due to the high degree of reliability (only one reported failure in 1984 was recorded in the Nuclear Plant Reliability Data Systsm) of these devices, replacement every 5 years would provide no significant increase in quality and safety but would present a hardship to the Owner, both in cost and radiation exposure.
2.2.2 Altemate Testing The licensee proposes:
Replacement of the Hydraulic Control Unit Ruoture Discs will be at the Owners Discretion but not to exceed 40 years of in-service life.
2.2.3 Evaluation OM Part 10, Paragraph 4.4.2 requires rupture disks, that protect systems which perform a required function in shutting c:own the reactor, in maintaining the cold shutdown condition, or in mitigating the consequences of an accident from overpressure, to meet the requirements of
.Part i for non-reclosing pressure relief devices. Part 1, Paragraph 1.3.4.2,- requires Class 2 and 3 non-reciosing pressure relief devices to be replaced every 5 years, unless historical data indicates a requirement for more frequent replacement.
At the March 1995 ASME O&M Committee Meeting, it was reported to the OM-1 Working Group that the BWR Owner's Group has reviewed the function of these rupture disks and determined that their active function to rupture is not safety related. The Working Group has since produced a white paper submitted with ASME Main Committee Letter Ba!!ot #209 that desenbes the function and consequences of the rupture disk failing, and recommends that these rupture disks be excluded from testing in OM 1. This ballot has not been approved by ASME. However, as discussed in Section 4.3.1 of NUREG-1482, if the rupture disks do not perform a necessary safety or overpressure protection function, such that they are not necessary, they may be removed from the scope of the IST program.
Additionally, these rupture disks are installed on the nitrogen side of the accumulators. The licensee should review the Code classification of the nitrogen system per the guidance in Regulatory Guide 1.26, " Quality Group Classifications and Standardu for Water , Steam , and Radioactive-Waste-Containing Components of Nuclear Power Plants," to evaluate if these rupture disks are within the scope of 10 CFR 50.55a.
A number of utilities have removed these rupture disks f.om their IST program (e.g., Duane Amold). Although they have determined that the rupture disks at their facilities are not required to be replaced in accordance with Section XI,10 CFR 50.55a requires components to be tested and inspected to quality standards commensurate with the importance of the safety function to be performed, in this case the passive pressure retaining function, and 10 CFR 50.65 would apply.
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Each licensee must make the safety and/or code, class Q?ermination for their specific facility. If j the licensee has determined that these disks are within the scope of the regulations (i.e., are ASME Code Class) and are necessary for the protection of the nitrogen system from ,
overpressure, then additionalinformation is required to support the request. To authorize ]
approval under 10 CFR 50.55a(a)(3)(ii), which states that alternatives may be authorized when j compliance wah the requirements of the Code would result in a hardship or unusual difficulty j without a compensating ir. crease in the level of quality and safety, the licensee must provide I information concarning the specific hardship of complying with the Code, and a discussion of the !
safety function of the rupture disks includi.ng the consequences of premature rupture during operation and failure to rupture when required.
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2.2.4 Conclusion Relief is denied. The licensee should review the classification and function of the hydraulic control unit rupture disks and revise, if hppropriate, the IST program scope or resubmit the relief -
request to include information on how compliance with the Code requirement is a hardship without a compensating increase in the level of quality and safety.
3.0 PUMP RELIEF REQUESTS 3.1 Relief Reauest PR-3 .
l The licensee has requested relief from the acceptance criteria stated in OMa-1988, Part 6, Paragraph 6.1 for various Class 2 and 3 pumps. The licensee proposes that the 1995 ASME OM Code, Paragraph ISTB 6.2.2 be used to allow it to perform an analysis of the pump and establish new reference values.
3.1.1 Licensee's Basis for Requesting Relief The licensee states:
As stated above, OM(6) requires doub5ng of test frequency or declaring a pump inoperable upon reaching tne Alert or Required Action Ranges, respectively. In some cases, where a pump has sufficient excess margin to its safety analyta limits and data trending and analysis only indicate a gradual decrease in pump performance, the requirements of OM(6) may result in taking unnecessary corrective action.
The 1995 ASME OM Code allows the ability to perform an analysis of the pump and establish new reference values. Paragraph ISTB 6.2.2 states that if the measured test parameter values fall wndn the required action range ... the pump shall be declared inoperable until either the cause of the deviation has been determined and the condition corrected, or an analysis of the pump is performed and new reference values are established in accordance with Paragraph ISTB 4.6. Paragraph ISTB 4.6 requires that the analysis include both a pump level and a system level evaluation of operationa!
readiness, the cause of the change in pump performance, and an evaluation of all trends indicated by available data, if such an analysis supports establishing new reference values in lieu of correcting the condition, then using the requirements of ISTB 6.2.2 and ISTB 4.6 as an alternative to OM(6)-6.1 would provida an acceptable level of quality and safety.
.6-Notes:. Where ISTB 4.6 and ISTB 6.2.2 refer to ISTB tab 1m, OM(6) Table 3 would be inserted. All references to ISTB in the preceding para; 1 refer to the 1995 ASME OM Code.
3.1.2 Altemate Testing The licensee proposes:
If supported by an analysis that meets the requirements of ISTB 4.6, corrective action may be is *stablish new reference values in accordance with ISTB 6.2.2 and ISTB 4.6.
3.1.3 Evaluation OMa-1988, Part 6, Paragraph 6.1, " Acceptance Criteria," specifies actions required to be taken if any of the measured pump parameters fall within the alert or required action ranges. For test results in the alert range, the test frequency is required to to doubled until the cause of the deviation is determined and the condition is corrected. For test rosults in the required action range, the pump shall be declared inoperable until the cause of the deviation has been determined and the condition corrected.
In ASME OM Code-1995, which is not currently referenced in 10 CFR 50.55a but is included in the proposed rulemaking without any modification or limitation, Subsection ISTB, Paragraph ISTB 4.6, "New Reference Values," allows that "[i]n cases where the pump's test parameters are either within the alert or required action rarges of ISTB 5.2.1.1, Table ISTB 5.2.1-2, Table ISTB 5.2.2-1, or Table ISTB 5.2.3-1, and the pump's continued use at the changed values is supported by an analysis, a new set of referer.ce values may be established." This paragraph clarifies that, if a pump can be shown to be capable of performing its safety function, it may be returned to service with adjusted reference values. This reflects that there are pumps that have a significant margin over the safety requirements that might degrade from their initial performance, but still are capable of meeting their safety function. Pumps which do not have margin would not be returned to service without repair or replacement. Paragraph ISTB 4.3 also states that the analysis shall include both a pump level and a system level verification of pump operational readiness, the cause of the change in pump performance, and an evaluation of all trends indicated by available data. Paragraph ISTB 6.2.2, which provides acceptance cuteria for the required action range explicitly states that an analysis may be performed and directly references Paragraph ISTB 4.6.
In NRC GL 91-18, which concems resolution of degraded and nonconforming conditions and operability, Paragraph 6.11, " Technical Specification Operability vs. ASME Code,Section XI Operative Criteria," the NRC indicates that in cases where the required action range limit is more conservative than its corresponding technical specification limit, the corrective action may not be limited to replacement or repair. The corrective action may consist of an analysis to demonstrate that the specific pump performance degradation does not impair operability and that the pump or valve will still fulfill its function, such as delivering the required flow. A new required action range may be established after such an analysis which would then allow a new determination of operatility. App. oval has been erthorized by the NRC to allow licensees to use the OM Code-1995, Psragraph 6.2.2 for pum'es in the required action range because licensees are already allowed to perform an analysis in accordance with GL 91-18.
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I The analysis should at least include a comparison of the current measurements for the particular parameter, i.e., flow rate, vibration, discharge pressure or differential pressure, to the baseline measurements, an evaluation of the trer.d of available data for the parameter, and a determination of the cause and the need for corrective action. Alternate available methods, such as vibration spectral analysis, are expected to be used to support the analysis. Any l analysis performed is subject to NRC inspection and must provide reasonable assurance that the degradation mechanism will not cause further degradation such that, before the next pump test or before repairs can be performed, the pump would fail. Additionally, it should be noted that changes to the vibration reference values would affect only the vibration relative alert and required action limits, and not the absolute limits specified by the Code. If the absolute limits are exceeded (i.e.,0.7 ips or 22 mils for the required action range), the licensee would be required I to declare the pump inoperable in accordance with the Code. l l
The use of this analysis is expected to be a rare occurrence. This analysis should be used cautiously, as it is not intended to be used regularly to evaluate the operability of all pumps that fall into the required action range in order to declare the pump operable and define new I reference values where significant degradation has occurred. Repeated application of analysis could lead to stair stepping the Code limits downward to the safety limits of the pump. The licensee should have an understanding of the margin of each pump above its design-basis requirements. This alternative will provide an acceptable level of quality and safety for monitoring the pumps and assuring that the pumps are capable of performing their safety function.
3.1.4 Conclusion The alternative to use the 1995 Edition of the ASME Code, Paragraph ISTB 6.2.2, for pumps in the required action range is authorized pursuant to 10 CFR 50.55a(a)(3)(i) based on the acceptable level of quality and safety that will be provided by the alternative.
3.2 Relief Reauest PR-6 The licensee has requested relief from the requirements of OMa-1988, Part 6, Paragraph 4.6.1.2(b) for various Class 2 and 3 pumps. This section of the Code requires that digital instruments be selected such that the reference value shall not exceed 70% of the calibrated range of the instrument. The licensee proposes to select digitalinstruments such that the measured parameter does not exceed the calibrated range of the instrument.
3.2.1 Licensee's Basis for Requesting Relief The licensee states:
Plant process computer (ERIS) points are used for instrumentation in numerous IST pump tests. The ERIS points are used in lieu of the associated analog indicators in order to meet ASME Code instrument loop accuracy requirements. As well as using ERIS points, temporary digital instruments (M&TE) are also used in IST pump testing. In many cases the reference values exceed 70% of the ERIS point or temporary digital instrument range, t
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According to NUREG/CP-0111, the basis for the 70% requirement is to avoid overranging an instrument if an unexpected situation is encountered. However, since the ERIS points utilize permanent plant instrumentation, the ranges are already selected to account for all expected operating conditions. Overranging is also not a concern with temporary digitalinstruments. Surveillance tests are written such that the temporary instrumentation would not be overranged, whether the instrument is digital or analog. In addition, digital instrumentation is significantly less susceptible to damage from overranging. Furthermore, reading higher in the instrument range results in greater accuracy since the instruments are calibrated as a percentage of full scale. Therefore, use of the ERIS points and temporary digital instrumentation within their full calibrated range would provide an acceptable level of quality and safety.
3.2.2 Altemate Testing The licensee proposes:
Digital instruments shall be selected such that the measured parameter does not exceed the calibrated range of the instrument.
3.2.3 Evaluation OMa-1988, Part 6, Paragraph 4.6.1.2(b), requires that the reference value of digital instruments not exceed 70 percent of the calibrated range of the instrument. The ASME OM Code committees recently approved Code Case OMN-6, which will be included in the OMa-1999 Addenda. This Code Case allows owners to use digitalinstruments such that the reference value does not exceed 90% of the calibrated range of the instrument. This Code Case was written to allow Owners additional flexibility, since the 70% was based on previousSection XI requirements for pressure testing equipment, and to ensure that if readings were in the required action range, they could be read. The licensee has proposed that digitalinstruments shall be selected such that the measured parameter does not exceed the calibrated range of the instrument.
Table 3b of OM Part 6 states that the maximum acceptable value of the measured parameter is 110% of the reference value. The licensee should ensure that Code acceptance criterion for the measured parameter is within the calibrated range of the selected instrument. Accordingly, the reference value should not exceed 90% of the calibrated range of the instrument. When selecting its digital instrument, the licensee should ensure that 110% of the measured ;
parameter's reference value is within the instrument's calibrated range. On this basis, the staff finds that the licensee's attemative provides an acceptable level of quality and safety.
3.2.4 Conclusion The proposed alternative to the Code digital instrument range requirements for various Class 2 ant.,3 pumps is authorized pursuant to 10 CFR 50.55a(a)(3)(i) based on the attemative providing an acceptable level of quality and safety.
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4.0 CONOLUSION The proposed alternatives described in Relief Request Nos. VR-6, PR-3, and PR-6 provide an acceptable level of quality and safety and are authorized pursuant to 10 CFR 50.55a(a)(3)(i).
Relief is denied for VR-8. However, the licensee should review the classification and function of the hydraulic control unit rupture disks and revise the IST program scope or resubmit the relief request to include information on how compliance with the Code requirement is a hardship without a compensating increase in the level of quality and safety.
Principal Contributors: J. Colaccino, M. Kotzalas Date: March 31, 1999
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