ML15047A003

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Request for Relief from ASME OM Code 5-Year Test Interval for Class 1 Safety Relief Valves (Srvs) (Relief Request MSS-VR-01, Revision 1)
ML15047A003
Person / Time
Site: Nine Mile Point 
(NPF-069)
Issue date: 02/16/2015
From: David Gudger
Exelon Generation Co
To:
Document Control Desk, Office of Nuclear Reactor Regulation
References
NMP2L 2575
Download: ML15047A003 (11)
v • d • e


Text

NMP2L 2575 February 16, 2015 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 Nine Mile Point Nuclear Station, Unit 2 Renewed Facility Operating License No. NPF-69 NRC Docket No. 50-410 10 CFR 50.55a

Subject:

Request for Relief from ASME OM Code 5-Year Test Interval for Class 1 Safety Relief Valves (SRVs) (Relief Request MSS-VR-01, Revision 1)

Attached for your review is Relief Request MSS-VR-01, Revision 1 associated with the third lnservice Testing (IST) interval for Nine Mile Point Nuclear Station, Unit 2 (NMP2).

The third interval of the NMP2 IST program complies with the American Society of Mechanical Engineers (ASME) Code for Operation and Maintenance of Nuclear Power Plants, 2004 Edition with no Addenda. This relief request would implement ASME OM Code Case OMN-17. We request your approval by February 16, 2016.

There are no regulatory commitments in this letter.

If you have any questions concerning this letter, please contact Tom Loomis at (610) 765-5510.

Respectfully, Davi

. Gudger Manager - Licensing & Regulatory Affairs Exelon Generation Company, LLC

Attachment:

Relief Request MSS-VR-01, Revision 1 cc: Regional Administrator, Region I, USNRC USNRC Senior Resident Inspector, NMP Project Manager, USNRC

ATTACHMENT RELIEF REQUEST MSS-VR-01, REVISION 1

10 CFR 50.55a RELIEF REQUEST: MSS-VR-01 Revision 1 (Page 1 of 9)

Proposed Alternative to the ASME OM Code 5-Year Test Interval for Class 1 Safety Relief Valves (SRVs) In Accordance with 10 CFR 50.55a(z)(1)

1.

ASME Code Component(s) Affected Component ID Class Cat.

Label 2MSS*PSV120 1 c

MAIN STEAM SRV 2MSS*PSV121 1 c

MAIN STEAM SRV (ADS*)

2MSS*PSV122 1 c

MAIN STEAM SRV 2MSS*PSV123 1 c

MAIN STEAM SRV 2MSS*PSV124 1 c

MAIN STEAM SRV 2MSS*PSV125 1 c

MAIN STEAM SRV 2MSS*PSV126 1 c

MAIN STEAM SRV (ADS) 2MSS*PSV127 1 c

MAIN STEAM SRV (ADS) 2MSS*PSV128 1 c

MAIN STEAM SRV 2MSS*PSV129 1 c

MAIN STEAM SRV (ADS) 2MSS*PSV130 1 c

MAIN STEAM SRV (ADS) 2MSS*PSV131 1 c

MAIN STEAM SRV 2MSS*PSV132 1 c

MAIN STEAM SRV 2MSS*PSV133 1 c

MAIN STEAM SRV 2MSS*PSV134 1 c

MAIN STEAM SRV (ADS) 2MSS*PSV135 1 c

MAIN STEAM SRV 2MSS*PSV136 1 c

MAIN STEAM SRV 2MSS*PSV137 1 c

MAIN STEAM SRV (ADS)

The SRVs are Dikkers I Model G471-6/125.04 (18 SRVs Installed) in 4 steam lines. The SRVs are located on the main steam lines between the reactor vessel and the first isolation valve within the drywell. The SRVs are designed to actuate by either of two modes - the safety mode or the auto depressurization system (ADS) mode. In the safety mode, the valve will open when reactor pressure exceeds a specific spring set-pressure.

In the auto depressurization mode, the valve will automatically open upon receipt of an overpressure signal {seven of the eighteen valves support this ADS function). The proposed changes do not impact either the safety mode of operation or the auto depressurization mode of operation.

10 CFR 50.55a RELIEF REQUEST: MSS-VR-01 Revision 1 (Page 2 of 9)

2.

Applicable Code Edition and Addenda

The Nine Mile Point Nuclear Station, Unit 2 (NMP2) lnservice Testing Program (IST) complies with the American Society of Mechanical Engineers (ASME) Operation and Maintenance (OM) Code-2004 Edition, No Addenda.

3.

Applicable Code Requirement(s)

  • ASME OM Code Mandatory Appendix I, "lnservice Testing of Pressure Relief Devices in Light-Water Reactor Nuclear Power Plants," Section 1-1320, "Test Frequencies, Class 1 Pressure Relief Valves," paragraph (a), "5-Year Test Interval," states that Class 1 pressure relief valves shall be tested at least once every 5 years.
  • Paragraph l-1320(b)(2) requires that for replacement of a full complement of valves, the valves removed from service shall be tested within 12 months of removal from the system.
  • Relief Request MSS-VR-01 was previously authorized by Reference 1. This authorized alternative to ASME OM Code-2004, Mandatory Appendix I, paragraph 1-1320, requires that Class 1 pressure relief valves be tested at least once every three refueling cycles.

A minimum of 20% of the valves from each valve group shall be tested within any 24-month interval. This 20% shall consist of valves that have not been tested during the current three cycle interval, if they exist The test interval for any individual valve shall not exceed three refueling cycles. However, this relief did not authorize an additional 6 months grace as provided in OMN-17.

4.

Reason for Request

By letter dated December 29, 2008 (Reference 1 ), the NRC authorized Relief Request MSS-VR-01 for NMP2 to increase the SRV test interval from 5 years to 3 refueling cycles (approximately 6 years), but did not include the 6 month grace. Revision 1 of request MSS-VR-01 would replace the currently approved test interval of "3 refueling cycles (approximately 6 years)" with a test interval of "6 years," and would allow a 6-month grace period for performing the tests. These revisions are consistent with the test interval and grace period described in American Society of Mechanical Engineers (ASME} Code Case OMN-17. Due to outage scheduling, the additional 6-months is necessary to avoid unnecessary testing.

Section ISTC-3200, "lnservice Testing," states that inservice testing shall commence when the valves are required to be operable to fulfill their required function(s). Section ISTC-5240, "Safety and Relief Valves," directs that safety and relief valves shall meet the inservice testing requirements set forth in Appendix I of the ASME OM Code. Appendix I, Section l-1320(a) of the ASME OM Code states that Class 1 pressure relief valves shall be tested at least once every 5 years, starting with initial electric power generation. This section also states a minimum of 20% of the pressure relief valves are tested within any 24-month interval and that the test interval for any individual valve shall not exceed 5 years. The required tests ensure that the SRVs, which are located on each of the main steam lines between the reactor vessel and the first isolation valve within the drywall, will open at the pressures assumed in the safety analysis.

10 CFR 50.55a RELIEF REQUEST: MSS-VR-01 Revision 1 (Page 3 of 9)

The SRVs have shown acceptable test history at NMP2 as described in Section 5 below.

However, given the current 24-month operating cycle at NMP2, Exelon Generation Company, LLC (Exelon) is required to remove and test approximately half of the SRVs every refueling outage in order to ensure that all valves are removed and tested in accordance with the ASME OM Code requirements. This ensures compliance with the ASME OM Code requirements for testing Class 1 pressure relief valves within a 5 year interval. With the current 5 year interval, NMP2 is required to remove all 18 SRVs over 2 refuel cycles (i.e., 4 years). Approval of extending the test interval to 6.5 years would reduce the number of SRVs removed during an individual outage, such that the full scope of 18 SRVs are replaced over 3 refuel cycles (i.e., 6 years, plus 6 months grace). Without Code relief, the incremental outage work due to the inclusion of the additional 2 - 3 SRVs per outage would be contrary to the principle of maintaining radiation dose As Low As Reasonably Achievable (ALARA). The removal and replacement of the additional 2 - 3 SRVs per outage without Code relief results in an additional exposure of approximately 2 -

4 Rem each outage. Additionally, the grace period allows for flexibility in the scheduling of as-left set and as-found set-pressure testing, which is based on a test to test frequency.

In accordance with 10 CFR 50.55a(z)(1), Exelon requests approval of an alternative to the 5 year test interval requirements of ASME OM Code, Appendix I, Section l-1320(a) for the SRVs at NMP2. Exelon requests that the test interval be increased from 5 years to 6.5 years. All other requirements of the applicable ASME OM Code would be met.

5.

Proposed Alternative and Basis for Use As an alternative to the Code required 5-year test interval per Appendix I, paragraph l-1320(a), Exelon proposes that the subject Class 1 pressure relief valves be tested at least once every three refueling cycles (approximately 6 years/72 months) with a minimum of 20% of the valves tested within any 24-month interval. This 20% would consist of valves that have not been tested during the current 72-month interval, if they exist. The test interval for any individual valve would not exceed 72 months except that a 6-month grace period is allowed to coincide with refueling outages to accommodate extended shutdown periods and certification of the valve prior to installation.

As-found testing using steam and subsequent valve maintenance are currently performed at an off-site test facility. Subsequent to completion of as-found testing, each SRV in the removed complement is disassembled to perform inspections and a complete valve overhaul. Any SRV that failed the as-found set-pressure test is inspected to determine the cause of the test failure. Valve overhaul is performed to ensure that parts are free of defects resulting from time related degradation or service induced wear. All identified adverse conditions are corrected, the disc and seats are lapped, and the valve is reassembled. Each SRV is then recertified for service through inspection and testing consistent with ASME OM Code requirements, including set-pressure, seat tightness, stroke time and disc lift verifications, solenoid coil pick up/drop out, and air actuator integrity tests.

10 CFR 50.55a RELIEF REQUEST: MSS-VR-01 Revision 1 (Page 4 of 9)

After recertification testing, the SRVs are stored at the test facility for future use. The storage area is inspected and maintained to ANSl/ASME N45.2.2 requirements, which will minimize the potential for any valve degradation.

The SRV as-found set-pressure test data in Table 1 and Table 2 demonstrates that the maintenance practices previously employed by NMP2 were effective. In the Spring 2010, prior to the Refueling Outage 12 (RF012), testing of the SRVs began at an offsite testing facility. These results are reflected in Table 2.

Only one as-found set-pressure test failure (2002) has been experienced during the time period encompassed by the data in Table 1. Note that testing performed on SRVs removed during these refueling outages utilized nitrogen, with a correlated set-pressure.

The data in Table 1 also illustrates that SRVs that have exceeded 6 years between tests have still demonstrated acceptable as-found set-pressure test results.

Additionally, there were a total of four as-found set-pressure failures experienced in 2010 (Table 2), which was determined not to be a result of set-pressure drift or a hardware degradation issue, rather the cause was determined to be common among the four SRVs which was due to minor inaccuracies associated with the correlation used to establish the as-left set-pressure using nitrogen, and the as-found set-pressure using saturated steam.

During RF013 (Spring of 2012) and RF014 (Spring of 2014), there were no as-found set-pressure failures (Table 3).

As noted previously, Relief Request MSS-VR-01 was approved in Reference 1, and permitted a test interval of "3 refueling cycles (approximately 6 years)." Revision 1 to this relief request merely allows an additional 6 months grace as provided in OMN-17.

Based on the above valve performance history and SRV maintenance practices, there is continued assurance of valve operational readiness, as required by ASME OM Code-2004, Mandatory Appendix I, paragraph l-1310(b). Therefore, this proposed alternative to include the 6-month grace will continue to provide assurance of the valves' operational readiness and provides an acceptable level of quality and safety pursuant to 1 O CFR 50.55a(z)(1).

6.

Duration of Proposed Alternative This proposed alternative is requested for the remainder of the NMP2 third 10-year lnservice Testing Program interval, which began on January 1, 2009 and is scheduled to end on December 31, 2018.

7.

Precedents

1. Peach Bottom Atomic Power Station, Units 2 and 3 Relief Request 01A-VRR-3 was approved in a Nuclear Regulatory Commission Safety Evaluation Report dated April 30, 2014 (ML14094A051).

10 CFR 50.55a RELIEF REQUEST: MSS-VR-01 Revision 1 (Page 5 of 9)

2. Quad Cites Nuclear Power Station, Units 1and2 Relief Request RV-05 was approved in a Nuclear Regulatory Commission Safety Evaluation Report dated February 14, 2013(ML13042A348).
8.

References

1. Letter from M. Kowal (U.S. Nuclear Regulatory Commission) to K. Polson (Nine Mile Point Nuclear Station, LLC), "Nine Mile Point Nuclear Station - Safety Evaluation of Relief Requests for the Unit No. 1 Fourth 10-Year and Unit No. 2 Third 10-Year Pump and Valve lnservice Testing Program (TAC Nos. MD9202 AND MD9203)," dated December 29, 2008.

10 CFR 50.55a RELIEF REQUEST: MSS-VR-01 Revision 1 (Page 6 of 9)

Table 1 Main Steam SRVs Test Results for NMP2 Refuel in~

Outages RF07 (2000) through RF011 (2008)<1 As-Found Set-Time Pressure Correlated Correlated from Set-Test Correlated Max Set-Min Set-Last Serial Results Set-Pressure Pressure Accept/

Test SRVTested No.

si si

+3%

Reect Years 2008 1195 1215 1248 1181 1205 1224.9 1258.7 1190.9 1165 1162 1184 1217 1151 8.42 1175 1200 1194 1227 1161 6.77 1185 1182 1205 1238 1171.4 6.77 1195 1197 1215 1248 1181 10.1 2MSS*PSV120 1171 6.44 1248 1181 6.40 1238 1171 8.11 1238 1171 8.12 1258 1191 6.42 1151 4.78 1228 1162 1193 1228 1162 1193 1215.5 1249 1181 1225 1225 1259 1191.6 1189 1195.2 1228 1162 239 1259.7 1191.6 Refuelin 195 219 1180 Acee t 4.09 1189 1247 1180 Acee t 5.88 1201 1224 1258 1190 Acee t 5.90 1176 1184 1216 1151 Acee t 4.08 1220 1224 1258 1190 Acee t 4.08 1181 1204 1237 1171 Acee t 5.16 1192 1224 1258 190 Acee t 5.18 1170 1214 1247 180 Reject 5.16 160962 1175 1186 1194 1227 Accept 5.17 160959 1165 1169 1184 1216 Accept 5.18

Serial SRV Tested No.

2MSS*PSV120 160915 2MSS*PSV121 160965 2MSS*PSV122 160950 2MSS*PSV123 160963 2MSS*PSV124 160906 2MSS*PSV125 160952 2MSS*PSV128 160958 2MSS*PSV129

~

2MSS*PSV135 2MSS*PSV136 2MSS*PSV137 4

10 CFR 50.55a RELIEF REQUEST: MSS-VR-01 Revision 1 (Page 7 of 9)

Table 1 (Continued)

As-Found Set*

Pressure Correlated Correlated Correlated Set-Test Set*

Max Set-Min Set*

Pressure Results Pressure Pressure Pressure (psig) tosig) losla)

+3%losia)

-3°/o (osia)

Refuelina Outaae 7, March 2000 1185 1219 1204 1238 1171 1195 1231 1215 1248 1181 1185 1222 1204 1238 1171 1175 1208 1194 1227 1161 1175 1189 1194 1227 1161 1185 1220 1204 1238 1171 1165 1193 1184 1217 1151 1205 1214 1225 1258 1191 1195 1244 1215 1248 1181 1175 1221 1194 1227 1161 1205 1222 1225 1259 1191 Accept/

Reiect Accept Accept Accept Accept Accept Accept Accept Acceot Accept Accept Accept Notes: (1) Testing was performed at the NMP2 onsite test facility using nitrogen as the test medium.

Time from Last Test (Years) 3.90 3.90 3.94 3.92 3.92 3.90 3.94 3.16 3.88 3.93 3.88 (2) SRV 2MSS*PSV135 (SN 160976) failed the as-found set-pressure test (relieved early) during Refueling Outage 8. Two additional valves (2MSS*PSV131 (SN 160962) and 2MSS*PSV133 (SN 160959)) were tested per Code requirements, and both passed. The cause for this failure was determined to be set-pressure drift. Minor adjustments were made to restore the set-pressure to the acceptance range. No additional causes for the set-pressure drift were found during valve maintenance. The valve was refurbished and re-certified.

10 CFR 50.55a RELIEF REQUEST: MSS-VR-01 Revision 1

{Page 8 of 9)

Table 2 Main Steam SRVs Test Results for NMP2 Refueling Outage RF012 (2010) (1l As-Found Set*

Time Set*

Max Set-Min Set*

from Last Serial Pressure Pressure Accept/

Test SRV Tested No.

Re'ect Years 2MSS*PSV120 1149.4 7.38 2MSS*PSV121 1159 7.29 2MSS*PSV122 1217 1220.5 1149.4 9.76 2MSS*PSV123 160914 1175 1193 1210 1139.7 13.03 2MSS*PSV124 160906 1175 1212 1210 1139.7 9.70 2MSS*PSV125 160950 1185 1220 1220.5 1149.4 9.75 2MSS*PSV126 1230.9 1159 7.44 2MSS*PSV127 5.30 2MSS*PSV128 1

7.46 2MSS*PSV129 7.46 2MSS*PSV130 160976 1195 7.4 2MSS*PSV131 160974 1175 1192 1210 1139.7 5.29 2MSS*PSV132 160969 1185 1197 1220.5 1149.4 3.31 2MSS*PSV133 160959 1165 1214 1199.9 1130 7.44 2MSS*PSV134 160955 1205 1211 1241 1174.4 7.39 2MSS*PSV135 160936 1195 1222 1230.9 1159 5.30 2MSS*PSV136 160962 1175 1204 1210 1139.7 7.46 2MSS*PSV137 160970 1205 1245 1241 1174.4 7.36 Notes: (1) All 18 SRVs were removed and replaced with pre-tested valves in Refueling Outage 12 (2010).

The testing was performed at an offsite test facility using saturated steam as the test medium.

10 CFR 50.55a RELIEF REQUEST: MSS-VR-01 Revision 1 (Page 9 of 9)

Table 3 Main Steam SRVs Test Results for NMP2 Refueling Outages RF013 (2012) and RF014 (2014)

As-Found Set-Pressure Time Set-Test Max Set-Min Set-from Last Serial Pressure Results Accept/

Test SRV Tested No.

Re"ect Years Refuelin Outa e 14, March 2014 SS*PSV122 160935 1185 1181 1220.55 1149.45 Acee t 4

S*PSV123 160963 1175 1170 1210.25 1139.75 Acee t 4

S*PSV126 160964 1195 1164 1230.85 1159.15 Acee t 4

SV134 160954 1205 1201 1241.15 1168.85 Acee t 4

SV135 160975 1195 1199 1230.85 1159.15 Acee t 4

2MSS*PSV137 160957 1205 1190 1241.15 1168.85 Acee t 4

Refuelin 2MSS*PSV129 160956 1205 1168.85 2

2MSS*PSV130 160965 1195 1196 2

2MSS*PSV131 160961 1175 1166 1210.25 2

2MSS*PSV132 160915 1185 1182 1220.55 2

2MSS*PSV133 160972 1165 1139 1199.95 2

2MSS*PSV136 160960 1175 1168 1210.25 2

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