ML083230512
| ML083230512 | |
| Person / Time | |
|---|---|
| Site: | Nine Mile Point  |
| Issue date: | 11/13/2008 |
| From: | Laughlin G Constellation Energy Group |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| TAC MD9202, TAC MD9203 | |
| Download: ML083230512 (12) | |
Text
P.O. Box 63 Lycoming, NY 13093 Constellation Nine Mile Point Nuclear Station Energy November 13, 2008 U. S. Nuclear Regulatory Commission Washington, DC 20555-0001 ATTENTION: Document Control Desk
SUBJECT:
Nine Mile Point Nuclear Station Unit Nos. 1 and 2; Docket Nos. 50-220 and 50-410 Inservice Testing (IST) Program Update and Associated 10 CFR 50.55a Requests -
Response to NRC Request for Additional Information (TAC Nos. MD9202 and MD9203)
REFERENCES:
(a) Letter from G. J. Laughlin (NMPNS) to Document Control Desk (NRC), dated June 30, 2008, Inservice Testing (IST) Program Update and Associated 10 CFR 50.55a Requests for the Next Ten-Year IST Intervals (b) Letter from R. V. Guzman (NRC) to K. J. Polson (NMPNS), dated October 14, 2008, Request for Additional Information Regarding Nine Mile Point Nuclear Station, Unit Nos. 1 and 2 (NMP 1 and 2), Pump and Valve Inservice Testing (IST) Program for 10-Year IST Interval (TAC Nos. MD9202 and MD9203)
Nine Mile Point Nuclear Station, LLC (NMPNS) hereby transmits supplemental information requested by the NRC in support of several previously submitted 10 CFR 50.55a requests associated with the Nine Mile Point Units 1 and 2 Inservice Testing Plan update that was submitted by letter dated June 30, 2008 (Reference a). The supplemental information, provided in the Attachment to this letter, responds to the request for additional information (RAI) documented in the NRC's letter dated October 14, 2008 (Reference b). This letter contains no new regulatory commitments.
Document Control Desk November 13, 2008 Page 2 Should you have any questions regarding the information in this submittal, please contact T. F. Syrell, Licensing Director, at (315) 349-5219.
Manager Engineering Services GJL/DEV
Attachment:
Nine Mile Point Units 1 and 2 - Response to NRC Request for Additional Information Regarding 10 CFR 50.55a Requests Associated with the Ten-Year Inservice Testing Program Update cc: S. J. Collins, NRC R. V. Guzman, NRC Resident Inspector, NRC
ATTACHMENT NINE MILE POINT UNITS 1 AND 2 RESPONSE TO NRC REQUEST FOR ADDITIONAL INFORMATION REGARDING 10 CFR 50.55a REQUESTS ASSOCIATED WITH THE TEN-YEAR INSERVICE TESTING PROGRAM UPDATE Nine Mile Point Nuclear Station, LLC November 13, 2008
ATTACHMENT NINE MILE POINT UNITS 1 AND 2 RESPONSE TO NRC REQUEST FOR ADDITIONAL INFORMATION REGARDING 10 CFR 50.55a REQUESTS ASSOCIATED WITH THE TEN-YEAR INSERVICE TESTING PROGRAM UPDATE By letter dated June 30, 2008, Nine Mile Point Nuclear Station, LLC (NMPNS) submitted the Nine Mile Point Units 1 and 2 Inservice Testing (IST) Program update and associated 10 CFR 50.55a requests. This attachment provides supplemental information in response to the request for additional information documented in the NRC's letter dated October 14, 2008, concerning several of the 10 CFR 50.55a requests. Each NRC request is repeated (in italics), followed by the NMPNS response.
Question 1 - ReliefRequest CRD-VR-01 (Unit 1)
L.a The relief request discusses various flow paths associated with the air supply to the scram discharge volume vent and drain valves. Pleaseprovide a simplified schematic of the referenced flow paths.
Response
The enclosed drawing C-18016-C, Sheets 1 and 2, illustrates the flow paths associated with the air supply to the scram discharge volume vent and drain valves that are discussed in Nine Mile Point Unit 1 (NMP 1) request CRD-VR-01.
L.b The reliefrequest states that the test solenoidflow path is not a fixed resistance system and can result in inaccuratestroke-time measurements. Pleaseprovide valve stroke-time data indicating the variation in quarterly stroke time measurements observed as a result of using the test solenoid flow path and discuss the corrective action consequences that resulted from the inaccurate stroke-time measurements.
Response
The following table provides stroke time data for the scram discharge volume vent valves (IV-44.2-15 and IV-44.2-16) and drain valves (IV-44.2-17 and IV-44.2-18). The "Test Solenoid Vent Path" closure times are from historical quarterly tests, whereas the safety-related exhaust path ("Scram Vent Path")
closure times are from recent refueling outage tests.
Valve No. Valve Closure Time Range (seconds)
Using Test Solenoid Vent Path Using Scram Vent Path IV-44.2-15 117 to 143 6.3 to 8.1 1V-44.2-16 6.1 to 13.3 5.4 to 9.1 IV-44.2-17 7.8 to 14.5 6.3 to 8.4 IV-44.2-18 126 to 142 5.2 to 6.8 As noted in request CRD-VR-01, the quarterly stroke closure times of the scram discharge volume vent and drain valves obtained utilizing the Test Solenoid Vent Path varied significantly due to the variable resistance that the test solenoid pilot valve represents. Additionally, the associated times were not representative of the times obtained during the refueling outage interval tests when the scram vent path could be used. This disparity in valve closure times resulted in submittal of a relief request (CRD-RR-4 1 of 7
ATTACHMENT NINE MILE POINT UNITS 1 AND 2 RESPONSE TO NRC REQUEST FOR ADDITIONAL INFORMATION REGARDING 10 CFR 50.55a REQUESTS ASSOCIATED WITH THE TEN-YEAR INSERVICE TESTING PROGRAM UPDATE for valves IV-44.2-15 and IV-44.2-18) by Niagara Mohawk Power Corporation in a letter dated June 20, 1989.
NMPNS believes that due to the significant difference in quarterly versus refueling interval stroke times for these valves, as well as the variation experienced within the quarterly stroke time data versus the variation within the refueling interval data, the performance of quarterly stroke time testing of these valves does not provide an effective means of monitoring and detecting valve degradation. The refueling interval stroke time testing using the scram vent path has been shown to be both repeatable and an effective means of detecting valve degradation and demonstrating operational readiness.
Question 2 - Relief Request CTNH202-VR-02 (Unit 1)
- 2. The reliefrequest states that the valves stroke in less than 2 seconds and that a limiting value of 2 seconds is assigned to the group. Subsequent to this statement, the reliefrequest states that if the slowest valve exceeds the acceptance criteria (50% of the group reference value or 2 second limiting value) the group is declared inoperable. The American Society of MechanicalEngineers (ASME) Code for Operation and Maintenance of Nuclear Power Plants (OM Code) states that valves that stroke in less than 2 seconds may be exempted from ISTC 5152(b) and that in such cases the maximum limiting stroke time shall be 2 seconds. Please clarify the acceptancecriteria to be utilized during valve stroke-time testing (2 seconds versus 50% of the group reference value).
Response
NMPNS hereby clarifies NMP1 request CTNH202-VR-02 to state that a fixed limiting stroke time value of 2.0 seconds is assigned for the four valves listed in the request. This limit is assigned in accordance with ISTC 5152(b) as all four of the subject valves stroke in 2.0 seconds or less.
Question 3 - ReliefRequest RBCLC-PR-01 (Unit 1) 3.a Please discuss the feasibility of installingpermanent or temporary flow instrumentation in the pump dischargelines to allow compliance with the ASME OM Code requirements.
Response
The current system piping configuration does not meet the ultrasonic flow meter vendor recommendations for having a sufficient length of straight piping to provide the necessary conditions to accurately and repeatedly measure individual pump flow rate with a temporary flow measurement device.
Additionally, turbulence caused by piping elbows creates very unfavorable conditions for employing a temporary flow measurement device. A major piping modification would be required to facilitate installation of permanent individual pump flow measuring devices which would be costly and burdensome, and would not provide a compensating increase in the level of quality or safety for the associated components or system.
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ATTACHMENT NINE MILE POINT UNITS 1 AND 2 RESPONSE TO NRC REQUEST FOR ADDITIONAL INFORMATION REGARDING 10 CFR 50.55a REQUESTS ASSOCIATED WITH THE TEN-YEAR INSERVICE TESTING PROGRAM UPDATE 3.b The use of analyticalmethods to determine individualpump flow rates has been authorized by the NRC in cases where single pump operation is not attainable during normal operation and individualpump flow instrumentation is not installed. Please discuss the feasibility of utilizing analyticalmethods to determine individualpump flow rates.
Response
An evaluation was performed to determine the feasibility of implementing analytical methods to determine individual pump flow rates for the three NMP1 Reactor Building Closed Loop Cooling (RBCLC) pumps. The evaluation considered testing of two pumps at a time, in various combinations, to monitor the performance of each pump. The following was determined during this evaluation.
The NMP 1 RBCLC system employs an automatic temperature control valve (TCV) that regulates supply or bypass flow to/around the system heat exchangers. To establish stable test conditions, the RBCLC TCV would need to be removed from automatic and taken to manual by Operations. To perform this activity quarterly would be burdensome to Operations and place the plant in a vulnerable condition if fluctuations in system heat loads or lake temperature were to occur. Additionally, the RBCLC heat exchangers are vulnerable to tube damage from flow-induced vibration. Such flow-induced vibration occurs when three RBCLC pumps are running. Currently, three-pump operation occasionally occurs during normal pump rotation, when the third (standby) pump is started prior to securing one of the two previously operating pumps. The RBCLC system operating procedure includes cautions to minimize the time that all three pumps are running. Quarterly two-pump combination testing would result in a significant increase in three-pump operation, which could potentially shorten heat exchanger tube life expectancy. Finally, gate valves would need to be throttled to establish test conditions. Gate valves are not the preferred style valve for throttling. Globe valves are better for flow control and more resistant to wear in a throttled position. Excessive wear and tear to the pump discharge gate valves would likely occur due to throttling each quarter.
NMPNS believes that the risk of RBCLC system equipment damage and the additional burden placed on plant operators outweigh the benefits that might be derived from performing quarterly two-pump combination testing. In addition, review of the monitoring and trending methodology that has been in place for many years indicates that current practice, as described in the "Proposed Alternative and Basis for Use" section of request RBCLC-PR-01, has been and will continue to be an effective means for detecting early degradation in pump performance and demonstrating pump operational readiness.
3.c Please discuss the feasibility of establishinghydraulicperformance acceptance criteriabased on dualpump operation.
Response
As stated in the response to RAI 3.b above, NMPNS believes that the risk of RBCLC system equipment damage and the additional burden placed on plant operators outweigh the benefits that might be derived from performing quarterly two-pump combination testing. Thus, NMPNS does not consider it feasible to establish hydraulic performance criteria based on two-pump operation.
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ATTACHMENT NINE MILE POINT UNITS 1 AND 2 RESPONSE TO NRC REQUEST FOR ADDITIONAL INFORMATION REGARDING 10 CFR 50.55a REQUESTS ASSOCIATED WITH THE TEN-YEAR INSERVICE TESTING PROGRAM UPDATE Question 4 - Relief Request MSS-VR-01 (Unit 2) 4.a The ASME OM Code has developed a code case addressing test frequencies of ASME Class 1 pressure relief/safety valves. The code case provides a 72-month test interval with a 6-month grace period to accommodate extended shutdown periods provided certain requirements are implemented. One of the requirements is that each valve is disassembled and inspected after as-found set pressure testing to verify that parts are free of defects resultingfrom time related degradationor service induced wear. Based on this inspection, the owner shall determine the need for additionalinspections or testing to address any generic concerns. Please discuss the feasibility of implementing the criteria established by the ASME OM Code for extending the safety reliefvalve (SRV) test interval beyond 5 years.
Response
The SRV testing and maintenance cycle at NMP2 consists of 2 stages: (1) as-found testing; and (2) maintenance activities performed on the valves and subsequent post-maintenance recertification testing.
Subsequent to completion of as-found testing, each SRV in the removed complement is disassembled to perform inspection and maintenance activities, including disc and seat inspection for evidence of degradation such as leakage or misalignment. Any SRV that failed the as-found set pressure test is inspected to determine the cause. In the event the as-found tests or the visual inspections indicate that spring pack degradation may be present, a set pressure load test is performed to determine the amount of friction present and hysteresis characteristics. The results of this test are evaluated by the test supervisor to identify irregularities in operation that might be indicative of subcomponent degradation. Based upon the results of the test review, a determination is made by the test supervisor to perform full or partial valve overhaul.
All 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.
The SRV as found set pressure test data for the last five NMP2 refueling outages (see response to RAI 4.c below) demonstrates that the current maintenance practices outlined above have been effective since only one as found setpoint test failure has been experienced during this time.
4.b The relief request states that 5 as-found setpoint tests exceeded the Code tolerance of plus or minus 3%. Pleaseprovide the as-found setpoint datafor the five failed tests, identify the cause of the failure if known, and identify any corrective actions taken to improve valve performance following the failed tests.
Response
The as-found setpoint data for the five (5) failed SRV as-found setpoint tests (i.e., the Code tolerance of
+/-3% was exceeded) is summarized below.
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ATTACHMENT NINE MILE POINT UNITS 1 AND 2 RESPONSE TO NRC REQUEST FOR ADDITIONAL INFORMATION REGARDING 10 CFR 50.55a REQUESTS ASSOCIATED WITH THE TEN-YEAR INSERVICE TESTING PROGRAM UPDATE 0 One SRV as-found setpoint test failed on the low side (setpoint less than the -3% tolerance). The following summarizes the test data for this SRV:
As Found Setpoint Correlated Correlated Correlated Test Set Max Set Min Set Serial Setpoint When Results Test Pressure Pressure Pressure SRV Tested No. (psig) Tested (psig) Medium (psig) +3% (psig) -3% (psig) 2MSS*PSVI35(¶) 160976 1195 Mar-02 1170 Nitrogen 1214 1247 1180 NOTES: (1) The cause for this failure was determined to be setpoint drift. Minor adjustments were made to restore the set pressure to the acceptance range. No additional causes for the setpoint drift were found during valve maintenance. The valve was refurbished and re-certified.
- Four SRV as-found tests failed on the high side (setpoint greater than the +3% tolerance). The following summarizes the test data for these SRVs:
As Found Max Set Min Set Serial Setpoint When Setpoint Test Test pressure pressure SRV Tested No. (psig) Tested Results (psig) Medium +3% (psig) -3% (psig) 2MSS*PSVI22(l) 160969 1185 Oct-90 1228 Steam 1221 1149 2MSS*PSVI21( 2) 160966 1195 Apr-92 1234 Steam 1230.8 1159.1 2MSS*PSVI23(3 ) 160960 1175 Oct-96 1219 Steam 1210.2 1139.7 3
2MSS*PSVI25( ) 160953 1185 Oct-96 1228 Steam 1220 1149 NOTES: (1) The cause for this failure was attributed to corrosion-induced frictional forces in the closely toleranced kinematic parts. The valve was refurbished and re-certified.
(2) The cause for this failure was determined to be setpoint drift most likely caused by corrosion of the setpoint spring kinematic part surfaces subject to relative motion. The valve was refurbished and re-certified.
(3) The cause for these failures was attributed to the use of a cleaning agent by the third-party test facility that was applied prior to as-found testing to reduce inlet nozzle contamination levels. The valves were refurbished and re-certified. The SRV test procedure was revised to assure that cleaning agents are not introduced into the SRV inlet during performance of as-found testing.
4.c Pleaseprovide a summary of the SR V testing conductedfor the last 5 refueling outages (valve, date tested, as-found setpoint, interval between previous test).
Response
A summary of the SRV testing conducted during the last five NMP2 refueling outages is provided in the following table. Note that all SRV testing performed during these refueling outages utilized nitrogen, with a correlated set pressure.
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ATTACHMENT NINE MILE POINT UNITS 1 AND 2 RESPONSE TO NRC REQUEST FOR ADDITIONAL INFORMATION REGARDING 10 CFR 50.55a REQUESTS ASSOCIATED WITH THE TEN-YEAR INSERVICE TESTING PROGRAM UPDATE As Found Correlated Correlated Correlated Interval Setpoint Set Max Set Min Set Between Serial Setpoint Test Results Pressure Pressure Pressure Accept/ Previous SRV Tested No. (psig) (psig) (psig) +3% (psig) -3% (psig) Reject Test Refueling Outage 11, April 2008 2MSS*PSV126 160965 1195 1212 1215 1248 1181 Accept 6 yrs 2MSS*PSVI27 160956 1205 1220 1224.9 1258.7 1190.9 Accept 6 yrs 2MSS*PSVl28 160972 1165 1162 1184 1217 1151 Accept 6 yrs 2MSS*PSV131 160961 1175 1200 1194 1227 1161 Accept 6 yrs 2MSS*PSV132 160915 1185 1182 1205 1238 1171.4 Accept 6 yrs 2MSS*PSV135 160964 1195 1197 1215 1248 1181 Accept 6 yrs Refueling Outage 10, April 2006 2MSS*PSV120 160935 1185 1203 1205 1238 1171 Accept 6 yrs 2MSS*PSV121 160966 1195 1224 1215 1248 1181 Accept 6 yrs 2MSS*PSV122 160951 1185 1222 1204 1238 1171 Accept 6 yrs 2MSS*PSV125 160968 1185 1194 1205 1238 1171 Accept 6 yrs 2MSS*PSVI29 160971 1205 1225 1225 1258 1191 Accept 6 yrs 2MSS*PSV133 160958 1165 1176 1184 1217 1151 Accept 6 yrs Refueling Outage 9, April 2004 2MSS*PSV123 160960 1175 1191 1195.2 1228 1162 Accept 6 yrs 2MSS*PSV124 160974 1175 1193 1195.2 1228 1162 Accept 6 yrs 2MSS*PSVI30 160936 1195 1193 1215.5 1249 1181 Accept 6 yrs 2MSS*PSV134 160954 1205 1225 1225 1259 1191.6 Accept 6 yrs 2MSS*PSV136 160973 1175 1189 1195.2 1228 1162 Accept 6 yrs 2MSS*PSV137 160905 1205 1239 1225.7 1259.7 1191.6 Accept 6 yrs Refueling Outage 8, March 2002 2MSS*PSV121 160939 1195 1219 1214 1248 1180 Accept 6 yrs 2MSS*PSV126 160967 1195 1189 1214 1247 1180 Accept 6 yrs 2MSS*PSV127 160955 1205 1201 1224 1258 1190 Accept 6 yrs 2MSS*PSVI28 160903 1165 1176 1184 1216 1151 Accept 6 yrs 2MSS*PSV129 160904 1205 1220 1224 1258 1190 Accept 6 yrs 2MSS*PSV132 160953 1185 1181 1204 1237 1171 Accept 6 yrs 2MSS*PSVI34 160970 1205 1192 1224 1258 1190 Accept 6 yrs 2MSS*PSV135() 160976 1195 1170 1214 1247 1180 Reject 6 yrs 2MSS*PSV131t) 160962 1175 1186 1194 1227 1161 Accept 6 yrs 2MSS*PSV133(') 160959 1165 1169 1184 1216 1151 Accept 6 yrs Refueling Outage 7, March 2000 2MSS*PSV120 160915 1185 1219 1204 1238 1171 Accept 4 yrs 2MSS*PSV121 160965 1195 1231 1215 1248 1181 Accept 4 yrs 2MSS*PSVI22 160950 1185 1222 1204 1238 1171 Accept 4 yrs 2MSS*PSV123 160963 1175 1208 1194 1227 1161 Accept 4 2MSS*PSV124 160906 1175 1189 1194 1227 1161 Accept 4yrs 2MSS*PSV125 160952 1185 1220 1204 1238 1171 Accept yr 6 of 7
ATTACHMENT NINE MILE POINT UNITS 1 AND 2 RESPONSE TO NRC REQUEST FOR ADDITIONAL INFORMATION REGARDING 10 CFR 50.55a REQUESTS ASSOCIATED WITH THE TEN-YEAR INSERVICE TESTING PROGRAM UPDATE As Found Correlated Correlated Correlated Interval Setpoint Set Max Set Min Set Between Serial Setpoint Test Results Pressure Pressure Pressure Accept/ Previous SRV Tested No. (psig) (psig) (psig) +3% (psig) -3% (psig) Reject Test 2MSS*PSV128 160958 1165 1193 1184 1217 1151 Accept 4 yrs 2MSS*PSV129 160956 1205 1214 1225 1258 1191 Accept 4 yrs 2MSS*PSV135 160975 1195 1244 1215 1248 1181 Accept 4 yrs 2MSS*PSV136 160961 1175 1221 1194 1227 1161 Accept 4 yrs 2MSS*PSV137 160954 1205 1222 1225 1259 1191 Accept 4 yrs NOTES: (1) SRV 2MSS*PSV135 failed the as-found set pressure test (relieved early) during Refueling Outage 8. Two additional valves (2MSS*PSV131 and 2MSS*PSV133) were tested per Code requirements, and both passed.
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THIS PAGE IS AN OVERSIZED DRAWING OR FIGURE, THAT CAN BE VIEWED AT THE RECORD TITLED:
"CONTROL ROD DRIVE P & I DIAGRAM" WITHIN THIS PACKAGE... OR BY SEARCHING USING THE D-01
THIS PAGE IS AN OVERSIZED DRAWING OR FIGURE, THAT CAN BE VIEWED AT THE RECORD TITLED:
"CONTROL ROD DRIVE SCRAM DUMP VOLUME P & I DIARAG" WITHIN THIS PACKAGE... OR BY SEARCHING USING THE D-02X