ML062230351

Relief Request from the ASME OM Code for the Third Inservice Test Interval

ML062230351
Person / Time
Site:	Byron
Issue date:	09/07/2006
From:	Dan Collins NRC/NRR/ADRO/DORL/LPLF
To:	Crane C Exelon Generation Co
kuntz, Robert , NRR/DORL, 415-3733
References
TAC MC9642, TAC MC9643, TAC MC9752, TAC MC9753, TAC MC9754, TAC MC9755, TAC MC9758, TAC MC9759, TAC MC9764, TAC MC9765
Download: ML062230351 (16)

Text

September 7, 2006 Mr. Christopher M. Crane, President and Chief Nuclear Officer Exelon Generation Company, LLC 4300 Winfield Road Warrenville, IL 60555

SUBJECT:

BYRON STATION, UNIT NOS. 1 AND 2 - EVALUATION OF RELIEF REQUESTS FROM THE REQUIREMENTS OF ASME OM CODE FOR THE THIRD INSERVICE TEST INTERVAL (TAC NOS. MC9642, MC9643, MC9752, MC9753, MC9754, MC9755, MC9758, MC9759, MC9764, AND MC9765)

Dear Mr. Crane:

By letter to the Nuclear Regulatory Commission (NRC) dated December 29, 2005, as supplemented by letter dated July 11, 2006, Exelon Generation Company, LLC (the licensee) submitted requests for approval of proposed alternatives to the American Society of Mechanical Engineers Code for Operation and Maintenance of Nuclear Power Plants (ASME OM Code) 2001 Edition through 2003 Addenda, for Byron Station, Unit Nos. 1 and 2, for the third 10-year interval, which began on June 30, 2006 and will end on July 1, 2016. The licensee requested relief from the inservice testing (IST) program for pumps and valves.

The NRC staff concludes, based on the enclosed safety evaluation, that 1 is authorized on the basis that compliance with the ASME OM Code results in a hardship without a compensating increase in the level of quality and safety. Pursuant to 50.55a(a)(3)(i), relief request RP-5 is authorized on the basis that the proposed alternatives provide an acceptable level of quality and safety. Pursuant to 10 CFR 50.55a(a)(3)(i), relief request RV-1 is authorized with additional modifications on the basis that the proposed alternative provides an acceptable level of quality and safety. The relief requests are authorized for the third 10-year interval which ends on July 1, 2016.

The NRC staff is continuing its review of relief request RP-2 and RP-3. Relief requests RP-2 and RP-3 will be addressed in future correspondence.

C. Crane The licensees December 29, 2005, submittal included relief requests RP-4 and RP-6 which were withdrawn as part of the licensees July 11, 2006, supplement. Consequently, RP-4 and RP-6 are not authorized.

Sincerely,

/RA/

Daniel S. Collins, Chief Plant Licensing Branch III-2 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket Nos. STN 50-454 and STN 50-455

Enclosure:

Safety Evaluation cc w/encl: See next page

C. Crane The licensees December 29, 2005, submittal included relief requests RP-4 and RP-6 which were withdrawn as part of the licensees July 11, 2006, supplement. Consequently, RP-4 and RP-6 are not authorized.

Sincerely,

/RA/

Daniel S. Collins, Chief Plant Licensing Branch III-2 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket Nos. STN 50-454 and STN 50-455

Enclosure:

Safety Evaluation cc w/encl: See next page DISTRIBUTION:

PUBLIC RidsNrrDciCptb LPL3-2 R/F RidsOgcRp RidsNrrDorlLpl3-2 RidsAcrsAcnwMailCenter RidsNrrPMRKuntz OYee, NRR RidsNrrLADClarke RidsRgn3MailCenter RidsNrrDorlDpr RidsSecyMailCenter Accession Number: ML062230351 NRR-028

• no legal objection OFFICE LPL3-2/PM LPL3-2/LA CPTB/BC(A)

OGC

• LPL3-2/BC NAME RKuntz:mw DClarke TLiu (TScarborough for)

TCampbell DCollins DATE 9/6/06 9/6/06 8/17/06 9/5/06 9/7/06 OFFICIAL RECORD COPY

Byron Station, Units 1 and 2 cc:

Regional Administrator, Region III U.S. Nuclear Regulatory Commission 2443 Warrenville Road, Suite 210 Lisle, IL 60532-4351 Illinois Emergency Management Agency Division of Disaster Assistance &

Preparedness 110 East Adams Street Springfield, IL 62701-1109 Document Control Desk - Licensing Exelon Generation Company, LLC 4300 Winfield Road Warrenville, IL 60555 Mr. Dwain W. Alexander, Project Manager Westinghouse Electric Corporation P.O. Box 355 Pittsburgh, PA 15230 Howard A. Learner Environmental Law and Policy Center of the Midwest 35 East Wacker Drive Suite 1300 Chicago, IL 60601-2110 U.S. Nuclear Regulatory Commission Byron Resident Inspectors Office 4448 North German Church Road Byron, IL 61010-9750 Ms. Lorraine Creek RR 1, Box 182 Manteno, IL 60950 Chairman, Ogle County Board P.O. Box 357 Oregon, IL 61061 Mrs. Phillip B. Johnson 1907 Stratford Lane Rockford, IL 61107 Attorney General 500 S. Second Street Springfield, IL 62701 Plant Manager - Byron Station Exelon Generation Company, LLC 4450 N. German Church Road Byron, IL 61010-9794 Site Vice President - Byron Station Exelon Generation Company, LLC 4450 N. German Church Road Byron, IL 61010-9794 Senior Vice President - Operations Support Exelon Generation Company, LLC 4300 Winfield Road Warrenville, IL 60555 Chairman Will County Board of Supervisors Will County Board Courthouse Joliet, IL 60434 Director - Licensing and Regulatory Affairs Exelon Generation Company, LLC 4300 Winfield Road Warrenville, IL 60555 Manager Regulatory Assurance - Byron Exelon Generation Company, LLC 4450 N. German Church Road Byron, IL 61010-9794 Assistant General Counsel Exelon Generation Company, LLC 200 Exelon Way Kennett Square, PA 19348

Byron Station, Units 1 and 2 cc:

Vice President - Regulatory & Legal Affairs Exelon Generation Company, LLC 4300 Winfield Road Warrenville, IL 60555 Manager Licensing - Braidwood and Byron Exelon Generation Company, LLC 4300 Winfield Road Warrenville, IL 60555 Senior Vice President - Midwest Operations Exelon Generation Company, LLC 4300 Winfield Road Warrenville, IL 60555

SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO INSERVICE TESTING OF PUMPS AND VALVES EXELON GENERATION COMPANY, LLC BYRON STATION, UNIT NOS. 1 AND 2 DOCKET NOS. STN 50-454 AND STN 50-455

1.0 INTRODUCTION

By letter to the Nuclear Regulatory Commission (NRC, the Commission) dated December 29, 2005 (Agencywide Documents Access and Management System (ADAMS) Accession Number ML060240261), as supplemented by letter dated July 11, 2006 (ADAMS Accession Number ML061930087), Exelon Generation Company, LLC (the licensee) requested relief from the American Society of Mechanical Engineers Code for Operation and Maintenance of Nuclear Power Plants (ASME OM Code) 2001 Edition through 2003 Addenda for Byron Station (Byron),

Unit Nos. 1 and 2, for the third 10-year interval, which began June 30, 2006 and will end on July 1, 2016. The licensee requested relief from the inservice testing (IST) program for pumps and valves.

The NRC staff has completed its review of relief requests RP-1, RP-5 and RV-1, which are addressed in the following safety evaluation. Relief requests RP-4 and RP-6 were withdrawn by the licensee in its July 11, 2006, letter. The NRC staff is continuing its review of relief requests RP-2 and RP-3. Relief requests RP-2 and RP-3 will be addressed in future correspondence.

2.0 REGULATORY EVALUATION

Title 10 of the Code of Federal Regulations (10 CFR) Section 50.55a(f)(4), requires that IST of certain ASME Code Class 1, 2, and 3 pumps and valves be performed in accordance with the specified ASME OM Code incorporated by reference in the regulations, except where alternatives have been authorized or relief has been requested by the licensee and granted by the Commission pursuant to paragraphs (a)(3)(i), (a)(3)(ii), or (f)(6)(i) of 10 CFR 50.55a. In accordance with 10 CFR 50.55a(f)(4)(ii), licensees are required to comply with the requirements of the latest edition and addenda of the ASME OM Code incorporated by reference in the regulations 12 months prior to the start of each 120-month IST program interval. In accordance with 10 CFR 50.55a(f)(4)(iv), IST of pumps and valves may meet the requirements set forth in subsequent editions and addenda that are incorporated by reference in 10 CFR 50.55a(b),

subject to NRC approval. Section 50.55a(f)(4)(iv) states that [p]ortions of editions or addenda may be used provided that all related requirements of the respective editions and addenda are met. In proposing alternatives or requesting relief, the licensee must demonstrate that:

(1) the proposed alternatives would provide an acceptable level of quality and safety (10 CFR 50.55a(3)(i)); (2) compliance would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety (10 CFR 50.55a(3)(ii)); or (3) conformance is impractical for the facility (10 CFR 50.55a(f)(6)(i)). Section 50.55a(a)(3) allows the Commission to authorize alternatives and to grant relief from ASME Code requirements upon making necessary findings. NRC guidance contained in Generic Letter (GL) 89-04, Guidance on Developing Acceptable Inservice Testing Programs, provides alternatives to Code requirements which are acceptable. Further guidance is given in GL 89-04, Supplement 1, and NUREG-1482, Revision 1, Guidance for Inservice Testing at Nuclear Power Plants.

The Byron third 10-year IST interval commenced June 30, 2006. The program was developed in accordance with the 2001 Edition through the 2003 Addenda of the ASME OM Code. By letter dated December 29, 2005, as supplemented on July, 11 2006, the licensee requested relief from certain requirements of the ASME OM Code for the third 10-year IST interval at Byron.

3.0 TECHNICAL EVALUATION

3.1 Relief Request RP-1, Essential Service Water Makeup Pumps Vibration Limits 3.1.1 Relief Request RP-1 Code Requirements Table ISTB-5200-1, Vertical Line Shaft and Centrifugal Pumps Test Acceptance Criteria, of the ASME OM Code specifies the vibration limits (Vr) for the vertical line shaft pumps operating at or above 600 revolutions per minute (rpm) as the following for both Group A and the comprehensive pump test (CPT):

Reference Value Acceptable Alert Required Action Vr

1. 2.5 Vr

>2.5 Vr to 6.0 Vr or

>0.325 in/sec

>6.0 Vr or

>0.70 in/sec 3.1.2 Specific Relief Requested for RP-1 The licensee requested relief from the ASME OM Code requirements of Table ISTB-5200-1 for Essential Service Water (SX) Makeup Pumps A and B (0SX02PA and 0SX02PB).

3.1.3 Licensees Basis for Requesting Relief RP-1 In its December 29, 2005, submittal, the licensee requested relief pursuant to 10 CFR 50.55a(a)(3)(i), stating the proposed alternative would provide an acceptable level of quality and safety.

The SX makeup pumps are a unique design. For each pump, a horizontal diesel drives a right angle gearbox located approximately 39 feet above the pump. The drive shaft from the gearbox to the pump consists of five coupled sections and is located in the pump discharge piping column. Pump thrust is carried by bearings physically located within the gearbox.

The centrifugal pump is submerged in river water.

This pump configuration is not addressed by the 2001 Edition through the 2003 Addenda of the ASME OM Code. Due to the monitoring limitations of this design, and because of its similarity to Code requirements for vertical line shaft pumps, vibration is monitored on the gearbox.

The limitation of taking the vibration readings at this location is that the resultant vibration readings are not attributable to the pump. Vibration analysis has indicated that the vibration readings obtained are the result of vibration induced by the diesel engine and gearbox itself, along with a resonant condition of the gearbox and its foundation.

A similar relief request was granted for Byron for the second 10-year IST interval. Since the previous request for relief, maintenance and inspection activities have indicated that the angle gearboxes have been operating properly and without degradation. Maintenance and inspection activities on the pumps have indicated that there has not been any pump degradation due to the vibration observed on the gearboxes. Likewise, the pump units have not caused vibration degradation of the gearboxes. The pump impellers have been replaced with stainless steel units and the wear rings replaced with a wear resistant alloy, due to the adverse quality of river water associated with SX makeup pumps. The new pump assemblies were tested at the vendor's facility and exhibited very low vibration levels.

Byron recently consulted an industry vibration expert and vendor representative from the gearbox company in an effort to ensure vibration levels are as low as achievable with this particular design, and to ensure the existing vibration levels are not indicative of pump degradation. These efforts included the following activities:

Field service representatives from the gearbox company supervised the refurbishment of the two gearboxes. Both refurbished units were then installed on the pumps. The units that were refurbished had seen a significant amount of service under the historically higher vibration conditions and when inspected, did not show any vibration related degradation.

Bi-directional support braces were installed on the gearboxes to address the vibration resonance problem.

The gearboxes were precision aligned and the couplings were balance checked upon installation.

These collective efforts resulted in some reduction in the vibration levels, however, not enough to remove the pumps from the ASME OM Code Alert Range. Since installation during plant construction, both pumps have experienced vibrations at the gearbox locations of up to 0.6 inches per second (ips). The licensee concluded those vibration levels recorded at the gearbox locations are normal for the unique design configuration and do not indicate an unusual condition of the gearbox or the pump. The limits established in the proposed alternate testing section (Section 3.1.4) will ensure that required action is taken if vibration levels increase while ensuring the pump is not prematurely declared inoperable.

The basis for the double test frequency (when pump vibration is in the alert range) is to provide for increased testing when vibration levels may indicate an abnormal pump condition. Since the gearbox normally exhibits relatively high vibration levels due to its unique design, the use of the Table ISTB-5200-1 alert range limits would result in pumps being placed into the alert range during normal pump operation. Raising the alert range limit for these pumps would ensure the pumps are placed in double test frequency at a vibration level that would be abnormal for the SX makeup pumps' design configuration.

3.1.4 Licensees Proposed Alternative Testing for Relief Request RP-1 The licensee proposes the use of the following limits when performing vibration testing of SX Makeup Pumps A and B (0SX02PA and 0SX02PB):

Reference Value Acceptable Alert Required Action Vr

1. 2.5 Vr or

1. 0.55 in/sec

>2.5 Vr to 6.0 Vr or

>0.55 in/sec

>6.0 Vr or

>0.70 in/sec Increasing the alert range limits for these pumps would ensure that pumps are placed in double test frequency at a vibration level that would be abnormal for the design configuration of the pump.

3.1.5 Evaluation of Relief Request RP-1 The ASME OM Code requires that safety-related pumps be tested quarterly. Hydraulic and mechanical data are taken at each test and compared with their respective reference values to measure any degradation that may have occurred. When certain performance parameters exceed the alert range limit, the test frequency of the pump is doubled to gather more information on the condition of the pump. When a pump is operating in the alert range, it is considered operable. The NRC has an expectation that pumps which are operating in the alert range and clearly demonstrate degrading performance, are addressed in a reasonable period of time. When a specific performance parameter exceeds the required action limit, the pump is immediately declared inoperable and appropriate action is taken in accordance with the ASME OM Code requirements and plant technical specifications (TSs).

The two SX makeup pumps at Byron have a safety-related function to provide an emergency source of water to the ultimate heat sink for both units. These pumps are multistage vertical line shaft pumps which are each driven by a diesel engine connected through a right angle gearbox. Paragraph ISTB-3540(b) of the ASME Code requires that for vertical line shaft pumps, measurements will be taken on the upper motor bearing housing in three orthogonal directions, one of which is the axial direction. Since the diesel drive is not directly connected to the pump, vibration measurements are taken at the gearbox. Certain measured gearbox vibration parameters exceed the absolute alert range vibration limit of 0.325 ips resulting in these pumps being on a test interval of approximately once every 6 weeks.

The NRC staff considered the following in evaluating the alternatives to increase the absolute vibration limits: (1) documentation of vibration history which verifies that the pump has operated satisfactorily at this vibration level for a significant period of time without degradation, (2) results of consultations with vendors or vibration experts to assess the operation of the pump at elevated vibration levels, (3) description of attempts to lower the vibration levels below the ASME OM Code absolute alert range limit, and (4) results of spectral analysis which identifies all significant contributors to the overall vibration level. The ASME OM Code currently has no mechanism to exit the absolute alert range limit based on any type of analysis.

With regard to vibration history, the licensee stated in its December 29, 2005, submittal that vibration levels measured at the gearbox have been up to 0.6 ips. The licensee has consulted with the vendor and vibration experts. The gearbox vendor has provided documentation stating that 0.550 ips is an acceptable absolute vibration alert range limit. The pump vendor has verified that the new factory tested stainless steel impellers had very low vibration levels which, at a minimum, are below the absolute vibration alert range limit. The material condition of the gearbox has been examined and no degradation due to vibration was noted.

The licensee has taken measures to reduce the measured overall vibration. These include adding supports to stiffen the right angle gearbox and better alignment of the gearboxes and couplings. Both efforts reduced the overall vibration levels but not to the level where they were consistently below the absolute vibration alert range limit.

With regard to spectral analysis, the licensees relief request for the second 10-year IST interval did not specifically reference spectral analysis. By letter dated January 3, 2002 (ADAMS Accession Number ML020370054), the licensee stated that the spectral analysis is performed as part of the ASME IST vibration data collection. Any pump vibration concerns are going to be met with more comprehensive special testing and appropriate corrective maintenance will be performed.

Continued implementation of the ASME OM Code absolute alert range limit requirement will subject these pumps to unnecessary testing. Therefore, the ASME OM Code requirement for these pumps is a hardship as further compliance does not result in a compensating increase in the level of quality and safety. The proposed alternative testing provides a reasonable assurance of operational readiness because (1) the licensee has established that the elevated vibration levels are characteristic of normal pump operation and that each pump is currently operating acceptably, (2) the licensee has consulted with vendor representatives and vibration experts, and they have concluded that the measured vibration levels do not result in degraded pump performance, and (3) the licensee has implemented modifications which have lowered the overall vibration levels, albeit not below the absolute alert range limit.

3.1.6 Relief Request RP-1 Conclusion The NRC staff authorizes the alternative proposed in Relief Request RP-1 pursuant to 10 CFR 50.55a(a)(3)(ii) for the third 10-year interval based on the finding that compliance with the vibration limits requirements in ASME OM Code Table ISTB-5200-1 for SX Makeup Pumps A and B (0SX02PA and 0SX02PB) results in a hardship without a compensating increase in the level of quality and safety. The third IST interval ends on July 1, 2016, at Byron.

3.2 Relief Request RP-5, Essential Service Water Makeup Pumps Suction Gauge Accuracy for the Comprehensive Test 3.2.1 Code Requirements for Relief Request RP-5 Table ISTB-3500-1 of the ASME OM Code specifies the instrument accuracy of different measurements for Group A and B tests, Comprehensive Tests and Preservice Tests, as the following:

Quantity Group A and B Test, %

Comprehensive and Preservice Tests, %

Pressure

+/- 2

+/- 0.5 Flow Rate

+/- 2

+/- 2 Vibration

+/- 5

+/- 5 Differential Pressure

+/- 2

+/- 0.5 3.2.2 Specific Relief Requested for RP-5 The licensee requested relief from the Code requirements of Table ISTB-3500-1 for SX Makeup Pumps A and B (0SX02PA and 0SX02PB).

3.2.3 Licensees Basis for Requesting Relief RP-5 Relief is requested pursuant to 10 CFR 50.55a(a)(3)(i), as the proposed alternative would provide an acceptable level of quality and safety.

Due to the design of the SX makeup pumps (vertical line shaft), the suction pressure is determined by using a combination of river level, traveling screen differential level and pump elevation.

Differential pressure is determined by subtracting the suction pressure from the discharge pressure. Due to the vertical design of these pumps, suction pressure is determined as follows:

Ps = [Lr - (DL/12) - 661.75]/2.31 Ps = suction pressure in pounds per square inch gauge (psig)

Lr = river level (feet)

DL = traveling screen differential level (inches) 661.75 = pump elevation (feet) 2.31 = constant conversion for water (feet of head to psi)

The river elevation (Lr) is the determining factor in the calculation of suction pressure. River elevation varies between approximately 670 to 680 feet based on seasonal factors. The traveling screen differential level is normally less that 12 inches. The accuracy of the existing level instrument is +/- 2 percent. This equates to a possible error of 0.24 inches. When converted to psi, the maximum error is 0.009 psi ([0.24 inches/12 inches/foot] / 2.31). For the CPT of these pumps, the ASME OM Code-required accuracy for pressure is 0.5 percent. This equates to a maximum possible error of 0.06 inches. When converted to psi, the maximum error in the suction pressure is 0.0022 psi ([0.06 inches/12 inches/foot] / 2.31). The difference between the permanently installed instrument and the ASME OM Code required 0.5 percent accuracy amounts to 0.007 psi. This difference is inconsequential when determining the suction pressure (normal range 3.0 to 5.0 psig).

Additionally, since the differential pressure parameter is driven by the discharge pressure of the pumps, the traveling screen differential level has little bearing on the overall calculation of pump differential pressure. The reference value for differential pressure for these pumps is approximately 150 psi differential. Using the installed 2 percent differential level instrument induces a maximum error of 0.006 percent (0.009 psi/150.0 psi). Increasing the accuracy of the differential level instrument to 0.5 percent would reduce the maximum error to.0015 percent (0.0022 psi/150.0 psi).

The traveling screen differential level instrument is manufactured by Prosonic model number FMU 862. This instrument is an ultrasonic level instrument. Due to high turbulence and inherent gauge quality, it is not possible to calibrate this instrument to less than 2 percent.

3.2.4 Licensees Proposed Alternative Testing for Relief Request RP-5 The licensee proposes to perform the CPT of these pumps using 2 percent accurate instruments for determining suction pressure. All other measurements and methods will meet the 0.5 percent accuracy requirements for determining pump differential pressure.

Quantity Group A and B Test, %

Comprehensive and Preservice Tests, %

Differential Pressure

+/- 2

+/- 2 3.2.5 Evaluation of Pump Relief Request RP-5 The ASME OM Code, Table ISTB-3500-1 requires that CPT differential pressure instrument accuracy be within +/- 0.5 percent. The licensee has requested relief from the above ASME OM Code requirement because they have determined that the traveling screen differential level comprehensive test instrument does not meet the ASME OM Code accuracy for the SX Makeup Pumps A and B (0SX02PA and 0SX02PB). The licensee has proposed an alternative to the requirements of Table ISTB-3500-1 that would measure the pumps differential pressure to the an accuracy of

+/- 2 percent.

The SX makeup pumps in question are meant to maintain the cooling tower basin level to compensate for drift losses, evaporation and blowdown. Differential pressure is driven by discharge pressure, while the traveling screen differential level has little effect on the overall calculation. With a reference value of 150 psi differential, a 2 percent accuracy would cause an error of 0.006 percent. Whereas, a 0.5 percent accuracy gauge would reduce the error to 0.0015 percent. The licensee has demonstrated in Section 3.2.3 above, that the effects of the small improvements are insignificant when compared to the reference values.

The NRC staff has reviewed the Table ISTB-3500-1 requirements. The intent of the requirements is to ensure that the accuracy readings obtained from differential pressure instrumentation is accurate enough to make degradation monitoring meaningful. The licensees proposed alternative meets the intent of the ASME OM Code requirements. The licensee will perform the CPT for these pumps using 2 percent accurate instruments for determining suction pressure. While all other measurements and methods will meet the 0.5 percent accuracy requirements for determining pump differential pressure. The NRC staff finds that the proposed alternative, to use differential pressure instrumentation that are accurate within 2 percent for determining suction pressure, will provide an acceptable level of quality and safety.

3.2.6 Conclusion for Relief Request RP-5 Pursuant to 10 CFR 50.55a(a)(3)(i), the NRC staff authorizes the alternative proposed in Relief Request RP-5 for the third 10-year interval. The NRC staff finds that the proposed alternative, to use differential pressure instrumentation that are accurate within 2 percent for determining suction pressure, will provide an acceptable level of quality and safety. The third IST interval ends on July 1, 2016, at Byron.

3.3 Relief Request RV-1, Containment Recirculation Sump Isolation Valve Test Frequency 3.3.1 Code Requirements for Relief Request RV-1 Paragraph ISTC-3510, Exercising Test Frequency, of the ASME OM Code requires Category A and B valves to be full-stroke exercise tested nominally every 3 months (i.e.,

quarterly), unless the conditions provided by ISTC-3521, Category A and Category B Valves, are used to justify an alternate test frequency. ISTC-3521(e) states that, if exercising is not practical during plant operation or cold shutdowns, it may be limited to full-stroke during refueling outages.

3.3.2 Specific Relief Requested for RV-1 The licensee requested relief from the ASME OM Code requirements of paragraph ISTC-3510 for containment sump recirculation suction valves (1SI8811A, 1SI8811B, 2SI8811A, and 2SI8811B) which are Class 2, Category B, 24-inch motor-operated gate valves.

These valves are located outside containment and are opened or closed to control the flow path from the containment recirculation sump to the RH removal and containment spray (CS) pump.

3.3.3 Licensees Basis for Requesting Relief RV-1 Relief is requested pursuant to 10 CFR 50.55a(a)(3)(i), as the proposed alternative would provide an acceptable level of quality and safety.

The 1/2SI8811A/B valves provide an isolation boundary between the suctions of the RH removal and CS pumps, and the containment recirculation sumps. Under normal plant operating conditions, the RH and CS systems are filled with borated water and the containment recirculation sumps are maintained in a dry state.

A stroke test of these valves requires the RH and CS pumps for a given train to be removed from service and the suction lines drained to prevent water flow from the refueling water storage tank and associated system piping into the normally empty containment recirculation sump. It takes approximately 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> to drain the RH and CS systems, perform the required valve tests, and refill and restore the systems to their normal configuration. An estimated 600 gallons of radioactive, borated water is drained and must be processed by the radioactive waste systems. This same amount of borated water must be used to refill the system. This sequence of events is required whether the testing is done online or during a refueling outage.

The history of both the maintenance and IST for all eight of these valves at Byron (as well as at Byrons sister plant, Braidwood) show good material condition and that testing is consistent with acceptable stroke times, demonstrating that an acceptable level of quality and safety is maintained with an 18-month test frequency.

The availability of the RH and CS systems can be optimized by performing the full-stroke tests of the containment recirculation sump valves during scheduled work windows for the RH and CS systems. Due to improvements in the logistics of planning and executing work, some maintenance of the RH system is performed online (i.e., Mode 1). At other times, the nature of the maintenance to be performed requires that the maintenance be performed during a refueling outage. The scope of the work on the system, the scheduling of work windows in the planning process, system availability requirements, personnel resources, and maintenance of an acceptable risk profile are impacted when this work is performed.

In order to minimize the number of drain/refill evolutions and the processing of radioactive, borated water described previously, it is advantageous to perform the containment recirculation sump valve exercise and stroke time tests during the same drain and refill evolution used to perform system maintenance.

3.3.4 Licensees Proposed Alternative Testing for Relief Request RV-1 The licensee proposes to test these valves at an 18-month frequency with a 25 percent allowance for flexibility in scheduling.

3.3.5 Evaluation of Valve Relief Request RV-1 In its relief request, the licensee stated, Due to improvements in the logistics of planning and executing work, some maintenance of the RH system is performed on line (i.e., Mode 1).

At other times, the nature of the maintenance to be performed requires that the maintenance be performed during a refueling outage...In order to minimize the number of drain/refill evolutions and the processing of radioactive, borated water described previously, it is advantageous to perform the containment recirculation sump valve exercise and stroke time tests during the same drain and refill evolution used to perform system maintenance.

The TS allowed outage time (AOT) for having one train of emergency core cooling system out of service in Modes 1 through 3 is 7 days. The total time necessary to complete the online RH system work window should be significantly less than this AOT. Addition of SI8811A/B valve work to the online work windows could require a work window of longer duration (than the existing online RH system work window) depending on the amount of work scheduled in the work window and the type of critical path activities.

The NRC staff recognizes that there is a trade-off, from a risk perspective, between testing these valves at power (when they could be needed to mitigate the consequences of a LOCA) and testing them during outages (when there may be a greater reliance on RH). The NRC staff also understands the impacts created when this work is performed.

Prior to performing either online or shutdown testing, its effect on risk must be evaluated in accordance with the requirements of 10 CFR 50.65(a)(4), Requirements for monitoring the effectiveness of maintenance at nuclear power plants. Section 50.65(a)(4) states, in part, before performing maintenance activities (including but not limited to surveillance, post-maintenance testing, and corrective and preventive maintenance), the licensee shall assess and manage the increase in risk that may result from the proposed maintenance activities. The licensee stated that the history of both the maintenance and IST for all eight valves at Byron (as well as at Byrons sister plant, Braidwood) show good material condition and that testing is consistent with applicable stroke times, demonstrating that an acceptable level of quality and safety is maintained with an 18-month test frequency.

Performing the exercise stroke time test of these valves online at an 18-month frequency (with a 25 percent allowance for flexibility in scheduling) during RH system maintenance work windows when the RH pump suction piping is drained, will reduce overall system/train out-of-service time, and thus, will provide an acceptable level of quality and safety. However, if there is not an online RH system maintenance work window that requires the RH pump suction piping to be drained, the exercise testing must continue to be tested during a refueling outage preferably when RH requirements are minimal.

3.3.6 Conclusion for Relief Request RV-1 On the basis of the above discussion, the NRC finds that the licensees proposed alternative is authorized pursuant to 10 CFR 50.55a(a)(3)(i) with additional modifications for the third 10-year interval based on the determination that it provides an acceptable level of quality and safety.

The additional modifications that apply are as follows: performing the exercise stroke time test of the valves online at an 18-month frequency (with a 25 percent allowance for flexibility in scheduling) during RH system maintenance work windows when the RH pump suction piping is drained will reduce overall system/train out of service time and, thus, will provide an acceptable level of quality and safety. If there is not an online RH system maintenance work window that requires the RH pump suction piping to be drained, the exercise and stroke time testing must continue to be tested during refueling outages (preferably when RH requirements are minimal).

The third IST interval ends on July 1, 2016, at Byron.

3.4 Withdraw of Relief Requests RP-4 and RP-6 The licensees December 29, 2005, submittal included Relief Request RP-4, Auxiliary Feedwater Essential Service Water Booster Pump Comprehensive Test, and RP-6, Comprehensive Pump Test Alert Range Frequency. The licensee, in its July 11, 2006, letter withdrew from NRC consideration RP-4 and RP-6. Consequently, the NRC staff did not complete its review of RP-4 and RP-6 and relief is not authorized.

4.0 CONCLUSION

The NRC staff concludes, pursuant to 10 CFR 50.55a(a)(3)(ii), that Relief Request RP-1 is authorized on the basis that compliance with the ASME OM Code results in a hardship without a compensating increase in the level of quality and safety. Pursuant to 10 CFR 50.55a(a)(3)(i),

Relief Request RP-5 is authorized on the basis that the proposed alternatives provide an acceptable level of quality and safety. Pursuant to 10 CFR 50.55a(a)(3)(i), Relief Request RV-1 is authorized with additional modifications on the basis that the proposed alternative provides an acceptable level of quality and safety. The additional modifications that apply for RV-1 are as follows: performing the exercise stroke time test of these valves online at an 18-month frequency (with a 25 percent allowance for flexibility in scheduling) during RH system maintenance work windows when the RH pump suction piping is drained will reduce overall system/train out-of-service time and, thus, will provide an acceptable level of quality and safety.

If there is not an online RH system maintenance work window that requires the RH pump suction piping to be drained, the exercise and stroke time testing must continue to be tested during refueling outages (preferably when RH requirements are minimal). The relief requests are authorized for the third 10-year interval which ends on July 1, 2016.

Principal Contributor: O. Yee Date: September 7, 2006