ML080360321

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License Amendment Nos. 183 and 170, Revision to Technical Specification Surveillance Requirement 4.5.2.d for Inspection of Emergency Core Cooling System Sumps
ML080360321
Person / Time
Site: South Texas  STP Nuclear Operating Company icon.png
Issue date: 03/25/2008
From: Thadani M
NRC/NRR/ADRO/DORL/LPLIV
To: Sheppard J
South Texas
Thadani, M C, NRR/DORL/LP4, 415-1476
Shared Package
ML080360209 List:
References
TAC MD5705, TAC MD5706
Download: ML080360321 (19)
v • d • e


Text

March 25, 2008 Mr. James J. Sheppard President and Chief Executive Officer STP Nuclear Operating Company South Texas Project Electric Generating Station P.O. Box 289 Wadsworth, TX 77483

SUBJECT:

SOUTH TEXAS PROJECT, UNITS 1 AND 2 - ISSUANCE OF AMENDMENTS RE: SURVEILLANCE REQUIREMENTS FOR EMERGENCY CORE COOLING SYSTEM SUMPS (TAC NOS. MD5705 AND MD5706)

Dear Mr. Sheppard:

The Commission has issued the enclosed Amendment No. 183 to Facility Operating License No. NPF-76 and Amendment No. 170 to Facility Operating License No. NPF-80 for the South Texas Project (STP), Units 1 and 2, respectively. The amendments consist of changes to the Technical Specifications (TS) in response to your application dated May 21, 2007, as supplemented by letter dated November 26, 2007.

The amendments revise TS Surveillance Requirement 4.5.2.d for the inspection of the emergency core cooling system sump for consistency with the new STP, Units 1 and 2, sump designs.

A copy of our related Safety Evaluation is also enclosed. The Notice of Issuance will be included in the Commission's next biweekly Federal Register notice.

Sincerely,

/RA/

Mohan C. Thadani, Senior Project Manager Plant Licensing Branch IV Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket Nos. 50-498 and 50-499

Enclosures:

1. Amendment No. 183 to NPF-76
2. Amendment No. 170 to NPF-80
3. Safety Evaluation cc w/encls: See next page

Pkg ML080360209, Amdt. ML080360321, License/TS Pgs ML080360328 (*) SE input memo OFFICE DORL/LPL4/PM DORL/LPL4/LA DSS/SSIB/BC DIRS/ITSB/BCA OGC - NLO w/comments DORL/LPL4/BC NAME MThadani (**) JBurkhardt (**) MScott (*) GWaig (**) AHodgdon (**) THiltz DATE 3/5/08 3/5/08 12/20/07 3/13/08 3/21/08 3/25/08 South Texas Project, Units 1 and 2 12/5/2007 cc:

Senior Resident Inspector E. D. Halpin, Site Vice President U.S. Nuclear Regulatory Commission STP Nuclear Operating Company P.O. Box 289 South Texas Project Electric Generating Station Wadsworth, TX 77483 P.O. Box 289 Wadsworth, TX 77483 C. M. Canady City of Austin S. M. Head, Manager, Licensing Electric Utility Department STP Nuclear Operating Company 721 Barton Springs Road P.O. Box 289, Mail Code: N5014 Austin, TX 78704 Wadsworth, TX 77483 J. J. Nesrsta/R. K. Temple C. T. Bowman, General Manager, Oversight E. Alercon/Kevin Pollo STP Nuclear Operating Company CPS Energy P.O Box 289 P.O. Box 1771 Wadsworth, TX 77483 San Antonio, TX 78296 Ms. Marilyn Kistler INPO Senior Staff Specialist, Licensing Records Center STP Nuclear Operating Company 700 Galleria Parkway P.O. Box 289, Mail Code 5014 Atlanta, GA 30339-3064 Wadsworth, TX 77483 Regional Administrator, Region IV Environmental and Natural Resources U.S. Nuclear Regulatory Commission Policy Director 611 Ryan Plaza Drive, Suite 400 P.O. Box 12428 Arlington, TX 76011 Austin, TX 78711-3189 Steve Winn/Christie Jacobs Mr. Jon C. Wood Eddy Daniels/Marty Ryan Cox, Smith, & Matthews NRC Energy, Inc. 112 East Pecan, Suite 1800 211 Carnegie Center San Antonio, TX 78205 Princeton, NJ 08540 Director, Division of Compliance & Inspection Mr. Nate McDonald Bureau of Radiation Control County Judge for Matagorda County Texas Department of State Health Services 1700 7th Street, Room 301 1100 West 49th Street Bay City, TX 77414 Austin, TX 78756 A. H. Gutterman, Esq. Mr. Ted Enos Morgan, Lewis & Bockius 4200 South Hulen 1111 Pennsylvania Avenue, NW Suite 422 Washington, DC 20004 Ft. Worth, TX 76109 Mr. Brian Almon Public Utility Commission of Texas P.O. Box 13326 Austin, TX 78711-3326

South Texas Project, Units 1 and 2 12/5/2007 Ms. Susan M. Jablonski Mr. Ken Coates, Plant General Manager Office of Permitting, Remediation STP Nuclear Operating Company and Registration South Texas Project Electric Generating Station Texas Commission on Environmental Quality P.O. Box 289 MC-122 Wadsworth, TX 77483 P.O. Box 13087 Austin, TX 78711-3087 Mr. Anthony P. Jones, Chief Boiler Inspector Texas Department of Licensing and Regulation Boiler Division E.O. Thompson State Office Building P.O. Box 12157 Austin, TX 78711

STP NUCLEAR OPERATING COMPANY DOCKET NO. 50-498 SOUTH TEXAS PROJECT, UNIT 1 AMENDMENT TO FACILITY OPERATING LICENSE Amendment No. 183 License No. NPF-76

1. The Nuclear Regulatory Commission (the Commission) has found that:

A. The application for amendment by STP Nuclear Operating Company (STPNOC)*

acting on behalf of itself and for NRG South Texas LP, the City Public Service Board of San Antonio (CPS), and the City of Austin, Texas (COA) (the licensees),

dated May 21, 2007, as supplemented by letter dated November 26, 2007, complies with the standards and requirements of the Atomic Energy Act of 1954, as amended (the Act), and the Commission's rules and regulations set forth in 10 CFR Chapter I; B. The facility will operate in conformity with the application, as amended, the provisions of the Act, and the rules and regulations of the Commission; C. There is reasonable assurance (i) that the activities authorized by this amendment can be conducted without endangering the health and safety of the public, and (ii) that such activities will be conducted in compliance with the Commission's regulations; D. The issuance of this license amendment will not be inimical to the common defense and security or to the health and safety of the public; and E. The issuance of this amendment is in accordance with 10 CFR Part 51 of the Commission's regulations and all applicable requirements have been satisfied.

  • STPNOC is authorized to act for NRG South Texas LP, the City Public Service Board of San Antonio, and the City of Austin, Texas, and has exclusive responsibility and control over the physical construction, operation, and maintenance of the facility.
2. Accordingly, the license is amended by changes to the Technical Specifications as indicated in the attachment to this license amendment, and Paragraph 2.C.(2) of Facility Operating License No. NPF-76 is hereby amended to read as follows:

(2) Technical Specifications The Technical Specifications contained in Appendix A, as revised through Amendment No. 183, and the Environmental Protection Plan contained in Appendix B, are hereby incorporated in the license. STPNOC shall operate the facility in accordance with the Technical Specifications and the Environmental Protection Plan.

3. The license amendment is effective as of its date of issuance and shall be implemented no later than July 31, 2008.

FOR THE NUCLEAR REGULATORY COMMISSION

/RA/

Thomas G. Hiltz, Chief Plant Licensing Branch IV Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation

Attachment:

Changes to the Facility Operating License No. NPF-76 and the Technical Specifications Date of Issuance: March 25, 2008

STP NUCLEAR OPERATING COMPANY DOCKET NO. 50-499 SOUTH TEXAS PROJECT, UNIT 2 AMENDMENT TO FACILITY OPERATING LICENSE Amendment No. 170 License No. NPF-80

1. The Nuclear Regulatory Commission (the Commission) has found that:

A. The application for amendment by STP Nuclear Operating Company (STPNOC)*

acting on behalf of itself and for NRG South Texas LP, the City Public Service Board of San Antonio (CPS), and the City of Austin, Texas (COA) (the licensees),

dated May 21, 2007, as supplemented by letter dated November 26, 2007, complies with the standards and requirements of the Atomic Energy Act of 1954, as amended (the Act), and the Commission's rules and regulations set forth in 10 CFR Chapter I; B. The facility will operate in conformity with the application, as amended, the provisions of the Act, and the rules and regulations of the Commission; C. There is reasonable assurance (i) that the activities authorized by this amendment can be conducted without endangering the health and safety of the public, and (ii) that such activities will be conducted in compliance with the Commission's regulations; D. The issuance of this license amendment will not be inimical to the common defense and security or to the health and safety of the public; and E. The issuance of this amendment is in accordance with 10 CFR Part 51 of the Commission's regulations and all applicable requirements have been satisfied.

  • STPNOC is authorized to act for NRG South Texas LP, the City Public Service Board of San Antonio, and the City of Austin, Texas, and has exclusive responsibility and control over the physical construction, operation, and maintenance of the facility.
2. Accordingly, the license is amended by changes to the Technical Specifications as indicated in the attachment to this license amendment, and Paragraph 2.C.(2) of Facility Operating License No. NPF-80 is hereby amended to read as follows:

(2) Technical Specifications The Technical Specifications contained in Appendix A, as revised through Amendment No. 170, and the Environmental Protection Plan contained in Appendix B, are hereby incorporated in the license. STPNOC shall operate the facility in accordance with the Technical Specifications and the Environmental Protection Plan.

3. The license amendment is effective as of its date of issuance and shall be implemented no later than July 31, 2008.

FOR THE NUCLEAR REGULATORY COMMISSION

/RA/

Thomas G. Hiltz, Chief Plant Licensing Branch IV Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation

Attachment:

Changes to the Facility Operating License No. NPF-80 and the Technical Specifications Date of Issuance: March 25, 2008

ATTACHMENT TO LICENSE AMENDMENT NOS. 183 AND 170 FACILITY OPERATING LICENSE NOS. NPF-76 AND NPF-80 DOCKET NOS. 50-498 AND 50-499 Replace the following pages of the Facility Operating Licenses, Nos. NPF-76 and NPF-80, and Appendix A Technical Specifications with the attached revised pages. The revised pages are identified by amendment number and contain marginal lines indicating the areas of change.

Facility Operating License No. NPF-76 REMOVE INSERT 4 4 Facility Operating License No. NPF-76 REMOVE INSERT 4 4 Technical Specifications REMOVE INSERT 3/4 5-4 3/4 5-4

SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NOS. 183 AND 170 TO FACILITY OPERATING LICENSE NOS. NPF-76 AND NPF-80 STP NUCLEAR OPERATING COMPANY, ET AL.

SOUTH TEXAS PROJECT, UNITS 1 AND 2 DOCKET NOS. 50-498 AND 50-499

1.0 INTRODUCTION

By letter dated May 21, 2007, as supplemented by letter dated November 26, 2007 (Agencywide Documents Access and Management System (ADAMS) Accession Nos. ML071560560 and ML073380340, respectively), STP Nuclear Operating Company (the licensee) proposed a change to the Technical Specifications (TS) for South Texas Project (STP), Units 1 and 2. The licensee indicated that the proposed change is intended to modify the TS to be consistent with the installation of new emergency core cooling system (ECCS) containment sump strainer assemblies. The licensee stated that the installation of new strainer assemblies is being performed to address concerns associated with Generic Safety Issue 191 (GSI-191),

Assessment of Debris Accumulation on PWR [Pressurized-Water Reactor] Sump Performance.

The specific change proposed by the licensee is to modify STP TS Surveillance Requirement (SR) 4.5.2.d. The primary purpose of the licensees revision to SR 4.5.2.d is to reflect that the replacement sump configuration does not include trash racks and to reflect the change from screens to strainers.

The supplemental letter dated November 26, 2007, provided additional information that clarified the application, did not expand the scope of the application as originally noticed, and did not change the staff's original proposed no significant hazards consideration determination as published in the Federal Register on July 31, 2007 (72 FR 41789).

2.0 REGULATORY EVALUATION

The licensee has proposed a change to the STP TS that relates to the design of the ECCS containment sump and the periodic inspection of the sump and its strainer assemblies.

Regulatory requirements concerning the ECCS containment sump and associated systems (e.g., the ECCS and containment spray system (CSS)) include the following:

  • Paragraph 50.46(b)(5) of Title 10 of the Code of Federal Regulations (10 CFR),

"Acceptance criteria for emergency core cooling systems for light-water nuclear

power reactors, states that after any calculated successful initial operation of the ECCS, the calculated core temperature shall be maintained at an acceptably low value and decay heat shall be removed for the extended period of time required by the long-lived radioactivity remaining in the core.

  • Section 50.36 of Part 50 of Title 10 of the Code of Federal Regulations (10 CFR 50.36) is the Commission's regulatory requirement that TSs are needed and that TSs are required to include items in five specific categories related to facility operation. One of the five categories is paragraph 50.36(d)(3), "Surveillance requirements." Surveillance requirements are requirements relating to test, calibration, or inspection to assure that the necessary quality of systems and components is maintained, that facility operation will be within safety limits, and that the limiting conditions for operation will be met. In this regard, SR 4.5.2.d is an inspection requirement for the ECCS.
  • Appendix A of 10 CFR Part 50, General Design Criterion (GDC) 35, Emergency core cooling, states that a system to provide abundant emergency core cooling shall be provided. The system safety function shall be to transfer heat from the reactor core following any loss of reactor coolant at a rate such that (1) fuel and clad damage that could interfere with continued effective core cooling is prevented and (2) clad metal-water reaction is limited to negligible amounts.

Suitable redundancy in components and features, and suitable interconnections, leak detection, isolation, and containment capabilities shall be provided to assure that for onsite electric power system operation (assuming offsite power is not available) and for offsite electric power system operation (assuming onsite power is not available) the system safety function can be accomplished, assuming a single failure.

  • GDC 38, Containment heat removal, states that a system to remove heat from the reactor containment shall be provided. The system safety function shall be to reduce rapidly, consistent with the functioning of other associated systems, the containment pressure and temperature following any loss-of-coolant accident (LOCA) and maintain them at acceptably low levels. Suitable redundancy in components and features, and suitable interconnections, leak detection, isolation, and containment capabilities shall be provided to assure that for onsite electric power system operation (assuming offsite power is not available) and for offsite electric power system operation (assuming onsite power is not available) the system safety function can be accomplished, assuming a single failure.
  • GDC 39, Inspection of containment heat removal system, states that the containment heat removal system shall be designed to permit appropriate periodic inspection of important components, such as the torus, sumps, spray nozzles, and piping to assure the integrity and capability of the system.
  • GDC 41, Containment atmosphere cleanup, states that systems to control fission products, hydrogen, oxygen, and other substances which may be released into the reactor containment shall be provided as necessary to reduce, consistent with the functioning of other associated systems, the concentration and quality of fission products released to the environment following postulated accidents, and to control the concentration of hydrogen or oxygen and other substances in the containment atmosphere following postulated accidents to assure that containment integrity is maintained.

The basis for PWR licensees to demonstrate compliance with the regulatory requirements and commitments is documented in Generic Letter (GL) 2004-02, Potential Impact of Debris Blockage on Emergency Recirculation during Design Basis Accidents at Pressurized-Water Reactors. The primary purpose of GL 2004-02 was to request that PWR licensees evaluate the performance of their containment recirculation sumps and implement any modifications necessary to assure compliance with applicable regulatory requirements on a mechanistic basis in light of the technical issues associated with GSI-191. GL 2004-02 requested that PWR licensees complete actions necessary to assure compliance with applicable regulatory requirements using the updated information associated with GSI-191 by December 31, 2007.

Prior to this date, GL 2004-02 concluded that licensees compliance with their current licensing bases was sufficient to support continued plant operation.

In light of the regulatory framework established by GL 2004-02, this safety evaluation reviews the licensees proposed TS change under current licensing basis assumptions for analyzing the effects of post-accident debris blockage. Assurance that PWR licensees proposed sump modifications are adequate in light of the technical issues associated with GSI-191 will be provided separately through the staffs review of GL 2004-02 supplemental responses.

3.0 TECHNICAL EVALUATION

3.1 Background The licensee stated in its letter dated November 26, 2007, that the old sump configuration, as described in the STP Updated Final Safety Analysis Report Section 6.2.2.2.3, included three independent sumps that served as reservoirs for the ECCS and CSS pumps during the recirculation phase of a design-basis accident (DBA). Each sump was stainless-steel lined, contained a vortex suppressor, and was covered with a two-stage stainless-steel framed debris-interceptor structure composed of the following components and structures:

  • a trash rack made from stainless steel grating with a 4-inch by 1 and 3/16-inch spacing (approximately 80 percent open area),
  • a toe plate/curb made from stainless steel plate that is 6 inches high, which was located inside of the trash rack on the base plate,
  • a screen made from stainless steel plate with 1/4-inch diameter perforations at 5/16-inch center-to-center spacing (approximately 58 percent open area), and
  • a solid cover made of stainless steel plate with a manway provided for internal inspections of the structure, vortex suppressor, and sump.

The licensee stated that the sumps were located at elevation (-) 11 feet 3 inches. The sumps were physically separated from each other with no high-energy piping in the area. The floor around the emergency sumps sloped away from the strainers and toward normal sumps located in the area. The drains from the upper levels of the containment building did not terminate in the immediate area of the sumps.

The licensee stated that the new strainer for each sump consists of two five-module assemblies, one four-module assembly, and one six-module assembly. Each module is made up of 11 strainer disks. The strainer consists of perforated plate with 0.095-inch diameter openings.

Flow leaving the strainer enters a four-inlet plenum box (one inlet for each strainer assembly).

The plenum box collects the flow from the strainer assemblies and directs it downward into the sump pit. An access cover is provided on the plenum box for internal inspection of the sump structures, vortex suppressor, and the strainer assemblies.

The sump fluid collected by the new strainers is directed into the same sump pits where the old screens had been installed. A number of the aspects of the previous sump configuration described above remain unchanged, including the three independent sumps that serve as reservoirs for the ECCS and CSS pumps, the sump pits stainless steel lining, and the vortex suppressors.

The licensee stated that installation of trash racks was not necessary for the new strainers since the new advanced design strainer serves as a trash rack. The new strainers have a much larger surface area than the original sump screens. The licensee stated that this results in a greatly reduced average approach velocity at the strainer face, which decreases the risk of impact from large debris in the sump flow stream.

The licensee stated that the old screen had perforations of 0.25 inches diameter. Water entering the suction pipe from the sump may contain small particles less than 0.25 inches diameter. These particles cannot clog the containment spray nozzles (3/8-inch orifice diameter) which are the limiting restrictions found in any system served by the sump. The new strainers have a screen hole size of 0.095 inches diameter and thus meet this design requirement.

Furthermore, the new strainers are an enhanced design as compared to the original screens, with an improved capability to filter fine debris due to their decreased opening size. While the decreased perforation size may tend to increase head loss, under the current licensing basis methodology, this effect is more than offset by the significant increase in strainer area, as discussed below.

The licensee stated that the previous STP sumps were designed according to Regulatory Guide (RG) 1.82, proposed Revision 1, dated May 1983. The guidance in proposed Revision 1 of RG 1.82 recommends a calculation of the sump screen head loss due to debris blockage. The licensee indicated that, utilizing the current licensing basis methodology from proposed Revision 1 of RG 1.82, the pump net positive suction head (NPSH) available is sufficient to accommodate this calculated head loss. The new strainers have a surface area of 1818.5 square feet per sump. The old screens had a surface area of 155.4 square feet per sump. Thus, for the current licensing basis debris loading, the debris head loss with the new strainers will be substantially smaller than for the old screens.

The licensee stated that the new STP Unit 1 and Unit 2 strainer installation does not affect the independence and redundancy of the ECCS and CSS sumps. Three independent sumps will be maintained by the new strainer design.

3.2 Proposed Change to SR 4.5.2.d The staff has evaluated the licensees analysis in support of the proposed license amendment, which is contained in the licensees application and supplementary submittal. The staffs evaluation below reviews the licensees proposed modification to the containment sump surveillance inspection prescribed by SR 4.5.2.d.

Currently, along with other surveillance inspections of specific ECCS components required by SR 4.5.2, SR 4.5.2.d states that each ECCS subsystem shall be demonstrated to be OPERABLE:

At least once per 18 months by visual inspection of the containment sump and verifying that the subsystem suction inlets are not restricted by debris and that the sump components (trash racks, screens, etc.) show no evidence of structural distress or abnormal corrosion.

The licensee has proposed to revise SR 4.5.2.d by deleting the parenthetical examples of sump components, i.e., (trash racks, screens, etc.), as follows:

At least once per 18 months by visual inspection of the containment sump and verifying that the subsystem suction inlets are not restricted by debris and that the sump components show no evidence of structural distress or abnormal corrosion.

3.3 Licensees Justification for Proposed TS Change The licensee stated that the proposed change to TS SR 4.5.2.d provides a more appropriate description of the sump configuration after the installation of the larger replacement strainers.

The licensee stated that the parenthetical list of sump components currently in SR 4.5.2.d is not comprehensive and is not necessary for the determination of what comprises sump components. The requirement that, .all necessary.other auxiliary equipment that are required for the system, train, component, or device to perform its function(s) are also capable of performing their related support function(s), in the STP TS definition of OPERABLE -

OPERABILITY provides guidance to determine the sump components that are subject to SR 4.5.2.d.

The licensee stated that inspection of the containment emergency sump is governed by procedure. The licensee further indicated that the proposed revision to SR 4.5.2.d would not involve a reduction in the inspection scope compared to the surveillance inspection for the old screens. A visual inspection of the entire exterior and the interior of each strainer would still be conducted along with a visual inspection of the sump and the vortex suppressor.

The licensee stated that the sump inspection procedure includes criteria to assure the following:

  • There is no external evidence of structural distress or abnormal corrosion.
  • There are no pathways that would allow foreign objects or debris to enter the sump.
  • There are no structural joints with gaps larger than 0.095 inches.
  • There are no gaps in the strainer modules or associated piping fit-up connections.
  • There are no foreign materials remaining on or lodged into the gaps of the strainer modules.
  • There are no foreign materials inside the strainer core tubes, including the two strainer modules connected on a 45-degree angle on sumps A and B.
  • The sump suction inlet is not restricted.
  • The sump is dry, free of foreign objects, debris, and boron crystal build-up.

The licensee stated that the inspection to ensure no foreign material is in the core tubes of the two strainer modules connected on a 45-degree angle to sumps A and B can be performed by shining a light from the exterior through the perforated holes in the core tube end caps.

3.4 NRC Staffs Evaluation 3.4.1 NRC Staffs Evaluation of Strainer Configuration In addition to the information provided in the licensees original submittal, dated May 21, 2007, in performing its review, the staff also evaluated sump strainer design drawings and additional information provided by the licensee in a letter dated November 26, 2007.

In determining the adequacy of the licensee's proposed change to SR 4.5.2.d, the staff's evaluation considered whether the new sump configuration reduced the independence and redundancy of the ECCS and CSS sumps. Based on the licensees descriptions of the old and new sump configurations, as stated above, the staff concludes that the new strainer configuration maintains the independence and redundancy of the existing three-train sump configuration.

In determining the adequacy of the licensee's proposed TS change regarding the surveillance of the sump strainer, the staff's evaluation considered whether the replacement strainer assembly is capable of fulfilling the design functions of the original screens under the current licensing basis. The containment sumps design basis function is to provide the ability to circulate filtered containment pool water to cool the reactor core and to remove decay from the containment building following a LOCA, via the ECCS and CSS pumps. Based on a review of the licensees summary of its NPSH analysis, the staff concludes that the licensee has demonstrated adequate sump functionality based on providing sufficient NPSH to the ECCS and CSS pumps and preventing debris particles large enough to clog the most limiting flow restrictions (i.e., the containment spray nozzles) from entering the ECCS, thereby satisfying the current sump licensing basis.

Further, while the licensee's removal of the previous trash rack (as evaluated below) resulted in an implicit reduction in the components subject to SR 4.5.2.d, the proposed change to SR 4.5.2.d does not represent a reduction in the scope of the inspection of the replacement strainers as compared to the inspection scope for the previous sump screens. Therefore, the staff concludes that the functionality of the sump strainers will continue to be assured under SR 4.5.2.d.

The staff also evaluated the licensees argument that the new sump strainers serve the current licensing basis functions associated with the previous trash rack. The staff agrees with the licensees statement that the reduced average strainer approach velocity will tend to decrease the potential for large pieces of debris in the flow stream approaching the sump from damaging the strainers. Also, the new strainers are of robust construction. The staff further considers the filtration capability of the new sump strainers to be superior to the combined capability of the old screens and trash racks because of the new strainers larger surface area and complex geometry. The NRC staff concludes that the new strainers satisfy the current licensing basis functions associated with the previously installed trash racks.

Based on the above evaluation, the NRC staff considers the replacement strainers configuration meets the intent of current sump performance licensing basis.

3.4.2 NRC Staffs Evaluation of Dynamic Effects and Structural Integrity To ensure that the removal of the trash racks does not create adverse effects associated with dynamic effects (e.g., jet impingement, pipe whipping, and missiles), or structural adequacy, the NRC staff reviewed these areas as follows.

3.4.2.1 Pipe Whip, Jet Impingement, and Missile Impact The staffs review focused on whether the planned replacement strainer evaluation has adequately considered the potential dynamic effects associated with high-energy line break, pipe whip, jet impingement, and missile impact. In response to the staffs RAI, the licensee provided drawings showing the strainer assembly general arrangement of Performance Contracting, Inc.

sure-flow strainers for sumps A, B, and C. There are three independent sumps to serve as reservoirs to the ECCS and CSS pumps during the post-DBA recirculation phase. The sumps are located at an elevation of -11.25 feet. The sumps are physically separated from each other and from high-energy piping in the area. There are no high-energy lines in the area of the emergency sumps except for the High Head Safety Injection lines which are used for accident mitigation and are not assumed to be the accident initiator. The licensee further stated that no reviews or evaluations needed to be performed for the dynamic effects associated with high-energy line breaks, pipe whip and jet impingement, and missile impact on the modified strainer assemblies. No piping re-routes were needed for installation of the new sump strainers.

Based on its review of the information provided by the licensee, the staff finds that the new sump strainer is adequately protected from pipe whip, jet impingement, and missiles.

3.4.2.2 Structural Design of the Replacement Strainer In response to the staffs request for information on a summary of evaluations performed for the structural adequacy, the licensee provided the following summary information.

The new strainer assemblies for each sump consist of two five-module assemblies, one four-module assembly, and one six-module assembly. Each module is made up of 11 strainer disks. The strainer consists of perforated plate with 3/32-inch diameter openings. Flow leaving the strainer assembly enters a four-inlet plenum box (one inlet for each strainer assembly). The plenum box collects the flow from the strainer assemblies and directs it downward into the sump pit. The new strainers have a surface area of 1818.5 square feet per sump which is much larger than the surface area of 155.4 square feet per sump of the old screens. The sumps are designed to RG 1.82, Revision 1, dated May 1983.

The new strainers are designed for loads due to weight, pressure, and dynamic loads. The dynamic loads represent seismic and hydrodynamic drag loads due to sloshing. The strainers are loaded due to the inertia effect caused by the motion of the containment floor during an earthquake. Hydrodynamic loads on the strainers are due to the motion of the water surrounding the strainer during a seismic event. Two weight loads are applicable. This includes the weight of the strainer components themselves and the weight of the debris that accumulates on the strainer. The design weight of the debris per strainer module is taken as 150 pounds which bounds the calculated weight. Thermal expansion loads are taken as zero because the strainers are essentially freestanding structures that are basically free to expand without restraint due to sufficient gaps built-in to the pin connections that secure the modules to the floor tracks.

Thermal expansion loads on the sump pit cover plate and the floor angles are considered negligible because these components have slotted holes or edge clips to allow for substantially unrestrained thermal growth. The pressure load acting on the strainer is the differential pressure across the strainer perforated plates in the operating condition. This is defined as 5.71 feet of water head.

The load combinations and the allowable stresses utilized in the sump strainer design are summarized below:

Load Condition Combination Allowable Normal Operating DW + DP + WD 1.0 S Normal Operating (Outage/Lift Load) DW + LL 1.0 S Operating Basis Earthquake DW + DP + WD + OBE 1.0 S Safe Shutdown Earthquake DW + DP + WD + SSE 1.6 S Notes:

DW = Dead Weight Load LL = Live Load (additional live loads acting on strainer assembly during outages only)

WD = Weight of Debris DP = Differential Pressure OBE = Operating Basis Earthquake SSE = Safe-Shutdown Earthquake S = Required section strength based on elastic design method and the allowable stress defined in the 7th edition AISC [American Institute of Steel Construction]

Specification, or other applicable specifications (ASCE [American Society of Civil Engineers] 8-00, N-690, etc.).

The licensee also stated that the calculation for seismic design margins for the strainers and their components shows that the stress Interaction Ratios (calculated stress/allowable stress) are less than one for both OBE and SSE loads. The strainer components are designed in accordance with the AISC Specification for the Design, Fabrication, and Erection of Structural

Steel for Buildings, 7th Edition, with supplement numbers 1, 2 and 3; and Structural Engineering Institute (SEI)/ASCE 8-02, Specification for the Design of Cold-Formed Stainless Steel Structural Members. The acceptance criteria are primarily in accordance with these codes. In circumstances where these specifications do not provide adequate guidance for a particular component, other codes, specifications or standards are used for guidance. For instance, the strainers are made from stainless steel materials. The AISC Specification does not specifically cover stainless steel materials. Therefore, American National Standards Institute (ANSI)/AISC N690-1994, Specification for the Design, Fabrication, and Erection of Steel Safety Related Structures for Nuclear Facilities, is used to supplement the AISC Specification in any areas specifically related to the structural qualification of stainless steel. The staff noted that only the allowable stresses are used from this Specification; however, load combinations and allowable stress factors for higher service levels are not used. For the perforated plates, the equations from Appendix A, Article A-8000 of the American Society of Mechanical Engineers (ASME)

Boiler and Pressure Vessel Code,Section III, 1998 Edition are used instead of the AISC code.

Appendix A, Article A-8000 is deemed more appropriate because it is written specifically for perforated plates. The strainer also has several components made from thin-gauge sheet steel, and cold-formed stainless steel sheet. SEI/ASCE 8-02, Specification of the Design of Cold-Formed Stainless Steel Structural Members, is used for certain components where rules specific to thin-gauge and cold-formed stainless steel are applicable. The rules for Allowable Stress Design (ASD) as specified in Appendix D of this specification are used. This is further supplemented by the American Iron and Steel Institute (AISI) Specification where the ASCE Specification is lacking specific guidance. Finally, guidance is also taken from American Welding Society (AWS) D1.6, Structural Welding Code - Stainless Steel, as it relates to the qualification of stainless steel welds.

The staff finds that the load combinations used in the structural design of the strainer meet the guidance of RG 1.82, and the licensee has adequately evaluated the dynamic effects on replacement sump strainer assemblies.

Based on the above evaluation, the NRC staff considers the evaluation of the replacement strainers dynamic effects impacts and structural adequacy meet the intent of current sump performance licensing basis.

3.4.4 Conclusions of NRC Staffs Evaluation Based on the above evaluation, the NRC staff considers the replacement strainers configuration, dynamic effects impacts, and structural adequacy meet the intent of current sump performance licensing basis for satisfying the requirements of 10 CFR 50.46(b)(5) for long-term reactor core cooling.

The NRC staff concluded that the new strainers satisfy the current licensing basis functions associated with the previously installed trash racks. Furthermore, the staff determined that the proposed change to SR 4.5.2.d does not reduce the scope of the surveillance inspection as compared to the inspection that was performed on the previously installed sump screens.

Therefore, since the replacement strainer serves the current licensing basis functions of both the previous sump screen and the trash rack, SR 4.5.2.d will continue to provide assurance of adequate sump performance under the current licensing basis. Thus, the staff concluded that the licensee's proposed change to SR 4.5.2.d is acceptable.

The staffs acceptance of these proposed changes do not imply approval of the licensees corrective actions to address GL 2004-02. Consistent with the intent of GL 2004-02, the licensees current licensing basis compliance is sufficient until June 30, 2008, the date for completion of corrective actions, as approved by the NRC staff in a December 19, 2007, letter.

Assurance that the licensee's replacement strainer design is adequate for satisfying the intent of GL 2004-02 will be provided by the staff's regulatory activities associated with the review of supplemental responses to GL 2004-02 and other GL 2004-02 and GSI-191 closeout activities.

4.0 STATE CONSULTATION

In accordance with the Commission's regulations, the Texas State official was notified of the proposed issuance of the amendment. The State official had no comments.

5.0 ENVIRONMENTAL CONSIDERATION

The amendments change a requirement with respect to installation or use of a facility component located within the restricted area as defined in 10 CFR Part 20. The NRC staff has determined that the amendments involve no significant increase in the amounts, and no significant change in the types, of any effluents that may be released offsite, and that there is no significant increase in individual or cumulative occupational radiation exposure. The Commission has previously issued a proposed finding that the amendments involve no significant hazards consideration, and there has been no public comment on such finding published in the Federal Register on July 31, 2007 (72 FR 41789). Accordingly, the amendments meet the eligibility criteria for categorical exclusion set forth in 10 CFR 51.22(c)(9).

Pursuant to 10 CFR 51.22(b) no environmental impact statement or environmental assessment need be prepared in connection with the issuance of the amendments.

6.0 CONCLUSION

The Commission has concluded, based on the considerations discussed above, that: (1) there is reasonable assurance that the health and safety of the public will not be endangered by operation in the proposed manner, (2) such activities will be conducted in compliance with the Commission's regulations, and (3) the issuance of the amendments will not be inimical to the common defense and security or to the health and safety of the public.

Principal Contributors: R. Torres J. Lehning C. Basavaraju Date: March 25, 2008

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