ML070380193

Issuance of Amendment No. 202 Under Exigent Circumstances TS 3.6.1.7, Suppression Chamber-to-Drywell Vacuum Breakers-Allow One-time Extension to Current Closure Verification SR

ML070380193
Person / Time
Site:	Columbia
Issue date:	02/27/2007
From:	Lyon C NRC/NRR/ADRO/DORL/LPLIV
To:	Parrish J Energy Northwest
Lyon C Fred, NRR/DORL/LPL4, 301-415-2296
Shared Package
ML070380187	List: ML070380193 ML070380205
References
TAC MD4221
Download: ML070380193 (16)

Text

February 27, 2007 Mr. J. V. Parrish Chief Executive Officer Energy Northwest P.O. Box 968 (Mail Drop 1023)

Richland, WA 99352-0968

SUBJECT:

COLUMBIA GENERATING STATION - ISSUANCE OF EXIGENT AMENDMENT RE: EXTENSION OF SURVEILLANCE INTERVAL TO VERIFY CLOSURE OF VACUUM BREAKER CVB-V-1JK (TAC NO. MD4221)

Dear Mr. Parrish:

The U.S. Nuclear Regulatory Commission (NRC/Commission) has issued the enclosed Amendment No. 202 to Facility Operating License No. NPF-21 for the Columbia Generating Station. The amendment consists of changes to the Technical Specifications (TSs) in response to your application dated February 2, 2007.

The amendment revises TS 3.6.1.7, Suppression Chamber-to-Drywell Vacuum Breakers, to allow a one-time extension to the current closure verification surveillance requirement for one of two redundant disks in one of nine vacuum breakers until reliable position indication can be restored in the main control room during the next refueling outage (R-18), which is scheduled to begin on May 12, 2007. You requested that this amendment be approved on an exigent basis; therefore, the NRC staff has treated it in accordance with paragraph 50.91(a)(6) of Title 10 of the Code of Federal Regulations.

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

Sincerely,

/RA/

Carl F. Lyon, Project Manager Plant Licensing Branch IV Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-397

Enclosures:

1. Amendment No. 202 to NPF-21

2. Safety Evaluation cc w/encls: See next page

Pkg ML070380187 (Amdt. ML070380193, License/TS Pgs ML070380205)

OFFICE LPL4/PM LPL4/LA SCVB/BC ITSB/BC OGC Nlo LPL4/BC NAME FLyon LFeizollahi* RDennig* TKobetz SETurk DTerao w/comments DATE 2/13/07 2/7/07 2/9/07 2/13/07 2/21/07 2/27/07 Columbia Generating Station cc:

Mr. W. Scott Oxenford (Mail Drop PE04) Mr. Dale K. Atkinson (Mail Drop PE08)

Vice President, Technical Services Vice President, Nuclear Generation Energy Northwest Energy Northwest P.O. Box 968 P.O. Box 968 Richland, WA 99352-0968 Richland, WA 99352-0968 Mr. Albert E. Mouncer (Mail Drop PE01) Mr. William A. Horin, Esq.

Vice President, Corporate Services/ Winston & Strawn General Counsel/CFO 1700 K Street, N.W.

Energy Northwest Washington, DC 20006-3817 P.O. Box 968 Richland, WA 99352-0968 Mr. Matt Steuerwalt Executive Policy Division Chairman Office of the Governor Energy Facility Site Evaluation Council P.O. Box 43113 P.O. Box 43172 Olympia, WA 98504-3113 Olympia, WA 98504-3172 Ms. Lynn Albin Mr. Douglas W. Coleman (Mail Drop PE20) Washington State Department of Health Manager, Regulatory Programs P.O. Box 7827 Energy Northwest Olympia, WA 98504-7827 P.O. Box 968 Richland, WA 99352-0968 Technical Services Branch Chief FEMA Region X Mr. Gregory V. Cullen (Mail Drop PE20) 130 228th Street, S.W.

Supervisor, Licensing Bothell, WA 98201-9796 Energy Northwest P.O. Box 968 Ms. Cheryl M. Whitcomb (Mail Drop PE03)

Richland, WA 99352-0968 Vice President, Organizational Performance & Staffing/CKO Regional Administrator, Region IV Energy Northwest U.S. Nuclear Regulatory Commission P.O. Box 968 611 Ryan Plaza Drive, Suite 400 Richland, WA 99352-0968 Arlington, TX 76011-4005 Assistant Director Chairman Nuclear Safety and Energy Siting Division Benton County Board of Commissioners Oregon Department of Energy P.O. Box 190 625 Marion Street, NE Prosser, WA 99350-0190 Salem, OR 97301-3742 Senior Resident Inspector U.S. Nuclear Regulatory Commission P.O. Box 69 Richland, WA 99352-0069 August 2006

ENERGY NORTHWEST DOCKET NO. 50-397 COLUMBIA GENERATING STATION AMENDMENT TO FACILITY OPERATING LICENSE Amendment No. 202 License No. NPF-21

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

A. The application for amendment by Energy Northwest (licensee), dated February 2, 2007, complies with the standards and requirements of the Atomic Energy Act of 1954, as amended (the Act) and the Commission's regulations set forth in 10 CFR Chapter I; B. The facility will operate in conformity with the application, 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 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.

2. Accordingly, the license is amended by changes to the Technical Specifications and paragraph 2.C.(2) of Facility Operating License No. NPF-21 as indicated in the attachment to this license amendment.

3. The license amendment is effective as of its date of issuance and shall be implemented within 14 days from the date of issuance.

FOR THE NUCLEAR REGULATORY COMMISSION

/RA/

David Terao, Chief Plant Licensing Branch IV Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation

Attachment:

Changes to the Facility Operating License and Technical Specifications Date of Issuance: February 27, 2007

ATTACHMENT TO LICENSE AMENDMENT NO. 202 FACILITY OPERATING LICENSE NO. NPF-21 DOCKET NO. 50-397 Replace the following pages of the Facility Operating License No. NPF-21 and Appendix A Technical Specifications with the attached revised pages. The revised pages are identified by amendment number and contain vertical lines indicating the areas of change.

Facility Operating License REMOVE INSERT Technical Specification REMOVE INSERT 3.6.1.7-3 3.6.1.7-3

SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NO. 202 TO FACILITY OPERATING LICENSE NO. NPF-21 ENERGY NORTHWEST COLUMBIA GENERATING STATION DOCKET NO. 50-397

1.0 INTRODUCTION

By application dated February 2, 2007 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML070370274), Energy Northwest (licensee) requested changes to the Technical Specifications (TSs) (Appendix A to Facility Operating License No. NPF-21) for the Columbia Generating Station (CGS). The requested change would revise TS 3.6.1.7, Suppression Chamber-to-Drywell Vacuum Breakers, to allow a one-time extension to the current closure verification surveillance requirement (SR) for one of two redundant disks in one of nine vacuum breakers until reliable position indication can be restored in the main control room during the next refueling outage (R-18), which is scheduled to begin on May 12, 2007. The licensee requested that this amendment be approved on an exigent basis; therefore, the Nuclear Regulatory Commission (NRC) staff has treated it in accordance with paragraph 50.91(a)(6) of Title 10 of the Code of Federal Regulations (10 CFR). Specifically the proposed change would revise:

1.1 SR 3.6.1.7.1 SR 3.6.1.7.1 requires the licensee to Verify each vacuum breaker is closed, every 14 days.

The licensee proposes to add a note to SR 3.6.1.7.1 stating:

Not required to be met for the rear (drywell-side) disk of vacuum breaker CVB-V-1JK until startup from refueling outage R-18 provided there is no evidence that the front disk has opened or that the rear disk has experienced a differential pressure in the direction that could cause the disk to open. If such evidence exists, then the surveillance requirement will be met within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> or the rear disk declared not closed.

The licensee also proposes associated changes to the TS Bases for SR 3.6.1.7.1.

The NRC has previously approved similar exigent amendments for Fermi 2 (ADAMS Accession No. ML020710481) and Nine Mile Point Nuclear Station, Unit No. 2 (ADAMS Accession No. ML012470451).

2.0 BACKGROUND

2.1 Description of Vacuum Breakers and Testing and Indication Circuitry The primary function of the suppression chamber-to-drywell vacuum breakers is to relieve vacuum conditions should they occur in the drywell. At CGS, nine vacuum breakers are mounted to downcomers connecting the drywell and the suppression pool. The vacuum breakers allow the flow of steam and non-condensable gases from the suppression chamber to the drywell when the drywell is at a negative pressure with respect to the suppression chamber.

Therefore, the suppression chamber-to-drywell vacuum breakers prevent an excessive negative differential pressure across the suppression chamber-to-drywell boundary that could adversely impact the structural stability of the drywell floor.

In the event of a primary system rupture, an initial flow of steam to the suppression pool takes place via the downcomers. During this initial purging of the drywell into the suppression pool, the vacuum breakers are closed to prevent bypass of the suppression function (i.e., leakage of steam directly to the suppression chamber and not to the suppression pool). This initial purging also carries non-condensable gasses from the drywell, leaving a steam atmosphere in the drywell. Subsequent condensation of the steam can be caused in two possible ways:

(1) emergency core cooling system flow from a recirculation line break, or (2) drywell spray actuation following a loss-of-coolant accident (LOCA). These two scenarios determine the maximum depressurization rate of the drywell.

The waterleg in the Mark II Vent System downcomer is controlled by the drywell-to-suppression chamber differential pressure. If the drywell pressure is less than the suppression chamber pressure, there will be an increase in the vent waterleg. This will result in an increase in the water clearing inertia in the event of a postulated LOCA and would increase the peak drywell pressure. This in turn will result in an increase in pool swell dynamic loads. The internal vacuum breakers limit the height of the waterleg in the vent system during normal operation.

Analytical methods and assumptions involving the suppression chamber-to-drywell vacuum breakers are presented in Section 6.2.1.1.4 of the CGS Final Safety Analysis Report (FSAR) as part of the accident response of the primary containment systems. Internal (suppression chamber-to-drywell) and external (reactor building-to-suppression chamber) vacuum breakers are provided as part of the primary containment to limit the negative differential pressure across the drywell and suppression chamber walls that form part of the primary containment boundary.

The safety analyses assume that the internal vacuum breakers are closed initially and are fully open at a differential pressure of 0.5 pounds per square inch differential (psid). Additionally, two of the nine internal vacuum breakers are assumed to fail in a closed position. The failure of a third internal vacuum breaker is also acceptable since the resulting pressure differential is bounded by the failure of an external vacuum breaker. The results of the analyses show that the design pressure is not exceeded even under the worst case accident scenario. The vacuum breaker opening differential pressure setpoint and the number of vacuum breakers required to be operable are a result of the requirement placed on the vacuum breakers to limit the vent system waterleg height.

2.2 Vacuum Breakers Design Description Each suppression chamber-to-drywell vacuum breaker assembly consists of two swinging disk check valves contained within a single valve body. The disk is maintained in the closed position during normal operation by means of a spring-actuated lever arm and magnets embedded in the periphery of the disk. The magnetic and spring forces are overcome, and the disk opens when the pressure differential across the valve is within the range of 0.10 to 0.35 psid. The disk is fully open when the pressure difference is 0.5 psid. Operation of these vacuum breakers is entirely passive and their design is discussed in Section 3.8.2.1 of the CGS FSAR.

Pneumatic actuators are provided for remote operation of the disk for testing purposes.

Compressed air is supplied by the plant control air system through the pneumatic operator accumulator and backup nitrogen supply. Each disk pneumatic operator consists of two air cylinders, one to open and one to close the disk. Each air cylinder is actuated by energizing a three-way solenoid pilot valve. The two solenoid pilot valves associated with each disk are operated by a remote manual switch in the control room. During normal operation the remote manual switches are in the neutral position and the solenoids are de-energized.

Position indication for each vacuum breaker consists of four separate states: (1) Closed, (2) Open, (3) Full Open, and (4) Air-to-Close. On each disk there are a number of position switches which are actuated depending on the state of the disk. For the closed and open position switches, the disk face itself contacts a plunger on a small switch. There are two closed/open position switches per disk. Both switches must be actuated for a closed indication in the main control room. For the full open position switch, a striker which is attached to an arm swings in an arc and strikes a position switch plunger. There is one full open switch per disk.

Finally, there is a striker attached to each close air operator which contacts a position switch plunger to indicate that the cylinder is applying a closing torque to the disk. There is one air-to-close switch per disk.

3.0 REGULATORY EVALUATION

3.1 Vacuum Breakers Technical Specifications The limiting condition of operation (LCO) for TS 3.6.1.7 stipulates that seven of the nine vacuum breakers be operable to perform an open safety function and all of the nine vacuum breakers be closed. If either of these conditions are not met, an action statement must be entered.

As each vacuum breaker assembly contains redundant disks that are independent from one another, TS 3.6.1.7 considers the operability of each disk when assigning required actions. For example, for a single vacuum breaker, if one of the redundant disks is not closed, the associated action would require the closure of this disk within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> as this state represents a potential communication path between the suppression chamber and the drywell (i.e., loss of single failure margin). If both disks are not closed, the associated action would require the closure of one of the open disks within 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> as this does represent a communication path between the suppression chamber and drywell.

SR 3.6.1.7.1 requires that each vacuum breaker be verified closed every 14 days. This verification ensures that a potential large bypass leakage path is not present. The surveillance is performed by observing the vacuum breaker position indication in the main control room.

Should position indication be lost, the surveillance can alternately be completed by verifying a differential pressure is maintained between the drywell and suppression chamber. When the alternate method is used, one vacuum breaker disk in the line being tested must be opened to permit the position verification of the other disk in the series.

3.2 Conformance to General Design Criteria of 10 CFR Part 50, Appendix A Section 3.1 of the CGS FSAR describes how the licensee conforms with the applicable general design criteria (GDC), GDC 16 and 50.

GDC 16, Containment design, states that reactor containment and associated systems shall be provided to establish an essentially leak-tight barrier against the uncontrolled release of radioactivity to the environment and to assure that the containment design conditions important to safety are not exceeded for as long as postulated accident conditions require.

GDC 50, Containment design basis, states that the reactor containment structure, including access openings, penetrations, and the containment heat removal system shall be designed so that the containment structure and its internal compartments can accommodate, without exceeding the design leakage rate and with sufficient margin, the calculated pressure and temperature conditions resulting from any LOCA. This margin shall reflect consideration of:

(1) the effects of potential energy sources which have not been included in the determination of the peak conditions, such as energy in steam generators and as required by § 50.44 energy from metal-water and other chemical reactions that may result from degradation but not total failure of emergency core cooling functioning, (2) the limited experience and experimental data available for defining accident phenomena and containment responses, and (3) the conservatism of the calculational model and input parameters.

As described in the TS Bases for TS 3.6.1.7, the results of the safety analyses, which credits opening of only six of the nine suppression chamber-to-drywell vacuum breakers, show that the design pressure of the primary containment is not exceeded even under worst case accident scenarios. In addition, the requirement for all suppression chamber-to-drywell vacuum breakers to be closed (except when performing their intended design function) ensures that there is no excessive bypass leakage should a LOCA occur. Therefore, the requirements of GDC 16 and 50 will continue to be met with the implementation of this proposed change.

The short duration of this request and the satisfactory completion of recently performed testing to verify the affected vacuum breaker is closed provides a measure of confidence that the necessary quality of the vacuum breaker (i.e., closure) will be maintained until repairs are performed in R-18. However, if reasonable evidence is discovered to conclude that the rear disk of vacuum breaker CVB-V-1JK may no longer be in a closed position, Energy Northwest states that it will take compensatory measures to ensure that this disk is verified to be closed within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> or declare the disk not closed and enter the appropriate action statement.

4.0 TECHNICAL EVALUATION

The proposed change does not physically modify the vacuum breakers. The close safety function of the vacuum breakers is to close to limit drywell-to-suppression chamber bypass leakage and to re-close following a suppression pool swell event. The licensee states that both disks of vacuum breaker CVB-V-1JK are currently closed and have been verified as such using the normal position indication in the control room for the front disk and by the differential pressure test for the rear disk. Therefore, all nine vacuum breakers are known to be in a closed position. The open safety function is to open to relieve vacuum in the drywell. Only seven of nine vacuum breakers are required to be operable for the open function to satisfy TS LCO 3.6.1.7 on the basis that only six are actually required (consideration of single failure) to mitigate the effects of a design-basis accident (DBA). Therefore, the licensee states that it will conservatively assume both disks of vacuum breaker CVB-V1JK to be inoperable for opening without a tangible degradation in the overall ability to mitigate the effects of a DBA.

The licensee states that both disks of vacuum breaker CVB-V-1JK are expected to maintain their current closed configuration unless acted upon by either functional testing or a pressure transient within the suppression chamber. With both disks of vacuum breaker CVB-V-1JK declared inoperable for opening, the requirements of SR 3.6.1.7.2 to cycle either of the disks from their current closed position are not applicable and will not be performed to help ensure that CVB-V-1JK remains closed.

The licensee performed a review to identify operational and maintenance activities that could affect the position of the vacuum breakers during the interval prior to R-18. Based on this review, the licensee concluded that the required quarterly residual heat removal (RHR) system operability test could cause the vacuum breakers to leave their closed position. This operability test requires the actuation of spraying in the suppression chamber. This actuation can create an initial pressurization of the suppression chamber and a pressure differential between the drywell and suppression chamber that has in the past caused the vacuum breaker disks to lift off their seats. Other operating experience with vacuum breakers at CGS indicates that the rear disk of vacuum breaker CVB-V-1JK has on occasion failed to close without assistance from a pneumatic operator. Evidence suggests that the rear disk fails to close only when intentionally cycled by the control room.

However, the disk has been verified closed by the recently performed functional test and, as discussed above, will not be cycled. Furthermore, the licensee states that the disk will be subsequently verified closed if evidence exists that the disk has opened or has been exposed to a differential pressure that could cause the disk to open. Based on these considerations, declaring vacuum breaker CVB-V-1JK inoperable for opening and maintaining both disks closed until the end of the cycle is appropriate to minimize the potential for an unidentified bypass path between the drywell and suppression chamber.

To minimize the potential for the rear disk to open during the RHR operability test, Energy Northwest states that it will verify that the closed position of the rear disk of vacuum breaker CVB-V-1JK has not changed by staging an observer to verify that the front disk does not change position during the evolution or by performing the differential pressure test following the RHR operability test.

Based on the above discussion and the licensees commitments as noted in Section 7.0 below, the NRC staff has reasonable assurance that safe plant operation will not be affected by the one-time extension of SR 3.6.1.7.1.

5.0 EXIGENT CIRCUMSTANCES

The Commissions regulations, as stated in 10 CFR 50.91, provide special exceptions for the issuance of amendments when the usual 30-day public notice cannot be met. One type of special exception is an exigency. An exigency exists when the NRC staff and the licensee need to act quickly and time does not permit the staff to publish a Federal Register notice allowing 30 days for prior public comment, and the staff also determines that the amendment involves no significant hazards consideration. In accordance with 10 CFR 50.91(a)(6)(i)(A), the NRC staff published a notice in the Federal Register on February 12, 2007 (72 FR 6606), regarding this amendment to be issued under exigent circumstances. No comments were received.

The licensee requested that the proposed change be approved on an exigent basis to minimize the risk of a plant transient due to performance of the alternate verification methodology for one of two redundant disks where the normal position indication is not reliable. On January 6, 2007, during a functional test of vacuum breaker CVB-V-1JK, the rear disk of the vacuum breaker did not meet the procedurally defined acceptance criteria for open or close due to an issue with position indication limit switches. When CVB-V-1JK was cycled from the control room, the close position indication did not extinguish and prevented the open position indication from illuminating. The separate full open indication did illuminate, indicating that the rear disk opened as expected; however, the closure of the disk could not be confirmed using normal position indication. With unreliable position indication in the main control room for the rear disk of vacuum breaker CVB-1JK, the alternate method of closure verification using the differential pressure test is required.

The licensee stated that when performing the vacuum breaker closure differential pressure test, drywell pressure is increased from near atmospheric conditions to approximately 45 percent of the Drywell Pressure - High scram setpoint. Frequent differential pressure testing places the plant in a condition with degraded margin for a reactor scram. This increases the risk of an inadvertent reactor scram from a minor drywell pressure transient which may have been managed by the operator if it occurred at a normal drywell pressure and can unduly challenge plant safety systems and personnel. Furthermore, when performing the differential pressure test to verify continued closure of the rear disk of vacuum breaker CVB-V-1JK, the front disk is required to be open for at least 60 minutes while the test is being performed which degrades the capability of the vacuum breaker assembly to prevent bypass leakage when required.

The licensee concluded that a more appropriate method to maintain public health and safety is to ensure that both disks of vacuum breaker CVB-V-1JK continue to maintain their current closed position without a change of state. Operating in this configuration, both the front and rear disks of vacuum breaker CVB-V-1JK would conservatively not be credited to perform the open safety function and would be declared inoperable for opening. Both disks are currently closed and have been verified as such using the normal position indication in the control room for the front disk and by the differential pressure test for the rear disk. This configuration is currently allowed by TS 3.6.1.7, since only seven of nine vacuum breakers are required to be

operable for opening while in Modes 1, 2, and 3. In addition, with vacuum breaker CVB-V-1JK declared inoperable for the open function, SR 3.6.1.7.2 would not be required to be performed and the breaker disks would not need to be cycled.

Continued operation in this manner until the end of R-18 would ensure that plant risk is minimized but also requires an extension from the current 14-day interval of SR 3.6.1.7.1. The proposed change is necessary because continued performance of SR 3.6.1.7.1 for the rear disk of CVB-V-1JK results in putting the plant in a condition that unduly increases the risk of an inadvertent reactor scram challenging both plant systems and personnel. Failure to perform the differential pressure test required by SR 3.6.1.7.1 would result in a failed verification of the current closed state of these vacuum breakers. TS 3.6.1.7 would then require placing the reactor in Mode 3 within the next 84 hours9.722222e-4 days <br />0.0233 hours <br />1.388889e-4 weeks <br />3.1962e-5 months <br /> and Mode 4 in the following 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />, and would also challenge plant system and personnel.

The NRC staff agrees that the failure of the position indication on CVB-V-1JK was unanticipated. Based on the above, the staff finds that exigent circumstances exist and the licensee has acted in a timely manner.

6.0 FINAL NO SIGNIFICANT HAZARDS CONSIDERATION

DETERMINATION The Commissions regulations in 10 CFR 50.92 state that the Commission may make a final determination that a license amendment involves no significant hazards considerations if operation of the facility in accordance with the amendment would not: (1) involve a significant increase in the probability or consequences of an accident previously evaluated; or (2) create the possibility of a new or different kind of accident from any accident previously evaluated; or (3) involve a significant reduction in a margin of safety. As required by 10 CFR 50.91(a), the licensee has provided its no significant hazards analysis which is presented below:

1. Does the proposed amendment involve a significant increase in the probability or consequences of an accident previously evaluated?

Response: No.

Proper functioning of the suppression chamber-to-drywell vacuum breakers is required for accident mitigation. Failure of the vacuum breakers is not assumed as an accident initiator for any accident previously evaluated. Therefore, any potential failure of a vacuum breaker to perform when necessary will not affect the probability of an accident previously evaluated.

During a LOCA [loss-of-coolant accident], the vacuum breakers are assumed to initially be closed to limit drywell-to-suppression chamber bypass leakage and must be capable of re-closing following a suppression pool swell event. The vacuum breakers open to prevent an excessive vacuum in the drywell. The proposed change will not affect the capability of the required vacuum breakers to perform their open and close safety functions since the change only affects position verification and high confidence is assured that the disk remains closed.

Therefore, the proposed changes do not involve a significant increase in the probability or consequences of an accident previously evaluated.

2. Does the proposed amendment create the possibility of a new or different kind of accident from any accident previously evaluated?

Response: No.

The suppression chamber-to-drywell vacuum breakers are used to mitigate the potential consequences of an accident. The proposed change does not affect the capability of required vacuum breakers to perform their open and closed safety functions. Thus, the initial conditions assumed in the accident analysis are not affected. The proposed amendment does not involve a change to plant design and does not involve any new modes of operation or testing methods.

Accordingly, the required vacuum breakers will continue to perform their accident mitigation safety functions as previously evaluated. Therefore, the proposed changes do not create the possibility of a new or different kind of accident from any accident previously evaluated.

3. Does the proposed amendment involve a significant reduction in a margin of safety?

Response: No.

The extension of the closure verification surveillance interval for one of the two disks in a vacuum breaker for approximately 4 months is not risk significant as all required safety functions will continue to be performed. The vacuum breakers are not modified by the proposed amendment. The accident analysis assumptions for the closed safety functions of the vacuum breakers are satisfied when at least one of the disks in each of the nine vacuum breaker lines are fully closed and capable of re-closing following a suppression pool swell. The additional disk in each line satisfies the single failure criterion. The open safety function of the vacuum breakers is satisfied when 6 of the 9 vacuum breaker assemblies open during a DBA. The other vacuum breakers satisfy the single failure criterion and provide additional defense-in-depth. Since all of the vacuum breakers are considered to perform their close safety function and 8 of 9 would be available to perform their open safety function, the proposed change will not involve a significant reduction in a margin of safety.

The NRC staff has reviewed the licensees analysis given above. Based on its review, the NRC staff concludes that the three standards of 10 CFR 50.92(c) are satisfied and, therefore, the amendment request involves no significant hazards consideration. Therefore, the staff has made a final determination that the proposed amendment does not involve a significant hazards consideration.

7.0 REGULATORY COMMITMENTS In its application dated February 2, 2007, the licensee made the following regulatory commitments:

1. Upon approval of this proposed license amendment, Energy Northwest will implement a change to the applicable TS Bases to add the following information:

This SR is not required to be met for the rear (drywell-side) disk of vacuum breaker CVB-V-1JK until startup from refueling outage R-18 provided there is no evidence that the front disk has opened or that the rear disk has experienced a differential pressure in the direction that could cause the disk to open. If such evidence exists then the surveillance requirement will be met within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> or the rear disk declared not closed.

Evidence that the front disk has opened includes observed changes in position indication from closed to open (even if it returns to closed) that are determined to be related to actual disk movement and not position indication problems where the disk is later determined to be actually closed.

Evidence that the rear disk has experienced a differential pressure in the direction that could cause the disk to open includes any identified pressure differential in that direction where the position of the front disk is not known for the entire duration of the pressure differential. If the front disk has been observed to remain closed during the entire pressure differential, the rear disk is considered to have not experienced the differential pressure.

This extension will ensure that the close safety function is maintained while minimizing risk to public health and safety. This extension expires upon startup from R-18.

2. Both the front and rear disks of vacuum breaker CVB-V-1JK would conservatively not be credited to perform the open safety function and would be declared inoperable for opening.

3. Energy Northwest will continue to verify that the front disk of CVB-V-1JK and both disks of the other 8 vacuum breakers are closed every 14 days as required by SR 3.6.1.7.1.

4. If reasonable evidence is discovered to conclude that the rear disk of vacuum breaker CVB-V-1JK may no longer be in a closed position (i.e., opening of the front disk in the vacuum breaker assembly or exposure of both disks to a differential pressure in the direction that could cause the disks to open), Energy Northwest will take compensatory measures to ensure that this disk is verified to be closed (i.e., perform the differential pressure closed verification) within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />.

The NRC staff has reviewed the licensees commitments and find that they provide reasonable assurance that safe plant operation will not be affected by the one-time extension of SR 3.6.1.7.1.

8.0 STATE CONSULTATION

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

9.0 ENVIRONMENTAL CONSIDERATION

The amendment changes a surveillance requirement. The NRC staff has determined that the amendment involves 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 made a final finding that the amendment involves no significant hazards consideration. Accordingly, the amendment meets 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 amendment.

10.0 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 amendment will not be inimical to the common defense and security or to the health and safety of the public.

Principal Contributor: F. Lyon Date: February 27, 2007