ML18152B657

Application for Amends to Licenses DPR-32 & DPR-37,revising TSs Re Refueling Water Chemical Addition Tank Min Vol

ML18152B657
Person / Time
Site:	Surry
Issue date:	04/28/1999
From:	Christian D VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
Shared Package
ML18152B658	List: ML18152B657 ML18152B659
References
99-128, NUDOCS 9905050012
Download: ML18152B657 (11)

Text

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e e VIRGINIA ELECTRIC AND POWER COMPANY RICHMOND, VIRGINIA 23261 April 28, 1999 U.S. Nuclear Regulatory Commission Serial No. 99.:128 Attention: Document Control Desk NL&OS/GDM RO Washington, D.C. 20555 Docket Nos. 50-280 50-281 License Nos. DPR-32 DPR-37 Gentlemen:

VIRGINIA ELECTRIC AND POWER COMPANY SURRY POWER STATION UNITS 1 AND 2 PROPOSED TECHNICAL SPECIFICATIONS CHANGE REFUELING WATER CHEMICAL ADDITION TANK MINIMUM VOLUME Pursuant to 10CFR50.90, Virginia Electric and Power Company requests amendments, in the form of revisions to the Technical Specifications to Facility Operating License Numbers DPR-32 and DPR-37 for Surry Power Station Units 1 and 2. The proposed change will reduce the minimum volume requirement for the refueling water chemical addition tank to permit implementation of a more reasonable level setpoint for maintaining tank level. Also incorporated in this submittal is a minor administrative revision to a Technical Specification table. A discussion of the proposed Technical Specifications change is provided in Attachment 1.

The proposed Technical Specifications change has been reviewed and approved by the Station Nuclear Safety and Operating Committee and the Management Safety Review Committee. It has been determined that the proposed Technical Specifications change does not involve an unreviewed safety question, as defined in 10CFR50.59. Marked-up Technical Specifications pages that reflect the proposed change are provided in Attachment 2. Revised Technical Specifications pages that incorporate the proposed change are provided in Attachment 3. The basis for our determination that the Technical Specifications change does not involve a significant hazards, as defined in 10CFR50.92, is provided in Attachment 4.

Should you have any questions or require additional information, please contact us.

I Very truly yours,

¥Jo('} I D. A. Christian Vice President - Nuclear Operations

\

( 9905050012 990428 I PDR ADOCK 05000280 P PDR

Attachments:

1. Discussion of Change

2. Mark-up of Technical Specifications

3. Proposed Technical Specifications

4. Significant Hazards Consideration Determination Commitments made in this letter: None.

cc: U.S. Nuclear Regulatory Commission Region II Atlanta Federal Center 61 Forsyth Street, SW Suite 23T85 Atlanta, Georgia 30303 Mr. R. A. Musser NRC Senior Resident Inspector Surry Power Station Commissioner Department of Radiological Health Room 104A 1500 East Main Street Richmond, VA 23219

' e COMMONWEALTH OF VIRGINIA )

)

COUNTY OF HENRICO )

The foregoing document was acknowledged before me, in and for the County and Commonwealth aforesaid, today by D. A. Christian, who is Vice President -

Nuclear Operations, for J. P. O'Hanlon, who is Senior Vice President - Nuclear, of Virginia Electric and Power Company. He has affirmed before me that he is duly authorized to execute and file the foregoing document in behalf of that Company, and that the statements in the document are true to the best of his knowledge and belief.

Acknowledged before me thisJ8m day of Q{Yil , 19C)CJ .

My Commission Expires: March 31, 2000.

Notary Public (SEAL)

e ATTACHMENT 1 DISCUSSION OF CHANGE VIRGINIA ELECTRIC AND POWER COMPANY SURRY POWER STATION UNITS 1 AND 2

e DISCUSSION OF CHANGE Introduction Virginia Electric and Power Company is proposing a revision to the Surry Power Station Technical Specification 3.4.A.4 to reduce the refueling water chemical addition tank (CAT) minimum volume requirement. As part of an overall engineering review of Technical Specifications (TS) setting limits, the minimum volume requirement for the refueling water CAT was re-evaluated. As a result of this re-evaluation, it was determined that the minimum refueling water CAT volume could be decreased to provide additional operating margin. The revised TS minimum CAT volume requirement reflects the re-evaluated CAT volume assumed in the accident analyses plus instrument uncertainties, as well as additional positive margin for conservatism.

No increase in the probability of occurrence or consequences of an accident or equipment malfunction will result from the proposed TS change. The revised minimum TS volume requirement only affects the required CAT volume used to mitigate accidents, and the revised minimum TS refueling water CAT volume continues to ensure that the available CAT volume is sufficient to meet accident analyses assumptions for accident mitigation. Implementing the proposed change does not create the possibility of an accident of a different type than was previously evaluated in the safety analysis report, since the minimum volume requirement for the CAT does not introduce any new accident precursors or modes of operation. The proposed change continues to ensure that accident analyses assumptions are maintained. Although the minimum CAT volume is being decreased, the revised limit continues to ensure that the.

post-LOCA containment spray and containment sump pH, and post-LOCA recirculation switchover are acceptable. Therefore, the margin of safety as defined in the TS bases is unaffected.

Minor administrative changes are also being implemented in TS Table 4.1-28 by this Technical Specifications change.

Background

As part of an overall engineering review of TS setting limits, the minimum volume requirement for the refueling water CAT was re-evaluated. The current Technical Specifications volume and concentration requirements for the refueling water CAT (i.e.,

4200 gallons of 17% to 18 % NaOH) ensure that the containment spray pH during a Loss of Coolant Accident is maintained above 8.5 and the containment sump pH remains above 7.0. These pH levels are necessary to ensure that: 1) the decontamination factors assumed in the accident analyses for elemental and particulate iodine removal coefficients are maintained, and 2) the potential for stress corrosion cracking is minimized.

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Operation**at the current TS limit of 4200 gallons is difficult, since the TS limit is near the volume capacity of the CAT (i.e. 4330 gallons). Consequently, when considering instrument error, only a limited operating margin is available. Therefore, a re-evaluation of the safety analysis limit for the minimum CAT volume was performed to determine whether a lower minimum CAT volume would be acceptable, thus permitting the CAT volume TS limit to be lowered. A lower TS limit would provide greater operational flexibility in maintaining the required CAT volume, including instrument error, and preclude inadvertently overflowing of the tank. The proposed TS minimum CAT volume also permits establishing an alarm setpoint above the proposed TS limit that will provide additional operational flexibility in maintaining the required tank volume.

Licensing Basis

• Minimum CAT volume change The minimum refueling water CAT volume specified in the original TS 3.4.A.4 was 3,360 gallons of solution with a sodium hydroxide concentration of 18 percent by weight. This value corresponded to the RWST minimum volume requirement to ensure that a sufficient amount of caustic was added to the containment spray system relative to the water provided by the RWST. This volumetric relationship ensured accident analysis assumptions for containment spray system performance were adequately met.

In 1980 and 1981, the TS were revised for Surry Unit 2 and Unit 1 via Amendment Nos.

59 and 71, respectively, to increase the required minimum volume for the CAT from 3360 gallons to 4200 gallons, and to establish a required concentration range for sodium hydroxide of not less than 17 percent and not greater than 18 percent. The increase in the CAT minimum volume was required to compensate for an increase in the minimum volume requirement for the Refueling Water Storage Tank due to containment spray system modifications.

A minor revision was made to the text of TS 3.4.A.4 in TS Amendment Nos. 180 and 180 for Surry Units 1 and 2 to make the wording more consistent in terminology and format.

• Administrative Changes Minor administrative changes are also being implemented by this TS change request.

In a letter dated January 30, 1996 (Serial No.96-005), Virginia Electric and Power Company requested changes to the TS to eliminate the surveillance requirement for certain reactor coolant liquid samples under particular specified conditions. These sampling changes were approved in TS Amendments 209 for Surry Units 1 and 2, and incorporated into TS Table 4.1-28, Minimum Frequencies for Sampling Tests.

However, separate from the requested TS changes, the test requirements for Item 6, Secondary Coolant, of the Table were inadvertently altered in format such that they no Page 2 of 6

longer aligned with the testing frequencies specified for that item. Consequently, the texf in thef "Test" section of Item 6 in Table 4.1-28 has been returned to its correct format to properly align with the corresponding test frequencies in the next column.

The symbols used for beta and gamma have also been spelled out for greater clarity, and the FSAR reference has been deleted as UFSAR section 10.3 provides no pertinent reference information for this item. The FSAR section reference header for the Table has also been revised to read UFSAR rather than FSAR to indicate that the Updated Final Safety Analysis Report is the accurate reference source.

Design Basis A refueling water CAT is located near the RWST for each unit. The CAT stores sodium hydroxide solution that is added to the containment spray system water from the RWST by balanced gravity feed directly to the suction of the containment spray pumps. The level in the CAT is designed to follow level in the RWST as the two tanks empty together. This ensures that the pressure head of each tank remains in the same proportion at the suction of the containment spray pumps, and that the concentration of the sodium hydroxide being injected into containment remains constant. The sodium hydroxide is injected into the containment via the containment spray system to enhance iodine removal from the containment atmosphere and to control sump water pH by keeping it slightly basic. A specific range of pH is required for effective removal of volatile iodine species from the containment atmosphere and retention in the containment sump water, and also serves as a preventative against chloride stress corrosion.

The CAT is a vertical, cylindrical tank with a capacity of 4330 gallons. Technical Specifications require that the CAT contain at least 4200 gallons of 17 to 18 % sodium hydroxide during normal plant operation. To address instrument uncertainties and the change in specific gravity of the liquid in the CAT caused by the difference in sodium hydroxide concentration, CAT level is currently not allowed to decrease below 98.4%

during normal operation to ensure that the minimum TS volume is not violated.

Discussion The impact of the reduction in the safety analysis limit minimum CAT volume to 3800 gallons was evaluated to determine an acceptable *TS setpoint limit for minimum CAT volume. It was determined that the proposed change potentially affected three aspects of the Surry accident analyses: *

1) The containment analysis (e.g., the CAT is a source of relatively cold water for injection into containment).

2) The containment spray and post-LOCA sump pH (e.g., a reduction in the quantity of the NaOH solution from the CAT could reduce the pH of the containment spray and the liquid in the sump, thereby diminishing the capacity of Page 3 of 6

the spray and sump liquid to remove and retain volatile iodine species from the containment atmosphere).

3) The post-LOCA recirculation switchover time (e.g., a reduction in the quantity of NaOH solution from the CAT could reduce the time to boric acid precipitation in the core region following a large break LOCA, necessitating a reduction in the post-LOCA cold-to-hot leg recirculation switchover interval presented in the Emergency Operating Procedures.)

• It was determined that the proposed reduction in the safety analysis limit for CAT inventory from 4200 gallons to 3800 gallons did not significantly impact the results of the containment analysis, the containment spray and post-LOCA sump pH analysis, or the post-LOCA recirculation switchover time analysis. Specifically:

• The CAT inventory is not credited as a source of energy removal in the containment analysis of record.

• Reducing the assumed CAT volume from 4200 gallons to 3800 gallons results in a small reduction in the calculated minimum sump and spray pH, but the calculated pH values remain above the minimum sump and spray pH acceptance criteria (7.0 and 8.5, respectively), consistent with NUREG-0800, Standard Review Plan, Section 6.5.2, "Containment Spray as a Fission Product Cleanup System," Revision 2, December 1988.

• The CAT volume is not considered in the analysis, which supports the currently applicable EOP recirculation switchover interval.

Therefore, an acceptable reduction in the safety analysis limit for the CAT inventory to 3800 gallons permits establishing a revised TS minimum CAT volume of 3930 gallons.

This value corresponds to a 91.0% tank level (for 18% sodium hydroxide concentration at 68°F). The 3800 gallon safety analysis limit CAT volume corresponds to an 87 .9%

tank level. The difference between this level (i.e., 87.9% level) and the level associated with the proposed TS minimum CAT volume (i.e., 91.0% level) is 3.1 %, which is greater than the Channel Statistical Allowance (CSA) of 2.6% associated with the CAT level indication and the emergency response facility computer system (ERFCS) computer point. The additional 0.5% level margin between the current licensing basis safety analysis limit CAT volume (3800 gallons, or 87.9% level) and the proposed TS minimum CAT volume (3930 gallons, or 91.0% level) remains available to compensate for potential future changes in the calculated CAT level CSA.

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r e

Specific Changes

• Technical Specification 3.4.A.4 is revised as follows to reflect the reduced refueling water CAT minimum volume requirement:

4. The refueling water chemical addition tank shall contain at least 3930 gallons of solution with a sodium hydroxide concentration of at least 17 percent by weight but not greater than 18 percent by weight.

• Technical Specification Table 4.1-28, Minimum Frequencies for Sampling Tests, Item 6, Secondary Coolant, is revised as follows to 1) indicate that two separate tests are required with different test frequencies, 2) replace the symbols used for beta and gamma activity with the actual words

• for clarity and 3) delete the inappropriate FSAR reference:

6. Secondary Coolant Fifteen minute degassed beta Once/72 hours and gamma activity DOSE EQUIVALENT 1-131 Monthly(4)

Semiannually (8)

The FSAR section reference header for Table 4.1-28 has also been revised to read UFSAR rather than FSAR to indicate that the Updated Final Safety Analysis Report is the accurate reference source.

Safety Significance This change to the TS reduces the minimum volume requirement for the refueling water CAT from 4200 to 3930 gallons. The proposed change continues to provide assurance to assure that accident analyses assumptions will remain valid, and that the effect of instrument uncertainties during accident conditions are adequately addressed. The changes to TS Table 4.1-28 are strictly administrative in nature.

The probability of occurrence or the consequences of an accident or malfunction of equipment important to safety previously evaluated are not increased. When the revised safety analysis limit minimum CAT volume of 3800 gallons was implemented, consideration was given to the effects of the proposed reduced CAT volume on containment integrity analyses, containment spray and post-LOCA sump pH analyses, and the post-LOCA recirculation switchover time interval specified in Emergency Operating Procedures. The reduced value was determined to be acceptable. The proposed TS minimum CAT volume (3930 gallons) includes an allowance for the CAT level Channel Statistical Allowance (CSA), so that the safety analysis limit CAT volume (3800 gallons) will not be violated when the measured CAT volume (i.e., tank level) is above the TS minimum CAT volume. Because the affected accident analyses have Page 5 of 6

been evaluated and found to meet their acceptance criteria with the reduced safety ana'lysis limit CAT volume, the consequences of an accident or malfunction of equipment important to safety previously evaluated is not increased. The proposed reduction in the TS minimum CAT volume has no bearing on the probability of occurrence of any accident previously evaluated, since neither the volume of the CAT nor the sodium hydroxide inventory in the CAT have any bearing on postulated accident initiators.

The possibility of an accident or malfunction of a different type than any evaluated previously in the safety analysis report is not created. The proposed reduction in the TS minimum CAT volume does not involve any alterations to the physical plant which introduce any new or unique operational modes or accident precursors. The proposed TS minimum CAT volume permits establishing an alarm setpoint above the proposed TS limit that will provide additional operational flexibility in maintaining the required tank volume.

The margin of safety as defined in the basis of the Technical Specifications is not reduced. It was determined that the affected safety analyses continue to meet their respective acceptance criteria with the revised minimum CAT volume assumption. By implementing the proposed change in the TS minimum CAT volume, a CAT level alarm setpoint may be established which includes a conservative allowance for level measurement uncertainty to ensure that neither the TS limit nor the safety analysis limit for minimum CAT volume will be violated at the time a CAT level alarm is received.

Therefore, it is concluded that the proposed change is being made to provide greater assurance that the margin of safety defined in the TS bases is maintained.

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