ML20236U857

Application for Amend to Licenses NPF-04 & NPF-07,revising TS 3/4.1.2 Re RWST & Boron Concentration Ph Range Bases Change

ML20236U857
Person / Time
Site:	North Anna
Issue date:	07/28/1998
From:	Ohanlon J VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
Shared Package
ML20236U860	List: ML20236U857 ML20236U865
References
98-436, NUDOCS 9807310118
Download: ML20236U857 (7)

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~9, Vin <;isir Ei.EcTHIC ANI) POWER COM PANY RICIIMONI), YIm;INI A 232fil July 28, 1998 U.S. Nuclear Regulatory Commission Serial No.98-436 Attention: Document Control Desk NL&OS/GSS/ETS R1 Washington, D.C. 20555 Docket Nos. 50-338 50-339 License Nos. NPF-4 NPF-7 l Gentlemen:

l VIRGINIA ELECTRIC AND POWER COMPANY NORTH ANNA POWER STATION UNITS 1 AND 2 TECHNICAL SPECIFICATION BASES CHANGE RWST AND BORON CONCENTRATION pH RANGE BASES CHANGE l

h j Virginia Electric and Power Company has changed the Bases for Technical l Specifications 3/4.1.2, "RWST Volume and Boron Concentration" and 3/4.5.5, "RWST Volume and Boron Concentration for Emergency Core Cooling." These changes are being made to address discrepancies between a previous NRC issued Safety Evaluation Report, the Technical Specification Bases, and the applicable sections of the Standard Review Plan. Therefore, we are providing the following Technical /

Specifications Bases changes to the pH ranges, which reflect the acceptance criteria of i the accident analysis, for your information. These changes are also consistent with the / I ranges of allowable pH values specified in the Standard Review Plan.

The Technical Specifications Bases changes have been reviewed and approved b Station Nuclear Safety and Operating Cornmittee and the Management Safety Review Committee. It has been determined that these changes do not involve an unreviewed safety question as defined in 10 CFR 50.59. A discussion and the Technical Specifications Bases changes are provided in Attachments 1 and 2 respectively.

If you have any further questions, please contact us.

Very truly yours, James P. O'Hanlon Senior Vice President - Nuclear 9007310118 990728 PDR ADOCK 05000338 P PDR

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f Attachments

1. Discussion of Changes

2. Technical Specifications Bases Changes Commitments made in this letter:

1. There are no commitments in this letter cc: . U.S. Nuclear Regulatory Commission Region ll t Atlanta Federal Center i 61 Forsyth Street, SW Suite 23T85 l Atlanta, Georgia 30303

, Mr. M. J. Morgan l NRC Senior Resident inspector North Anna Power Station l

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Attachment 1 t

l Discussion of Bases Change t

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North Anna Power Station l Units 1 and 2 Virginia Electric and Power Company l

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DISCUSSION OF CHANGES Introduction Virginia Electric and Power Company proposes changes to the bases for Technical Specifications TS 3/4.1.2 (RWST Volume and Boron Concentration) and TS 3/4.5.5 (Refueling Water Storage Tank Volume and Boron Concentration for Emergency Core Cooling). These changes are being made to address discrepancies between the Reference (1) NRC Safety Evaluation Report (SER), the TS 3/4.5.5 bases, and the applicable sections of the NRC Standard Review Plan (SRP) referenced by the Reference (1) SER.

Background

Limitations on post-LOCA sump and quench spray pH are established to ensure the effectiveness of recircu!ation spray and quench spray iodine removal and retention, and to ensure that post-LOCA environmental conditions inside containment are compatible with stainless steel components. The NRC Standard Review Plan, Section 6.5.2, Revision 2 (3) specifies that "Long-term iodine retention may be assumed only when the equilibrium sump solution pH, after mixing and dilution with the primary coolant and ECCS injection, is above 7. Standard Review Plan Section 6.1.1, Revision 2 (Engineered Safety Features Materials) (4) states that "the composition of containment spray and core cooling water should be controlled to ensure a minimum pH of 7.0 as given in Branch Technical Position MTEB 6-1 Experience has shown that maintaining the pH of borated solutions at this level will help inhibit initiation of stress corrosion cracking of austenitic stainless steel components." MTEB 6-1 (5) also states "For the spray water recirculated from the containment sump, the higher the pH in the 7.0 to 9.5 range, the greater the assurance that no stress corrosion cracking will occur."

Standard Review Plan Section 6.5.2, Revision 1 (6) requirements for the " injection spray solutic,n" state that "the spray system should be designed such that the spray solution inaintains the highest possible pH, within material compatibility constraints.

This requirement is satisfied by a spray pH in the range of 8.5 to 10.5." SRP Section 6.5.2, Revision 2 (3) generalized these requirements to state that "the spray system should be designed so that the spray solution is within material compatibility constraints, lodine scrubbing credit is given for sprzy solutions whose chemistry, including any additives, has been demonstrated to be effective for iodine absorption and retention under post-accident conditions." This provision gives licensees greater flexibility in demonstrating the effectiveness of iodine removal systems, and creates the possibility of eliminating caustic addition systems if such elimination is justified by material compatibility constraints, and iodine removal capability as demonstrated by radiological dose analysis. Taken together, these limitations suggest that the pH of the quench spray system must be demonstrated to be between 8.5 and 10.5, and the pH of the post-LOCA sump water must be demonstrated to be between 7.0 and 9.5.

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i9 A Technical Specification change request to increase the allowable boric acid

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concentration range in the Refueling Water Storage Tank (RWST) from 2000-2100 ppm to 2300-2400 ppm was submitted to the NRC in Reference (2). Because the proposed increase in RWST boric acid concentration made the quench spray and post-LOCA sump pH more acidic, only the minimum quench spray and post-LOCA sump pH were re-evaluated for the propoced changes. Reference (2) concluded that the proposed boric acid concentration increase was acceptable from the perspectives of quench spray and post-LOCA sump pH on the basis that the minimum quench spray pH remained above the minimum allowable value specified in the NRC Standard Review Plan (SRP) Section 6.5.2 Revision 1 (6) (i.e., 8.5), and that the minimum post-LOCA sump pH remained above the minimum allowable value specified in the NRC SRP Section 6.1.1 Revision 2 (4) and in the associated Branch Technical Position MTEB 6-1 (5) (i.e.,7.0) The Reference (2) submittal stated that the maximum pH remained within the limits established by Technical Specification 3/4.5.5 and its associated bases, which limit the quelch spray pH to a maxirnum of 11.0. Finally, Reference (2) concluded that the pH values changed only slightly and remained within the limits specified in the SRP.

The proposed basis for Technical Specification 3/4.5.5 indicated that the limits on contained water volume and boron concentration of the RWST ensure a pH value between 8.5 and 11.0 for quench spray, and between 7.7 and 9.0 for the solution recirculated within the containment after a LOCA.

In the Reference (1) Safety Evaluation Report (SER), the NRC concluded that the change in post-LOCA samp and quench spray pH resulting from the increased RWST boric acid concentration was small, but also stated that "the effects [of the RWST boron concentration increase) on stress corrosion cracking and iodine evolution are negligible because the pH rerr'ains within the Standard Review Plan limits." This conclusion calls into question two elements of the bases for Technical Specifications 3/4.1.2 and 3/4.5.5. Specifically, the acceptance criteria which are presently specified in the basis for Technical Specification 3/4.5.5 are 8.5 s pH s 11.0, whereas the SRP section referenced by the Reference (2) submittal specifies quench spray analysis acceptance criteria of 8.5 s pH s 10.5. Further, the TS 3/4.5.5 and 3/4.1.2 bases refer to the pH of the sump water as being between 7.7 and 9.0, whereas the SRP section referenced by the Reference (2) submittal specifies sump pH analysis acceptance criteria of 7.0 s pH s 9.5. The quench spray pH range presented in the TS 3/4.5.5 bases (i.e.,8.5 s pH s 11.0) is clearly intended to represent analysis acceptance critena, whereas the post-LOCA sump pH range presented in TS 3/4.5.5 and 3/4.1.2 (i.e., 7.7 s pH s 9.0) includes the minimum post-LOCA sump pH analysis result (i.e., 7.7) rather than the analysis acceptance critenon. These inconsistencies create ambiguity regarding the appropriate acceptance criteria for analyses performed and evaluated under the provisions of 10 CFR 50.59. Therefore, Virginia Electric and Power Company proposes i modification of the bases for Technical Specifications 3/4.1.2 and 3/4.5.5 to make them consistent with the acceptance criteria specified in the SRP sections referenced by the Reference (2) submittal and the Reference (1) SER. 1

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Specific Changes The following changes are proposed for the North Anna Units 1 and 2 Technical Specifications Bases:

l Basis for TS 3/4.1.2 (RWST Volume and Boron Concentration): The basis for TS l 3/4.1.2 presently states: "The limits on contained water volume and boron concentration of the RWST ensure a pH value of between 7.7 and 9.0 for the solution

recirculated within the containment after a LOCA." It is proposed that this statement be ,

i changed to read as follows: "The limits on contained water volume and boron j concentration of the RWST ensure a pH value of between 7.0 and 9.5 for the solution

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recirculated within the containment after a LOCA."

l TS 3/4.5.5 (Refueling Water Storage Tank Volume and Boron Concentration for Emergency Core Coolipg): The basis for TS 3/4.5.5 presently states: "The limits on contained water volume and boron concentration of the RWST also ensure a pH value of between 8.S and 11.0 for quench spray and between 7.7 and 9.0 for the solution i recirculated within the containment after a LOCA." It is proposed that this statement be changed to read as fellows: "The limits on contained water volume and boron i concentration of the RWST also ensure a pH value of between 8.5 and 10.5 for quench spray and between 7.0 and 9.5 for the solution recirculated within the containment after a LOCA."

i Safety Significance Based on the discussion provided in the Background section, it is concluded that the acceptance criteria which are currently applicable to the North Anna Units 1 and 2 quench spray and post-LOCA sump pH analysis are those which are presented in the referenced sections of the Standard Review Plan. The quench spray and post-LOCA sump pH have been reanalyzed and verified to meet their respective analysis acceptance criteria (i.e., 8.5 s pH s 10.5 and 7.0 s pH s 9.5, respectively) with greater i than 95% probability and 95% confidence. The analysis includes allowances for <

measurement instrument uncertainty and variation within the administratively controlled tank volume and solute concentration bands. The proposed modifications to the bases for TS 3/4.1.2 and 3/4.5.5 may be implemented without increasing the consequences of any accident or malfunction of equipment important to safety previously analyzed in the safety analysis report, or diminishing the margin of safety as defined by the bases for the affected sections of the Technical Specifications.

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References 4

(1) Letter from L. B. Engle to W. L. Stewart, Serial No.87-241, dated April 14,1987 (North Anna Boron Concentration increase TS Change Approval Letter).

(2) Letter from W. L. Stewart to H. R. Denton, " Virginia Electric and Power Company; North Anna Power Station Units 1 and 2; Proposed Technical Specification Change; Boron Concentration increase," Serial No.86-690, dated December 22,1986.

l (3) " Containment Spray as a Fission Product Cleanup System," NUREG-0800, Standard Review Plan Section 6.5.2, Revision 2, dated December,1988.

(4) " Engineered Safety Features Materials," NUREG-0800, Section 6.1.1, Revision 2, dated July,1981.

(5) "pH for Emergency Coolant Water for PWRs," Branch Technical Position 6-1, Attachment to NUREG-0800, Section 6.1.1, Revision 2, dated July,1981.

l (6) " Containment Spray as a Fission Product Cleanup System," NUREG-0800, l Standard Review Plan Section 6.5.2, Revision 1, dated July,1981.

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