NPL-97-106, Forwards Response to 970228 RAI Re TS Change Request 191 Revising Boron Concentration to Support 18-month Fuel Cycles

Forwards Response to 970228 RAI Re TS Change Request 191 Revising Boron Concentration to Support 18-month Fuel Cycles

ML20138A966
Person / Time
Site:	Point Beach
Issue date:	04/17/1997
From:	Dante Johnson WISCONSIN ELECTRIC POWER CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
NPL-97-106, NUDOCS 9704290003
Download: ML20138A966 (5)

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• Wisconsin Electnc POWER COMPANY 231 W MicNgon. PO Box 2046 Mihvoukee, WI S32012046 (414)221-2345 NPL 97-106 10 CFR 50.4 10 CFR 50.90 April 17,1997 l

! Document Control Desk l US NUCLEAR REGULATORY COMMISSION Mail Station PI 137 l Washington,DC 20555 j Ladies / Gentlemen:

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l DOCKETS 50-266 AND 50-301 l )

SUPPLEMENT TO TEC11NICAL SPECIFICATIONS CHANGE REOUEST 191 l

POINT BEACH NUCLEAR PLANT. UNITS 1 AND 2 '

In a letter dated January 16,1997, Wisconsin Electric requested Technical Specifications Change Request (TSCR) 191. This l TSCR proposes to change the minimum boron concentration required in storage tanks during normal operation, and proposes to change the minimum boron concentration of primary coolant during refueling conditions. These changes are required to l maintain the design basis shutdown criteria when PBNP units transition to 18-month core designs.

In a letter dated February 28,1997, the NRC Office of Nuclear Reactor Regulation requested additional information related l to TSCR 191. By attachment, we provide our reply to that request.

l l We have determined that the additional information does not involve a significant hazards consideration, authorize a significant change in the types or total amounts of any effluent release, or result in any significant increase in individual or cumulative occupational exposure. Therefore, we conclude that the proposed amendments meet the requirements of 10 CFR 51.22(c)(9) and that an environmental impact statement or negative declaration and environmental impact appraisal need not be prepared. The original"No Significant flazards" determinations for operation under the proposed Technical i Specifications remain applicable.

Please contact us if you have any questions. AM l Sincerely, Q ##

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Douglas F. Johnson Manager-Regulatory Services l and Licensing l

GDAh Subscribed and sworn to before me J thisAlsr day of$c; \ 1997.

1 cc: NRC Resident inspector, NRC Regional Administrator, PSCW

&t0 YW/ j Notary Public, State of Wisconsin  !

My commission expires M/ / 9 /M 9704290003 970417 PDR ADOCK 05000266 PDR P _

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RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION FOR TSCR 191 BORON CONCENTRATION CHANGES TO SUPPORT 18-MONTH FUEL CYCLES l 1. Provide a copy of the Unit 1 Cycle 25 reload evaluation report.

RESPONSE: The reload safety evaluation report is conducted in accordance with 10 CFR 50.59 and will be available for your review when it is l l complete. However, these analyses are not routinely completed until about 2 weeks prior to startup. Therefore, the Unit 1 Cycle 25 reload safety i j evaluation report is not available at this time.

l l 2. Describe in detail the analysis for determining release of halogens i (iodine) from the borated solution during refueling. Especially, explain ,

l why specific requirements for boron concentration or solution pH were established in the analysis. j l

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l RESPONSE: A detailed description of the iodine-retention analysis is

, provided in PBNP FSAR Section 14.2.1, " Fuel Handling Accidents". This

! analysis references a 1965 study, " Iodine Clean-up in a Steam Suppression System", International Symposium on Fission Product Release and Transport Under Accident Conditions, Oak Ridge, Tennessee, CONF-65047, Vol. 2, Pg.

776-804, H.R. Diffey, et. al., (1965). As described in the FSAR analysis,

and as summarized in the Technical Specification Change Request (TSCR),

I there are no specific requirements for boron concentration or pH established in the analysis. The TSCR 191 safety evaluation simply j identified the potential that there could be an effect. That evaluation  :

concluded that the small change in boron concentration (from 1800 to 2100 l l ppm) and a small change in pH (from 4.69 to 4.61) would not affect the results of the analysis.

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3. Describe in detail the analysis for predicting change of the pH of spray ,

and sump solutions after increase of boric acid concentration in RWSTs l l

l [ refueling water storage tanks), BASTS (boric acid storage tanks), and SI i I (safety injection) accumulators. Also, provide the results of this i analysis.

RESPONSE: A Wisconsin Electric calculation was developed to track the boron and sodium concentration in the containment spray solution and the containment sump during a large break loss of coolant accident (LBLCCA).

Based on the concentrations of boron and sodium, the pH of these solutions was calculated in the computer software program "CEQUIL". The purpose of the calculation is to verify that enough sodium hydroxide can be added to achieve the minimum sump pH, as well as verifying that an appropriate spray solution pH is provided.

This calculation is segmented into the various stages of a LBLOCA, based on the manual actions and credible single failures that could occur at various points in the event. In each stage, the calculation considers the

pump operating conditions and tank concentrations that result in the j worst-case minimum sump pH and the worst-case values of spray pH.

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1 Based on the prescribed emergency operating procedure (EOP) response, the l limiting single failure which leads to a minimum sump pH is the loss of a I single high-head SI pump.

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Based on the prescribed EOP actions for particular values of RWST level, the analysis of the LBLOCA was segmented into the following stages:

a. RWST Level 100% to 60% - During this stage, the SI accumulators l inject, one high-head SI pump and two low-head SI pumps inject RWST l-water into the reactor coolant system, and two containment spray pumps ,

draw from the RWST and spray additive tank. After approximately 13 minutes in the worst-case analysis, the RWST level is reduced to approximately 60% and preparations are initiated to switchover to sump recirculation. During this stage, the maximum and minimum containment spray pH conditions have been analyzed as follows: 4 To determine maximum spray pH, the RWST minimum boron concentration -

(2700 ppm) is assumed along with a maximum sodium hydroxide concentration (330 g/kg) from the spray add tank and a minimum l containment spray pump flowrate (1200 gpm). The resulting spray pH is approximately 9.4. Note that the most significant factors in spray pH are the flow rate of the containment spray pump (s) and the boron concentration of the suction source (RWST or sump).

To determine minimum spray pH, the RWST maximum boron concentration (2900 ppm) is assumed along with a minimum sodium hydroxide concentration (300 g/kg) from the spray add tank and a maximum containment spray pump flowrate (1555 gpm). The resulting spray pH is approximately 8.7.

To determine the effect of these conditions on the final sump pH, it ,

is assumed that all the solution drawn from the RWST during this stage is contributed to the sump. The maximum RWST boron concentration (2900 ppm) is assumed and the nominal rate of NaOH addition (14.3 gpm) from each containment spray train is assumed.

b. RWST Level 60% to 6% - At the 60% RWST level, EOP-1.3, " Transfer to Containment Sump Recirculation" directs the operator to secure one train of high-head SI, one train of low-head SI, and one train of containment spray. However, if one train of high-head SI is inoperable, EOP-1.3 directs the stopping of one spray pump and provides for the continued operation of both low-head SI trains (RHR) down to the 6% RWST level. Therefcre, the analysis assumes 2 RHR pumps, 1 SI pump, and 1 spray pump until the 6% RWST level is achieved per EOPs. Assuming the single failure of a high-head SI pump during this stage will maximize safety injection flowrate because emergency operating proceduras (EOPs) would require the operation of both low-head SI pumps, and therefore, a higher net safety injection rate, i This stage was defined so as to maximize the safety injection rate of j boric aciddgminimize the duration of NaOH addition, and thereby l

minimize the sump pH.

The maximum flowrate was assumed from all running SI pumps and containment spray pumps. Also, the maximum boron concentrations in l ,

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i the RWST, SI accumulators and RCS were assumed while the minimum NaOH concentration in the spray additive tank was minimized in order to 4 minimize the sump pH results in the calculation.

e In addition to the aforementioned conservatisms, the calculation also considers the refueling cavity drain failure reported in LER 266/97-006-00. This drain failure could result in the retention of approximately 46,000 gallons of containment spray solution in the refueling cavity. It is assumed that this solution does not drain to the containment sump.

The minimum sump pH at the conclusion of this stage was calculated to

! be 7.3. This is assumed to be the final sump pH for the recirculation phase; however, any addition of NaOH as a result of containment spray during the recirculation phace would raise the sump pH. The pH remains greater than the minimum value of 7.0 described in WCAP 11611,

Methodology for Elimination of the Containment Spray Additive", March 1988. Therefore, we believe that this incremental change in pH will not significantly affect the operability of materials used in the SI system. At this stage, equipment submersed in the sump would be

, subject to the buffered boric acid solution (pH as low as 7.3).

Likewise, any equipment wetted by containment spray would be subject j to this solution if containment spray is reinitiated during the a recirculation phase. It is our judgment that the chemical composition of this solution will not adversely affect the operability or I equipment qualification (EQ) of essential equipment inside containment. At this stage, the composition of the chemical solution j would be less severe than the most severe chemical environment assumed 4

for the EQ program.

This calculation contains many conservatisms including maximum pump runout values.

4. Describe the review performed for the 18-month fuel cycle length and describe how you reached your conclusion that no additional applications for Technical Specifications will be required to support this change.

RESPONSE: Westinghouse Electric Corporation was consulted to ascertain those parameters and analyses affected by the longer operating cycle and the estimated core designs. In addition, a Wisconsin Electric interdisciplinary team investigated the effects of the cycle change.

Industry experience was used. License amendments from similar plants were reviewed. Also, Wisconsin Electric reviewed the Technical Specifications to ascertain those maintenance, surveillance, calibratien, inspection, or operating requirements presently related to the " refueling interval". As discussed below, the present Technical Specifications (Table 15.4.1) allow an instrument calibration frequency that may axtend to 18 months, so no 3 such TS changes were necessitated.

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5. Identify the WCAP reports referenced in the submittal by number, title, j date, and NRC staff approval document, or identify the staff Safety Evaluation Report for a plant-specific methodology by NRC letter and date.

i Ensure similar information is provided for WCAPs referenced in the Unit 1 Cycle 25 reload evaluation report.

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RESPONSE: Two WCAPs are referenced in the submittal: WCAP-9273-NP-A,

" Westinghouse Reload Safety Evaluation Methodology", July 1985, approved by NRC SER dated May 28, 1985, and WCAP-11611, " Methodology for Elimination of the Containment Spray Additive", March 1988. WCAP-11611 was not specifically approved for PBNP application; however, it has been referenced in submittals by V.C. Summer, D.C. Cook, Indian Point, and others.

6. Have you performed an evaluation of information similar to that incleded in Generic Letter 91-004, " Changes in Technical Surveillance Intervalu to Accommodate a 24-Month Fuel Cycle" for your planned extension from 12-month to 18-month cycles? Specifically, have you addressed instrument' drift? If you have such an evaluation of the cycle length change, please

( provide it.

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! RESPONSE: Our current Technical Specifications (TS Table 15. 4.1-1) require instrument calibrations on a refuel 1ng basis, not to exceed 18 months. Therefore, the scope of this TSCR does not include any request to

! change the calibration frequency. Therefore, the TSCR contains no evaluation of the instrument drift that might be expected in a license amendment request made pursuant to GL 91-04, " Changes in Technical Specification Surveillance Intervals To Accommodate a 24-Month Fuel Cycle".

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For those effects of the 18-month fuel cycle that do not relate to Technical Specifications, a 50.59 evaluation is being prepared for issuance prior to the Unit i reload for Cycle 25. This 50.59 evaluation is being prepared with consideration of GL 91-04 factors, including the effect of increased calibration interval on instrument errors. However, 2 the GL 91-04 " Guidance For Addressing The Effect Of Increased Surveillance Intervals On Instrument Drift And Safety Analysis Assumptions" is not explicitly applied to our 50.59 evaluation. Using historical drift data from 1-year surveillance, 24-month drift values have been calculated for the most numerous and safety-significant instruments. No setpoints l

verified to date in'this program have required revision due to the use of l 24-month drift values. This information and vendor-provided drift l information is being used in an ongoing setpoint verification program.

The 24-month drift values calculated to date have all been less than the j vendor-determined drift values. Pursuant to 10 CFR 50.59, our 50.59 evaluation and supporting references will be available for your review when complete. If an unreviewed safety question is identified or if a Technical Specification change is required, a license amendment request will be submitted pursuant to 10 CFR 50.90.

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