ML081990266

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License Amendment Request 238: Increase in Technical Specification Minimum Injection Accumulator Boron Concentration
ML081990266
Person / Time
Site: Kewaunee Dominion icon.png
Issue date: 07/16/2008
From: Gerald Bichof
Dominion, Dominion Energy Kewaunee
To:
Document Control Desk, Office of Nuclear Reactor Regulation
References
08-0339
Download: ML081990266 (23)
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Text

Dominion Energy Kewaunee, Inc.

,(10(1 Dominion Boulevard, Glen Allen, V A 2511(,0 July 16, 2008 ATTN: Document Control Desk Serial No. 08-0339 U. S. Nuclear Regulatory Commission L1C/JF/RO Washington, DC 20555-0001 Docket No.: 50-305 License No.: DPR-43 DOMINION ENERGY KEWAUNEE, INC.

KEWAUNEE POWER STATION LICENSE AMENDMENT REQUEST 238:

INCREASE IN TECHNICAL SPECIFICATION MINIMUM REQUIRED SAFETY INJECTION ACCUMULATOR BORON CONCENTRATION Pursuant to 10 CFR 50.90, Dominion Energy Kewaunee, Inc. (DEK) requests an amendment to Facility Operating License Number DPR-43 for Kewaunee Power Station (Kewaunee). This proposed amendment would change Kewaunee Technical Specifications (TS) 3.3.a.1.A and TS 3.3.a.2.A to increase the minimum required boron concentration in the Safety Injection (SI) accumulators from 1900 parts per million (ppm) to 2400 ppm.

The proposed amendment is required to align the Kewaunee TS with the results of an evaluation performed in Westinghouse Nuclear Safety Advisory Letter (NSAL-07-7),

"Short-Term Recriticality During a PWR Large-Break LOGA." NSAL-07-7 determined that the potential exists for recriticality to occur during a Large Break Loss-of-Coolant-Accident in the short-term (reflood stage). Westinghouse determined that Kewaunee is not susceptible to the issue based on the current plant practice of maintaining SI accumulator boron concentration at or above 2500 ppm. However, to ensure the Kewaunee TS are conservative with respect to the results of NSAL-07-7, DEK proposes to raise the minimum required boron concentration for the SI accumulators in the TS from 1900 ppm to 2400 ppm.

DEK requests approval of the proposed amendment by August 2009. Once approved, the amendment shall be implemented within 60 days. to this letter contains a description, a safety evaluation, a significant hazards determination and environmental considerations for the proposed changes. contains the marked-up Technical Specification page TS 3.3-1.

The Facility Safety Review Committee has approved the proposed change and a copy of this submittal has been provided to the State of Wisconsin in accordance with 10 CFR 50.91 (b).

Serial No. 08-0339 License Amendment Request 238 Page 2 of 3 If you have any questions or require additional information, please contact Mr. Gerald Riste at (920) 388-8424.

Very truly yours, Gi~~f--6 Vice President - Nuclear Engineering COMMONWEALTH OF VIRGINIA )

)

COUNTY OF HENRICO )

The foregoing document was acknowledged before me, in and for the County and Commonwealth aforesaid, today by Gerald T. Bischof, who is Vice President, Nuclear Engineering of Dominion Energy Kewaunee, Inc. He has affirmed before me that he is duly authorized to execute and file the foregoing document in behalf of that Company, and the statements in the document are true to the best of his knowledge and belief.

Acknowledged before me this /(,,"" day of ~ , 2008.

My Commission expires: ~.uA z;- 3 ~ doo8 MMQARET t. IENNITT Notary Public 3)"tf30),

Commonwealth of VttSJlnlO

~Pd&:~4~ Notary Public My Comrnllllon Expire. Aug S1. 2001 t Attachments:

1. Discussion of Change, Safety Evaluation, Significant Hazards Determination and Environmental Considerations
2. Marked-Up Technical Specifications Page TS 3.3-1 Commitments made by this letter: None

Serial No. 08-0339 License Amendment Request 238 Page 3 of 3 cc: Regional Administrator, Region '"

U. S. Nuclear Regulatory Commission 2443 Warrenville Road Suite 210 Lisle, IL 60532-4352 Mr. J. R. Cushing Project Manager U.S. Nuclear Regulatory Commission One White Flint North, Mail Stop 08-H4A 11555 Rockville Pike Rockville, MD 20852-2738 NRC Senior Resident Inspector Kewaunee Power Station Public Service Commission of Wisconsin Electric Division P.O. Box 7854 Madison, WI 53707

Serial No. 08-0339 ATTACHMENT 1 LICENSE AMENDMENT REQUEST 238 INCREASE IN TECHNICAL SPECIFICATION MINIMUM REQUIRED SAFETY INJECTION ACCUMULATOR BORON CONCENTRATION DISCUSSION OF CHANGE, SAFETY EVALUATION, SIGNIFICANT HAZARDS DETERMINATION AND ENVIRONMENTAL CONSIDERATIONS KEWAUNEE POWER STATION DOMINION ENERGY KEWAUNEE, INC.

Serial No. 08-0339 Attachment 1 Page 1 of 17 INCREASE IN TECHNICAL SPECIFICATION MINIMUM REQUIRED SAFETY INJECTION ACCUMULATOR BORON CONCENTRATION DISCUSSION OF CHANGE, SAFETY EVALUATION, SIGNIFICANT HAZARDS DETERMINATION AND ENVIRONMENTAL CONSIDERATIONS

1.0 DESCRIPTION

Pursuant to 10 CFR 50.90, Dominion Energy Kewaunee, Inc. (DEK) requests an amendment to Facility Operating License Number DPR-43 for Kewaunee Power Station (Kewaunee). This proposed amendment would change Kewaunee Technical Specification (TS) 3.3.a.1.A and TS 3.3.a.2.A to increase the minimum required boron concentration in the Safety Injection (SI) accumulators from 1900 parts per million (ppm) to 2400 ppm.

The proposed amendment is required to align the Kewaunee TS with the results of an evaluation performed in Westinghouse Nuclear Safety Advisory Letter (NSAL-07-7),

"Short-Term Recriticality During a PWR Large-Break LOGA." NSAL-07-7 determined that the potential exists for recriticality to occur during a Large Break Loss-of-Coolant-Accident (LBLOCA) in the short-term (reflood stage). Westinghouse determined that Kewaunee is not susceptible to the issue based on the current plant practice of maintaining SI accumulator boron concentration at or above 2500 ppm. However, to ensure the Kewaunee TS are conservative with respect to the results of NSAL-07-7, DEK proposes to raise the minimum required boron concentration for the SI accumulators in the TS from 1900 ppm to 2400 ppm.

The proposed amendment qualifies for a no significant hazards consideration under the standards set forth in 10 CFR 50.92(c). The proposed amendment meets the eligibility criterion for categorical exclusion set forth in 10 CFR 51.22(c)(9). Therefore, pursuant to 10 CFR 51.22(b), no environmental impact statement or environmental assessment need be prepared in connection with the proposed amendment.

Serial No. 08-0339 Attachment 1 Page 2 of 17

2.0 PROPOSED CHANGE

The proposed amendment would change Kewaunee TS 3.3.a.1.A and TS 3.3.a.2.A.

The current Kewaunee TS 3.3.a.1.A states:

"Each accumulator is pressurized to at least 700 psig and contains 1250 tf .:!: 25 tf of water with a boron concentration of at least 1900 ppm, and is not isolated. "

The proposed amendment would change the SI accumulator required minimum boron concentration in TS 3.3.a.1.A from "at least 1900 ppm" to "at least 2400 ppm." The final changed TS 3.3.a.1.A would read as follows:

"Each accumulator is pressurized to at least 700 psig and contains 1250 tf .:!: 25 tf of water with a boron concentration of at least 2400 ppm, and is not isolated. "

The current Kewaunee TS 3.3.a.2.A states:

"One accumulator may have a boron concentration < 1900 ppm for 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />."

The proposed amendment would change the SI accumulator required minimum boron concentration in TS 3.3.a.2.A from "< 1900 ppm for 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />" to "< 2400 ppm for 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />." The final changed TS 3.3.a.2.A would read as follows:

"One accumulator may have a boron concentration < 2400 ppm for 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />."

In summary, this proposed amendment would change Kewaunee TS 3.3.a.1.A and TS 3.3.a.2.A to increase the minimum required boron concentration in the SI accumulators from 1900 ppm to 2400 ppm.

No TS Bases changes are needed in conjunction with this amendment request.

Serial No. 08-0339 Attachment 1 Page 3 of 17

3.0 BACKGROUND

Kewaunee Power Station is a two-loop Westinghouse Pressurized Water Reactor. The Emergency Core Cooling System (ECCS) is designed to provide emergency cooling to the reactor core during transients and accidents including the loss of coolant accident (LOCA). The ECCS systems, structures, and components (SSCs) operate in three modes. These modes are delineated as passive SI accumulator injection, active safety injection, and containment sump recirculation. The SI accumulators function only during the passive SI accumulator injection mode.

The SI accumulators are pressure vessels filled with borated water and pressurized with nitrogen gas. One SI accumulator is attached to each of the cold legs of the Reactor Coolant System (RCS). During normal plant operation each SI accumulator is isolated from the RCS by two swing-disc check valves in series. Should the RCS pressure fall below the SI accumulator pressure, the check valves open and borated water is injected from the accumulator into the RCS. Mechanical operation of the check valves is the only action required to open the injection path from the SI accumulators to the core via the RCS cold legs. The SI accumulators are passive engineered safety features because the nitrogen gas pressure forces injection and no external source of power or signal transmission is needed to obtain fast-acting, high-flow capability if the need arises.

The Kewaunee Updated Safety Analysis Report (USAR) contains a detailed description of the ECCS and its ability to meet its design criteria (Reference 1, Section 6.2, "Safety Injection System"). The LBLOCA, Small Break LOCA (SBLOCA) and Main Steam Line Break (MSLB) are postulated design bases events that include SI accumulator injection and require ECCS for event mitigation. The safety analyses for these events are presented in Kewaunee USAR (Reference 1, Section 14). The design parameters for the SI accumulators are provided in Kewaunee USAR (Reference 1, Table 6.2-4, "Accumulator Design Parameters').

The Kewaunee plant design and licensing bases presently assume and require SI accumulator boron concentration be in the range of 1900 ppm to 2625 ppm as a precondition for successful mitigation of design basis accidents. The proposed amendment described herein increases the minimum SI accumulator boron concentration from 1900 ppm to 2400 ppm. The effect of this change is to further constrain the allowable SI accumulator boron concentration within the range of Sl accumulator boron concentrations already considered in the plant design and licensing bases.

This change is necessary based on a recent evaluation performed by Westinghouse and documented in Nuclear Safety Advisory Letter (NSAL-07-7), "Short-Term Recriticality During a PWR Large-Break LOCA." This analysis determined that the potential exists for recriticality to occur during a LBLOCA accident in the short-term (reflood phase of the LBLOCA). Westinghouse determined that current Kewaunee

Serial No. 08-0339 Attachment 1 Page 4 of 17 practices* do not make the plant susceptible to the issue. However, to ensure the Kewaunee TS remain conservative with respect to the results of NSAL-07-7, DEK is proposing to raise the minimum required boron concentration for the SI accumulators in the TS.

The current Kewaunee USAR Chapter 14 safety analyses assume that Sl accumulator boron concentration is maintained between 1850 and 2625 ppm. Therefore, increasing TS required minimum boron concentration from 1900 to 2400 ppm does not require changes to the Kewaunee USAR Chapter 14 safety analysis. A discussion regarding the effects of the proposed change on the current Kewaunee USAR Chapter 14 safety analyses is provided in section 4 below.

See section 4.0 for details.

Serial No. 08-0339 Attachment 1 Page 5 of 17

4.0 TECHNICAL ANALYSIS

The proposed amendment would change Kewaunee TS 3.3.a.1.A and TS 3.3.a.2.A to increase the minimum required boron concentration in the SI accumulators from 1900 ppm to 2400 ppm.

4.1 Reason and Basis for Change The current Kewaunee U8AR (Reference 1, Table 6.2-4) requires 81 accumulator boron concentration be maintained within the range of 1900 ppm to 2625 ppm. The Kewaunee U8AR Chapter 14 safety analyses for LBLOCA, 8BLOCA and M8LB conservatively assume a minimum SI accumulator boron concentration of 1850 ppm is available for reactor core shutdown (Reference 1, LOCAs - Table 14.3.3-4; MSLB -

Section 14.2.5.2). This value is 50 ppm less than the minimum value (1900 ppm) permitted by the current Kewaunee TS. The analysis of minimum Containment sump pH assumes the maximum boron concentration (2625 ppm). The proposed revised SI accumulator minimum boron concentration (2400 ppm) is within the current minimum and maximum 81 accumulator boron concentration limits as described in the U8AR. As a result of selecting the revised required minimum 81 accumulator boron concentration within the current minimum and maximum limits, the safety analyses that use minimum (1900 ppm) or maximum (2625 ppm) SI accumulator boron concentration as a design input will be unaffected and will remain bounding and valid.

Westinghouse identified in Nuclear Safety Advisory Letter (NSAL-07-7), "Short-Term Recriticafity During a PWR Large-Break LOGA," that the potential exists for recriticality to occur during a LOCA transient in the short-term unless the SI accumulator minimum required boron concentration is raised.

N8AL-07-7 states the issue as follows:

"Westinghouse has identified a potential safety issue with maintaining the core subcritical in the short term during the initial reflood stage of the large-break loss-of-coolant accident (LBLOGA). For the Westinghouse fleet of PWR plants, LBLOGA safety analyses currently do not take credit for control rod insertion but rely on the fact that the core is shut down on voids. ... The core is assumed to remain subcritical because there is sufficient boron in the reactor vessel and safety injection water to preclude recritica/ity. If recriticality were to occur, existing design basis LBLOGA analyses may not be bounding.

Immediately following the blowdown phase in a LBLOGA, the boron concentration in the core is determined by the initial reactor coolant system (RGS) water boron level at the time of the event, the amount of initial liquid inventory left at the end of the blowdown stage, and the accumulator boron concentration. If the cumulative boron concentration in the core is too low, the core may not remain subcritical in the short term, following a LBLOGA. .. ,

Serial No. 08-0339 Attachment 1 Page 6 of 17 With respect to long term aspects, other borated water sources, primarily the refueling water storage tank (RWST), will add to the total water inventory by high and low head pumped injection while the accumulators are in the process of injecting their contents and after the accumulators have emptied. The combined inventory is sufficient to maintain the core subcriticality criteria for the long term.

However, during the short-term reflood, the RWST contribution via the pumped injection is small compared to the accumulator. Thus, the subcriticality requirement is dependent on the accumulators for the short term following a LBLOCA."

Westinghouse determined that Kewaunee will remain subcritical during the reflood stage of a LBLOCA, thus no safety issue currently exists. This conclusion is based on the current plant practice of maintaining boron concentration in the SI accumulators at or above 2500 ppm-. However, the current TS minimum boron concentration of 1900 ppm for the SI accumulators is not sufficient to assure that short-term subcriticality can be maintained in the initial reflood phase following a LBLOCA during the short-term.

Based on their evaluation of Kewaunee, Westinghouse has recommended an increase in the minimum boron concentration of the SI accumulators to 2400 ppm. This value accounts for measurement uncertainties and boron recycling.

Westinghouse, in the reload safety evaluation (RSE) performed for Kewaunee Cycle 29 (the current fuel cycle which began in May 2008) evaluated Kewaunee core subcriticality during the LOCA reflood phase as described in NSAL-07-7. One purpose of this evaluation was to determine the boron concentration value required to keep the core subcritical during the LOCA reflood phase. The Cycle 29 RSE provides a basis for maintaining SI accumulator minimum boron concentration at or above 2400 ppm. As shown in the RSE analysis, Cycle 29 beginning of cycle (BOC) critical boron concentration is relatively high; indicating there is less burnable absorber loaded for BOC reactivity hold down. Thus, Cycle 29 is a good representative fuel cycle for the post-LOCA reflood stage recriticality analysis.

The post-LOCA reflood subcriticality analysis was performed for Kewaunee Cycle 29, consistent with the methodology outlined in NSAL-07-6 and NSAL-07-7. Westinghouse credited an SI accumulator boron concentration of 2400 ppm, instead of the current Technical Specification minimum value of 1900 ppm, at Dominion's request. Historical data shows that the SI accumulators at Kewaunee are maintained above 2400 ppm. In addition, an administrative limit on the minimum SI accumulator boron concentration of 2400 ppm was established prior to operation of Kewaunee in Cycle 29.

For Kewaunee, the most reactive time of Cycle 29 is at the BOC. Full power equilibrium conditions were evaluated consistent with the full power initial conditions of the limiting LOCA accidents. The nominal RCS boron concentration at hot full power, all rods out,

  • The practice is based on the SI accumulators being filled from the Refueling Water Storage Tank (RWST). The minimum boron concentration in the RWST is required to be at least 2500 ppm per the KPS TS.

Serial No. 08-0339 Attachment 1 Page 7 of 17 equilibrium xenon condition is 1799 ppm at 150 MWD/MTU. This value was used to compute the reflood boron concentrations required per the methodology of NSAL-07-6.

The Cycle 29 analysis reported the following results:

Accident Reflood Boron Concentration keff value Analyzed Required to Achieve Subcriticality LBLOCA 2386.4 ppm 0.995189 SBLOCA 2264.2 ppm 1.009099-The required post-LOCA reflood core boron concentration is based on the core analysis for Cycle 29. The required core boron concentration must be less than the post LOCA calculated boron concentration (the calculated value based on ECCS systems analysis assuming some initial RCS boron concentration).

Based upon these calculation results for Cycle 29, the selection of 2400 ppm boron concentration for the SI accumulators provides assurance that the core will remain subcritical because there is sufficient boron in the reactor vessel and safety injection water to preclude recriticality. Therefore, the post-LOCA reflood subcriticality criterion is considered satisfied. Subsequent Kewaunee operating cycles are required to be evaluated as described in TS 6.9.a.4 and will address reflood phase boron concentration requirements.

4.2 Analysis of the Proposed Change DEK has evaluated the impact of the proposed TS change to raise minimum required SI accumulator boron concentration on the following:

  • Post-LOCA boron precipitation - evaluated to confirm that boron concentrations in the post-LOCA core remain below the solubility limit for boron.
  • Post-LOCA sump boron concentration limit - evaluated for each reload core design to ensure long-term post-LOCA subcriticality.

Per the Westinghouse methodology, if the value of keff is less than 1.01, the xenon credit (worth at least 2000 percent milli-rho (pcm)) can be credited to show acceptable results.

Serial No. 08-0339 Attachment 1 Page 8 of 17

  • Assessment of Boron Solubility in the SI Accumulator - evaluated to determine the margin to the temperature-dependent boric acid solution solubility limit.

A discussion regarding each of the evaluations performed in support of the proposed change is presented below.

4.2.1 Non-LOCA USAR Chapter 14 Transients And Accidents The USAR Chapter 14 non-LOCA transients and accidents were evaluated. The only non-LOCA transient analysis that credits ECCS and that relies on the SI accumulator borated water for reactor shutdown is the MSLB accident described in Kewaunee USAR (Reference 1, Chapter 14.2.5). The current MSLB analysis assumes 1850 ppm for SI accumulator boron concentration. Increasing the assumed boron concentration in the SI accumulator from 1850 ppm to 2400 ppm would make the MSLB analysis results less limiting since increased boron concentration provides increased negative reactivity and additional reactor shutdown margin. Thus, the current MSLB analysis that assumes 1850 ppm for SI accumulator boron concentration remains bounding and valid if the actual SI accumulator boron concentration is maintained at a minimum of 2400 ppm.

4.2.2 LBLOCA Accident The Kewaunee USAR (Reference 1, Chapter 14.3.2) describes the SI accumulator and its design function in mitigating the consequences of a LBLOCA design bases accident as follows:

"When the RGS depressurizes to approximately 750 psig, the accumulators begin to inject borated water into the reactor coolant loops. Borated water from the accumulator in the faulted loop is assumed to spill to containment and be unavailable for core cooling for breaks in the cold leg of the RGS. Flow from the accumulator in the intact loop may not reach the core during depressurization of the RGS due to the fluid dynamics present during the EGGS bypass period.

EGGS bypass results from the momentum of the fluid flow up the downcomer due to a break in the cold leg, which entrains EGGS flow out toward the break. Bypass of the EGGS diminishes as mechanisms responsible for the bypassing are calculated to be no longer effective.

The blowdown phase of the transient ends when the liquid level in the lower plenum reaches its minimum. After the end of the blowdown, refill of the reactor vessel lower plenum begins. Refill is completed when emergency core cooling water has filled the lower plenum of the reactor vessel, which is bounded by the bottom of the active fuel region of the fuel rods (called bottom of core (BOG) recovery time).

The reflood phase of the transient is defined as the time period lasting from BOG recovery until the reactor vessel has been filled with water to the extent that the core temperature rise has been terminated. From the latter stage of blowdown and on

Serial No. 08-0339 Attachment 1 Page 9 of 17 into the beginning of reflood, the intact loop accumulator tank rapidly discharges borated cooling water into the RGS. Although a portion injected prior to end of bypass is lost out the cold leg break, the accumulator eventually contributes to the filling of the reactor vessel downcomer. ...

Spilled borated water is drawn from the engineered safety features (ESF) containment sumps by the LHSI pumps (also called the Residual Heat Removal pumps, or RHR pumps) and returned to the upper plenum and RGS cold legs."

The effects of the proposed increased boron concentration on the LBLOCA analysis were evaluated. The LBLOCA is characterized by a rapid depressurization that causes the generation of significant voiding in the RCS. In accordance with 10 CFR 50 Appendix K, the LBLOCA analysis does not assume control rod insertion. As a result, heat generation in the core is reduced to decay heat levels by void reactivity.

Therefore, during the blowdown phase of the LBLOCA, the core is shutdown and remains shutdown due to void reactivity.

The refill/reflood portion of the injection phase is the period of potential recriticality discovered in the Westinghouse NSAL described above. Assuming the increased minimum TS limit for SI accumulator concentration, the refill/reflood portion of the injection phase begins with a highly voided core and continues from downcomer refill through core reflood. Initially, void reactivity is of primary importance and gradually begins to be replaced by boron as the primary source of negative reactivity. The reload analysis for Cycle 29 indicates that core reactivity (potential recriticality) is acceptable; therefore, the peak cladding temperature (PCT) in the LBLOCA is not changed based on the revised boron concentration proposed for the SI accumulators. Therefore, the current LBLOCA core response analysis remains bounding and valid.

For a given reload core, an increase in the SI accumulator minimum boron concentration results in an increase in the margin by which the plant is calculated to be shutdown following a LBLOCA. Thus, an increase in the actual boron concentration (sources include the RWST, the SI accumulators, the high head SI system piping, and the reactor coolant system) is a conservative change with respect to post-LOCA subcriticality. However, post-LOCA subcriticality is a Kewaunee design and licensing basis criterion governing the establishment of the volume and concentration levels of borated water (Le., Reference 1, Section 14.3.2 states that, An average ReS sump mixed boron concentration is calculated to ensure that the post-LOGA core remains subcriticaf'). Therefore, it is necessary to increase the minimum SI accumulator boron concentration specified in Technical Specifications in order to credit an increased SI accumulator boron concentration in the post-LOCA subcriticality analysis.

Safety analyses that use the minimum SI accumulator boron concentration of 1850 ppm (e.g. LBLOCA analysis) are unaffected and remain valid if the minimum required SI accumulator boron concentration is increased from 1900 ppm to 2400 ppm. This is because these safety analyses credit SI accumulator injection. If the boron

Serial No. 08-0339 Attachment 1 Page 10 of 17 concentration of the injected SI accumulator water is increased to a minimum of 2400 ppm, then the reactor coolant system (Le., the system that is receiving the injected accumulator borated water) boron concentration will increase as compared to what it would have been if the SI accumulator had a boron concentration of 1900 ppm.

On this basis, it may be concluded that the safety analyses that use the minimum SI accumulator boron concentration as an input (e.g., LBLOCA) will be unaffected and will remain bounding and valid if the minimum SI accumulator boron concentration is increased from 1900 ppm to 2400 ppm.

4.2.3 SBLOCA Accidents The SBLOCA analysis falls into the category of design basis accidents that cause ECCS actuation. The SBLOCA analysis assumes the insertion of control rods via the Reactor Protection System. Consequently, the SI accumulator boron concentration required to achieve the level of subcriticality for the SBLOCA is significantly lower than the concentration required for a LBLOCA. The proposed increase in SI accumulator boron concentration provides additional conservatism for the SBLOCA. The current SBLOCA analysis would remain bounding and valid if the minimum SI accumulator boron concentration is increased from 1900 ppm to 2400 ppm.

4.2.4 Post-LOCA Boron Precipitation Following a LOCA, borated water from the RWST and SI accumulators enters the core region through the cold leg during the injection and reflood phases of the accident.

Assuming a cold leg break, borated coolant enters the core region from the intact cold leg, down the downcomer, and into the core. Steam exits through the hot leg, and excess safety injection water spills out of the break. Although the water vapor exits the core and condenses in the containment, only a fraction of the dissolved boron is carried off in the steam. Therefore, the concentration of boron increases over time in the reactor vessel. If the boron concentration reaches the solubility limit, boron will begin to precipitate, forming a paste that can block the coolant flow channels in the core. Such a condition may lead to inadequate cooling of the fuel.

For the boron precipitation analysis, higher assumed values of boron concentration are conservative; that is, boron precipitation is more likely to occur during a LOCA when higher initial boron concentrations are present in the RCS, SI accumulators and RWST.

The boron precipitation analysis conservatively assumes injected Sl accumulator and ECCS fluid at the maximum boron concentration (Le., 2625 ppm). Furthermore, the analysis assumes an at power critical boron concentration (initial RCS condition prior to the accident) of 2400 ppm, which conservatively bounds the maximum plausible at-power critical boron concentration for reload cores. Thus, in the case of the post-LOCA boron precipitation analysis, selection of a revised required minimum SI accumulator boron concentration within the current range of allowable boron concentrations (Le.,

1900 ppm to 2625 ppm) ensures that the safety analysis will remain bounding and valid.

Serial No. 08-0339 Attachment 1 Page 11 of 17 The current boron precipitation analyses were evaluated. These analyses assume a conservatively bounding maximum full power critical boron concentration in the RCS (2400 ppm), in the SI accumulator (2625 ppm) and in the RWST (2625 ppm). The boron precipitation analyses are bounding and are not affected by increasing the minimum required SI accumulator boron concentration to 2400 ppm. Therefore, the boron precipitation analyses remain bounding and valid.

4.2.5 Post-LOCA Sump Boron Concentration Limit Following a SBLOCA or LBLOCA, fluid from various sources accumulates in the containment sump. These fluid sources include the RWST, the Caustic Storage Standpipe, the SI accumulators, the safety injection system piping, and the reactor coolant system. All of these volumes contain boric acid solution with the exception of the Caustic Storage standpipe, which contains a sodium hydroxide solution.

Depending on the magnitude of the LOCA, some or all of the liquid contained in these fluid sources will be introduced into containment, and will ultimately accumulate in the containment sump. It is assumed in the containment sump boron analysis for the design basis LBLOCA that all of the liquid in these fluid sources is transferred into containment.

The limit for the maximum allowable critical boron concentration at post-LOCA core conditions is determined as a function of the minimum critical boron concentration at pre-LOCA conditions. Conservative assumptions regarding pre-LOCA and post-LOCA coolant temperature, control rod position, xenon concentration, and cycle burnup are employed in the analysis. In the Kewaunee Cycle 29 post-LOCA sump boron concentration analysis, a SI accumulator boron concentration of 1900 ppm resulted in a calculated post-LOCA sump boron concentration (long term) that was greater than the calculated maximum critical boron concentration for the reload core at post-LOCA core conditions. Therefore, use of a boron concentration of 2400 ppm in the analysis would result in additional margin in the post-LOCA sump boron concentration limit.

It is necessary to have a sufficiently high boric acid concentration in the sump mixture to ensure that the reactor remains subcritical following an accident. The proposed increased minimum required SI accumulator boron concentration would increase the post-LOCA boron sump concentration and ensure post-LOCA core subcriticality.

Reload safety evaluations performed in accordance with the currently approved methodology will continue to incorporate this minimum sump post-LOCA boron concentration limit.

4.2.6 Post-LOCA Containment Sump pH Analysis Limits are placed on the post-LOCA containment sump pH to minimize the potential for stress corrosion cracking of stainless steel components in containment.

The results of the current Kewaunee analysis for post-LOCA containment sump pH demonstrate that sump pH will remain within the acceptable post-LOCA sump pH range

Serial No. 08-0339 Attachment 1 Page 12 of 17 of 7.0 to 9.5, assuming upper and lower bounding values of SI accumulator boron concentration of 2625 ppm and 1900 ppm, respectively. The post-LOCA sump pH range of 7.0 to 9.5 was established to ensure that radioactive iodine forms chemical species that remain in solution and therefore do not adversely affect post-LOCA radiological dose analysis results. The acceptable range of post-LOCA sump pH was also established to minimize corrosion of metallic surfaces within containment. The proposed change (i.e. increasing the minimum SI accumulator boron concentration from 1900 ppm to 2400 ppm) will have no adverse impact on the results of the containment sump pH analysis, since the proposed minimum accumulator boron concentration remains within the current containment sump pH analysis range for SI accumulator boron concentration (i.e., 2400 ppm is in the range of 1900 ppm to 2625 ppm).

As an example, the actual Kewanee SI accumulator boron concentration could be controlled to a minimum boron concentration greater than 1900 ppm (e.g., 2550 ppm).

This control would be consistent with the existing Kewaunee safety analyses, since it constrains the allowable SI accumulator boron concentration within the range of SI accumulator boron concentrations already considered in the plant design and licensing bases. Therefore, with the proposed increase in 51 accumulator boron concentration from 1900 ppm to 2400 ppm, the current containment sump pH analyses will remain valid, and the acceptance criterion of a sump pH between 7.0 and 9.5 will be satisfied.

The pH of the post-LOCA sump is determined by a mass-weighted concentration of the boric acid and sodium hydroxide from each analyzed volume. Calculations of containment sump pH consider a range of SI accumulator boron concentrations from 1900 ppm to 2625 ppm. Therefore, the proposed change in minimum SI accumulator boron concentration from 1900 ppm to 2400 ppm is still within the analyzed range. The containment spray and post-LOCA containment sump pH analysis limits continue to be satisfied after consideration of increasing minimum SI accumulator boron concentration to 2400 ppm.

4.2.7 Assessment of Boron Solubility in the SI Accumulator The current maximum allowed SI accumulator boric acid concentration of 2625 ppm is approximately 1.5-weight percent boric acid. The maximum limit will remain unchanged. The proposed new minimum 51 accumulator boron concentration of 2400 ppm is well below the maximum allowed boric acid concentration of 2625 ppm. At 40 OF (minimum containment temperature, Reference 1, Section 5.2.1.5.4) the solubility limit of boric acid is approximately 3-weight percent. A borated water mixture of approximately 5400 ppm would be required before the boron solubility limit would be reached at 40 of. Therefore, the allowable concentrations of boric acid in the SI accumulator (minimum required concentration, nominal operating concentration, and maximum allowed concentration) remain well below the boron solubility limit of about 5400 ppm at 40 OF.

Serial No. 08-0339 Attachment 1 Page 13 of 17 4.3 Conclusions A change to the TS is required to implement an increase in the minimum boron concentration in the Kewaunee SI accumulators. Evaluations of the effects of increasing minimum boron concentration in the SI accumulators from the current TS miminum of 1900 ppm to a minimum of 2400 ppm have been completed with the following results.

1. The acceptance criteria of all non-LOCA accidents continue to be satisfied.

All current non-LOCA safety analyses remain bounding and valid.

2. LOCA considerations, including boron precipitation limits, the post-LOCA sump boron concentration limit, and post-LOCA sump pH have been evaluated. The boron precipitation and the post-LOCA sump pH analyses remain bounding and valid.
3. The proposed new minimum SI accumulator boric acid concentration of 2400 ppm remains well below the boron solubility limit.

Based on these evaluations, the proposed increase in minimum 81 accumulator boron concentration will not adversely affect the safe operation of the plant.

No changes to the Kewaunee TS Bases are necessary to support this amendment request.

Serial No. 08-0339 Attachment 1 Page 14 of 17 5.0 REGULATORY SAFETY ANALYSIS 5.1 No Significant Hazards Consideration The proposed amendment would change Kewaunee Technical Specification (TS) 3.3.a.1.A and TS 3.3.a.2.A to increase the minimum required boron concentration in the Safety Injection (SI) accumulators from 1900 parts per million (ppm) to 2400 ppm.

Dominion Energy Kewaunee has evaluated whether or not a significant hazards consideration is involved with the proposed amendment by focusing on the three standards set forth in 10 CFR 50.92, "Issuance of amendment," as discussed below:

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

Response: No.

Increasing the minimum required boron concentration in the SI accumulators does not add, delete, or modify any Kewaunee systems, structures, or components (SSCs). The SI accumulators and their contents are not accident initiators. Rather, they are designed for accident mitigation. The effects of an increase in the minimum SI accumulator boron concentration from 1900 ppm to 2400 ppm are bounded by previous evaluations and determined to be acceptable. Thus, the proposed increase in minimum SI accumulator boron concentration has no adverse effect on the ability of the plant to mitigate the effects of design basis accidents.

Therefore, the proposed change does 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.

Increasing the minimum required boron concentration in the SI accumulators does not change the design function of the SI accumulators or the SSCs designed to deliver borated water from the SI accumulators to the core.

Increasing the minimum required boron concentration in the SI accumulators does not create any credible new failure mechanisms or malfunctions for plant equipment or the nuclear fuel. The reactivity control function of the borated water in the SI accumulators is not being changed.

Serial No. 08-0339 Attachment 1 Page 15 of 17 Therefore, the proposed change does not create the possibility of a new or different kind of accident from any previously evaluated.

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

Response: No.

An evaluation has been performed that shows that maintaining boron concentration at a minimum of 2400 ppm is sufficient to assure that acceptable results for design basis accident analyses will be maintained considering the reactivity of the core. Increasing the minimum boron concentration in the Sl accumulator from 1900 ppm to a minimum of 2400 ppm increases the margin of safety in the Kewaunee safety analyses, since additional post-accident negative reactivity will be available to the core. This additional negative reactivity compensates for the potential for recriticality occurring during the short-term reflood period during the Large Break Loss-of-Coolant-Accident. Additionally, the proposed new minimum boron concentration of 2400 ppm is within the range required by current safety analyses (i.e., 1900 ppm to 2625 ppm), and well below the currently acceptable maximum boron concentration of 2625 ppm.

The proposed amendment does not result in altering or exceeding a design basis or safety limit for the plant. All current fuel design criteria will continue to be satisfied, and the safety analysis of record, including evaluations of the radiological consequences of design basis accidents, will remain applicable.

Therefore, the proposed change does not involve a significant reduction in a margin of safety.

Based on the above, Dominion Energy Kewaunee, Inc. concludes that the proposed amendment presents no significant hazards consideration under the standards set forth in 10 CFR 50.92(c), and, accordingly, a finding of "no significant hazards consideration" is justified.

5.2 Applicable Regulatory Requirements/Criteria The US Atomic Energy Commission (AEC) issued their Safety Evaluation (SE) of the Kewaunee Power Station (KPS) on July 24, 1972 with supplements dated December 18, 1972 and May 10, 1973. The SE, section 3.1, "Conformance with AEC General Design Criteria," described the conclusions the AEC reached associated with the General Design Criteria in effect at the time. The AEC stated:

"The Kewaunee plant was designed and constructed to meet the intent of the AEC's General Design Criteria, as originally proposed in July 1967. Construction of the plant was about 50% complete and the Final

Serial No. 08-0339 Attachment 1 Page 16 of 17 Safety Analysis Report (Amendment No.7) had been filed with the Commission before publication of the revised General Design Criteria in February 1971 and the present version of the criteria in July 1971.

As a result, we did not require the applicant to reanalyze the plant or resubmit the FSAR. However, our technical review did assess the plant against the General Design Criteria now in effect and we are satisfied that the plant design generally conforms to the intent of these criteria. "

As such the appropriate General Design Criterion Kewaunee is licensed to, from the Final Safety Analysis Report (Amendment 7), which has been updated and titled the Updated Safety Analysis Report (USAR) is listed below:

Criterion:

An Emergency Core Cooling System with the capability for accomplishing adequate emergency core cooling shall be provided. This core cooling system and the core shall be designed to prevent fuel and clad damage that would interfere with the emergency core cooling function and to limit the clad meta/-

water reaction to acceptable amounts for all sizes of breaks in the reactor coolant piping up to the equivalent of a double-ended rupture of the largest pipe. The performance of such emergency core cooling systems shall be evaluated conservatively in each area of uncertainty (GDC 44).

In conclusion, based on the considerations discussed above:

(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.

Serial No. 08-0339 Attachment 1 Page 17 of 17

6.0 ENVIRONMENTAL CONSIDERATION

A review has determined that the proposed amendment would change a requirement with respect to installation or use of a facility component located within the restricted area, as defined in 10 CFR 20, or would change an inspection or surveillance requirement. However, the proposed amendment does not involve (i) a significant hazards consideration, (ii) a significant change in the types or significant increase in the amounts of any effluent that may be released offsite, or (iii) a significant increase in individual or cumulative occupational radiation exposure. Accordingly, the proposed amendment meets the eligibility criterion for categorical exclusion set forth in 10 CFR 51.22(c)(9). Therefore, pursuant to 10 CFR 51.22(b), no environmental impact statement or environmental assessment need be prepared in connection with the proposed amendment.

7.0 REFERENCES

1. Kewaunee Power Station Updated Safety Analysis Report, Revision 20.

Serial No. 08-0339 ATTACHMENT 2 LICENSE AMENDMENT REQUEST 238 INCREASE IN TECHNICAL SPECIFICATION MINIMUM REQUIRED SAFETY INJECTION ACCUMULATOR BORON CONCENTRATION MARKED-UP TECHNICAL SPECIFICATIONS PAGE:

TS 3.3-1 KEWAUNEE POWER STATION DOMINION ENERGY KEWAUNEE, INC.

Serial No. 08-0339 3.3 ENGINEERED SAFETY FEATURES AND AUXILIARY SYSTEMS APPLICABILITY Applies to the OPERATING status of Engineered Safety Features and Auxiliary Systems.

OBJECTIVE To define those LIMITING CONDITIONS FOR OPERATION that are necessary: (1) to remove decay heat from the core in emergency or normal shutdown situations, and (2) to remove heat from containment in normal OPERATING and emergency situations.

SPECIFICATIONS

a. Accumulators
1. The reactor shall not be made critical unless the following conditions are satisfied, except for LOW POWER PHYSICS TESTING and except as provided by TS 3.3.a.2.

A. Each accumulator is pressurized to at least 700 psig and contains 1250 fe +/-

25 fe of water with a boron concentration of at least ..:t-QOO-2400 ppm, and is not isolated.

B. Accumulator isolation valves SI-20A and SI-20B shall be opened with their power breakers locked out at or before the Reactor Coolant System pressure exceeds 1000 psig.

2. During power operation or recovery from an inadvertent trip, the following conditions of inoperability may exist during the time interval specified:

A. One accumulator may have a boron concentration < 1900 2400 ppm for 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />.

B. One accumulator may be inoperable for a reason other than TS 3.3.a.2.A for 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />.

If OPERABILITY is not restored within the time specified, then within 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> action shall be initiated to:

Achieve HOT STANDBY within the next 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br />.

Achieve HOT SHUTDOWN within the following 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br />.

Achieve COLD SHUTDOWN within an additional 36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br />.

Amendment No. 178 TS 3.3-1 10105/2004

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