ML20203F838
| ML20203F838 | |
| Person / Time | |
|---|---|
| Site: | Perry  |
| Issue date: | 02/08/1999 |
| From: | NRC (Affiliation Not Assigned) |
| To: | |
| Shared Package | |
| ML20203F829 | List: |
| References | |
| NUDOCS 9902180324 | |
| Download: ML20203F838 (5) | |
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UNITED STATES
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NUCLEAR REGULATORY COMMIS810N WASHINGTON, D.C. Sege64001 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NO. 97 TO FACILITY OPERATING LICENSE NO. NPF-58 FIRSTENERGY NUCLEAR OPERATING COMPANY i
PERRY NUCLEAR POWER PLANT. UNIT 1 l
DOCKET NO. 50-440 1
1.0 INTRODUCTION
l By letter dated June 30,1998, FirstEnergy, the licensee for the Perry Nuclear Power Plant, Unit No.1, submitted proposed changes to Technical Specification 3.1.7, " Standby Liquid Control System," and the accompanying Bases section to permit operation of the Standby Liquid Control l
System (SLCS) with an increased shutdown boron concentration. Supplementalinformation was provided by letter dated December 9,1998. The supplemental information was within the scope of the original Federal Register notice and does not change the proposed no significant hazards consideration.
l The SLCS is a standby reactivity control system and is maintained in an operable status whenever the reactor is critical. The system is designed to bring the reactor from rated power to a cold shutdown condition at any time in core life pursuant to_10 CFR Part 50, Appendix A, General Design Criterion (GDC) 26.- For each operating cycle, the reload safety analysis confirms that the SLCS boron concentration will satisfy the shutdown margin requirements. The Cycle 8 fuel design incorporates increased fuel bundle enrichment to increase power production efficiency. As fuel bundle U-235 enrichment increases, the required shutdown boron concentration is increased to continue to satisfy the reactivity control requirements. Therefore, j
in order to meet the shutdown margin for Cycle 8 operation, the minimum cold shutdown boron -
I concentration is being increased from 660 to 816 ppm.
i The following changes are being made:
1 1.
Increase the molar ratio Na20/B 0 in the neutron absorbing solution (borax-boric acid 1
2 3 mixture) from 0.200 to a nominal value of 0.229.
2.
Increase the solution design nominal concentration from the current 2.38 to 2.85 weight percent boron in saturated solution. This results in an increase of the minimum reactor coolant boron post SLCS injection concentration from 660 to 816 ppm (825 ppm to 1020 ppm with the specified 25% margin).
i 3.
Change the concentration design requirements from the weight percent of sodium pentaborate to the weight percent of boron.
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1 4.
Increase the maximum solution saturation temperature from 61.5'F to 65.0*F.
5.
Increase the stored solution volume, which results in an increase in the tank high-and low-level alarm level setpoints by approximately 3.4 inches (135 gallons).
6.
Decrease the minimum SLCS pump flow rate from 41.2 gpm to 32.4 gpm for each pump.
The supplemental information contained clarifying information and did not change the initial no significant hazards consideration determination and did not expand the scope of the original application.
2.0 BACKGROUND
The SLCS is an independent reactivity control system that provides shutdown margin under normal and ATWS conditions.
The basic requirement for the SLCS is specified in paragraph (c) (4) of 10 CFR 50.62 (ATWS rule) which states,in part:
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"Each boiling water reactor must have a standby liquid control system (SLCS) with the capability of injecting into the reactor pressure vessel a borated water solution at such a flow rate, level of boron concentration and boron-10 isotope enrichment, and accounting for reactor pressure vessel volume, that the resulting reactivity control is at least equivalent to that resulting from injection of 86 gallons per minute of 13 weight percent sodium pentaborate decahydrate solution at the natural boron-10 isotope abundance into a 251-inch inside diameter reactor pressure vessel for a given core design."
Equivalent reactivity control can be obtained by increasing the pump flow rate, boron concentration or boron enrichment. Perry selected the increased pump flow rate (two pump operation) option to meet the rule.
At present Perry is operating in fuel Cycle 7. The Perry Cycle 8 core will consist of:
36 bundles of GE 10 fuel enriched to 3.06 %
180 bundles of GE 11 fuel enriched to 3.38 %
252 bundles of GE 12 fuel enriched to 3.69 %
280 bundles of GE 12 fuel enriched to 3.99 %
Total: 748 bundles.
i As shown above, the enrichment of the new fuel types is steadily increasing. As fuel bundle enrichment increases, the required shutdown boron concentration must be increased to continue to satisfy the reactivity control requirements. With the constant changing of bundle product lines, bundle average enrichment, batch sizes, and bundle Gadolinium loadings, no
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specific correlation between bundle enrichment and shutdown boron concentration has been developed. A cycle specific SLCS shutdown margin is calculated for each cycle's core design.
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w The Cycle 8 SLCS shutdown margin caicuht!cn necessitated the proposed technical specification change.
3.0 -
EVALUATION Over the years, the boron solution used in SLCS has continued to be specified an " sodium pentaborate". The term " sodium pentaborate" is used to describe the solution formed by mi. wing borax and boric acid in water with a sodium oxide to borate molar ratio of 0.200. Since the molar ratio is increased to 0.229, the solution is now appropriately called " boric acid-borax solution".
The proposed change continues the practice of preparing the neutron absorber solution using the two compounds, borax and boric acid, but using proportions that result in a nominal sodium oxide to borate ratio of 0.229. The change in molar ratio allows for an increase in the design boron concentration from 2.38 to 2.85 weight percent of boron. The change in molar ratio is achieved by increasing the weight of borax relative to the weight of boric acid.
A cold shutdown boron concentration of 816 ppm is bounding for a 24-month equilibrium cycle.
The 24-month equilibrium cycle is projected to use GE 12 fuel bundles with 4.1 % enrichment with a 296 batch size and have a SLCS shutdown margin of 1.8 % (GE design specification Emit is more than 1.6 %). The new analytical values for the molar ratio of 0.229 and the minimum shutdown boron concentration of 816 ppm will continue to maintain the SLCS design-basis requirements.
Since the boron concentration in the solution is increased, the maximum solution aaturation temperature is also increased from 61.5'F to 65'F. Ambient temperatures v;Rnin the building that houses the SLCS storage tank will maintain the solution tempercture above the precipitation temperature. Additional!y, the solution temperature is maintained by the auto initiated tank heaters and pipe heat 44g. Sie the minimum temperabre allowed in the TS for the solution temperature and the pump suction piping is 70*F, the 5'F margin specified by GE in the system design specification is still maintained. The tenk temperature operating range and tank temperature alarm set points are not changed. Thb 5'F margin provides the adequate margin for inaccuracies associated with tank temperatura.
The increase in boron concentration also increases the liquid volume in the tank by 135 gallons, which corresponds to an increase in the weight of solution in the tank. The additional tank inventory will require an increase in the existing alarm set points (Iow and high) by approximately 3.4 inches. The additional weight is insignificant in relation to the tank's seismic, structural and equipmer,i qualification requirements.
Since the boron concentration is increased, the required pump flow is reduced from 41.2 gpm to 32.4 gpm. The licensee verified by calculation that there is sufficient NPSH margin for the pump taking int'.s consideration the new flow rate and system losses. The licensee verifed that the existing minimum discharge pressure of 1220 psig is not impacted. The margin for the system relief valve is not reduced. The licensee has informed us that they will perform tests to verify the pump NPSH and the relief valve setting before the start-up of Cycle 8.
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The licensee performed calculations to verify that the SLCS complies with the ATWS rule discussed previously. Using the revised boron concentration, a new minimum required pump l
flow rate was determined. The 86 gpm requirement for Perry is now satisfied by a reduced flow of 64.8 gpm compared with the previous value of 82.4 gpm (two pump operation).
4.0 TECHNICAL SPECIFICATION CHANGES (a) TS Surveillance Requirement (SR) 3.1.7.1, SR 3.1.7.2 - The term " sodium pentaborate solution" is changed to " borax-boric acid solution". As previously discussed, since the molar ratio is increased from 0.200 to 0.22g, the solution is more appropriately called
- borax-boric l
acid solution" as opposed to " sodium pentaborate." The changes are acceptable.
(b) TS SR 3.1.7.7 - The pump flow rate is changed from 41.2 gpm to 32.4 gpm. The change is j
acceptable as explained above.
(c) TS Figure 3.1.7-1-The new figure correctly incorporates the new tank volume, and both the new low-and high-level alarm set points. The changes are acceptable as explained above.
(d) TS Bases 3.1.7, Applicable Safety Analyses-boron concentration is changed from 660 ppm to 816 ppm. The change is acceptable as explained above.
In conclusion, the Staff has reviewed the proposed increase of the cold shutdown boron concentration for the Perry Cycle 8 reload and the corresponding technical specification changes. The proposed TS changes are acceptable since the SLCS will continue to provide the i
l required shutdown margin under normal operating conditions pursuant to 10 CFR 50, Appendix A, GDC 26 and ATWS conditions pursuant to 10 CFR 50.62.
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5.0 STATE CONSULTATION
l l
In accordance with the Commission's regulations, the Ohio State official was notified of the l
proposed issuance of the amendment. The State official had no comments.
6.0 ENVIRONMENTAL CONSIDERATION
l This amendment changes a requirement with respect to installation or use of a facility component located within the restricted area as defined in 10 CFR Part 20 or changes a surveillance requirement. The staff has determined that the amendment involves no significant increase in the amounts, and no significant change in the types, of any effluent that may be released offsite and that there is no significant increase in individual or cumulative occupational radiation exposure. The Commission has previously issued a proposed finding that this i
amendment involves no significant hazards consideration and there has been no public comment on such finding (63 FR 40562). Accordingly, this amendment meets the eligibility criteria for categorical exclusion set forth in 10 CFR 51.22(c)(g). Pursuant to 10 CFR 51.22(b),
no environmental impact statement or environmental assessment need be prepared in connection with the issuance of this amendment.
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7.0 CONCLUSION
The staff has concluded, based on the considerations discussed above, that: (1) there is reasonable assurance that the health and safety of the public will not be endangered by l
operation in the proposed manner, (2) such activities will be conducted in compliance with the Commission's regulations, and (3) the issuance of this amendment will not be inimical to the common defense and security or to the health and safety of the public.
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PrincipalContributor G. Thomas Date: February 8, 1999 1
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