ML20078K548
| ML20078K548 | |
| Person / Time | |
|---|---|
| Site: | Dresden, Quad Cities  |
| Issue date: | 11/16/1994 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20078K538 | List: |
| References | |
| NUDOCS 9411230130 | |
| Download: ML20078K548 (4) | |
Text
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_' j SJ'1(, ) y NUCLEAR REGULATORY COMMISSION WASHINGTON. D.C. 30666-0001 SAFETY EVALUATION BY'THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NO.130 TO FACILITY OPERATING LICENSE NO. DPR-19.
AMENDMENT NO.124 TO FACILITY OPERATING LICENSE NO. DPR-25.
AMENDMENT NO.151 TO FACILITY OPERATING LICENSE NO. DPR-29 AND AMENDMENT N0.147 TO FACILITY OPERATING LICENSE NO. DPR-30 COMMONWEALTH EEISON COMPANY MQ IOWA-ILLIN0IS GAS AND ELECTRIC COMPANY DRESDEN NUCLEAR POWER STATION. UNITS 2 AND 3 0VAD CITIES NUCLEAR POWER STATION. UNITS I AND 2 DOCKET NOS. 50-237. 50-249 19-254 AND 50-265
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1.0 INTRODUCTION
NRC Information Notice 91-12, " Potential loss of Net Positive Suction Head (NPSH) of Standby Liquid Control System Pumps," resulted from a Standby Liquid Control System (SLCS) operability test performed at Quad Cities, Unit 1 on February 11, 1991. The test was being performed to determine if the SLCS could perform its intended function. The results of this test suggested that the SLCS pumps at Quad Cities and Dresden Station might not have adequate NPSH at the highest allowable tank temperature of 120*F and at the lowest tank level. Subsequent testing performed at Dresden, Unit 2 and Quad Cities, Unit I demonstrated adequate NPSH to be available for single or dual pump ope' ation r
with corresponding temperature and tank level restrictions enforced.
Calculations were performed for Commonwealth Edison Company (Comed, the licensee) to determine more accurate requirements for the minimum volume of sodium pentaborate to be maintained in the SLCS storage tank.
By letter dated October 15, 1992, the licensee requested that the Dresden, Units 2 and 3, and Quad Cities, Units 1 and 2, Technical Specifications (TS) be modified to permit a wider operating range by varying the concentration of sodium pentaborate decahydrate from 14 to 16.5 weight percent inside the SLCS storage tank. Specifically, the proposed amendment would incorporate a map of acceptable SLCS storage tank icvels versus sodium pentaborate solution concentrations.
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9411230130 941116 PDR ADOCK 05000237 P
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. 2.0 EVALUATION Quad Cities and Dresden Station are proposing to modify the SLCS storage tank temperature and storage tank level requirements within Section 3/4.4 of the Technical Specifications. The proposed change would provide an acceptable operating region for sodium pentaborate solution volume requirements for the SBLC system that is based on temperature, concentration, and minimum gross volume rather than the current TS which requires a single minimum temperature, concentration, and minimum gross volume. The minimum net and gross SLCS storage tank volumes and levels have been calculated for various maximum storage tank temperatures and sodium pentaborate concentrations.
The licensee has stated that the purpose of these changes is to determine the amount of natural boron that must be injected into the reactor vessel to bring the reactor from full power to a xenon-free, cold shutdown, 3% Ak/k subcritical condition, assuming no control rod movement, and to establish a map of acceptable SLCS storage tank levels versus sodium pentaborate solution concentrations.
Sargent & Lundy has recently completed calculations that determine the mass of the water in the reactor vessel, the recirculation piping, and the SDC/RHR systems.
Current design bases require a minimum concentration of 600 ppm of boron based on the original design specifications for the volume of the reactor vessel and the recirculation loops.
An additional 20% of boron, or a total of 720 ppm, was required to conservatively account for the dilution by water of the recent unknown volume in the connected systems.
GE Services Information Letter (SIL) No. 325 informed utilities of calculational results that showed that 2.6% Ak/k would shut down a reactor.
For the purpose of the licensee's updated calculations, 750 ppm is used as a conservative account of the imperfect mixing and potential losses of sodium pentaborate solution. This conservatism requires a 25% margin to the minimum requirements that both sites must maintain in order to meet safe shutdown requirements.
The minimum concentration of sodium pentaborate required per current Technical Specifications is 14%. The anticipated transients without scram (ATWS) rule requires an injection rate of 86 gpm of 13% solution.
For Dresden and Quad Cities, the equivalent injection rate is 80 gpm of 14% solution.
By maintaining the minimum equivalent solution, the licensee believes a wider operating range can be achieved by varying the concentration of the sodium pentaborate decahydrate from 14 to 16.5 percent inside the SLCS storage tank.
Additionally, the licensee stated that the minimum temperature requirements maintain a ten degree margin above the saturation temperature for any given concentration.
The current and the proposed SLCS TS require a 24-hour surveillance to verify certain characteristics of SLCS (e.g., the volume and temperature of the l
borated solution in the storage tank), thereby ensuring SLCS operability without disturbing normal plant operation.
These surveillances ensure that the proper borated solution volume and temperature are maintained.
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. Maintaining a minimum specified borated solution temperature is important in ensuring that the boron remains in solution and does not precipitate out in the storage tank or in the pump suction piping.
Figure 3.4.2 (3.4-2 for Quad Cities) ensures that a 10*F margin will be maintained above the saturation temperature. This requirement is administratively controlled and verified by site operating personnel during operator's rounds to assure that temperatures remain above the minimum allowable.
The 24-hour frequency of these Surveillance Requirements was based on operating experience, which demonstrates relatively slow variations in the measured parameters of volume and temperature.
In the event that the required instrumentation to monitor volume and temperature of the borated solution in the SLCS storage tank is found inoperable, the affected SLCS subsystems are considered inoperable. This is administratively controlled to assure that temperatures and volumes remain above the minimum allowable.
Failure to satisfy the Surveillance Requirements will make the SLCS subsystems inoperable since the boron solution storage tank and the majority of the pump suction piping is common to both subsystems; the appropriate TS limiting conditions for operation would have to be entered.
The above requirements are consistent to the requirements outlined in NUREG-3433, the Improved Standard Technical Specifications (ISTS).
The Staff has reviewed the licensee's proposed TS changes and determined that they are acceptable.
This conclusion is based on the following:
the results of the calculations and proposed TS changes do not adversely impact the requirements to maintain a minimum sodium pentaborate concentration of 14%;
the maintenance of the 14% solution will not affect the ATWS requirements and will permit flexibility in maintaining the equivalent sodium pentaborate I
solution with no adverse consequences to any previously analyzed accident; and the increased boron in solution will adequately shut down the reactor with additional conservatism.
3.0 STATE CONSULTATION
In accordance with the Commission's regulations, the Illinois State official was notified of the proposed issuance of the amendments.
The State official had no comments.
4.0 ENVIRONMENIAL CONSIDERATION The amendments change a requirement with respect to the installation or use of a facility component located within the restricted area as defined in 10 CFR Part 20.
The NRC staff has determined that the amendments involve no significant increase in the amounts, and no significant change in the types, of any effluents 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 the I
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, amendments involve no significant hazards consideration, and there has been no public comment on such finding (57 FR 58245). Accordingly, the amendments meet the eligibility criteria for categorical exclusion set forth in 10 CFR 51.22(c)(9).
Pursuant to 10 CFR 51.22(b), no environmental impact statement or environmental assessment need be prepared in connection with the issuance of the amendments.
5.0 CONCLU.11QM The Commission 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 operation in the proposed manner, (2) such activities will be conducted in compliance with the Commission's regulations, and (3) the issuance of the amendments will not be inimical to the common defense and security or to the health and safety of the public.
Principal Contributor: John F. Stang; Jr.
Date:
November 16, 1994 i
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