ML20070K995
| ML20070K995 | |
| Person / Time | |
|---|---|
| Site: | Salem  |
| Issue date: | 07/20/1994 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20070K992 | List: |
| References | |
| NUDOCS 9407280139 | |
| Download: ML20070K995 (5) | |
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WASHINGTON, D.C. 205554001 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NO.133 TO FACILITY OPERATING LICENSE NO. DPR-75 l
PUBLIC SERVICE ELECTRIC & GAS COMPANY PHILADELPHIA ELECTRIC COMPANY DELMARVA POWER AND LIGHT COMPANY ATLANTIC CITY ELECTRIC COMPANY SALEM NUCLEAR GENERATING STATION. UNIT N0. 2 DOCKET NOS. 50-311
1.0 INTRODUCTION
By letter dated June 11, 1993, as supplemented July 19, 1.993, August 3, 1993, and September 16, 1993, the Public Service Electric & Gus Company (the licensee) submitted a request for changes to the Salem Nuclear Generating Station, Unit No. 2 Technical Specifications (TS). The requested change would allow the concentration of boric acid in the boric acid tanks (BATS) to be reduced to the point where heat tracing for the associated piping would not be required.
The August 3,1993, and Se)tember 16, 1993, letters provided clarifying information that did not c1ange the initial proposed no significant i
hazards consideration determination.
At the reduced boron concentration, the normally anticipated ambient room temperatures would be high enough to keep the boric acid from precipitating out of the fluid causing deposits to form. To show that the plant is capable of being shut down safely with the reduced boron concentration.in the BATS, the licensee has submitted an ABB Combustion Engineering report entitled,
" Boric Acid Concentration Reduction Effort CEN-606, Rev. 00 Technical Basis and Operational Analysis for Salem Nuclear Generating Station Units 1 and 2."
The boric acid concentration in the BATS will be reduced from approximately 12 percent by weight to between 3.75 and 4.0 percent by weight. The high temperature and high boron concentration required presently make the boric acid system less reliable and adversely affect plant availability.
Significant maintenance is also required to keep the boric acid system i
The required 12 percent by weight is based on the ability to provide the required reactor coolant system (RCS) boron concentration to obtain a 1.6% &./k shutdown margin at 200*F from the BATS through a feed and bleed operation before the plant starts to cool down. The boron concentration is then kept constant durir.g cooldown with makeup water being provided for RCS shrinkage with the temprature reduction. The BAT boron concentration necessary for this type of operation is very high.
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. The proposed change in shutdown methodology allows for a much lower boron concentration in the BATS.
Rather than borate the primary system before cooldown, the new methodology in boration and cooldown enables the RCS to be borated while the cooldown is in progress. As the RCS contracts with the dropping temperature, borated water is added keeping the pressurizer level constant.
To compensate for the lost boron in the feed and bleed operation, a much higher boron concentration is required for the present methodology.
In the proposed methodology, to compensate for the lower boron content in the BAT water, the volume and the delivered flowrate are increased accordingly.
2.0 EVALUATION 2.1 Supportina Calculations There were two sets of calculations that were carried out to support boron concentration reduction in the BATS.
The first is the required boron concentration to maintain a sufficient shutdown margin throughout the cooldown process.
For a series of RCS average temperatures a corresponding set of required RCS boron concentrations were calculated.
The second set of calculations determines the boron delivery into the RCS through the boric acid system from the BATS and.the refueling water storage tank (RWST) for a set of cooldown scenarios.
The shutdown margin is maintained throughout the cooldown as lon.) as the minimum required boron concentration is present in the core.
The following is the NRC staff's evaluation of the licensee's calculation.
2.1.2 lhtquired Boron Concentration These calculations were performed using codes previously approved by the NRC, as discussed in the licensee's letter dated September 16, 1993. The shutdown margins required in the calculations are specified by the Salem Technical Specifications.
The requirements are 1.6% Ak/k when the reactor is above 200*F and 1.0% Ak/k when the reactor is below 200*F. The reactivity balance included positive reactivity insertion from the plant cooldown as a result of the moderator temperature coefficient and from the xenon decaying from the core. Conservative core physics assumptions were made to bound the analysis for any point in the fuel cycle. The faiiowing assumptions were intended to maximize the boron demand:
End-of-life (E0Q initial boron concentration in the RCS, assumed to be zero.
E0L moderator cooldown effects.
E0L inverse boron worth (IBW) values, Most negative moderator temperature coefficient of reactivity.
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Conservative (slow) cooldown rate of 10*F/hr, to allow for the greatest xenon reactivity insertion rates.
Prior to plant shutdown the reactor has a 100% power equilibrium xenon inventory.
Most reactive control rod stuck in the fully withdrawn position.
2.1.3 Boron Delivery to the RCS These calculations establish the new minimum BAT boron concentration, and the w w minimum required BAT and RWST volumes. These calculations are separated into two sets. The first is for the cooldown from 200*F to 135'F in Modes 5 and 6.
The second is for the cooldown when RCS temperature is between 547'F and 200*F in Modes 1, 2, 3, and 4.
In Modes 5 and 6, the cooldown process was calculated with boron being delivered to the RCS from the residual heat removal (RHR) pumps.
Calculations were made with the pump taking suction from either the BAT or the RWST.
In Modes 1, 2, 3, and 4, the charging pump suction was taken initially from the BATS and then from the RWST. Transition from the charging pumps to the RHR pumps occurs at 350*F and 350 psi in the primary system.
The I
inventory in the RHR system is then included as part of the total mass of the system in the mass balance equations.
In Modes 1, 2, 3, and 4, the borated water delivered to the core was only to replace water shrinkage due to cooldown.
Conservative assumptions were utilized in the use of system volumes, boron mixing, and initial boron concentrations.
The licensee has demonstrated that there is sufficient boron present in the core at any given temperature for the given cooldown scenarios, There is also enough boron in the supplied water sources to provide i
enough boron to maintain the required shutdown margins as calculated earlier.
Based on the above, we find the licensee's calculation of actual boron concentration during cooldown to be acceptable and provides an adequate basis for determinir.g the required volumes for the RWST and the BATS.
2.2 Response to Emeroency Situations 2.2.1 Transient and Accident Analysis Accidents and transients addressed in Chapter 15 of the Updated Final Safety Analysis Report (UFSAR) do not take credit for borated water i
delivered to the RCS from the BATS. The charging pumps are aligned to the RWST during safety injection, so reduction of the boric acid concentration in the BATS has no effect on the accident analysis covered i
in the FSAR.
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., 2.2.2 Shutdown Marain Recoverv Current Technical Specifications 3.1.1, 3.1.2, 3.9.1, and 3.10.1 require RCS boration at a rate of 10 gpm to commence when the shutdown margin is lost. The new Technical Specifications with the reduced concentration in the BATS will require boration at a higher rate of 33 gpm. The increased flowrate makes up for the reduction in the injected boron concentration.
Technical Surveillance Requirement 4.1.2.2 requires verification that the injected flowrate is above the current requirement of 33 gpm. We find these modifications acceptable.
2.2.3 Emeroency Boration The licensee has examined the ability to borate the core in an emergency situation given that one or more rod cluster control assemblies are not fully inserted into the core.
In this event the boric acid transfer pumps are aligned directly to the suction of the charging pumps. The lower concentration of boron in the BATS requires that BAT volume be increased to be able to provide sufficient boron to the core.
The licensee has adequately provided for this.
2.3 Technical Soecification Chanaes The planned reduction of the minimum boric acid concentration from 20,000 ppm to 6,560 ppm and the increase in delivery capacity from 10 gpm to 33 gpm require all the applicable TS and the associated Bases sections to be changed accordingly.
The minimum BAT and the minimum RWST volumes for modes 5 and 6 are increased to 2600 gallons and 37000 gallons respectively.
Figure 3.1-2 has been added to the TS to define the minimum BAT requirements for boron concentration and volume. Heat tracing requirements to prevent boric acid precipitation are eliminated completely from the TS.
The proposed surveillance requirements for the Technical Specifications have also been changed to reflect the new concentrations, flowrates, and volumes stated above.
The requirements for heat tracing have been eliminated and the temperature in the BATS is monitored so that it will remain above 63*F rather than 145'F.
The temperature in the pipe from the recirculation line to the charging pump will be monitored to assure it remains above 50*F.
In addition, TS 3/4.1.1 note (**) has been deleted. This note increased the shutdown margin requirement from 1.6% delta k/k to 1.85% delta k/k during cycle 7 of operation.
Salem 2 is currently in Cycle 8 of operation and therefore, the note is not applicable.
This deletion was not addressed in the licensee's submittal or supplements:
however, it was discussed in a telephone conversation with the licensee and they agreed to the change.
The staff has reviewed the chanae and finds it acceptable.
) The staff has reviewed the proposed reduction in boric acid concentration, the removal of heat tracing elements from the associated piping, the resulting Technical Specification changes, and the analytical basis for the change, as described in the licensee submittal and supplements.
Based on the evaluation provided, we find the proposed changes to the plant and the Technical Specification modifications acceptable.
3.0 STATE CONSULTATION
In accordance with the Commission's regulations, the New Jersey State official was notified of the proposed issuance of the amendments.
The State official had no comments.
4.0 ENVIRONMENTAL CONSIDERATION
The amendments change a requirement with respect to installation or use of a facility component located within the restricted area as defined in 10 CFR Part 20 and change surveillance requirements.
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 amendments involve no significant hazards consideration, and there has been no public comment on such finding (58 FR 43932). 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 @NCLUSION The Commission has concluded, based on the considerations discussed above, that:
(1) there is raasonable 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:
C. Jackson, SRXB Date:
July 20, 1994