ML20128E515
| ML20128E515 | |
| Person / Time | |
|---|---|
| Site: | Limerick  |
| Issue date: | 01/29/1993 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20128E511 | List: |
| References | |
| NUDOCS 9302100491 | |
| Download: ML20128E515 (5) | |
Text
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e SAFETY EVALVATION BY THE OFFICE OF NVCLEAR REACTOR REGULATION RELATED TO AMENDMENT N05. 50 AND 24 TO FACILITY OPERATJftQ LICENSE NOS. NPF-39 AND NPF-85 PtLRADELPHIA ELECTRIC COMPANY i
LJE RLE _0ENERATING STATION. UNITS 1 AND 2 DOCKET N05. 50-352 AND 50-353
1.0 INTRODUCTION
By letter dated April 3, 1992, as supplemented January 21 and 22, 1993, Philadelphia Electric Company (PEco or the licensee) submitted a request for changes to the Limerick Generating Station, Units 1 and-2. Technical Specifications (TS).
The requested changes would revise the TS Surveillance Requirements (SRs) for the Standby Liquid Control (SLC) system to:
- 1) use the daily check of the SLC pump suction piping temperature to verify system 1
operability, rather than heat tracing operability; 2) verify that the piping is not blocked by pumping from the storage tank to a test drum, rather than to the test tank; and 3) require only one SLC storage tank heater to be operable, rather than two which are currently required.
The supplemental letters provide clarifying information that did not change the initial proposed no significant hazards consideration determination.
2.0 DISCUSSION The current TS SRs do not permit removing the heat tracing system or storage tank heaters from service without declaring the SLC system inoperable. When the SLC system is declared inoperable as a result of removing the heat tracing system or storage tank heaters from service, the plant must be placed in a hot shutdown condition unless the heat-tracing system or storage tank heaters are returned to service within eight (8) hours.
In addition, TS SRs require.that SLC fluid be pumped from the _ storage tank to the test tank every 18 months.to determine if any heat traced piping is blocked.
This flow test is also required when the heat tracing system is found to be inoperable.
Following this test, portions of the system must be-drained and flushed with demineralized water prior to restoring the system to operation. As a result:
of.this flushing, over 1000 gallons of waste water is generated requiring ~ a significant amount of mangower to ensure the proper disposal of this waste water.
Current TS SR 4.1.5.a.3 requires that the SLC system be demonstrated operable at least once per 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> by verifying that the heat tracing circuit installed on the-pump suction piping is operable by determining that the temperature of the pump suction piping is greater than or equal to 9302100491-930129 PDR ADOCK 05000352 P
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. 70 degrees F.
In addition, the current SR 4.1.5.d.2 stipulates that at least once per 18 months all heat traced piping be verified to be unblocked by pumping from the SLC storage tank to the test tank, sr.d then draining and flushing the piping with demineralized water.
Furthermore, current SR 4.1.5.d 3 requires that at least once per 18 months, the SLC storage tank heaters (i.e.,
"A" and "B") be demonstrated operable by verifying the expected temperature rise of the sodium pentaborate solution in the storage tank after the heaters are energized, lhe licensee proposes to change SR 4.1.5.a.3 such that the SLC system will be demonstrated operable once per 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> by simply verifying that the pump suction piping temperature is equal to or greater than 70 degrees F, rather than by verifying heat tracing operability.
In addition, the licensee proposes to revise the 18-month SR 4.1.5.d.2 to verify that the pump suction piping is unblocked by pumping from the SLC storage tank to test drums, rather than the test tank, and proposes to change the 18-month SR 4.1.5.d.3 to demonstrate that only the "A" storage tank heater is operable, rather than both heaters.
3.0 f1ALUATION The design of the SLC system is mainly described in Sections 7.4.1.2 and 15.8.3.5 of the Updated Final Safety Analysis Report (UFSAR)._ The SLC system provides a redundant, independent, and alternate method of making the reactor core subtritical, and maintaining it subcritical, as the reactor cools.
The system makes possible an orderly and safe shutdown in the event that not enough control rods can be inserted into the reactor core to accomplish normal shutdown.
The normal reactivity control systems are the Control Rod Drive (CRD) system or the Alternate Rod Insertion (ARI) system.
The SLC system is designed to compensate for the positive reactivity effects associated with a reactor shutdown from rated full power to a cold shutdown candition at any time during core life.
To satisfy this design objective, a solution containing boron is injected into the reactor core.
The boron absorbs thermal neutrons and, when present in sufficient concentration in the reactor, will cause the reactor to become subtritical.
This neutron absorber solution is an aqueous solution of sodium pentaborate and is stored in a storage tank.
The saturation temperature of the sodium pentaborate solution is approximately 60 degrees F at the recommended concentration of 13.4%.
The boron injection capacity of the system also meets the requirements of 10 CFR 50.62, " Requirements for the Reduction of Risk from Anticipated Transients Without Scram (ATWS) Events for Light-Water-Cooled Nuclear Power Plants."
The equipment containing the sodium pentaborate solution is installed in an area where the ambient air temperature is maintained within the range of 65 degrees F to 104 degrees F.
An electrical resistance heating system containing two heaters provides a heat source which maintains the temperature of solution in the storage tank between 75 degrees f and 85 degrees F to prevent precipitation of the sodium pentaborate from the solution.
Each of
~. the two (2) heaters is powered from a separate Class IE power supply.
However, only one (1) heater is necessary for maintaining storage tank temperature.
The second heater provides a backup heating source and is used primarily during mixing operations.
In addition, heat tracing with automatic temperature control provides a heating source for the pump suction piping between the stcrage tank and pump inlet to prevent precipitation of sodium pentaborate in the suction piping.
This piping heat tracing system is nonsafety-related and does not receive electrical power from a safety-related power supply.
The heat tracing is provided because the sodium pentaborate solution, at its maximum concentration of 13.8%, has the potential to precipitate out of solution if the temperature falls below approximately 61 degrees F.
Current TS SR 4.1.5.a.3 requires that the pump suction line temperature be checked once per 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> to verify the operability of the heat tracing.
Since the ambient temperature is almost always above the low temperature setpoint of 73 degrees f for automatic heat tracing initiation, this SR does not serve its intended purpose.
Instead, this SR actually serves to demonstrate SLC system operability by verifying the suction line temperature is such that no sodium pentaborate could have precipitated from solution.
The proposed change to this SR will more clearly state the safety-related function without requiring operability of the nonsafety-related heat tracing.
The heat tracing system design and operation will remain the same upen implementation of this proposed change.
The licensee stated that administrative controls will be instituted to require operations personnel to check heat tracing operability if a low temperature condition is detected in the SLC pump suction piping. This will help ensure that the heat tracinu is available when required, implementation of these administrative controls will provide an opportunity for plant personnel to i
take compensatory measures such as adding temporary heat tracing as opposed to initiating shutdown of the unit.
1he current TS SR 4.1.5.d.2 requires that, at least once per 18 months, the heat traced piping be checked to verify that'it is unblocked by pumping the sodium pentaborate solution from the SLC storage tank to the test tank, and then draining and flushing the associated piping with demineralized water.
This action is also required when the heat tracing circuits have been found to be inoperable.
Performance of this test procedure produces a considerable amount of waste solution and injects sodium pentaborate solution into the piping system,. which requires flushing to prevent precipitation.
The proposed change to the SR will allow this test to be performed; however, rather than pumping from the storage tank to the test tank, the solution will be pumped to'a test drum through each discharge line, in addition, flow testing will be performed by pumping demineralized water from the test tank back to the test tank through each loop.
Therefore, this proposed change will reduce the-amount of piping requiring flushing, thereby reducing the amount of. waste water generated.
1he licensee will establish a baseline flowrate value following a storage tank to test tank flowpath pump.run and this value will be incorporated into the revised surveillance test procedure, t
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The current TS SR 4.1.5.d.3 requires that, at least once per 18 months, both SLC storage tank heaters (i.e., the "A" and "B" heaters) se demonstrated operable by verifying the expected temperature rise of the sodium pentaborate solution after the heaters are energized.
The proposed change to this SR would only require the "A" heater to be operable to maintain SLC system operability.
The "A" heater is a 10 KW heater and is used to maintain solution temperature in both automatic and manual modes of operation.
The "B" heater is a 40 KW heater and is used in the manual mode only during solution mixing operations.
The basis for this proposed change is that the "B" heater, by design, is not required during normal operation to maintain SLC system operability.
Heater "A" will automatically initiate in the unlikely event that the solution temperature in the storage tank drops below the setpoint of 75 degrees F.
The ambient temperature in the storage tank area is generally above this setpoint.
Additionally, low tank temperature is alarmed in the Main Control Room (MCR) to alert Operations personnel that the "A" heater is not functioning properly. Operations 1ersonnel would then take the necessary actions, including energizing the "B" Teater, in order to maintain the required solution temperature, in the event that the "A" heater is inoperable while ambient temperatures are greater than 75 degrees F, this proposed change will require that a tank temperature check be performed every eight (8) hours.
This proposed change will permit removal of the heater from service for maintenance purposes, but will still ensure that the solution temperature is maintained within the required limits to ensure SLC system operability.
We have concluded that the proposed change to the SR for determining pump suction line temperature is a more direct means of verifying SLC system i
operability and is acceptable.
The proposed change to the SR concerning the flow blockage test will utilize a similar flowpath. The test drum will serve an identical purpose as the present test tank and will still identify any blockage which adversely impacts pump operation. The aroposed change is acceptable.
The proposed change to the SR to permit tie "B" heater to temporarily be removed from service for maintenance without declaring the SLC inoperable is acceptable, since only the "A" heater is necessary to ensure SLC system operability.
4.0 STATE CONSULTATION
In accordance with the Commission's regulations, the Pennsylvania State official was notified of the proposed issuance of the amendments.
The State official had no comments.
5.0 ENVIRONMENTAL CONSIDERATION
The amendments change the 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
9 5-proposed finding that the amendments involve no significant hazards consideration, and there has been no public comment on such finding (57 FR 20515). Accordingly, the amendments meet the eligibility criteria for categorical exclusion set forth in 10 CFR 51.22(c)(9).
Pursuant to 10 CFR Sl.22(b) no environmental impact statement or environmental assessment need be prepared in connection with the issuance of the amendments.
6.0 00f4CLUS10t1 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 Contributors:
R. Clark F. Rinaldi Date: January 29, 1993
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