ML18052A914
| ML18052A914 | |
| Person / Time | |
|---|---|
| Site: | Palisades  |
| Issue date: | 03/23/1987 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML18052A913 | List: |
| References | |
| NUDOCS 8704020529 | |
| Download: ML18052A914 (4) | |
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UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D. C. 20555 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION SERVICE WATER TEMPERATURE LIMIT CONSUMERS POWER COMPANY PALI SADES P.lANT DOCKET NO. 50-255
1.0 INTRODUCTION
During recent testing of the service water system at Palisades, the licen-see, Consumers Power Company, detennined that the original design flow requirements for mitigation of design basis events as specified in the Final Safety Analysis Report (FSAR) could not be provided to various essen-tial components served by the system.
To correct this condition, the licensee has initiated a program to assure sufficient service water flow to required equipment.
The licensee is determining which post-loss-of-coolant accident (LOCA) service water requirements not specified in the FSAR could be reduced or eliminated and how post-LOCA service water flow could be increased to permit operation with service water inlet temperatures of 75°F or above.
In the interim, the licensee has determined that plant operation when the service water inlet temperature is above 58°F must be limited to assure adequate cooling of required safety equipment with the available service water flow.
Based on the studies and tests performed, the licensee proposed several modifications and technical specification changes.
By letter dated October 20, 1986, the licensee proposed the removal of Con-tainment Air Cooler Fan V4A from Technical Specification Section 3.4. The licensee stated that credit was not taken for this component to mitigate the consequences of a loss-of-coolant accident (LOCA) or a Main Steam Line Break Event (MSLBE).
The licensee proposed to block the service water flow to this component during conditions which initiate a safety injection signal (SIS). This action would increase service water flow to the coolers and heat exchangers required to mitigate the consequences of a LOCA or a MSLBE; i.e.:
- 1.
Engineered Safeguards Room Coolers (VHX-27A/B)
- 2.
Component Cooling Water Heat Exchangers (E-54A/B)
- 3.
Control Room Coolers (VC 10/11)
. 4.
Diesel Generator Heat Exchangers (0/G 1-1/1-2)
- 5.
Containment Air Coolers (V-1A/2A/3A)
This deletion from the Technical Specifications is the subject of a separate action.
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- Also, by letter dated December 2, 1986, the licensee proposed to add two diesel driven fire pumps (K5/P9B and K10/P41) to Technical Specifica-tion Section 3.4.lb. These pumps could be used to augment nonnal service water flow from the service water pumps in the event of a LOCA with a coincident loss of offsite power (LOOP) and single failure (loss of diesel generator 1-2). Under these conditions, only one service water pump is available. The flow from one service water pump is not adequate to cool the required coolers and heat exchangers when the containment spray pumps are circulating hot water from the containment sump through the shutdown heat exchangers.
However, testing showed that, with the added capacity of two diesel fire pumps, sufficient cooling was available if the inlet service water temperature was 55°F or lower. Consequently, the December 2, 1986 letter also included a proposed technical specification limit on operation of the plant when the service water inlet temperature is greater than 53°F.
By letters dated December 1, 1986, January 28, 1987 and February 25, 1987, the licensee provided additional information on the above changes.
In the letter dated February 25, 1987, the licensee stated that modifica-tions described in their January 28, 1987 letter (Attachment 5, Item 11) were completed. These include (1) a modification to the service water air operated temperature.control valve on the component cooling water (CCW) heat exchanger to close on a recirculation actuation signal (RAS); (2) backfiling impellers for the three service water pumps as in the original design, to provide additional flow; and (3) adding nitrogen backup supplies to the service water isolation valves to and from containment to ensure valve operability following a LOOP.
The licensee also provided the results of service water system flow balance testing that was perfonned after these modifications were made.
Based on these test results, the licensee proposed to rely on isolation of the service water to the containment air coolers rather than the alignment of the fire pumps to the service water system in order to provide adequate service water cooling for the required loads.
2.0 EVALUATION This evaluation concerns the proposed Technical Specification changes regarding the service water inlet temperature.
The licensee perfonned calculations for the Engineered Safeguards Room Coolers, Control Room Coolers, and Shutdown Cooling Heat Exchangers to detennine the service water inlet temperature limit required to ensure that the present FSAR temperatures controlled by these components can be maintained with the presently available service water flow rates.
The most limiting inlet temperature was detennined to be 58°F for the West Room Engineered Safeguards Room Cooler.
In addition, the licensee demonstrated by test that the diesel generator coolers were adequately cooled with the diesel generator heat exchanger inlet pressure of 10 psig and a service water inlet temperature of 55°F.
The service water system has been balanced with a 22 psig inlet pressure at the diesel generator that will actually produce a higher flow rate and cooling margin.
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.:,, a result of the above analysis, the licensee proposed a technical specification limit of 53°F on the service water inlet temperature which provides margin below the maximum allowable temperature of 58°F and thereby ensures satisfactory heat removal capability for the most limiting component and provides additional margin for other components.
The licensee performed flow tests to establish the service water flow available to the coolers and heat exchangers identified in Section 1.0 when only one service water pump is operating with the containment air coolers isolated and not isolated, and when one service water pump and one diesel fire pump are operating with containment air coolers isolated and not isolated. These tests simulate both the injection and recircula-tion phase of the LOCA mitigation scenario. The test data indicate that one service water pump powered by diesel generator 1-1 can provide adequate flow during the injection phase of the LOCA and one service water pump can provide adequate service water flow during the recirculation phase of the LOCA as long as the service water inlet temperature is below 58°F.
The licensee has determined that the injection phase of the LOCA with only diesel generator 1~1 available will last at least 30 minutes *and that service water flow to the containment air coolers can be isolated within that time period. Isolation of the containment air coolers will divert additional flow to the other heat loads, providing additional margin.
The licensee also performed flow tests and procedural walkdowns to demonstrate
- that (1) the service water and fire pu~ps ~re at stable operating points within their design capability, (2) adequate flows are available to all required components, and (3) procedures and available instrumentation are adequate to diagnose adverse conditions and do not place undue burdens on the operator. Isolating the containment air coolers is acceptable because, under the postulated condition (i.e. LOCA, LOOP and failure of diesel gene-rator 1-2), the three containment air coolers would be inoperable because of lack of power to the fan motors. Containment cooling capability is main-tained by the two containment spray pumps powered from diesel generator 1-1.
The containment air cooler isolation valves are operated by a control switch in the control room.
The valves are normally powered by instrument air. Because instrument air cannot be relied on during a LOOP, the licensee has. installed a back-up supply from nitrogen bottles. The operability of the isolation valves must be maintained under the requirements of existing Technical Specification 3.4.4.
On the basis of the above evaluation, the staff concludes that the proposed limit of 53°F for the service water inlet temperature will ensure sufficient service water system heat removal capability in accordance with the requirements of GOC 44 concerning cooling water system function and is, therefore, acceptable.
The proposed surveillance would require monitoring service water inlet temperature at least once every 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />. and at least once every 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> when the temperature exceeds 51°F.
We conclude that these intervals are appropriate considering the natural temperature inertia of Lake Michigan, the source of service water, and the margin of safety between the 53°F limit and the 58°F required.
3.0 FUTURE ACTIONS The licensee is reviewing additional options for assuring adequate service water flow with the objective of raising the service water temperature limit on plant operation. Staff reviews of the interim and final proposed long term modifications will be provided in the future as a basis for any changes to the operating requirements and restrictions associated with this action.
Date: March 23, 1987 Principal Contributors:
R. Ferguson T. Wambach
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