ML20202E446
| ML20202E446 | |
| Person / Time | |
|---|---|
| Site: | LaSalle  |
| Issue date: | 01/23/1998 |
| From: | NRC (Affiliation Not Assigned) |
| To: | |
| Shared Package | |
| ML20202E442 | List: |
| References | |
| NUDOCS 9802180150 | |
| Download: ML20202E446 (4) | |
Text
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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NO.122 TO FACILITY OPERATING LICENSE NO. NPF-11 AND AMENDMENT NO.107 TO FACILITY OPERATING LICENSE No. NPF 18 ffMQtM&IliEQl80N COMPANY LASALLE COUNTY STATION. UNITS.1 AND 2 DOCKET NOS. 50 373 AND 50 374
1.0 INTRODUCTION
By letter dated August 12,1997. Commonwealth Edison Company (Comed, the licensee) submitted a request to revise the Technical Spec 6fications (TS) for LaSal e County Station, Units 1 and 2. The proposed amendments would remove Surveillance Requirement (8R) l 4.7.1.3.c, which requires that all areas within the lake screenhouse be inspected to ensure that sediment has not been deposited to a depth greater than 12 inches.
2.0 EVALUAT1QN The ultimate heat sink (UHS) at LaSalle is an 83 acre section located within the LaSalle cooling lake. Water from the lake enters the plant via the lake screenhouse a building which houses the circulating water pumps, traveling screens, anti a service water tunnel which is the source of water for the non safety related service water system, the safety-related service water (Core Stantiby Cooling System (CSCS)) and the fire pumps. Water enters the lake screenhouse through a bargrtil and traveling screens into the circulating pump suction bays. The service water -
tunnelis connected to the circulating pump suction bays by six 36-l.,
%s located 18 inches from the floor of the suction bays. The CSC8 draws water from the se,31 > eter tunnel through six pipes located 11 inches from the bottom of the tunnel. A 54 inch diamw, JC8 cooling water screen bypass supply line is located upstream of the traveling screens and discharges into the service water tunnel. This bypass is provided to ensure t'.4ess to a continuous supply of water to the service water tunnel in the event that the traveling screens (which are not seismically designed nor supplied with essential power) become blocked. This line is normally closed by a butterfly isolation valve.
Technical Specifica' on 3,7.1.3, "Uitirrate Heat Sink,' requires that the CSC8 pond be operable.
8R 4.7.1.3.c requires a determination every 18 months tha', sediment deposition anywhere within the lake screenhouse behind the bargrillis not greater than 12 inches in thickness. This requires that measurements be taken of sediment in all areas of the screenhouse including the circulating pump suction bay, the service water tunnel, and the bypass line, in its response to Generic Letter (GL) 8913, ' Service Water System Problems Atfecting Safety Related Systems,* Comed stated that the service water tunnel would not be visually inspected due to safety concems and that the use of a blocide/ silt dispersant treatment system and the turtpulent conditions in the
____ tunnel would preclude the need to inspect this portion of the lake screenhouse, k YD 0
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2 Because the lake scroonhouse cordaina low flow and/or no flow areas, material could settle out and collect to depths greater than 12 inches in some areas between surveillances. Per the curroni T8, if sediment deposhion is greater than 12 inches in thickness anywhere in the lake screenhouse, the CJC8 pond must be declared inoperable. The most limiting action statement in this case is to bring the plant to hot shutdown in 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> and cold shutdown in the following 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />. The licensee proposes to remove this SR from the TS because it is more suited to an administratively controlled program.
The requirement that sediment deposition be no greater than 12 inches in thicloess was established at the time oflicensing. NUREG-051g, Supplement 2, ' Safety EvaluAn Report Related to the Operation of LaSalle County Station Units 1 and 2", Section g.2.2 states that a 16mit of 1 foot of sedimentation in the lake screenhouse would ensure that any sedim6nt buildup would be below the bottom of the core stanttby cooling system inlet pipes.
Since initial operation, Comed has recorded the locations and depths of sediment identified during the 18-month inspections. The licensee has stated that at no time during the fourteen years of operhtion has sediment built up or accumulated either in front of the inlet to the CSCS cooling water screen bypass supply line or the six normal tunnel supply lines in such a manner that the flow of water through these lines could have been reduced or blocked. Inspection records have shown that sediment collects in areas near the traveling screens, under the outlets l
of the normal tunnel supply lines in the service wat tunnel, and downstream of the butterfly isolation valve in the bypass supply line. The sedi.e snt that collects in the service water tunnel does not build up in a,, anner such that CSCS, non essential service water, or fire pump suctions from the tunnel are affected, based on inspections since 19g2. Therefore, the original l
concem that resulted in the development of this TS requirement has been determined, throgh operating experience, not to be valid. Based on the locations at which the sediment collects, an accumulation of more than 12 inches of sediment in the lake screenhouse would not affect the operability of the CSCS.
Of the areas where sediment has been found to accumulate, the area downstream of the t
normally closed butterfly valve in the 54 inch CSCS cooling wwter screen bypass supply line is a concem. This line provides a supply of water for safety related functions in the event that the -
service water tunnel supply is blocked. To ensure the bypass line is available, the manual butterfly valve is being added to the ASME Section IX Inservice Testing Program to cycle the valve quarterty. This will provide assurance that sediment will not impede the travel of the valve and assist in maintaining sediment levels at a low level due to flow during the cycling of the valve.
The licensee proposes to control the surveillances of the lake screenhouse through the Service Water Performance Monito:ing Program which was developed in accordance with the recommended actions of GL 8913. The program controls sedimentation in the intake structure in accordance with recommended action A of Enclosure i to GL 8913, including inspection, evaluation, and cleaning of the ir,take structure for sediment and fouling once per refueling outage. The program also ensures operability of the CSCS through performance monitoring, inspections, and tests of heat exchanger and system performance. While the licensee will-continue to inspect and clean the intake structure, they will not be required by the TS to declare the UHS inoperable if sedimentation greater than 12 inches is discovered.
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3 TS 3.7.1.1.b requires an operable flow path capable of taking suction from the CSCS water tunnel and transfening the water through the associated residual heat removal heat exchanger.
TS 3.7.1.2.b contains a similar requirement for the diesel generator cooling water systems.
These TS will continue to provide regulatory controls to ensure that sedimentation does not develop to such an extent that the systems can not perfomi their safety functions.
Regulatory Guide 1.27, ' Ultimate Heat Sink for Nuclear Power Plants," provides guidance on General Det on Cetteria 4*. The stated regulatory position is that the capacity of the UHS should i
be sufficient to provide cooling for a specified period of time. The Bases for TS 3.7.1.3 also state that this TS and its SR ensure that seWicient cooling capacity is available to safety-related equipment during normal and accident conditions. The licensee has demonstrated in the Updated Final Safety Analysis Report that the UHS has the capability to provide sufficient cooling for 30 days following an accident. In addition, the licensee will continue to implement a TS SR (TS 4.7.1.3.a) that ensures that the depth of the pond will not be decreased by se'limentation to a point that willimpact the cooling capability of the CSCS water. Limits on the depth of sediment inside the intake structure are not inciudod in the Standard Technical Specifications, NUREG-1434, to ensure operability of the safety-related service water systems. The design of the intake structure at LaSalle was intended to eliminate the concem of sedimentation by locating the inlets to the service water tunnel and the traveling screen bypass line 18 inches from the floor of the lake screenhouse. There are no unique aspects of the design that would result in significant sediment accumulation in front of these inlets that would necessitate additional controls be included in the LaSalle TS.
Because inclusion of a limit on sediment thickness within the lake scroonhouse has not been shown to be an accurate indication of operability of the UHS and because the licensee will control fouling of the UHS and CSCS through an administratively controlled program, deletion of this requirement from the TS is acceptable. However, TS 4.7.1.3.c was credited in the licensee's response to GL 8913. The licensee has committed to submit an updated response to the generic letter.
3.0 STATE CONSULTATION
in accordance with the Commission's regulations, the Illinois State official was notified of the proposed issuance of the amendmerits. The State official had no comments, 4.0 ENVIRONMENTAL. CONSIDERATION The amendments change a surveillance requirement. The NRC staff has determined that the amendments involve no significani increase in the amounts, and no significant change in the types, of any effluents that may be released offsite, ar.d 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 (62 FR 54870). Accordingly, the amendments meet 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 lasuance of the amendments.
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5.0 CONCLUSION
The Commission has concluded, based on the considerations discussed above, that: (1) there is reasonable assurance that the health and safety of the public wit' not '>e 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 securtty or to the health and safety of the public.
PrincipalContributor: D. Skay Date: January 23, 1998