ML20205K506
| ML20205K506 | |
| Person / Time | |
|---|---|
| Site: | LaSalle  |
| Issue date: | 02/16/1999 |
| From: | NRC (Affiliation Not Assigned) |
| To: | |
| Shared Package | |
| ML20205K499 | List: |
| References | |
| NUDOCS 9904130252 | |
| Download: ML20205K506 (7) | |
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NUCLEAR REGULATORY COMMISSION wAsHaworow, n.c. soses.com SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RFI ATED TO AMENDMENT NO.115 TO FACILITY OPERATING LICENSE NO. NPF-18 COMMONWEALTH EDISON COMPANY LASALLE COUNTY STATION. Uffl.I.2 DOCKET NO. 50-374
1.0 INTRODUCTION
- By letter dated November 9,1998, Commonwealth Edison Company (Comed, the licensee) proposed revisions to the LaSalle County Station, Unit 2, Technical Specifications (TS). The proposed changes add or revise isolation setpoints for leak detection of the reactor water cleanup (RWCU) system. The changes are necessary to support modifications that will restore RWCU pump suction from " cold" to " hot" and also to correct design deficiencies identifed during re-evaluation of the high energy line break analysis. In addition, the amendment eliminates isolation actuation trip functions for the residual heat removal (RHR) system steam condensing mode and some trip functions for the shutdown cooling mode. A similar amendment was issued for LaSalle, Unit 1, on July 6,1998. The proposed changes for Unit 2 are essentially the same as those approved for Unit 1.
2.0 BACKGROUND
The original RWCU system design for LaSalle, Unit 2, included " hot" pump suction from the reactor recirculation system. Because of problems with the pump seal design, the RWCU system was modified to provide the pumps with " cold" suction from downstream of the non-regenerative heat exchangers. The temperature monitoring function of the leak detection system in the pump rooms was no longer needed and was eliminated by license Amendment No. 7 to NPF-18. The licensee plans to install a modification to retum the design to the original
" hot" pump suction by utilizing improved design pumps. The proposed design consists of two 100 percent cepacit pumps in separate rooms separated by an intervening valve room. The temperature monitoring function of the leak detection system will be re-established in the pump and valve rooms and associated TS are proposed to be added for the instruments.
The licensee has also proposed to add temperature monitoring in the RWCU Holdup Pipe and Filter /Demineralizer Valves Rooms and flow monitoring for RWCU pump suction to provida a more rapid response to these areas, should a break occur. The proposed setpoints to actuate isolation of the system are based on a High Energy Line Break analysis and ensure that the i
piping will isolate in time to prevent temperatures in adjacent areas from exceeding environmental qualification limits.
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. A change is also proposed for the isolation actuation setpoints for the RWCU heat exchanger
' rooms to correct a design deficiency. The licensee discovered that the current temperature setpoint would have required a leak of greater than 25 gallons per minute (gpm) to actuate isolation during nominal and winter conditions. The licensee proposed revised temperature setpoints for this area based on new leak rate and setpoint calculations for the modified system design.
The licensee has also proposed changes to the leak detection setpoints for the RHR system.
The steam cendensing mode of RHR was deleted as reported to the NRC in igg 2. The licensee has proposed deleting the setpoints for this mode from TS 3/4.3.2 at this time for consistency. The shutdown cooling mode of RHR currently contains temperature sensors and associated TS setpoints. The licensee has determined that, because the shutdown cooling lines are moderate energy lines, the temperature sensors are not affected significantly by a leak and, therefore, the high temperature and differential temperature functions for this mode are proposed to be deleted.
3.0 EVALUATION 3.1 Reactor Water Cleanun System The RWCd system consists of pumps, heat exchangers, filter-domineralizers and associated valves and piping. The majority of the components are located outside of primary containment and, therefore, require a system to detect leaks and isolate the system in the event of a break..
The proposed modifications to LaSalle, Unit 2, will change the flow path so that high temperature water will be pumped directly from the reactor coolant system. Other changes to the system design will be made to correct problems reported in LER g7-033 related to the capability to meet design basis criteria. The following changes are proposed to TS Table 3.3.2-2 to support these modifications:
- A.3.b Heat Exchanger Area Temperature - High trip setpoint of s181 degrees Fahrenheit i
would be changed to s14g degrees Fahrenheit.
A.3.b Heat Exchanger Area Temperature - High allowable value setpoint of s187 degrees 1
- Fahrenhe'.t muld be changed to n156.8 degrees Fahrenheit.
A.3.c Heat Exchanger Area Ventilation AT-High trip setpoint of s85 degrees Fahrenheit would be changed to s33 degrees Fahrenheit.
'3 A.3.c Heat Exchanger Area Ventilation AT-High allowable value of sg1 degrees Fahrenheit would be changed to s40.3 degrees Fahrenheit.
newts would be added as follows:
A.3.f Pump and Valve Area Temperature - High, with a setpoint of s201 degrees Fahrenheit and an allowable value of s20g degrees Fahrenheit.
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F A3.g Pump and Valve Area Ventilation AT-High, with a setpoint of sB6 degrees Fahrenheit
- and an allowable value of s92.5 degrees Fahrenheit.
A.3.h Holdup Pipe Area Tongarature - High, with a setpoint of s201 degrees Fahrenheit and an allowable value of s209 degrees Fahrenheit.
A.3.1 Holdup Pipe Area Ventilation AT - High, with a setpoint of s86 degrees Fahrenheit and
- an allowable value of s92.5 degrees Fahrenheit.
A.3.J Filter /Demineralizer Valve Room Area Temperature - High, with a setpoint of s201 degrees Fahrenheit and an allowable value of s209 degrees Fahrenheit.
A.3.k Filter /DemineralizerValve Room Area Ven*ilation AT-High, with a setpoint of s86 degrees Fahrenheit and an allowable value of s92.5 degrees Fahrenheit.
A.3.1 Pump Suction Flow-High, with a setpoint of sESO gpm and an allowable value of sB10 gpm.
These functions would also be added to TS Table 3.3.2-1, " Isolation Actuation instrumentation
- and associated surveillance requirements are proposed to be added to TS Table 4.3.2.1-1.
The functions are also added to Table 3.3.2-3," Isolation System Instrumentation Response Time" which !ndicates that response time testing is not required because this valve group depends on an emergency diesel generator start time of 13 seconds for valve movement to begin.
l The new and mvised setpoints are based on analyses described ;n the summaries of I
calculations which were submitted by the licensee. The calculation methodologies used to determine tha ambient and differential temperature analytical limits and the pump suction flow analytical limit are the same as those that were used and approved for Unit 1 (as discussed in the safety evaluation dated July 6,1996). In its safety evaluation, the staff stated that conservative methodology has been used. The licearse verified that these calculations and their results are also appReable to LaSalle, Unit 2. The temperature limits have been seiected to be low enough to meet the established leakage limit of 25 gpm, yet high enough to preclude unwanted actuations due to weather and ventilation system transients. The Pump Saction Flow
- High trip function analytical limit provides assurance that th1 break flow will be detected prior to exceeding the environmental qualification limits.
The licensee also submitted sumruries of the calculations which provide the basis for the difference between the analytical, setpoint, and allowable values. The calculations are based on a setpoint methodology which wn reviewed by the NRC as part of an instrumentation and controls inspection at Dresden Nuciaar Power Station in 1994. Inspection report 50-237/94016, 50-294/94016 issued October 21,1994, documents the staff's conc;usion that the methodology is technically sound and sufficiently comprehensive. In its July 6,1998, safety evaluation of the Unit 1 TS change, the staff concluded that ths methodology was suitable for use in the calculations of RWCU room setpoint margin analysis and RWCU high flow isolation error
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-4 analysis. Because the licensee used these same calculations to determine the Unit 2 setpoints, the stafi conobdes that the setpoints for Unit 2, will ensure, with a high degree of reliability, that the analytical limits will not be exceeded. Based on the licensee's analyses, the proposed setpoints are acceptable.
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' The applicability and action statements for the new isolation functions listed in Table 3 3 21
.. - are consistent with the existing RWCU instrumentation TS and are acceptable.
The surveillance requirements for the new isolation functions listed in Table 4.3.2.1-1 consist of quarterly channel functional tests, quarterly channel calibrations, and no channel checks.
These are consistent with the existing RWCU instrumentation TS with the exception of the FiWCU Pump Suction Flow-High trip function. This trip function utilizes analog loops which t
require Channel Checks once per shift.
3.2 RHR System !so!=Han 3.2.1 RHR System Steam Cendensina Mode The steam condensing mode of RHR is no longer utilized as reported by the licensee in an October 20,1992, letter to the NRC. This change was reflected in the Updated Final Safety Ana!ysis Report (UFSAR). As stated in LER 97-031-01, the licensee did not, at that time, remove the related TS requirements for isolation instrumentation because it was considered low priority and the action statements were being met by isolating the function. The licensee now
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proposes to delete these functions from the TS for consistency with the design basis.
The hcensee proposes to delete the following TS from Tables 3.3.2-1,3.3.2-2, 3.3.2-3, and l
l 4.3.2.1-1:
1 A.5.a RHR Equipment Area AT-High l
A.5.b RHR Area Temperature - High (Tables 3.3.2-2 and 3.3.2-3 Identify this trip function as RHR Area Cooler Temperature - High) t A.S.c RHR Heat Exchanger Steam Supply Flow-High Guidance to evaluate the scope of the Technical Specifications is provided in 10 CFR 50.33, as follows:
l Criterion 1 Installed instrumentation that is used to detect, and indicate in the control room, a l
significant abnormal degradation of the reactor coolant pressure boundary.
Cnterion 2 A process varicble, design feature, or operating restriction that is an initial condition of a design basis accident or transient arsysis that either assumes the fa;iure of or presents a cha!lenge to the integrity of a fission product barrier.
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Criterion 3 A structure, system, or component that is part of the primary success path and which functions or actuates to mitigate a design basis accident or transient that either assumes the failure of or presents a challenge to the integrity to fission product barrier.
Cntenon 4 A structure, system, or component which operating experience or probabilistic safety assessment has shown to be significant to public l'ealth and safety.
Requirements that are in the existing Technical Specifications but do not meet the guidance set forth in 10 CFR 50.36 for inclusion in TS, can be removed from TS. The applicability of the four criteria in 10 CFR 50.36 to the proposed TS changes are discussed below.
Criteria 1 The temperature and flow measurement instrumentation for the RHR system steam condensing mode isolation was originally used to detect leaks in the RHR system. However, the steam condensing mode is no longer utilized and was removed from the plant's design basis. The Reactor Core isolation Cooling system outboard motor-operated valves that supply the RHR heat exchangers in the steam condensing mode are closed with power removed during modes 1,2, and 3. Therefore, the steam condensing function is always isolated in modes 1,2, and 3 and the instrumentation is not used to detect leaks in these modes.
Therefore, this criterion does not apply.
Criterion 2 The isolation actuation trip functions are not process variables, design features, or operating restrictions..Therefore, this criterion does not apply.
. Criterion 3 The trip functions related to RHR steam condensing mode isolation have been isolated because the function is no longer used. Therefore, these functions are not used to mitigate an accident and this criterion does not apply.
Criterion 4 Because the isolation actuation functions discussed above do not function to isolate the RHR system, they are not significant to public health and safety. Therefore, this criterion does not apply.
Since TS Tabies 3.3.2-1,3.3.2-2,3.3.2-3, and 4.3.2.1-1 trip functions A.5.a, A.S.b, and A.S.c do not satisfy any of the four criteria from 10 CFR 50.36, they may be removed from the TS.
3.2.2 RHR System Shutdown Coolina Mode TS Tables 3.3.2-1,3 3.2-2,3.3.2-3, and 4.3.2.1-1 contain isolation
-tion trip functions for the shutdown cooling mode of RHR. The variables used to detect a leak and isolata the system while in shutdown cooling include: reactor vessel water level, reactor vessel pressure, RHR pump suction flow, RHR area temperature, and RHR differential temperature. The licensee has determined that the RHR shutdown cooling lines are modercie energy lines rather than high energy lines and, therefore, area temperature monitoring and differential temperature j
monitoring would not hcve sufficient sensitivity to detect leaks in these lines. The licensee's I
analyses indicate that these functions are incapable of providing leak de'.ectiun because the heating effect from a 25 gpm break would not produce a detectable increase in area temperature. Therefore, the licensee proposes to delete the temperature and differential temperature isolation trip function from this TS. In addition to the other isolation actuation trip
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l functions listed above, adequate leak detection for the RHR system in the shutdown cooling mode is also provided by sump and aren radiat;on monitoring, periodic viv.41 inspection, and monitoring of reactor coolant makeup flow rate.
The licensee proposes to delete the following TS from Tables 3.3.2-1, 3.3.2-2, 3.3.2-3, and 4.3.2.1-1:
I A.6.d RHR Area Temperature - High (Tables 3.3.2-2 and 3.3.2-3 identify this trip function as L RHR Area Cooler Temperature - High) i A.6.e RHR Equipment Area AT-High i
Requirements that are ir, the existing TSs, but do not meet the guidance set forth in 10 CFR 50.36 for inclusion in TSs can be removed from TSs. The cr%ria of 10 CFR 50.36 are
. addressed below.
Criterion 1 The RHR area ambient and differential temperature instrumentation was originally designed to 6etect leaks while in the RHR shutdown cooling mode. However, it was determined that these sensors are not affected significantly as a result of a leak because the shutdown cooling lines are moderate energy lines. Therefore, these functions are not used to detect degradation of the reactor coolant pressure boundary and this criterion does not apply.
- Criterion 2 The isolation actuation trip functions era not process variables, design features, or operating restrictions. Therefore, this criterion does not apply, i
Criterion 3 The RHR area ambient and differential temperature sensors for RHR shutdown cooling mode isolation are not used to mitigate an accident because they are ineffective at
- detecting a leak in moderate energy lines and actuating isolation. Therefore, this criterion does not apply.
1 Criterion 4 Because the isolation actuation functions discussed above do not function to isolate the RHR system, they are not significant to public health and safety. Therefore, this l
criterion does not apply.
1 Since TS Tables 3.3.2-1,3.3.2-2,3.3.2-3, and 4.3.2.1-1 trip functions A.6.d and A.6.e do not satisfy any of the four criteria from 10 CFR 50.36, they may be removed.
4.0 STATE CONSULTATION
in accordance with the Commission's regulations, the lilinois S: ate official wss notified of the proposed issuance of the amendment.' The State official had no commenM.
5.0 E.NVIRONMENTAL CONSIDERATION The amendment changes 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 and changes
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- l survelliance requirements. The NRC staff has determined that the amendment involves 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 amendment involves no significant hazards consideration, and there has been no public comment on such finding (63 FR 69335). Accordingly, the amendment meets 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 amendment.
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6.0 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 will not be endangered by operation in the proposed manner, (2) such activities will be conducted il compliance with the Commission's regulations, and (3) the issuance of the amendment will not be inimical to the common defense and security or to the health and safety of the public.
Principal Contributors: J. Kudrick P. Looser D. Skay Date: February 16,1999