ML20214Q872
| ML20214Q872 | |
| Person / Time | |
|---|---|
| Site: | San Onofre  |
| Issue date: | 09/09/1986 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20214Q871 | List: |
| References | |
| TAC-54724, TAC-54725, TAC-54866, TAC-54867, TAC-54868, TAC-54869, TAC-57301, TAC-57302, TAC-57310, NUDOCS 8609260391 | |
| Download: ML20214Q872 (4) | |
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SAFETY EVALUATION AMENDMENT NO. 54 TO NPF-10 AMENDMENT N0. 43 TO NPF-15 SAN ON0FRE NUCLEAR GENERATING STATION, UNITS 2 & 3 DOCKET NOS. 50-361 AND 50-382 INTRODUCTION Southern California Edison Company (SCE), on behalf of itself and the other licensees, San Diego Gas and Electric Company, The City of Riverside, California, and The City of Anaheim, California, has submitted a number of applications for license amendments for San Onofre Nuclear Generating Station (SONGS), Units 2 and 3.
The NRC staff's evaluation of several of these applications is described below.
PCN-109 By letter dated April 2, 1984, SCE requested that Technical Specification (TS) 3/4.2.3, " Azimuthal Power Tilt-Tq" be changed. This TS requires that periodically, the azimuthal power tilt shall be determined to be within acceptable limits.
Specifically, TS 4.2.3.c requires that this detennination be made using the incore detectors once per 31 days, in order to independently confirm the validity of the azimuthal power tilt calculated by the core operating limit supervisory system (COLSS). The proposed modification would change the phrase "at least once per 31 days" to "at least once per 31 EFPD's."
The NRC staff has reviewed the proposed change and finds th.' updating azimuthal power tilt based on reactor operation (effective full power days, or EFPD) more appropriately reflects its actual change with core operation rather than being based on an arbitrary number of calendar days. Since this does not affect the operational ability of the safety equipment (the core protection calculators) relied upon to perform safety functions, but merely reflects the burnup effect on the incore nuclear instru;aantation system, we find the proposed change acceptable.
PCN-119 By letter dated April 27, 1984, SCE requested that Technical Specification Bases 3/4.2.3, " Azimuthal Power Tilt", be revised to state that the core operating limits supervisory system (COLSS) calculates azimuthal power tilt based on input from the fixed incore neutron detectors and does not receive 8609260391 860'709 PDP ADOCK 05000361 P
input from the core protection calculators (CPC's). Specifically, the proposed change would revise Technical Specification Bases 3/4.2.3, which concerns the methods of computing the azimuthal power tilt, a calculation which reflects the power variation in the core between symmetrically located fuel assemblies. This parameter is required to be kept within limits which ensure that design safety margins are maintained. The azimuthal power tilt is calculated by both the core operating limit supervisory system (COLSS), which monitors the reactor and provides infonnation to the operator, and the core protection calculators (CPC's). The CPC's monitor several core parameters and will trip the reactor if one of these parameters exceeds its limit. The current TS Bases 3/4.2.3 wording could be misinterpreted to infer that the CPC's provide an input to the COLSS for azimuthal power tilt when the reactor is operating below twenty percent rated thermal power.
In reality, the COLSS and the CPC's perform calculations independently of each other, and the COLSS performs calculations at all power levels, although it is inaccurate at power levels below twenty percent rated thermal power because the incore neutron detectors, which provide inputs to the COLSS, have a low signal-to-noise ratio during plant operation at low power levels. The proposed change to TS Bases 3.4.2.3 clarifies the fact that the COLSS and the CPC's perfonn calculations independently and explains that the COLSS azimuthal power tilt calculation is inaccurate at power levels below twenty percent rated thermal power. This is due to the incore neutron detectors' inaccuracy at low power levels. However, the CPC's assume a minimum power level of twenty percent rated thermal power which results in highly conservative calculations at low power levels and, therefore, ensures that design safety margins are maintained. The proposed change also specifically states that, because of the COLSS inaccuracy at low power levels, the Limiting Condition for Operation of TS 3.4.2.3 is not applicable at operation below twenty percent rated thermal power.
In sumary, the proposed change would revise TS Bases 3.4.2.3 in order to:
(1) clarify the fact that the COLSS and the CPC's perfonn calculations independently; (2) explain why the COLSS azimuthal power tilt calculation is inaccurate at power levels below twenty percent rated thermal power; and (3) explain why the limiting condition for operation of TS 3.4.2.3 is not applicable at operation below twenty percent rated thermal power.
4 The NRC staff has reviewed the proposed change and concludes that it is acceptable, because it clarifies and corrects the bases of TS 3.4.2.3, and therefore constitutes an improvement to the bases.
PCN-123 By letter dated April 27, 1984, SCE requested that Technical Specification Bases 2.2.1, " Reactor Trip Setpoints" be changed to clarify and correct the wording of the TS. The specific changes are:
1.
The section heading is changed from "DNBR-Low" to " Departure from Nucleate Boiling Ratio (DNBR)-Low." This is strictly an editorial change.
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2.
Two sentences in the first paragraph indicating that a DNBR-Low trip occurs if pressurizer pressure drops below 1825 psia are deleted. This information is included in the later table of trip values. There is no reason to emphasize the low pressurizer pressure trip over any of the J
other DNBR-Low trip parameters.
3.
The paragraph above the table of trip values was changed to emphasize that the limits specified apply only to the DNBR algorithm used for the DNBR-Low trip. The actual plant limiting condition for operation for a specific parameter may be more restrictive than the value used for the CPC DNBR-Low trip.
4.
Parameter (1) in the table of trip values is changed from " Quality Margin-Low 0" to " Hot Leg Quality 0 (no net quality)." Hot leg quality is the correct trip variable. Quality Margin is used in the DNBR algorithm but is not a trip variable.
The NRC staff has reviewed these changes and has found them to be acceptable because they are editorial, or correct errors in this section of the technical specifications.
PCN-188 By letter dated March 18, 1985, SCE requested that a change be made in Technical Specification 3/4.3.2, " Engineered Safety Features Actuation System Instrumen-tation." Technical Specification 3/4.3.2 requires that Engineered Safety Features Actuation System (ESFAS) instrumentation channels be operable and defines a number of functional tests and response time tests that must be conducted periodically in order to verify operability. TS 3/4.3.2 identifies the instruments required for the Toxic Gas Isolation System (TGIS). The TGIS is
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actuated when concentrations of toxic gases (e.g., chlorine, butane / propane or ammonia) in the control room supply ducts exceed the concentration setpoints.
Upon receipt of a TGIS signal, the control room heating ventilation and air conditioning (HVAC) system is automatically isolated. The setpoints are selected such that the toxic gas concentration in the control room will not exceed allowable limits during the first two minutes after the detector responds. This provides adequate protection for the control room operators by allowing sufficient time to don protective gear.
Recently, Amendments 29 and 18 to the operating licenses for San Onofre Nuclear Generating Station Unit 2 and 3, respectively, deleted the requirement for TGIS carbon dioxide instrumentation. Analysis in support of this amendment demonstrated that the maximum control room concentration of carbon dioxide at any time without control room isolation would be also included in Table 3.3-3, "ESFAS Instrumentation," and Table 4.3-2, "ESFAS Instrumentation Surveillance Requirements". The proposed change corrects this oversight by deleting the remaining references to the TGIS carbon dioxide instrumentation from these tables.
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j l The staff has reviewed the requested change.
In the Safety Evaluation of Amendments 29 and 18, the staff approved the proposed license modification to delete the requirement to actuate the control room toxic gas isolation system (TGIS) on carbon dioxide based on a staff assessment of the time dependent toxic gas concentration at the control room air intake.
In these Amendments, the staff concluded, "On this basis the staff concurs with the licensees that protection of the control room operators from a postulated carbon dioxide release on-site is not required." For the reasons given in the earlier Safety Evaluations, the staff concludes that the requested change of PCN-188 is consistant with the earlier staff findings and is, therefore, acceptable.
Contact With State Official The NRC staff has advised the Chief of the Radiological Health Branch, State Department of Health Services, State of California, of the proposed deteminations of no significant hazards consideration. No coments were received.
4 Environmental Consideration These amendments involve changes in the installation or use of facility components located within the restricted area. The staff has determined that the amendments involve no significant increase in the amounts of any effluents that may be released offsite and that there is no significant increase in individual or cumulative occupation radiation exposure. The Commission has previously issued proposed findings that the amendments involve no significant hazards consideration, and there has been no public coment on such findings.
(PCN-123 required no prior notice of consideration of issuance of amendments because it is a change to the Bases only.) Accordingly, the amendments meet the eligibility criteria for categorical exclusion set forth in 10 CFR Sec.
51.22(c)(9). Pursuant to 10 CFR 51.22(b), no environmental impact statement or environmental assessment need to be prepared in connection with the issuance of these amendments.
Conclusion l
Based upon our evaluation of the proposed changes to the San Onofre Units 2 and 3 Technical Specifications, we have concluded that: there is reasonable assurance that the health and safety of the public will not be endangered by operation in the proposed manner, and such activities will be conducted in compliance with the Commission's regulations and the issuance of the amendments will not be inimical to the comon defense and security or to the health and safety of the public. We, therefore, conclude that the proposed changes are acceptable, and are hereby incorporated into the San Onofre 2 and 3 Technical Specifications.
Dated: September 9, 1986 i
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