ML20212C281
| ML20212C281 | |
| Person / Time | |
|---|---|
| Site: | South Texas  |
| Issue date: | 09/13/1999 |
| From: | NRC (Affiliation Not Assigned) |
| To: | |
| Shared Package | |
| ML20212C277 | List: |
| References | |
| NUDOCS 9909210205 | |
| Download: ML20212C281 (3) | |
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UNITED STATES NUCLEAR REGULATORY COMMISSION o
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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED_TO AMENDMENT NOS.116 AND 104 TO FACILITY OPERATING LICENSE NOS. NPF-76 AND NPF-@0 STP NUCLEAR OPERATING COMPANY. ET AL.
SOUTH TEXAS PROJECT. UNITS 1 AND 2 DOCKET NOS. 50 498 AND 50-499
1.0 INTRODUCTION
By application dated June 7,1999, STP Nuclear Operating Company (the licensee) requested changes to the South Texas Project, Units 1 and 2 (STP), Technical Specifications (TSs). The proposed changes would revise TS 2.2.1, Reactor Trip System (RTS) Instrumentation Setpoints, and TS 3.3.2, Engineered Safety Features Actuation System (ESFAS)
Instrumentation, and the associated Bases, by removing the Total Allowance (TA), Sensor Error (S), and Z terms (Z is the statistical summation of errors excluding sensor and rack drift) from the RTS and ESFAS instrumentation trip setpoints tables. This would replace the five-column methodology with a two-column methodology that consists of the trip setpoint and allowable value columns.
The licensee stated that the proposed change is included in the STP application for Improved Technical Specifications (ITS) and the proposed change is consistent with the guidance in NUREG-1431, " Standard Technical Specifications, Westinghouse Plants"; however, implementation of the STP ITS has been deferred.
2.0 BACKGROUND
in 1976, Regulatory Goide (RG) 1.105, Revision 1, " Instrument Setpoints," was issued.
RG 1.105, Revision 1, addressed NRC concerns associated with the frequent drift of protection system setpoints past the TS trip setpoint limit. RG 1.105, Revision 1, provided general guidance that the setpoints should be established with sufficient margin between the TS limits for the process variable and the nominal trip setpoints to allow for (a) the inaccuracy of the instrument, (b) uncertainties in the calibration, and (c) the instrument dnft that could occur during the interval between calibrations. This was the first opportunity for many plants to include uncertainties in the calculation of an Allowable Value (AV). During this process, Westinghouse proposed the five-column methodology which was subsequently approved containing provisions that would provide some operating flexibility, if a plant identified that an AV had been exceeded, the five-column methodology included provisions which, in some cases, could eliminate the need for filing a formal Licensee Event Report (LER).
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The five-column methodology contains the Nominal Trip Setpoint (NTS), AV, TA, S, and the
' Z termsi This five-column methodology was designed to reduce the number of LERs by allowing the plant the opportunity to prove that a channel was operable, even though the AV has been exceeded l
When the NRC issued 10 CFR 50.73, " Licensee Event Report System,"in 1983, the filing I
requirements associated with an LER were changed. An LER must be filed only in cases where l
the unit has experienced loss of a function, and not just a single inoperable channel. With that LER filing requirement change, the benefits associated with the five-column methodology is no l
longer applicable (i.e., to minimize filing LERs). Westinghouse no longer recommends the five-column TS format. NUREG-1431 has adopted the two-column format which contains the
" Trip Setpoint" and " Allowable Value" columns.
3.0 EVALUATION The STP TSs adopted a five-column setpoint methodology when the units were licensed. This TS change request proposes that the TA, S, and Z terms be removed from the ESFAS and RTS instrumentation trip setpoints tables such that the two-column form will be implemented.
The proposed change eliminates the option to evaluate Equation 2.2-1 (Z+R+SsTA), from TSs 2.2.1 and 3.3.2, within 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />, when the Trip Setpoint is outside the AV limit. The equation originally established a threshold for submitting an LER. With implementation of j
two-column format, any time an AV is exceeded it will be evaluated against 10 CFR 50.73 to I
determine if filing an LER is required.
With a two-column approach, channel operability is based on the AV/ Trip Setpoint relationship as determined by the plant setpoint methodology and confirmed through plant surveillance.
With the values of TA; Z, and S deleted, the channel must be declared inoperable when its setpoint is found less conservative than the AV or found inconsistent with the assumptions of the setpoint methodology. The two-column approach is more conservative than the five-column approach, and therefore, is acceptable to the staff.
In summary, the staff has reviewed the proposed changes to TS 2.2.1, TS 3.3.2, and the associated Bases. The change eliminates the five-column methodology and transitions to a two-column methodology. The staff finds that the two-column methcdology is more conservative than the five-column methodology and is consistent with NUREG-1431, and
' therefore, is acceptable.
4.0 STATE CONSULTATION
' In accordanca with the Commission's regulations, the Texas State official was notified of the proposed issuance of the amendments. The State official had no comments.
5.0.
ENVIRONMENTAL CONSIDERATION The amendments change 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. 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
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3-significant increase in individual or cumulative occupational radiation exposure. The Commission has previously issued a proposed finding that the amendments in /olve no i
significant hazards consideration, and there has been no public comment on such finding i
_. (64 FR 35211). Accordingly, the amendments meet the eligibility criteria for categorical exclusion set forth in 10 CFR 51.22(c)(9). Pursuant to 10 CFR 51.22(h), no environmental impact statement or environmental assessment need be prepared in connection with the issuance of the amendments.
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 in compliance with the Commission's regulations, and (3) the issuance of the amendments will not be inimical to the common c; noe and security or to the health and safety of the public.
Principal Contributor: H.Li Date: September 13, 1999 l
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