ML20085B000
| ML20085B000 | |
| Person / Time | |
|---|---|
| Site: | Comanche Peak  |
| Issue date: | 05/31/1995 |
| From: | NRC (Affiliation Not Assigned) |
| To: | |
| Shared Package | |
| ML20085A978 | List: |
| References | |
| NUDOCS 9506140316 | |
| Download: ML20085B000 (4) | |
Text
y
.,e l I
N
[C Qtto[\\ -
.umiso smes g
NUCLEAR REGULATORY COMMISSION j
i WASHINGTON, D.C. ensas ann 3 t
-...../
SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION i
RELATED TO AMENDMENT N05. 41 AND27 TO FAClLITY OPERATING LICENSE NOS. NPF-87 AND NPF-89
' TEXAS UTILITIES ELECTRIC COMPANY COMANCHE PEAK STEAM ELECTRIC STATION. UNITS 1 AND 2 DOCKET NOS, 50-445 AND 50-446 l.0 INTRODUCTION By.. application dated February 14, 1994 (TXX-94046), Texas Utilities Electric Company (TU Electric /the licensee) requested changes to the Technical Specifications (TSs) (Appendix A to Facility Operating License Nos. NPF-87 and NPF-89) for-the Comanche Peak Steam Electric Station (CPSES), Units 1 and 2.
The proposed changes would revise TS for CPSES Units 1 and 2 in the following three areas: 1) a change to the allowable value for the Unit 2 pressurizer pressure-low and Unit 2 overtemperature N-16 (OTN-16) reactor trip setpoints;
- 2) an administrative change to delete an option which allowed continued operation for a period of time when a reactor trip system (RTS) or engineered safety features actuation system (ESFAS) instrumentation or interlocks trip setpoint is found less conservative than the allowable value; and 3) an administrative change to combine the Unit I and Unit 2 line items for RTS or ESFAS trip setpoint and allowab'.e values which are the'same.
2.0 BACKGROUND
On Nay 27, 1993, TU Electric was informed by Rosemount Aerospace Inc.
(Rosemount) that Model 1154 Series H transmitters with improved temperature performance. were not meeting the published temperature specifications. The notification, required by 10 CFR Part 21, stated that the transmitter output variation over the 40*F - 130*F ranges was greater than expected. An assessment by the licensee identified an impact on the Unit 2 allowable values for pressurizer pressure-low and OTN-16. The same channels on-Unit I are not affected as they do not use Rosemount Transmitters.
Equation 2.2-1 (Z + R + S 1 TA) is used in TS 2.2.1 and TS 3.3.2 to determine the operability of a channel if its setpoint is less conservative than its allowable value.
The channel may be considered operable if the setpoint is.
adjusted to be consistent with the trip setpoint and Equation 2.2-1 is confirmed satisfied within 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />.
In practice, the licensee does not exercise this option.
If the setpoint exceeds the allowable value, the licensee declares the channel inoperable, applies the applicable action requirements and calibrates the channel to restore its operability.
Even 9506140316 950531 f
ADOCK O 5
. though the option offered by Equation 2.2-1 is not used, it is an administrative burden to confirm and revise the values provided for the elements in this equation (TA, Z and S) as provided in Tables 2.2-1 and 3.3-3.
For example, the Rosemount temperature effect described above was another in a series of items that potentially impacted these values and required assessment and possibly a TS change. This burden can be eliminated with the deletion of this equation and.the associated values in the instrumentation tables.
I 3.0 EVALUATION Overtemperature N-16 The OTN-16 trip provides core protection to prevent departure from nucleate boiling (DNB) for all combinations of pressure, power, coolant temperature, and axial power distribution, provided that the transient is slow with respect to piping transit delays from the core to the N-16 detectors, and pressure is within the range between the pressurizer high and low pressure trips.
The calculated setpoint for OTN-16 trip is a function of reactor coolant temperature, pressurizer pressure, and axial power distribution.
The CPSES statistical setpoint study (SSS) identifies the uncertainties associated with the channel.
The added uncertainties reported by Rosemount increase the required allowance in the SSS for the sensor temperature effect (STE).
The STE represents an allowance for changes in the transmitter response when operating at a temperature different from the temperature at which it was calibrated. The STE is used to calculate both the allowable value and nominal trip setpoint presented in the TSs. The increased uncertainties reported by Rosemount change the Unit 2 OTN-16 allowable value so that, as stated in revised Note 2 of Table 2.2-1, the maximum trip setpoint (allowable value) shall not exceed its computed trip setpoint by more than 2.85-percent of the span for Unit 2.
Reducing the maximum allowable value from 2.88-percent of span above the trip setpoint to 2.85-percent of span above the trip setpoint is a change in the conservative direction. The change, however, merely compensates for the increased uncertainty of the channel's transmitter due to temperature effects and actually maintains the same level of safety intended in the original allowable value.
Therefore, the staff concludes that the proposed TS change does not adversely affect plant safety and is acceptable.
Pressurizer Pressure - Low. Unit 2 The pressurizer pressure-low reactor trip function protects against depressurization of the primary system while at power which could lead to DNB.
The pressurizer pressure-low trip will shutdown the reactor in the event of loss of coolant accidents either small or large break, a steam generator tube rupture event, and other loss of inventory or increased cooling from the secondary side events.
a 9 The increase in the minimum allowable value for Unit 2 pressurizer pressure-low from 2 1863.6 psig to 2 1865.2 psig is a change in the conservative direction. Pressurizer pressure could have decreased to a lower value before the trip actuated with the existing allowable value. The change, however, merely compensates for the increased uncertainty of the channel's uncertainty due to temperature effects and actually maintains the same level of safety intended in the original allowable value. Therefore, the staff concludes that the proposed TS change does not adversely affect plant safety and is acceptable.
Eouation 2.2-1 Currently, TS 2.2.1 and TS 3.3.2 allow adjustment of a bistable if the "as found" setpoint value is found to be less conservative than its corresponding i
allowable value. These TSs allow either of two options to be used in making the bistable adjustment. ACTION b.l. requires adjustment of the bistable to remove the difference between the trip setpoint and the "as found" trip value.
This adjustment compensates for, but does not necessarily restore the accuracy of the channel in that the bistable is adjusted consistent with the setpoint value listed in Table 2.2-1 or Table 3.3-3 but the drift in the other channel components is not removed. This ACTION further requires that within 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> of making the bistable adjustment, a determination that the sum of the pre-adjustment rack drift ("R" term of Equation 2.2-1) and other uncertainty allowances in the channel ("Z" and "S" terms of Equation 2.2-1) do not exceed the total allowance (TA) value listed in Table 2.2-1 or Table 3.3-3.
In the alternative, ACTION b.2. requires that if a setpoint is found to be less conservative than its corresponding allowable value, the channel be declared inoperable, and the applicable action statements be applied until the channel is restored to operable status.
A channel is restored to operable status by performing a full channel calibration thereby removing the as found deviations in the channel.
This calibration in effect will force channel operation closer to the nominal setpoint, which is a more conservative operating point.
The proposal to remove the option provided by ACTION b.1. in TS 2.2.1 and TS 3.3.2, as well as Equation 2.2-1 with its definitions and values, deletes a potentially less conservative option and assures a more conservative operating point for the RTS and ESFAS instrument setpoints than allowed by the current TSs. Therefore, the staff concludes that the proposed changes to the TSs and j
Bases do not adversely affect plant safety, will result in a net benefit to i
the safe operation of the facility, and are acceptable.
finally, the change to combine the Unit I and Unit 2 line items for RTS or ESFAS trip setpoint and allowable values in Tables 2.2-1 and 3.3-3, which are identical, is an administrative change.
Therefore, the staff concludes that the proposed TS change does not adversely affect plant safety, will result in a net benefit to the safe operation of the facility, and is acceptable.
o 9
4.0 STATE CONSULTATION
In accordance 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 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 significant increase in individcal 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 (59 FR 32238). 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(b) 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 defense and security or to the health and safety of the public.
Principal Contributor:
Timothy Polich Date: May 31, 1995
,