ML20067D811
| ML20067D811 | |
| Person / Time | |
|---|---|
| Site: | Browns Ferry  |
| Issue date: | 02/06/1991 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20067D801 | List: |
| References | |
| NUDOCS 9102130255 | |
| Download: ML20067D811 (3) | |
Text
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'es UNITED STATES l'
i NUCLEAR REGULATORY COMMISSION i
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,4 ENCLOSURE 2 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR. REGULATION 1
SUPPORTING AMENDMENT NO. 18,9 TO FACILITY OPERATING LICENSE.NO. DPR-52 TENNESSEE VALLEY AUTHORITY BROWNS' FERRY ~ NUCLEAR PLANT. UNIT 2 L
DOCKET NO. 50-260 l
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-1.0 _ INTRODUCTION
- By letter dated. June 4,1990, Tennessee Valley Authority (TVA or the licensee) submitted a request to change the Technical Specifications (TS) for Browns Ferry Nuclear plant (BFN),, Unit 2.
The proposed TS amendment would replace the current Reactor Water Cleanup (RWCU) system 'ligh temperature detection L
instruments in TS Tables _3.2.A 4 ? h and 3.7. A. with new temperature loops.
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.The new temperature _ loops:would consist of environmentally qualified resistance l4
- temperature detectors (RTDs) and IEEE class '.E qualified analog trip units (ATUs)-..In addition, the Bases Section 3.2 would be modified to describe the
-locations'of-the RTDs.
K 2.0 BACKliROUND AND DISCUSSION L
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- The:RWCU system functions to maintain high reactor water purity to limit L
chemica r.and corrosive action, thereby limiting fouling.and deposition L
from occurring-on heat transfer surfaces of the Reactor Coolant System (RCS).
The system also' removes corrosion products to limit. impurities-available for 1
activation by' neutron flux and,the resulting-radiation-from deposition of
-corrosion products. The RWCU system arovides continuous purification of a-portion of-the recirculation flow. T1e RWCU system also provides a means of removing reactor water during plant heatup operations.
Upon indication of high temperature in the RWCU system spaces, the RWCU system automatically isolates the reactor coolant pressure boundary by closure-of two RWCU suction.line. isolation valves, and -closure of the RWCU return line valve.
l Such isolation is needr.d to preclude a radioactive release in the case of a'
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'li ne _ brea k.'.
- The licensee. stated in-its application for amendment dated June 4,1990, that
'an analysis of High Energy Line Break (HELB) in the: reactor building hat.
identified certain. pipe breaks which could-not be automatically detected and
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' isolated in a -reasonable timeframe using the presently installed temperature switches.. The breaks identified were RWCU pipe critical cracks lin the main steam valve vault,:as well as in RWCU pump rooms, RWCU pipe trench, and the RWCU heat exchanger room. The proposed changes to the TS reflect a plant modification aimed at replacing the existing non-environmentally qualified terperature -
L switches with environmentally qualified temperature loops to improve timeliness of detection' and isolation of. line breaks.
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) 3.0 EVALUATION The four existing temperature switches located in the floor drains in the backwash receiving room will be abandoned and replaced by four RTDs located in RWCU pump rooms A and B.
The four temperature switches located in the RWCU pipe trench and the four located in the RWCU heat exchanger rooms are being replaced by the same number of RTDs at each location.
Additionally, four RTDS are being added to the main steam valve vault, where no temperature switches were located previous to this modification.
The new RTD/ATU temperature loops were cnosen by TVA to decrease the time needed to close the RWCU valves.
The setpoints for the new RTD/ATU temperature loops are set above the maximum expected room temperature to avoid spurious actuation due -to ambient conditions, and below the analytical limits for timeliness in detecting a pipe break. The logic arrangement does not change from that of the temperature switches, i.e., high temperature signals from one of two RTDS in each of two divisions in a given avea are required to produce a RWCU primary i:;olation signal (one-out-of-two taken twice). With this logic the licensee states that the failure of a single RTD, ATU, or power feed will not prevent isolation nor produce a spurious isolation.
The licensee has stated in its amendment request that the new devices do not alter or aftect the function or isolation of the valves. The modifications were made to ensure 6 quicker means of detecting RWCU pipe breaks and provide snore accurate temperature measurement. The NRC has analyzed and approved designs at Boiling Water Reactor (BWR) plants with such ATVs (NEDO-21617, Analog) Transmitter / Trip Unit System for Engineered Safeguard Sensor Trip Input.
The changes to the TS proposed by the licensee are necessary to reflect the replacement of the temperature switches with the RTD/ATU loops. The requirements pertaining to the function and surveillance of these devices have not been changed. The NRC staff finds the TS changes acceptabie. A sumary of the individual changes with each basis for approval follows:
1.
Replacement of the RWCU system temperature switches on TS Tables 3.2.A and 4.2.A by the new ATU instrumentation is acceptable.
Such devices have been approvtd by the NRC in the past and perform the same function as the fonner temperature switches. Additionally, the new devices are environmentally and IEEE-qualified.
2.
Deletion of Note 14 5r n Table 3.2.A is acceptable. The note applies to the temperature switches that are being deleted from the table.
3.
Revision of Bases Section 3.2 is appropriate as described by the licersee.
The reviset Bases describe the locations of the RTDs.
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3 4.
The Notes on Table 3.7.A are being revised to indicate that the new RTD/ATV temperature loops actuate Group 3 primary cor.tainment isolation valves.
The NRC staff agrees with the licensee's proposal to provide isolation in the event that high temperatures are indicated in the RWCU pump rooms 2A and 2B, the RWCU heat exchanger room, the main steam valve vault, or in the space near the pipe trench containing RWCV piping.
4.0 ENVIRONMENTAL CONSIDERATION
This amendicent inycives a change to a requirement with respect to the installation or use of a f acility component located within the restricted area as defined in 10 CFR Part 20 and changes to the surveillance requirements. The staff has determined tiut the amenoment 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 occupa,tional radiation exposure. The Commission has previously issued a proposed finding that this amendment involves no significant hazards consideration and there has been no public coment on such finding. Accordingly, the amendment meets the eli forth in 10 CFR 51.22(c)(9)gibility criteria for categorical exclusion set Pursuant to 10 CFR 51.22(b), no environmental isnpact stateinent nor environmental assessment need be prepared in connection with the issuance of the amendment.
5.0 C0NCLUS10N The Comission made a proposed detennination that the amendment involves no significant hazards consideration which was published in the Federal Register (55 FR 30312) on July 25, 1990, and consulted with the State liOTaTama. No public cuments were received, and the State of Alabama did not have any comen ts.
The staff has concluded, based on the considerations discussed above, that:
(1) theru 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 Comission's regulations, and (3) the issuance of the einendments will r,et be inimical to the comon defense end security nor _to the health and safety of the public.
Principal Contributor:
B. M0zafari Dated: February 6,1991
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