ML20066D628
| ML20066D628 | |
| Person / Time | |
|---|---|
| Site: | Browns Ferry  |
| Issue date: | 01/09/1991 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20066D625 | List: |
| References | |
| NUDOCS 9101150240 | |
| Download: ML20066D628 (3) | |
Text
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UNITED STATES NUCLEAR REGULATORY COMMISSION n
f WASHINGTON, D, C. 20666
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ENCLOSURE 2 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION SUPPORTING AMENDMENT NO.185 TO FACILITY OPERATING LICENSE NO. DPR-52 TENNESSEE VALLEY AUTHORITY BROWNS FERRY NUCLEAR PLANT. UNIT 2 DOCKET NO. 50-260
1.0 INTRODUCTION
By letter dated July 6,1990, the licensee, Tennessee Valley Authority (TVA),
proposed changes to the Technical Specifications (TS) for Browns Ferry Nuclear PlantUnit2(BFN2). The pro Depressurization System (ADS) posed amendment will revise (1) the Automatic initiation and high drywell pressure bypass timer names and set oints, (2) the number of ADS valves required to be operable prior tostartup,(
valves, and ( )) the ADS bases. ADS limiting conditions for operation (LCO) with inope 2.0 EVALUATION The ADS high drywell pressure bypass timer was added to meet the requirements i
of NUREG-0737, Item II.K.3.18 and provide for automatic actuation of the ADS for certain Loss of Coolant Accident (LOCA) events where a high drywell-pressure does not exist (e.g., pipe breaks outside containment). Automatic actuetion eliminates the need for~ manual operator action to assure adequate core cooling. The BFN2 TS settings for the~ ADS initiation timer and the ADS high drywell pressure bypass timers are being revised. The changes resulted from review of the calculation for the ADS high drywell pressure bypass timer i
function and a recalculation of the accuracy of the ADS. initiation timer.
TVA replaced the Yarway columns for the reactor water level instruments which were located inside the containment with the instrumentation outside the containment. The change eliminates the correction factor or bias of the reactor low level setpoint for the ADS assumed in the setpoint determination for the original ADS high drywell pressure bypass timer. The bias was the result of the high drywell temperature effect associated with water leg columns.
ThenewbypasstimersetpointwasassessedbyGeneralElectric(GE)usingdata from the previous Browns Ferry bypass timer analyses and data from similar plants. The assessment took into account differences between the original calculation assumptions and the current plant configuration. These differences include four ADS valves (versus three in-earlier analyses), no water. leg column bias, and a higher uncertainty in' the ADS timer (due to installation of new
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2 timer hardware. The licensee's assessment concluded that for en ADS high drywell pressur)e bypass timer enelytical limit of 360 seconds, the temperature (PCT) is not expected to exceed 1500'F. The estimated PCT based upon the previous timer setpoint was 1424'F.
The licensee's assessment did not include a specific Appendix K calculation to evaluate the new bypass timer setting. -Powever, based upon our experience with similar calculations, the Browns Ferry plant design, and the assumptions discussed by the licensee, the NRC staff agrees that the licensee's less rigorous analysis is reasonably conservative. Since the assessment results indicate a large margin between the expected PCT (less than 1500'F) and the 10 CFR 50.46 acceptance criteria of 2200'F, the setting for the bypass timer is acceptable.
The ADS timer has been replaced. The new ADS timer har. a higher uncertainty.
4 Therefore, a time delay of 130 seconds was used in the bounding analysis referred above.
The LC0 for the ADS currently requires only four valves to te operable prior to startup. A single failure or loss of a 250V DC reactor motor operated valve (POV) board during a high pressure coolant injection (HPCI) line break could make two ADS valves inoperable.
Analyses have shown that reactor depressuriza,
tion with two ADS valves and no high pressure coolant injection system will result in exceeding the PCT of 2200*F. The bounding analysis confinns that four ADS valves are sufficient to mitigate the accident and that the PCT will not be exceeded even in the event of a single failure (loss of a DC reactor MOV board during a HPCI line break).
be operable before startup.
The proposed LCO requires six ADS valves to with the worst single failure.A minimum of four valves would be available even Thus, the proposed LCO is acceptable.
2.1 Technical Specification Changes (1) TS Table 3.2.B remarks for the function " Instrument Channel-Reactor Low Water Level" (LS-3-5BA-D) and " Instrument Channel Drywell High Pressure" (PIS-64-57A-D)
The term "105 second delay timer
- is changed to "A05 timer".
Since the ADS timer setting is changed, the 105 second timer termi-nology is not correct.
The proposed change to " ADS timer" is acceptable.
In Remark f 2 the term "126 minute delay timer" is changed to " ADS high drywell, pressure bypass timer" to reflect the change from the 121 minute setting. This is acceptable.
(2) Table 3.2.B on Page 3.2/4.2-17 is relocated to Page 3.2/4.2-22a with necessary char.ges in the ADS timer's trip settings. The allowable values of less than or equal to 115 seconds for ADS timer and less than or equal to 322 seconds for ADS high drywell pressure are within the analyzed values of 130 seconds and 360 seconds and, hence, are acceptable.
(3) Table 4.2.B on Page 3.2/4.2-45 -- The cid timer settings of 105 seconds and 12i minutes are deleted in the proposed version. This is acceptable.
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. (4) Page 3.2/4.2-66, Bases 3.2 -- The proposed changes to the bases are acceptable, because they reflect the changes required by the new timer settings.
(5) LCO and Bases 3.5.G 1, 2, 3 - The current LCO requires only four of the six ADS valves to be operable. The proposed change reouires all six ADS valves to be operable.
This is more conservative and is supported by the bounding analysis, and is therefore acceptable. The proposed change allows one ADS to be inoperable for 14 days if the HPCI, the core spray and the low pressure coolant system (LPCI) systems are operable.
This is accept-able. The proposed bases accurately reflect the specification and equip-ment changes and are acceptable.
3.0 ENVIRONMENTAL CONSIDERATION
This amendmcrt involves Changes to requirements With respect to the installation or use of facility components located within the restricted area as defined in 10 CFR Part 20 and changes to the surveillance requirements. The 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 si occupational radiation exposure.gnificant increase in individual or cumulative a
The Comission has previously issued a proposed finding that this amendment involves no significant hazards considera-tion and there has been no public coment on such finding. Accordingly, the amendment meets the eligibility criteria for categorical exclusion set forth in 10CFR51.22(c)(9). Pursuant to 10 CFR 51.22(b), no environmental is?ct statement nor environmental assessment need be prepared in connectics with the irsuance of the amendment.
4.0 CONCLUSION
The Comission made a proposed determination that the amendment involves no significant hazards consideraticn which was published in the Federal Register l
(55 FR 36351) on September 5,1990 and consulted with the State of Alabama.
l No public coments were received and the State of Alabama did not-have any coments.
The staff has concluded, based on the considerations discussed above, that:
l (1) there is reasonable assurance that the health and safety of the-public i
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 amendments will not be inimical to the comon defense and security nor to the health and safety of the public.
Principal Contributor:
G. Thomas Dated: January 9, 1991
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AMENDHENT NO.185 FOR BROWNS FERRY UNIT 2 - DOCKET NO. 50-260 DATED:
Januarv 9.1991 Distribution Docket File NRC PDR Local PDR BFN Reading File S. Varga G. Lainas F. Hebdon S. Black M. Krebs T. Ross D. Moran B. Mozafari OGC D. Hagan E. Jordan G. Hill (4)
Wanda Jones J. Calvo G. Thomas ACR$(10)
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