ML20246B835
| ML20246B835 | |
| Person / Time | |
|---|---|
| Site: | Byron  |
| Issue date: | 08/15/1989 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20246B832 | List: |
| References | |
| NUDOCS 8908240033 | |
| Download: ML20246B835 (4) | |
Text
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' SAFETY EVALUATION BY THE 0FFICE OF NUCLEAR REACTOR REGULATION SUPPORTING AMENDMENT NO. 32 TO FACILITY OPERATING LICENSES N05.
NPF-37 AND NPF-66 COMMONWEALTH EDISON COMPANY.
BYRON STATION. UNITS 1 AND 2' DOCKET NOS. 50-454 AND 5-455
1.0 INTRODUCTION
. By letter dated May 24, 1989, Connonwealth Edison Company (the licensee) proposed changes to Technical Specification 3/4.7.5 for Byron Station, Units
-1 and 2. -The proposed changes allow the seismically-qualified deep well pumps to be used at certain times instead of the essential service water make-up pumps to satisfy the design. bases of the ultimate heat sink (UHS).. Our detailed Safety Evaluation accepting the seismic qualification of the deep well pumps was issued on August 7, 1989.
2.0 BACKGROUND
The Rock River is one of the two make-up sources for Syron Station's UHS. One source is the essential service water make-up pumps which take suction from the Rock River.. This system is designed to withstand all oesign basis natural phenomena' events and combination of events except for seismic events during low Rock River flow rates,' design basis tornado events and river flood events.
The other UHS makeup source is the deep well pumps. These pumps are designed to withstand the tornado and river flood events..For these instances, the deep)well pumps were accepted in the original Byron Safety Evaluation Report (SER, page 9-14, as being adequate to supply the required cooling tower make-up water assuming a single failure, and they can be powered from the emergency (Class IE) power sources.
However, the deep well pumps were not seismically qualified and were not assumed to provide UHS make-up if a seismic event occurred during low Rock
. River flow rates. In a seismic event, the Oregon Dam is assumed to totally disappear. This is a conservative assumption since the most probable failure modes for this earth and rock structure would probably result in some settlement or spreading of the structure. Total loss of the dam combined with low Rock River flow rates could result in loss of suction to the ESW make-up pumps; thus, TS 3.7.5 required shutdown of both units when Rock River flow was below700cubicfeetpersecond(cfs).
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.. Cy letter deted November 30, 1988, the licensee has demonstrated that the deep wells and deep well pumps are seismically qualified, and we agree. Thus, the
' deep wells can provide make-up water for seismic events during low Rock River flow rates when it is assumed that ESW make-up pumps will not be able to provide this water. The May 24, 1989 amendment request was, in part, based on the seismic qualification of the deep wells.
3.0 EVALUATION The original Limiting Condition for Operation 3.7.5 was misleading in several instances; 1.
TS 3.7.5 stated "two independent ultimate heat sinks (UHS) cooling towers shall be OPERABLE, each with..." LCO c. specified one ESW make-up pump power train, implying a total of four ESW make-up pumps at the station. Similarly, LCO f. specified two deeps wells, l
implying four deep wells at the station. There are only two ESW mcke-up pumps and two deep wells at the station.
2.
LCO f. listed three conditions: Rock River water level above 702 feet, below 670.6 feet, and a tornado watch. These are unacceptable conditions for which action is required. However, the wording in the TS could have been misinterpreted to imply that these are the acceptable conditions.
3.
LCO's e, and f(2) were redundant.
The proposed changes in the May 24, 1989 letter corrected these problems, and we find them acceptable.
l The licensee proposed to change ACTION c. which would have allowed the deep L
well pumps to be used as a substitute for the ESW make-up pumps in all instances. However, the deep well pumps do not meet all of the requirements of Appendix B to 10 CFR Part 50. The deep well pumps have aircady been approved for limited instances (tornado and river flows events), and we are now approving them for seismic events during low Rock River flows. We do not, however, agree that they can be considered equivalent to the ESW make-up pumps in all instances since they do not meet all the Appendix B requirements. By letter dated July 20, 1989, the licensee proposed revised wording for ACTION c.
l The revised wording extends the allowable cutage time for an ESW makeup pump 7 i
days if the deep well pump is operable, and 14 days for extended maintenance activities if the deep well pump is operable and one of the units is in Mode 5 or 6.
The licensee baseo these extended times on estimates of the times needed to perform various maintenance activities. We find that, for these i
limited times, the deep wells can be used as a replacement for the ESW makeup l
pumps. We, therefore, conclude that the revised ACTION c. proposed in the July 20, 1989 letter is acceptable.
ACTIONS e. (1) and (3) required that both units be shut down in the event of low Rock River level or flow. As previously mentioned, this shutdown requirement is ro longer necessary now that the deep wells have been seismically qualified. The requirement to notify the NRC of contingencies to
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. ensure adequate cooling water is also unnecessary since this cooling water rm.
now be supplied by the deep wells. ACTION e.(3) has been located in ACT10N g.
Thus, we find the deletion of ACTION e. acceptable.
ACTION f. has been split into three ACTIONS: f, g, and h.
They are the actions that need to be taken in the event that the ESW make-up pumps cannot supply water and the deep wells will be used instead. The actions require that the UHS cooling tower basin levels be at least 82%. The 82% is based on a conservative, worst-case analysis which shows that there is sufficient time to manually initiate deep well make-up to the UHS. We find this acceptable.
The three actions f, g, and h also state that the provisions of TS 3.0.4 are not applicable. TS 3.0.4 prohibits changing operational modes unless the particular LCO is satisfied without relying on the ACTION statements. Since we find that the deep wells will provide sufficient level of protection in these limited instances to permit mode changes, we conclude that the inapplicability of TS 3.0.4 is acceptable.
The proposed ACTION h. stated that, with a tornado watch and one deep well pump inoperable, both deep well pumps had to be restored to OPERABLE status within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />.
(This requirement also existed in the original TS ACTION f).
During a July 31, 1989 teleconference, we told the licensee that this action should be revised. Since a tornado watch would probably not last for 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />, the ACTION statement is effectively of no use.
In response to our concern, the licensee submitted a revised ACTION h. by letter dated August 1,1989.
Also included in this letter is the Byron Operating Abnormal procedure that contains the specific actions that would be taken if a tornado were to make the ESW make-up pumps inoperable coincident with the deep well pumps failure to start. We find the revised ACTION h. acceptable.
l The licensee proposed to eliminate surveillance f., which had required that the deep well pumps be run immediately prior to declaring them operable. This prectice is not consistent with any of the other requirements in the TS.
Furthermore, the monthly surveillance will be revised to require the recording of pump amps. Trending these readings should allow early detection of pump degradation. Thus, we conclude that the deletion of Surveillance f is acceptable.
l Lastly, the licensee has proposed changes to Bases Section 3/4.7.5 to reflect some of the changes made to TS 3/4.7.5. We have changed the licensee's proposal to limit the use of the deep wells to the three aforementioned instances. With i
l this change, the bases are now acceptable.
4.0 ENVIR0lWENTAL CONSIDERATION These amendments involve a change in the installation or use of the facilities components located within the restricted areas as defined in 10 CFR Part 20.
The staff has determined that these 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 individual
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issued a proposed finding that these amende.ents involve no significant hazards 1
consideration and there has been no public comnent on such finding. Accordingly, these amendments meet the eligibility criteria for categorical exclusion set l
forth in 10 CFR 51.22(c)(9). Pursuant to 10 CFR 51.22(b) no environmental I
impact statement or environmental assessnent need be prepared in connection with l
the issuance of.these pnendments.
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5.0 CONCLUSION
We have concluded, based on the considerations discussed above, that: (1) there is reasonable at,surance that the health and safety of the public will not be endangered by operation il the proposed manner, and (2) such activities will be conducted in compliarce with the Commission's regulations and the issuance of these anendments will not be inimical to the common defense and security or to the health and safety of the public.
6.0 Princips1 Contributor: Leonard N. 01shan Dated: August 15, 1989
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