ML20058B165
| ML20058B165 | |
| Person / Time | |
|---|---|
| Site: | Davis Besse  |
| Issue date: | 11/22/1993 |
| From: | Storz L CENTERIOR ENERGY |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| 2181, TAC-M84912, NUDOCS 9312010427 | |
| Download: ML20058B165 (4) | |
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6 CENTERIOR 4
ENERGY r
300 Madison Avenue Louis F. Sforz Toledo. OH 43652-0001 Vice President-Nuclear 419-249-2300 Davis-Besse Docket Number 50-346 License Number NPF-3 Serial Number 2181 November 22, 1993 United States Nuclear Regulatory Commission Document Control Desk Vashington, DC 20555 Subj ec t :
Supplemental Information for License Amendment Request to Revise Technical Specification (TS) 3/4.5.2, Emergency Core Cooling Systems, TS Bases 3/4.5.2 and 3/4.5.3, Emergency Core Cooling Systems, and TS Bases 3/4.6.2.1, Containment Spray System Gentlemen:
Toledo Edison submitted an application (TE Serial No. 2084) on November 9, 1992, for an amendment to the Davis-Besse Nuclear Power Station (DBNPS), Unit Number 1, Operating License Number NPF-3, Appendix A Technical Specifications (TS). This application requested revision of TS 3/4.5.2, Emergency Core Cooling Systems - ECCS Subsystems
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> 280"F; TS Bases 3/4.5.2 and 3/4.5.3, Emergency Core Cooling SysT Ns - ECCS Subsystems; and TS Bases 3/4.6.2.1, containment Systems -
Depressurization and Cooling Systems - Containment Spray System, to reflect the proposed de-energization of the Borated Vater Storage Tank (BVST) outlet isolation Valves DH-7A and DH-7B in their open position, during operational Modes 1, 2, 3, and 4.
On September 2, 1993, a conference call was held with the NRC Staff during which three questions were posed by the NRC Staff regarding the subject License Amendment Request (Number 91-0002). Toledo Edison informally responded to these questions on September 13, 1993. This 4
letter (see attachment) formally submits the responses per the NRC Staff's request.
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' License Number NPF-3 Serial Number 2181 Page 2 Should you have any questions.or require additional information, please contact Mr. Villiam T. O'Connor, Manager - Regulatory Affairs, at (419) 249-2366.
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Attachment J. B. Hopkins, NRC Senior Project Manager
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J. B. Martin, Regional Administrator, NRC Region III S. Stasek, DB-1 NRC Senior Resident Inspector j
J. R. Villiams, Chief of Staff, Ohio Emergency Management Agency, State of Ohio (NRC Liaison)
Utility Radiological Safety Board r
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e Docket Number 50-346 License Number NPF-3 Serial Number 2181 4
Page 1 Supplemental Information for License Amendment Request Number 91-0002 NRC Ouestion 1:
If the proposed license amendment were implemented, hov 4
would the Individual Plant Examination (IPE) Core Damage Frequency (CDF) be affected?
TE Response to Question 1:
An assessment was made of the impact the proposed de-energization of valves DH-7A and B in the open position during Operational Modes 1 through 4 would have on the overall DBNPS CDF.
Per the DBNPS IPE, Loss of Coolant Accidents (LOCAs) are not dominant contributors to core-damage for DBNPS.
As depicted in Table 4-1 (Part 3, Section 4) and Figure 4-1 (Part 1) of the DBNPS IPE submittal (TE Serial No. 2119 dated February 26, 1993, TAC M74402), LOCAs comprise less than ten percent of the overall CDF. While operator actions are important contributors to the risk associated with LOCAs, equally important are common cause failures and individual component failures.
If valves DH-7A and B are de-energized in the open position, additional operator actions would be necessary to facilitate recirculation of the inventory from the containment emergency sump following a LOCA. The additional actions vould be similar to those currently in place for containment emergency-sump valves DH-9A and B.
The operator responsible for locally closing the breakers for valves DH-9A and B vould also close those for valves DH-7A and B.
Valves DH-7A and B are interlocked with valves DH-9A and B, precluding the simultaneous opening of one or both sets of valves which could cause draining of the Borated Water Storage Tank to the Containment Emergency Sump.
Once the breakers are closed, the interlock between the valves would be functional.
Consequently, when valves DH-9A and B are opened via the control room handsvitch, the interlock would close valves DH-7A and B.
To assess the impact of this proposed change on the CDF, the operator actions associated with going to recirculation were revised to account for closing the breakers for valves DH-7A and B.
All operator actions associated with going to recirculation following a LOCA vere modified. The results showed only a slight increase in overall CDF (approximately one-half percent).
NRC Ouestion 2:
Did Toledo Edison consider various alternatives to de-energizing valves DH-7A and B, such as adding fire barriers?
TE Response to Question 2:
Presently, with valves DH-7A and B not depovered, 10 CFR 50 Appendix R compliance is achieved via the use of manual operator action to trip the appropriate breaker and open the respective valve in the event that a fire would spuriously close one of the valves.
4 Docket Number 50-346 License Number NPF-3 Berial Number 2181
-Attachment.1 Page 2 To achieve compliance with Appendix R in a way other than desettibed above or that proposed in the License Amendment Request would be costly, complicated and not likely to fully protect the circuits for all scenarios. Tnis is similar to the situation that was discussed with the NRC for valves DH-9A and DH-9D in 1989 (
Reference:
TE 9erial 1744, dated January 11, 1990).
Listed below are some of the reasons why adding a fire barrier would not be a practical means of achieving compliance:
Since the length of the circuitry is extensive, the initia) installation
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cost of a barrier and long term inspection and maintenance costs are expected to be significant.
Portions of the circuits terminate in places that can not be wrapped, if-the capability of performing other plant functions is to be preserved.
For example, access to motor control centers is required for operation of the breakers and the maintenance of the breakern. Another_ example is the main control panel in the Control Room, where the switches to operate the valves and the indicating lights to determine the valves position are located. Vrapping these items would result in the loss of function of the i
devices.
At the present time the availability of acceptable fire barrier materials is under NRC and industry review.
NRC Question 3:
Vill operators be trained and the necessary procedures revised prior to implementation of the license amendment?
i TE Response to Question 3:
'I As a matter of standard practice, the necessary procedure changes vill be effective concurrent with or prior to implementation of the license amendment.
In addition, appropriate operator training vill'be provided prior to implementation of the license amendment, t
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