ML20137Q282
| ML20137Q282 | |
| Person / Time | |
|---|---|
| Site: | Beaver Valley |
| Issue date: | 09/13/1985 |
| From: | Carey J DUQUESNE LIGHT CO. |
| To: | Knighton G Office of Nuclear Reactor Regulation |
| References | |
| 2NRC-5-133, TAC-62874, NUDOCS 8509200106 | |
| Download: ML20137Q282 (5) | |
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Nuclear Construction Division Telecopy (412) 787 2629 Robinson Ptaza. Building 2. Suite 210 Pittsburgh. PA 15205 September 13, 1985 United States Nuclear Regulatory Commission Washington, DC 20555 ATTENTION:
Mr. George W. Knighton, Chief Licensing Branch 3 Office of Nuclear Reactor Regulation
SUBJECT:
Beaver Valley Power Station - Unit No. 2 Docket No. 50-412 Request for Additional Infonnation - Post-Fire Safe Shutdown Capability
REFERENCES:
- 1. NRC letter to OLC, dated June 18, 1985
- 2. 2NRC-5-ll6, August 7,1985 Gentlemen:
Enclosed are responses to the two requests for additional infonnation concerning post-fire safe shutdown capability contained in your letter dated June 18, 1985.
Your letter also indicated that Duquesne Light Company (DLC) was to provide supplemental information concerning safe shutdown and al t er-nate shutdowl by the end of June 1985.
DLC is not aware of any conmitnent that has been nade to supply this infonnation by the end of June i985.
OLC's schedule for coupleting the spurious signal analysis, which will resolve the open iten associated witn alternate and safe shutdown capability, is August 1986.
If the NRC requires this infonnation earlier to support a licensing milestone, please notify E. T. Eilmann of my staff at (412) 787-5141.
The analysis discussed in the response to Iten 2 of your letter is still in progress.
A supplement to this response-will be submitted at the completion of this analysis.
DUQUESNE LIGHT COMPANY SUBSCRIBEDANDSy0RNTOBEFOREMETHIS A8 DAY OF J/nhMw),1985.
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By _ f SHu s rm otary Public
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ETE/wjs Enclosures cc:
Mr. B. K. Singh, Project Manager (w/e)
Mr. G. Walton, NRC Resident Inspector (w/e) 8509200106 850913
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e Unitee' States Nuclear Regulatory Comission Mr. George W. Knighton, Chief Request for Additional Information -
Post-Fire Safety Shutdown Capability Page 2 C0tHONWEALTH OF PENNSYLV NIA )
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On this
/j,dday of o/7JAdu), /f,f[, before me, a Notary Public in and for said Commonwealth and County, personally appeared J. J. Ca rey, who being duly sworn, deposed and said that (1) he is Vice President of Duquesne Light, (2) he is duly authorized to e(ecute ad file the foregoing Submittal on behalf of said Company, and (3) the state:nents set forth in the Submittal are true and correct to the best of his knowledge.
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Notary Public SMillA u. FATToef. NOTARY PutlIC
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i RESPONSE TO ASB REQUEST FOR ADDITIONAL INFORMATION C01CERNING POST-FIRE SAFE SHUTDOWN QUESTION 1:
A recent plant inspection at another facility revealeJ that for a fire in the control roon, isolation transfer switches for certain hot shut-down systens/conponents had to be switched to the alternate or isolated position prior to damage occurring to these circuits.
If this were not accomplished in time, fuses would have to De replaced in order to make safe shutdown system / component operable.
This situation existed because the transfer switches did not place new/ redundant fuses into tne control power circuit, but lef t the existing (assu.ned blown) set of fuses in the circuit. For most of the transfer switches, the situation did not cause a proulem since the desired effect af ter isolation was the de-energiza-tion of power.
In other instances where the systen/conponent had to be operable or where operation might be required to override a spurious actuation (such as a motor operated valve) replacenent of fuses would be required if blown.
Althaugh the present isolation switches at Beaver Valley Unit 2 do isolate the required equipnent or component fron the control roon, it has not been demonstrated that it is unnecessary to replace fuses in order to place the equipinent/conponent in the desired mode of operation or position.
In order for us to conduct a review to detennine if fuse replacement is necessary for the oeration of a safety systen af ter a control roon fire, please provide the following:
a.
The results of your review of electrical design drawings for the existing isolation transfer switches to detennine where and if this situation exists, b.
If tha Seaver Valley Unit 2 design necessitates the changing of fuses ta achieve an1 naintain hot shutdown after a control roon fire, provide audifications to existing switches and/or install new isolation switches where necessary to provide redundant fusing such that a blown fuse will not require replacenent to achieve and main-tain hot shutdown.
R_esponse:
There are no plant operational requirenents to replace blown fuses for the 3VPS-2 transfer of control power fron the main control roon to the alternate shatdown panel ( ASP) room in the event of any single exposure fire in any BVPS-2 fire area.
As depicted in Figure A5-12 of the Fire Protection Evaluation Report (FPER), two fuses are provided for the protection of each 480V l oad that requires a motor starter and is controlled by either the ASP and/or the main control roon.
One fuse protects the leg of the circuit that has control cable routings to the main control room and its controls; the other fuse protects the leg of the ASP control circuit that allows independent transfer to the ASP.
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this manner, no single exposure fire postulated in any fit e area, e.g.,
main control roon, fire areas that adjoin main control roon to ASP, and ASP roon, etc., would disable the otaer pr.)tected leg.
An explanation of the above is being added to Section 3.3.2 of the FPER to eliminate any further concerns, i
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RESPONSE TO ASB REQUEST FOR ADDITIONAL INFORMATION CONCERNING POST-FIRE SAFE SHUTDOWN QUESTION 2:
We have a concern regarding the patMtlal for multi-high impedance f aults in AC power circuits which could result in the loss of power to safe shutdown equipment.
Figure 1 contains a sketch of circuit designs which could result in the loss of needed power to safe stiatdowri equip-ment.
As can be seen in Figure 1, redundant divisions of safe shutdown cables are properly separated in accordance with Appendix R criteria.
However, a fire in fire area A would result in loss of Division A safe shutdown equipment and cause damage to nonsafe shutdown cables associ-aled WIth th9 Division A bus.
Further, the individual fault current resulting froa the fire damage in the nonsafe shutdown cables may not be enough to trip the individual breakers (81 and Bg), but the sum of the f aults may be sufficient to trip the main breaker (8 ).
If this were to 3
occur, the Division B bus and the corresponding redundant Division B safe shutdown would be lost.
You must shon that multi-high impedance f aults in AC power circuits resulting fron a single fire c.annot result in the loss of function of any safety-related systen as outlined above.
R,esponse:
e The plant electrical systens will be reviewed by means of a circuit breaker coordination study to verify that faults (both high or low impedance) within the electrical systen are cleared properly.
As described in Section 3.1.5 to the FPER, circuit breaker coordination studies have been performed on all 4,160 V ac and 480 V ac power switch-gear (unit substations) which provide power to the.r respective safe shutdown circuits. The balance of the 480 V ac (motor control centers),
125 V de and 120 V ac systens will have coordination studies conpleted for safe shutdosi circuits.
DLC is presently investigating the spurious signal analysis Aich will be used in conjunction with the breaker coordination stuJies.
The results of these analyses will be submitted to the ASB upon their completion which is scheduled for August 1986.
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