ML19329C224
| ML19329C224 | |
| Person / Time | |
|---|---|
| Site: | Davis Besse  |
| Issue date: | 11/08/1976 |
| From: | Roe L TOLEDO EDISON CO. |
| To: | Rusche B Office of Nuclear Reactor Regulation |
| References | |
| 145, NUDOCS 8002120944 | |
| Download: ML19329C224 (4) | |
Text
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u.s. NUCLE 4m mEcutArr.y Cr-"uiss CN DOCKET NUMIE51 NRC eO u 195 50-346 is.tes, NRC DISTRIBUTION POa PART 50 DOCKET MATERIAL TO:B.C. RUSCHE FROM: IOLEDO EDISON DATE OF DOCUMENT TOLEDO.0FIO 11-8-76 L.E. ROE DATE nECEivED 11-12-76 OLETTEm C NCTORIZE D PROP INPUT FORM NUM8ER OF COPlES RFCEIVED
@m4GINAL D UNC LASSIFIE D OC&v 1
DESCT PTION ENCLOSU M LTR. RE. THEIR 5-17-76 LTR..TRANS THE FOLLOW REVISED RESPONSE TO REQUEST FOR ADDITIONAL ING......
INFCRMATION #7C, CONCERNING THE ECCS ANALYSIS.
(1 SIGNED CY. RECEIVED)
( 3 PAGES)
ACKNOWLEDGED DONCT mn
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PLANT NAME: DAVIS BESSE
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Mr. Benard C. Rusche, Director
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Dear Mr. Rusche:
Enclosed is a revised response to Request for Additional Information-Number 7c, which was transmitted to you in a letter dated May 17,- 1976 ,
concerning the ECCS analysis for Davis-Besse, Unit 1.
This revised response has been discussed with your review staff.
Yours very truly, wr pc/29-35 11565 THE TCLEDO EDISCN COMPANY ECISON PLAZA 300 MAOl5CN AVENUE TCLECO, OHIO 43652
D-B Discuss common power supply problems and the procedure to restore a 7c.
loss of power to essential valves. Also, address possible access problems due_to high doses should such a power loss occur after the 4
shift to the recirculation mode.
RESPONSE
There are four valves that the operator would open in order to provide
.the flow paths for the boron dilution modes of operation, as listed below:
Valve MCC Line Valve Channel MCC Location Location Auxiliary pressuri-HV 2735 1
EllB Inside con-El. 585' outside tainment mechanical penetration zer spray room No. 303 Auxiliary pressuri-HV 2736 2
Fila Dutside con-El. 603' in electrical tainment penetration room No. 427 zer spray Decay heat suction HV DH 11 2
F11A Inside con-El. 503' in electrical tainment penerration room No. 427 Decay heat suction HV DH 12 1
EllB Inside con-El. 585' outside mechanical tainment penetration room No. 303 The power. supply failures postulated were: control cable or power failure to a single valve, a diesel or 4KV bus f ailure, a failure of one of the above mentioned MCCs or unit substation.
Should a control cable or power cable to one of the above valves fail, the alternate path would not be affected. Boron dilution flow is, therefore, assured with no further action required.
Should a f ailure of MCC E11B or MCC Fila occur, it would be necessary to pro-vide power to at least onc of the affected two valves from the unaffected A spare magnetic or manual reversing motor start which are available source.'
from stock, and temporary cables would be required.
The temporary cables would be used to connect the unit substation breaker to the motor starter and from the motor starter to the affected MCC.
The power leads of the cable feeding the valve motor would be disconnected at the MCC_end and connected to the new temporary cable. This operation is anticipated to take no more than one hour. The valve will be opened The opening will be confirmed by valve with this new temporary power.
position indication.
1 D-B Using conservative assumptions based on the TID-14844 LOCA source term parameters, the dose rate has been calculated to be in the range of 5-10 2/hr during the 7-day period following the LOCA at both MCC EllB and 2.5 to 5 R/hr at MCC Fila, principally due to the radiation source from the containment spray system at MCC EllB and 250 mr/hr to 500 mr/hr at MCC Fila during the recirculation mode of operation from the containment A myre realistic estimate, based on gap activity, would emergency sump.
be a factor of appros_imately 10 lower, i.e., 500 mr/hr to 1 R/hr at MCC E113 and 250 mr/hr to 500 mr/hr at MCC Fila. This dose rate should not preclude the work as outlined above.
It is probable that, even given the situation of the power failures discussed above, at least one flow path can be established within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />. An early assessment of the nature of the failure would be expected since the operators would attempt to accomplish the boron dilution modes in a short period of time after the LOCA, well within a 24-hour period. A flow path can definitely be established within the 7 days required as per the B&W analysis.
pc 29/35-37