ML19269C801
| ML19269C801 | |
| Person / Time | |
|---|---|
| Site: | Pilgrim |
| Issue date: | 02/01/1979 |
| From: | Andognini G BOSTON EDISON CO. |
| To: | Ippolito T Office of Nuclear Reactor Regulation |
| References | |
| 79-31, NUDOCS 7902120205 | |
| Download: ML19269C801 (4) | |
Text
..
BODTON EDISON COMPANY GENERAL OFFICES 800 BOYLsTON STREET BosTom. M AssacNust? Ta 0 2199 pgg7gg7y 1, yg7g BECo. Ltr. #79-31 G. CARL ANDOGNINI MANAGER NUCLEAR OPERATIONS DEPARTMENT Mr. Thomas A. Ippolito, Chief Operating Reactors Branch #3 Division of Operating Reactors Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission Washington, D. C.
20555 License No. DPR-35 Docket No. 50-293 Fire Protection
Dear Sir:
This letter and its attachment advise you of the results of the analysis required to be completed per Table 3.2 of the Safety Evaluation supporting Amen;fment No. 35 to our operating license.
If you have any further questions on this subject, please contact us at your convenience.
Very truly yours, l
l wrTV,)
(
a
~
r
- lsd attachment 7902120205
ATTACHMENT Response to:
SER Section 3.2.7, Incomplete Items.
3.2.7 DC Power System Hazard Analysis The licensee will analyze the effects of postulated fire damage and provide modifications as necessary to the 125/250 volt DC systems to preserve the plant's safe shutdown capability.
The analysis will include the considerations outlined in Section 3.2.1 cf this report.
BECo Response The 125/250 VDC power systems are divided into safety divisions A & B which provide DC power and control to conventional station emergency loads and selected safeguard loads.
The DC systems are shown on figure 8.0-9, section 8 of the FSAR.
Section 8.4 of the FSAR describes the power feeds for the DC battery chcrgers.
The batteries provide all DC power upon loss of off-site powr.r and have adequate capacity for 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> before they are recharged through bat'.ery chargers.
125 VDC Fower System A DC power system A consists of 125V DC battery A,125V DC battery charger, 125V DC control bus and distribution panels.
125V DC control bus A (D16) is fed fron battery A and 480V load center BI through 480V MCC B15 and battery charger A.
The backup battery charger to the control bus is fed from 480V load center B6 through 480V MCC B10.
(Both B10 and B6 are on swing bus X).
The control bus feeds 125V DC distribution panel A (D4), 125V DC MCC D7 and through automatic transfer switches to distribution panel C (Swing bus X).
Page 1 of 3
125/250 VDC System B Safety division B DC power system consists of 125V DC as well as 250V DC systems to accommodate certain large conventional DC emergency loads.
Tha 250V DC system consists of a 250V DC battery, 250V DC normal charger, backup charger and distribution panels. 125V DC System B has 125V DC battery B, battery charger, backup charger and distribution panels.
125V DC control bus B (D17) is fed from battery B and 480V load center B2 through 480V MCC B14 and battery charger B.
The backup battery charger to the control bus is fed from 480V load center B6 through 480V MCC B10 (B10 &
B6 are on swing bus X).
The control bus D feeds 125V DC MCC D8, and through automatic transfer switches to distribution panel C (Swing bus X).
250V DC power bus is fed from 250V DC battery and 480V load center B2 through 480V MCC B14 and normal battery charger.
It is also fed from 480V load center B6 through 480V MCC B10 and 250V DC backup battery charger.
The 250V DC power bus feeds power directly to conventional station emergency loads with include the vital MG set.
Cables and components of A and B DC power systems are separated by a combination of space, fire barriers, concrete walls, or floors to maintain maximum separation in all plant areas except the fire area 1.10 (West CRD area) at el. 23'-0" in the Reactor Building.
This area contains Division A, (D7) and Division B (D8 & D9)
MCCS.
An analysis was performed postulating a fire in fire area 1.10 and the effect on safe shutdown capability was evaluated.
The loss of DC power and associated loads from MCC D7, D8 & D9 will result in the loes of HPCI, RCIC and shutdown cooling mode of the RHR system along with the diesel generator standby fuel oil booster pumps A & B.
The diesel day tanks have sufficient capacity for 8 hour9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> operation. Availability of offsite power was assumed at the end of 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />. The ability to safely shutdown the plant would not be jeopardized as the following systems Page 2 of 3
4 would be available to support a safe shutdown. These systems include the Automatic blowdown system, either of the two core spray pumps, the torus water cooling mode of the RHR system, the LPCI mode of the RHR System and the control rod drive water pumps A & B.
Assumption A fire is postulated along with loss of offsite power for the first 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> when the plant would be brought to a hot shutdown mode. Availability of offsite power is assumed at the end of 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> to bring the plant to cold shutdown in 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />.
Page 3 of 3