ML20246N712
| ML20246N712 | |
| Person / Time | |
|---|---|
| Site: | Maine Yankee |
| Issue date: | 04/14/1989 |
| From: | Whittier G Maine Yankee |
| To: | Office of Nuclear Reactor Regulation |
| References | |
| GDW-89-142, MN-89-60, TAC-68563, NUDOCS 8905190511 | |
| Download: ML20246N712 (6) | |
Text
,
s-J MaineYankee RELIABLE ELECTRICITY FOR DAAINE SINCE 1972 j
EDISON DRIVE. AUGUSTA, MAINE 04330.(207) 622 4868 A
April 14, 1989 MN-89 GDH-89-142 Director of Nuclear Reactor Regulation United States Nuclear Regulatory Commission Washington, D. C.
20555 Attention:
Mr. Richard H. Hessman, Project Director I-3 Division of Reactor Projects I/II
References:
(a)- License No. DPR-36 (Docket No. 50-309)
Subject:
Generic Response to Station Bla'ckout Rule Gentlemen:
Maine Yankee has evaluated the plant against the requirements of the SB0 rule using guidance from NUMARC 87-00 except where RG 1.155 takes precedence.
The results of this evaluation are detailed below.
A.
ProDosed Station Blackout Duration NUMARC 87-00 Section 3 was used to determine a proposed SB0 duration of four hours.
The following plant factors were identified in determining the proposed station blackout duration.
1.
AC Power Design Characteristic Group is P2, based on:
a.
Expected frequency of grid-related LOOPS - does not etceed once per 20 years (Section 3.2.1, Part 1A, p. 3-3);
b.
Estimated frequency of LOOPS due to extremely severe weather places the' plant in ESH Group 3, (Section 3.2.1, Part IB, p.
3-4);
c.
Estimated frequency of LOOPS due to severe weather places the plant in SH Group 3, (Section 3.2.1, Part IC, p. 3-7);
d.
At Maine Yankee in the event of a loss of the normal ac power source, there is an automatic transfer of all safe shutdown buses to the preferred alternate power source.
If this source fails, one safe shutdown bus may be manually transferred to the remaining preferred power source.
The offsite power system is l
considered to be in the 11/2 Group, (Section 3.2.1, Part ID, p.
3-10).
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'2.
The emergency AC power configuration group is C based on:
(Section 3.2.2, Part 2C, p. 3-13).
a.
There are two emergency AC power supplies not credited as alternate AC power sources Section 3.2.2, Part 2A, p. 3-15);
b.
One emergency AC power supply is necessary to operate safe shutdown equipment following a loss of offsite power (Section 3.2.2, Part 28, p.3-15).
3.
The target EDG reliability is 0.975.
4.
An alternate AC (AAC) power source will be utilized at Maine Yankee which meets the criteria specified in Appendix B to NUMARC 87-00.
l The AAC power source is available within thirty minutes of the onset of the station blackout event and has sufficient capacity and-capability to operate systems necessary for coping with a station blackout for the required SB0 duration of foer hours to bring and maintain the plant in safe shutdown. An AC independent coping analysis was performed for the one hour (as established by NUMARC 87-00) required to bring the AAC power source on line.
AAC
Description:
Maine Yankee has previously installed an alternate l
AC power supply as a part of demonstrating Appendix R Safe Shutdown
}
capability.
The Appendix R alternate power supply consists of a 250 kW diesel generator and 480 V ac, 125 V de, and 120/240 V ac distribution system as shown on the attached figure.
All 480 V ac power for alternate shutdown equipment is supplied from 1
motor control center (MCC) 981 which also includes a 120/240 V at distribution panel.
Normally, power to MCC 9B1 is supplied by MCC
- 98. A breaker transfer arrangement is provided to allow the alternate power supply diesel generator, DG-2 to supply power as required.
All 125 V de power for alternate shutdown equipment is supplied by a separate battery, battery charger, and distribution panel.
Uninterruptible 120 V ac power for certain instrumentation is fed from the dc bus through an inverter. A static switch is provided to transfer the inverter loads to the 120 V ac distribution panel should the inverter fail.
DG-2 is a 250 kW, radiator air-cooled unit, capable of supplying, 1
with margin, all required post-fire and station blackout shutdown loads.
The diesel may be controlled from the alternate shutdown panel or locally. A 500-gallon fuel oil day tank feeds DG-2, with the capability to transfer oil from the underground fuel oil storage
{
tanks.
The DG-2 building is located adjacent to the auxiliary boiler i
room.
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Procedure Description Prior to the issuance of the staff's Station Blackcat rule, Maine Yankee had established, trained operators and implemented Abnormal Operating Procedures for response to severe weather conditions and a total loss of ac power.
These procedures have been reviewed to the guidelines in NUMARC 87-00, Section 4 for the following areas:
1.
AC power restoration per NUMARC 87-00, Section 4.2.2; 2.
Severe weather per NUMARC 87-00, Section 4.2.3.
3.
Station blackout response per NUMARC 87-00, Section 4.2.1; The existing procedures provide sufficient guidance in responding to a severe weather condition and a total loss of ac power. Certain changes to the severe weather and station blackout procedure can be made however, to further enhance these procedures as described below.
C.
Prooosed Modifications and Schedule There are no plant modifications required to utilize the AAC power source.
The AAC source has the capacity and capability to power the equipment necessary to cope with a station blackout in accordance with NUMARC 87-00, Section 7 for the required coping duration determined in accordance with NUMARC 87-00, Section 3.2.5.
1.
Condensate Inventory for Decay Heat Removal (Section 7.2.1).
It has been determined from Section 7.2.1 of NUMARC 87-00 that 60,000 gallons of water are required for decay heat removal for four hours.
The minimum permissible demineralized water storage tank level per technical specifications provides 100,000 gallons of water, which exceeds the required quantity for coping with a four hour station
- blackout, a.
No plant modifications or procedure changes are needed to utilize these water sources.
2.
Class lE Battery (ies) Capacity (Section 7.2.2)
Review of the existing battery capacity calculation verifies that the Class lE batteries have sufficient capacity to meet station blackout loads for one hour.
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Compressed Air (Section 7.2.3)
Air operated valves relied upon to cope with a station blackout for one hour can either be operated manually or have sufficient backup sources independent of the areferred and blacked out unit's Class 1E power supply. Valves requiring manual operation or that need backup sources for operation are identified in plant procedures.
4.
Effects of Loss of Ventilation (Section 7.2.4)
The assumption in NyMARC 87-00, Section 2.7.1, that the control room will cot exceed 120 F during a station blackout has been assessed using the methodology presented in NUMARC 87-00,,Section 7.2.4.
The control room at Maine Yankee does not exceed 120 F during a station blackout.
Therefore, the control room is not a dominant area of concern.
HVAC systems serving the control room are not available during station blackout.
HVAC systems serving the Main Steam and FH Valve area, (the steam driven AFH Pump Room), the dominant area of concern for Maine Yankee, are not available during station blackout.
The calculated steady state ambient air temperature for this area during a station blackout induced loss of ventilation is conservatively estimated to be 144*F.
The operability of station blackout response equipment in the steam driven AFH pump room has been assessed using Appendix F to NUMARC 87-00 and the Topical Report.
No modifications are required to provide reasonable assurance for equipment operability. However, to improve habitability for workers in the area should plant operators elect to operate the atmospheric steam dump valve, the Station Blackout procedure (A0P 2-90-1) will be modified by June 1, 1989 to require operators ventilate the room by opening access doors as conditions require.
In order to maintain ambient temperature in the protected switchgear l
room within 120*F, it will be necessary to block open the doors to that room within 30 minutes of the onset of a station blackout event. A0P 2-90-1 will also be revised by June 1,1989 accordingly.
5.
Containment Isolation (Section 7.2.5)
The plant list of containment isolation valves has been reviewed to verify that valves which must be capable of being closed or that must be operated (cycled) under station blackout conditions can be positioned (with indication) independent of the preferred and blacked-out unit's Class 1E power supplies.
The following procedure change is required to ensure appropriate containment integrity is provided under station blackout conditions.
Attachment A of APO 2-90-1 will be revised by June i,1989 to require that closure of the Containment Spray Pump Suction Valves (CS-M-91/92) be verified at the valve operators.
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Reactor Coolant Inventory (Section 2.5)
The AAC source powers the necessary make-up systems including an auxiliary charging pump for adequate reactor coolant system inventory to ensure that the core is cooled for the required coping duration.
He trust this information is satisfactory; however, if you have any questions, please contact us.
Very truly yours, MAINE YANKEE-f[X224 b
[<G.D.Whittier, Manager Nuclear Engineering and Licensing GDH:BJP c: Mr. Hilliam T. Russell Mr. Patrick H. Sears Mr. Cornelius F. Holden 0970L-GDH
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