ML20205T612
| ML20205T612 | |
| Person / Time | |
|---|---|
| Site: | Maine Yankee |
| Issue date: | 06/10/1986 |
| From: | Whittier G Maine Yankee |
| To: | Thadani A Office of Nuclear Reactor Regulation |
| References | |
| 7664L-GDW, GDW-86-142, MN-86-78, NUDOCS 8606160100 | |
| Download: ML20205T612 (2) | |
Text
i MAME HARHEE ATOMICPOWERCOMPARSe
,uaugr,Q,in"g@a's (207) 623-3521 June 10, 1986 O
HN-86-78 GDH-86-142 Director of Nuclear Reactor Regulation United States Nuclear Regulatory Commission Washington, D. C.
20555 Attention:
Mr. Ashok C. Thadani, Director PHR Project Directorate #8 Division of Licensing
References:
(a)
License No. DPR-36 (Docket No. 50-309)
(b) USNRC Letter to HYAPC0 dated March 24, 1983
Subject:
DHST Level Indication and Alarms Gentlemen:
Members of the NRC staff have requested Maine Yankee Atomic Power Company to backfit the Maine Yankee plant to provide redundant demineralized water storage tank (DHST) level indication and alarms in the control room. He understand that the staff is concerned that the tank might empty during accident conditions, resulting in damage to the Emergency Feedwater Pumps.
The existing plant design already provides multiple level indications and alarms for the DHST.
Two level indicators are provided, one on the main control board, and one local at the tank.
The control board level indicator and its transmitter are powered from an ac distribution panel, which is capable of being fed from either emergency bus through a manual transfer switch.
The local level indication consists of a tank mounted pressure-type gauge which is regularly monitored and is independent of the remote t ransmi tter.
Two level alarms are provided at the main control board annunciator, one indicating minimum operating level, and the other indicating low-low level.
Both alarms are independent of the level transmitter.
The set point for the minimum operating leve! alarm is 100,000 gallons which provides a minimum of six hours of emergency feedwater supply.
The setpoint for the low-low level alarm is 10,000 gallons which represents more than an hours worth of additional supply.
Each alarm is actuated by an individual level switch.
The annunciator itself is powered from a dc distribution panel which is fed from a Class lE battery.
During power operation, the DHST is a stable reserve of emergency feedwater which is not used for other operational needs and, therefore, is not subject to frequent or rapid changes in inventory. Normally approximately 120,000 gallons of water are maintained in the tank.
$000 7664L-GDH 8606160100 860610 DR ADOCK 05000309 hD p
9 MAIME VANKEE AVOMIC POWER COMPANY United States Nuclear Regulatory Commission Page Two Attention: Mr. Ashock C. Thadani, Director HN-86-78 The multiple instruments and power supplies providing DHST level information make the total loss of level indication highly unlikely.
Furthermore, the parameter being monitored has a very slow rate of change.
He believe the existing design is adequate to ensure that the DHST would not empty and result in damage to the EFH pumps during accident conditions.
Nevertheless, in order to be more responsive to staff concerns, we propose to backfit the Maine Yankee plant to provide for an additional alarm in the control room at approximately 15,000 gallons in the DHST.
This alarm would use a different sensor and power supply than the existing alarms.
This would assure that in the event of a single failure, there would be at least one alarm in the control room indicating 10,000 or 15,000 gallons in the DHST.
Reference (b) stated that separate Class lE power supplies to the existing 100,000 gallon alarm and the 10,000 gallon alarm would be adequate to resolve the staff's concerns in this matter. He believe the suggested modification meets the intent of the staff recommendation and should, therefore, resolve their concerns in this matter.
Maine Yankee believes that the addition of an additional level instrument on the main control board is not necessary to be responsive to the staff's concern stated above. He also believe that the addition of the instrument could have an adverse impact on public health and safety since unnecessary and excessive displays on the main control board are contrary to good human factors practices.
He, therefore, request that you reconsider the necessity for an additional DHST level instrument, since the additional instrument is not necessary to address the NRC's concerns and a requirement for an additional DHST level instrument would constitute a backfit pursuant to 10 CFR 50.109.
He believe our proposed modifications should resolve the staff's concerns and, therefore, be acceptable. He would be pleased to meet with you to discuss this matter further if you should have any questions.
Very truly yours, MAINE YANKEE ATOMIC POWER COMPANY AbW G. D. Whittier, Manager Nuclear Engineering and Licensing GDH/bjp cc: Mr. Ashok C. Thadani
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Dr. Thomas E. Murley Mr. Pat Sears Mr. Cornelius F. Holden 7664L-GDH
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