ML20008E200
| ML20008E200 | |
| Person / Time | |
|---|---|
| Site: | Maine Yankee |
| Issue date: | 10/17/1980 |
| From: | Groce R Maine Yankee |
| To: | Clark R Office of Nuclear Reactor Regulation |
| References | |
| TASK-2.E.1.2, TASK-TM WMY-80-141, NUDOCS 8010240393 | |
| Download: ML20008E200 (4) | |
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ENGINEERING OFFICE WESTBORO, M ASSACHUSETTS 01581 3,
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617-36G-9011 m ym $
B.3.2.1 kHY 80-141 October 17, 1980 nited Scates Nuclear Regulatory Commission Washington, DC 20555 Attention: Office cf Nuclear Reactor Regulation Division of Licensing Mr. Robert A. Clark, Chief Operating Reactors Branch 3
References:
(a) License No. DPR-36 (Docket No. 50-309)
(b) USNRC Letter to MYAPC dated March 27, 1980 (c) USNRC Letter to All Operating Nuclear Power Plants dated October 30, 1979 (d) MYAPC Letter to USNRC dated July 25, 1980 (WMY 80-116)
(e) MY APC Letter to USNRC dated April 14, 1980 (WMY 80-65)
Subject:
Safety Grade Automatic Initiation of Auxiliary Feedwater System (AFWS)
Dear Sir:
This letter is written to provide design information ( Attachment I) relative to upgrading the automatic AFWS initiation circuitry from control to safety grade, as detailed in your letters, References (b) and (c).
In our letter, Reference (d), we requested the staff grant Maine Yankee a six month delay on the safety grade installation. Your staff prefers to reserve judgement on our request as a result of schedule changes which are possible in a forthcoming NRC clarification letter.
However, Maine Yankee believes at this time, it is prudent to proceed with the installation as originally committed in our letter, Reference (e).
As a result of the circumstances described above, we trust your staff can appreciate the cause for delay in this submittal. Since your letter, Reference (b), requires NRC review prior to implementation, we urge your staff to expedite the necessary review actions.
We trust this information is satisfactory; however, if you have any questions, please do not hesitate to contact us.
Very truly yours, MAINE YANKEE ATOMIC POWER COMPANY h
Robert H. Groce Senior Engineer - Licensing M 20240 K'3
Enclosures:
Attachment I Drawing A h
Pg. 1 of 2 N
,1 Attachnent I Automatic Initiation of the Auxiliary Feedwater System - Safety Grade REFERENCES l
(a) NUREGc0578, Issued July 1979
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(b) NRC letter, dated September 12, 1979, " Follow-up Actions Resulting from tne NRC Staff Reviews Rcgarding the Three Mile Island Unit 2 Accident" (c) Lettc", Maine Yankee to the NRC, WMY 80-65 dated April 14, 1980 (d) Lette., Maine Yankee to the NRC, WMY 80-19 dated February 1,1980 REASON FOR CHANGE During the incident at the Three Mile Island (TMI) plant, the auxiliary feedwater system (AFWS) was unavailable for use due to operator error. The NRC has determined, as a result of their evaluation of the incident, that
" consistent with preventing the steam generators from drying out following loss of main feedwater and minimizing operator errors that could delay the timely initiation of the auxiliary feedwater system in a PWR plant the AFWS snould be automatically initiated" [ Reference (A)]. Therefore, recent Yankee meetings on the TMI incident have resulted in a commitment [ Reference (c)] to install safety Rrade equipment to automate the AFWS at Maine Yankee.
DESCRIPTION OF CHANGE The change will automatically start the two electric driven auxiliary feedwater pumps on a low water level in any one steam generator. The low water level signal will be generated by new Acromag bistables installed as part of the loo 9s of steam generator water level channels LIA-1213A-D,
~LIA-1223A-D, and LIA-1233A-D. These units will provide the relays needed to form the 2/2 logic shown on Drawing A.
The setpoint for these bistables will be the same as the present RPS reactor trip on low S.G. level.
The time delay will remain as was installed in the control grade change as described in [ Reference (d)]. This will be removed when the automatic isolation of t eedwater (main and auxiliary) change is installed.
All other features (annunciators, bypass and test switches) will remain as described in Reference (u).
DESIGN CRITERIA This safety grade change assures that no interaction with the protectise channels will degrade the protective systems. Also, the NRC criteria stated in [ Reference (a)] and listed below were employed:
1.
The design shall provide for the automatic initiation of the auxiliary feedwater system.
2.
The automatic initiation signals and circuits shall be designed so that a
Pg. 2 cf 2
, *g cinglo failura will not r3sult in tha loss of tuxilicry fs dwatsr systcm function.
e 3
Testability of the initiating signals and circuits shall be a feature of the design.
4.
The initiating signals and circuits shall be powered from the emergency buses.
5 Manual capability to initiate the auxiliary feedwater system from the l
control room shall be retained and shall be implemented so that a single y
failure in the manual circuits will not result in the loss of system function.
6.
The a-c motor driven pumps and valves in the auxiliary feedwater system shall be included in the automatic actuation (simultaneous and/or sequential) of the loads to the emergency buses.
7 The automatic initiating signals and circuits shall be designed so that their failure will not result in the loss of manual capability to initiate the AFWS from the control room.
Also, the capability for manual override for individual AFWS pumps will be retained so that the operators may override when parameters indicate the AFWS is no longer needed.
Tne auxiliary feedwater system is a safety system.
This change will add a safety grade automatic start logic circuit to replace the present control grade initiation of the motor driven auxiliary feedwater pumps. A failure of this safety grade system will not prevent the AFWS from l
operating manually.
In the light of the above discussion and the analysis by NSD [ Reference (d)],
l the proposed modification does not increase the probability of occurrence of a previously evaluated accident, create the possibility of a new type of l
accident, or reduce the margin of safety as defined in the basis of any Technical Specifications.
l Therefore, the proposed modification does not create an unreviewed safety l
l question as defined in 10CRF59 59(a)(2).
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