ML19317F771
| ML19317F771 | |
| Person / Time | |
|---|---|
| Site: | Maine Yankee |
| Issue date: | 02/01/1980 |
| From: | Groce R Maine Yankee |
| To: | Eisenhut D Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML19317F772 | List: |
| References | |
| WMY-80-19, NUDOCS 8002070255 | |
| Download: ML19317F771 (3) | |
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ENGINEEn'NG OFFICE WESTBOnO, MASSACHUSETTS 01581 WMY 80-19617-366-9011
%:y rn O B.3.2.1 February 1, 1980 United States Nuclear Regulatory Commission Washington, D. C.
20555 Attention: Office of Nuclear Reactor Regulation Mr. Darrell G. Eisenhut, Acting Director Division of Operating Resctors
References:
(a) License No. DPR-36 (Docket No. 50-309)
(b) USNRC letter to HYAFC dated October 18, 1979 (c) USNRC letter to MYAPC dated September 11, 1979 (d) MYPAC letter to USNRC dated November 20, 1979 (WMV 79-138)
(e) MYPAC letter to USbRC date'd November 15,197if (WMY 79-133)
Subject:
Automatic Initiation of Auxiliary Feedwater Systo
Dear Sir:
This lettar i; written to provide supplementary design information of the automatic initiation of the aoxiliary Ludwater syste.m cent rol grade installation at Maine Yankee (Attachment I); hereupon addressing your requirements identified during the course of the NRR Bulletins and Orders Task Force review, Reference (b).
Your letter, Reference (c) required information regarding a possible steam generator vater hammer under the influencing automatic initiation of auxiliary feedwcter f.ow.
Experience gained at Yankee Rowe was utilized in the design of the Maine Yankea plant. As a result, the only water hammer event ever to occur in t.he Maine Yankee feedwater system was caused by rapid cycling of the feedwater regulating valve due to a loss of control air. There is.no reason te.txpect cdditional s ter hammer events as a result of automatic initiation cf eniif ery feedwater.
k% trust thio infornation is satisfactory; however, if you have any questions, please feel free to contact us at your coavenience.
Very truly yours, 11AINE YANKEE AYOMIC POWER COMPANY W$'$
Robert F. Groce Senior Engineer - Licensing RHG/ die-Attach s t 8002070 3 p
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ATTACHMENT 1 AUTOMATIC' INITIATION OF.THE AUXILIARY FEEDWATER SYSTEM - CONTROL GRADE REFERENCES-(a) NUREG 0578, Issued July 1979 (b) NRC Letter, dated September 13, 1979, " Followup Actions Resulting from the NRC Staff Reviews Regarding the Three Mile Island Unit 2 Accident."
(c) Letter, Maine Yankee. to the NRC, WMY 79-113, dated October 18, 1979 (d). Letter, Maine Yankee'to the NRC, WMY 80-4, dated January 9, 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 operatoc errors that could delay the timely initiation of the auxiliary feedwater system in a PWR plant the AFWS
-should be automatically initiated" (Reference (a)). Therefore, recent Yankee staff meetings on the TML incident have resulted in a conmitment (Ref. (c)) to install control grade' equipment to automate the AFWS at Maine Yankee. A safety grade system will be installed in 1981 when the design and procurement of safe'.y grade equipment has been completed.
DESCRIPTION OF CHANGE This change will automatically start the two electric driven auxiliary feedwater pumps on a delayed one-out-of-three logic signal from a low water level in an'y one steam generator. This delay will be set for 5 minutes as per Reference-(d). The low S.G. water level signals will be from the reactor regulating system (RRS) cabinets (UT1211X, Y, LT-1T11X, Y, and 1231X, Y).
The setpoint for this low water level signal will be the same as the present Reactor Protective System (RPS) low S.C. water level trip.
The installed system will be single failure proof with o'n-line testing capability which will be accomplished by the use of a test switch as shown on 11550-ESK-11AD. This system will also be designed to allow the operator to bypass a failed or inoperative train of the actuator logic provided that the other trair. is not in test. This will be done using a key lock switch with one key fitting the bypass switch of one train and the test logic of the other train.
The capability for manual override of this signal for individual AFWS pumps will be retained so that the operators may override when parameters indicate L
I the AFWS is'no longer needed.
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'Also,.an annunciator will be used to indicate an automatic AFWS start signal has.been generated when the pumps have-started, when the system is in test, or when.the. system has been bypassed.
.e Attachment l' 4
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DESIGN CRITERIA By deeign, this control grade change uses sound engineering judgenent and
. practice to assure;no interaction with protective channels. Also, the criteria stated;inLReference (a) and listed below were employ 1:
1.
The design shall provide for the automatic init.ation of the auxiliary
-feedwater system.
2.
The automatic initiation signals and circuits shall be designed so that a single failure will not result in the loss of auxiliary feedwater system function.-
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 control, room shall be retained and : hall be implemented so that a single 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.
The auxiliary.feedwater system is a safety system.
This change will add a control grade automatic start logic circuit to the present manual. initiation of the moter driven auxiliary feedwater pumps. A
. failure of this' control grade system will not prevent the AFWS from operating
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manually.
'In the -light of the above discussion and the analysis by NSD (Reference (d)),
- the. proposed modification does not increase the probability of occurrence of a
-previously e' valuated accident, create the possibility of a new type of accident, or reduce.the margin of~ safety as defined in the basis of any Technical Specifications.
.The proposed modification has been analyzed to assure that it does not create
.any unreviewed safety questions as defined in 10CFR59.59(a)(2).
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