05000309/LER-1986-001, :on 860104,manual Reactor Trip Initiated When Differential Pressure Between Condensers a & B Exceeded Operating Limit.Caused by Operator Closing Valve to Water Pump.Human Factors Evaluation Being Performed
| ML20151Y452 | |
| Person / Time | |
|---|---|
| Site: | Maine Yankee |
| Issue date: | 02/03/1986 |
| From: | Mcdougold D, Whittier G Maine Yankee |
| To: | NRC OFFICE OF ADMINISTRATION (ADM) |
| References | |
| 7061L-SDE, GDW-86-29, LER-86-001, LER-86-1, MN-86-17, NUDOCS 8602120704 | |
| Download: ML20151Y452 (4) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(iv), System Actuation 10 CFR 50.73(a)(2)(v), Loss of Safety Function 10 CFR 50.73(a)(2)(vii), Common Cause Inoperability 10 CFR 50.73(a)(2)(1) 10 CFR 50.73(a)(2) 10 CFR 50.73(a)(2)(viii)(B) 10 CFR 50.73(a)(2)(iii) 10 CFR 50.73(a)(2)(x) |
| 3091986001R00 - NRC Website | |
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MAINE YANKEE ATOMIC POWER COMPANY INRC Form 366 U.S. Nuclear Regulatory Commission l l(9-83)
Approved OMB No. 3150-0104 l
,I LICENSEE EVENT REPORT (LER)
Expires: 8/31/85 1
l l
4 1l Facility Name(l) 100cket Number (2) l Page(3) l l
Maine Yankee Atomic Power Company l
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l 10 15 10 10 10 l 31 Ol 91 llofl 3 l l
>liitle(4) Manual Reactor Trip on Condenser Differential Pressure l
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l Event Date(5) l LER Number (6)l l Report Date(7) i Other Facilities Involved (8) l
- lMontnl Day lYearlYearl l Sequential l l Revision l Month l Day lYearl Facility Names IDocket Number (s)l l
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l This Report is Submitted Pursuant to the Requirements of 10 CFR 5 l
l Operating l
l (Check one or more of the following) (11) l l
Mode (9) 17 l 120.402(0)
I 120.405(c) lXl50.73(a)(2)(iv) l l/3.71(b) l l Power l l 120.405(a)(1)(1) l~l50.36(c)(1) l~l50.73(a)(2)(v)
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!l Danny P. McDougcid, Nuclear Safety Engineer l Area Code l l
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l l ABSTRACI (Limit to 1400 spaces, i.e., approximately fif teen single-space typewritten lines) (16)
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l On January 4,1986 a manual reactor trip was initiated when differential pressure between l
4 l Condenser A and B exceeded its administrative operating limit for equipment safety. The l'
l high condenser differential pressure resulted from cognitive error by a licensed operator.
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l l Circulating water pump, P-268, as shown on the attached process schematic, was secured to l
l allow backwashing the tubesheet on the inlet side of Condenser A North. Af ter backwashing, l,
3 The operator mistakenly closed l
- ll the licensed operator attempted to return P-260 to service.
the discharge valve to circulating water pump, P-26A, which caused the pump to trip and all l'
- l cooling water flow to Condenser A to cease. Condenser A pressure increased and the ll
' I differential pressure between Condenser A and B exceeded the administrative limit.
The l
} l operator tripped the plant as required by procedure.
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The Plant Engineering Department will perform a human factors evaluation of this l
l equipment to determine if any improvements could prevent a recurrence.
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fHC Form 366 j
(9-03) i TCJJ l
0602120704 060203 PDR ADOCK 0500
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7061L-SOE
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MAINE YORKEE ATOMIC POWER COMPANY i
, INRC Form 366A U.S. Nuclear i.egulatory Commission ll l(9-83)
Approved OMB No. 3150-0104 l1 l
Expires: 8/31/85 l
l LICENSEE EVENT REPORT (LER) TEXT CONTINUATION l'
4 "l
l l Facility Name(l)
IDocket Number (2)l LER Number (6) l Pane (3) l, l
l l Year l l$equential l l Revisioni l
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l Maine Yankee Atomic Power Company l
l l l Number l l Number l l
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' l TEXT (If more space is required, use additional NRC Form 366A's) (17) l l
l l On January 4,1986 a manual reactor trip was initiated when condenser (CONO) differential l
l pressure exceeded its administrative operating limit. The differential pressure between the l
) two low pressure turbine (TRB) condenser shells exceeded the 2.5 inches Hg limit when a l
I licensed operator mistakenly closed the wrong circulating water (RE) pump (P) discharge valve I
f l (20). The personnel error was cognitive and not a result of a procedural error.
The operator I
( l tripped the plant for equipment safety as required by procedure.
l l
l l The plant was operating at 75% power while operators were performing condenser backwash l,
l operations. Backwashing the condensers was necessary to remove sea water debris from the ll l inlet tubesheets to increase the flow through the condenser tube bundles. Condenser A North, l'
I as shown on the attached process schematic, had recently been backwashed. The associated l
I circulating water pump, P-268, was secured with the pump circuit breaker (52) open and the l
l pump discharge valve, CW-M-3,100% open. A licensed operator was attempting to return P-268 l
ll to service. Each circulating water pump and its associated discharge valve are controlled by l
l l a common control switch located in the control room (NA) on the Main Contro l
l' l
ll l The licensed operator mistakenly selected the control switch for P-26A in lieu of P-260.
I l The operator immediately realized his mistake, but the circuitry o, the pump and val e is l,
1 I such that the valve continues to close and the pump trips at 25% valve openinq, The ll l circuitry also prevents either pump from restarting when both pumps in the same condenrer l'
4 l are shut off. When the second pump breaker opens, contacts open in the start circuitry for l
l both pumps to block (OLK) them from starting for two minutes.
Therefore the operator l
l could not immediately restart P-26A. The vacuum breakers (VACB) on the outlet of the l
l condensers are also opened and blocked open for two minutes. Without vacuum assist, l
' I circulating water flow decreases through the condenser.
l l
l l Isolating the circulating water to both Condenser A tube bundles caused the Condenser Shell A l
l pressure to increase and the differential pressure between Condenser Shells, A and 8, to reach l
l 2.5 inches Hg.
This is an administrative limit which is imposed to protect plant equipment.
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l l Post trip system parameters were normal and plant equipment responded properly.
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I l l The safety consequences of a plant trip from full load are not significantly different than l
j l this trip from 75 percent power.
In any case, the initial conditions relative to this event, I
l 1.e., one condenser out of service, cannot be established with the plant at full load.
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l 1.
The Plant Engineering Department will perform a human factors evaluation of this l
l equipment to determine if any improvements could prevent a recurrence.
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'(9-83)
. 7061L-SDE
M AINC Y ANKEE ATOMIC POWE A COMP ANY lNRC Form 366A U.S. Nuclear Regulatory Commission l l(9-83)
Approved (NB No. 3150-0104 l
I Expires: 8/31/85 l
l LICENSEE EVENT REPORT (LER) TEXT CONTINUATION l
l l
IFacility Name(l) l Docket Number (2)l LER Number (6)
Page(3) l l
l lYear l l Sequential l l Revision l
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l Maine Yankee Atomic Power Company l
l Number l l Number l l
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February 3, 1986 MN-86-17 GDW-86-29 Director, Office of Nuclear Reactor Regulation United States Nuclear Regulatory Commission Washington, D. C.
20555 Attention: Document Control Desk
Reference:
License No. OPR-36 (Docket 50-309)
Subject: Maine Yankee Licensee Event Report 86-001 Manual Reactor Trip on Condenser Differential Pressure Gentlemen:
Please find enclosed Maine Yankee Licensee Event Report //86-001-00.
This report is submitted in accordance with the requirements of 10 CFR 50.73(a)(2)(iv).
Very truly yours, MADE YANKEE ATOMIC POWER COMPANY YJh llV G. D. Whittier, Manager Nuclear Engineering and Licensing GDW:bjp Enclosure: Three pages cc:
Mr. Ashok C. Thadani Dr. Thomas E. Murley Mr. Pat Sears Mr. Cornelius F. Holden American Nuclear Insurers ifh 5
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