05000249/LER-1984-001, :on 840323,reactor Water Level Decreased to Low Level Alarm Point.Coolant Loss Compounded by Two Open Bypass Valves.Procedures Revised to Remind Operators to Close Turbine Valves

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:on 840323,reactor Water Level Decreased to Low Level Alarm Point.Coolant Loss Compounded by Two Open Bypass Valves.Procedures Revised to Remind Operators to Close Turbine Valves
ML20094R283
Person / Time
Site: Dresden Constellation icon.png
Issue date: 08/09/1984
From: Bergan G, Scott D
COMMONWEALTH EDISON CO.
To:
NRC OFFICE OF ADMINISTRATION (ADM)
References
LER-84-001, LER-84-1, NUDOCS 8408200519
Download: ML20094R283 (4)


LER-1984-001, on 840323,reactor Water Level Decreased to Low Level Alarm Point.Coolant Loss Compounded by Two Open Bypass Valves.Procedures Revised to Remind Operators to Close Turbine Valves
Event date:
Report date:
Reporting criterion: 10 CFR 50.73(a)(2)(iv), System Actuation
2491984001R00 - NRC Website

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Updated report: Initial report dated April 17, 1984

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u om During a reactor startup subsequent to a refueling outage, with Reactor heat up and pressurization under way, reactor water level decreased to the low level alarm point. With the low-flow feedwater regulating valve

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wide open in response to the low water level, the first reactor feed pump was started. Excessive cold water entering the reactor caused a high l

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Following a refueling outage, with Unit 3 reactor in the startup mode, reactor power had increased to the heating range with control rods being notched out to maintain proper heat up rate. A second Nuclear Station Operator (NS0) was assisting in maintaining the appropriate heat up rate by increasing the turbine pressure set.

One condensate / booster pump was on and supplying coolant to the reactor vessel. At 310 psig reactor pressure and with two turbine steam bypass valves open, it was noticed by the NSO pulling control rods that the reactor water level was decreasing and the low flow feedwater regulating valve was wide open. After verifying the condensate pump had not

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tripped, the NSO attempted to open a main feedwater isolation valve. While attempting to open the main feedwater isolation valve, water level continued to drop to the low level alarm point of 20 inches. The NSO then started a first reactor feed pump to recover the loss of coolant inventory. This action introduced excessive cold water in the vessel via a wide open low i

flow feedwater regulating valve. The reactor scrammed on high neutron flux l

4 conditions at 15 percent APRM power while the reactor mode switch was in the l

startup position. All appropriate protective systems performed as designed.

l Coolant loss was compounded by the fact that two bypass valves were open.

Surveillances, DOS 250-5, Automatic Blowdown System at Low Pressure and l

Rated Pressure, and DOS 2300-3, HPCI System Pump Test, require some bypass steam flow as a prerequisite to avoid any reactor pressure and flux transients.

The two bypass valves remained open after testing, resulting in a drop in I

water level which the condensate / booster pump was unable to restore.

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Corrective action consisted of submitting permanent revisions to procedures DOS 250-5 and DOS 2300-3, reminding the NSO to close turbine bypass valves when testing is complete.

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SUPPLEMENT TO DVR I DVR No.

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YEAR NO, D.

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PART I iTITLE OF EVENT OCCURRED Reactor Scram 3/23/84 1308 DATE TIME REASON FOR SUPPLEMENTAL REPORT Update original report to include a cause for this event.

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.. ACCEPTANCE BY STATION REVIEW A _

_3 dam DATE F/pajgf r/3/Sp u

i SUPPLEMENTAL REPORT APPROVED

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AND AUTHORIZED FOR DISTRIBUTION

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Telephone 815/942-2920 August 9, 1984 DJS Ltr #84-789 r

U.S. Nuclear Regulatory Commission Document Control Desk Washington, D.C. 20555 I

Updated Licensee Event Report..#84-001-1, Docket #050-249 is being

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submitted as required by Technical Specification 6.6, NUREG 1022 and j

10 CFR 50.73 (a)(2)(iv). This report specifies a cause for this 4

event. The initial report, dated April 17, 1984, contained no event cause due to a misunderstanding in the use of the new Licensee Event Report form.

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. Scott Station Superintendent Dresden Nuclear Power Station DJS/kjl.

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Enclosure J.G. Keppler, Regional Admniistrator, Region III cc:

File /NRC File / Numerical i

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