ML20106B909
| ML20106B909 | |
| Person / Time | |
|---|---|
| Site: | Oyster Creek |
| Issue date: | 09/25/1992 |
| From: | J. J. Barton GENERAL PUBLIC UTILITIES CORP. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| C321-92-2244, GL-89-10, NUDOCS 9210050269 | |
| Download: ML20106B909 (2) | |
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GPU Nuclear Corporation
.FU Muclear
= e 388 f oned Rwer, New Jcrsey 087310388 609 971 4000 Wr,ter s DJoct D.al Number.
(609) 971 4814 September 25, 1992 C321-92-2244 V
S. Nuclear Regulatory Commission Attention:
Document Control Desk c
Washington, DC 20555 Gentlemen:
Subject:
Oyster Creek fluclear Generating Station (OCliGS)
Operating License No. DPR-16 Docket No. 50-219 Generic letter 89-10, Motor Operated Valve Response to Request for Additional Infornntion This letter is in response to NRC request for additional information, dated July 20, 1992, regarding the 35 second delay in closure of the isolation condenser system (ICS) isolation valves.
The 35 second time delay is assumed in the valve differential pressure calculation for Valves V-14 34, 35, 36 and 37, ICS condensate return line isolation valves.
The worst case postulated differential pressure scenario (GL 89-10 design basis) for these motor operated valves assumes the high energy line break (HELB) occurs at the approximate time of ICS initiation wnich conservatively produces the highest initial reactor coolant pressure for the transient.
The ICS provides decay heat retroval for reactor isolation events where the normal heat sink (main condenser) is unavailable, and is initiated by reactor vessel high pressure or low-low water level.
It also provides alternate shutdown capability in the event of damage f rom a fira or natural phenomenon.
The ICS high flow trip setpoints provide automatic isola.an if a pipe rupture is detected.
The setpoint of three hundred percent of normal flow lasting over 35 seconds affords protection against pipe rupture without causing spurious system o-isolation due to operating transients.
The 35 second isolation signal time ns$
delay is part of the licensing and design basis for OCNGS to provide assurance yOL that the ICS system is not inadvertently isolated.
So The ICS Pigh flow Alarm panel indication is annunciated only if the 'igh steam flow or high condensats ilow signal has been sustained for 35 seco,sas.
If the g
og high flow signal has bean sustairied for 15 seconds, the panel alarm window Era annunciates Condenser A or B High flow - Possible Rupture.
The OCNGS Alarm 04 Response Procedure (2000-RAP-3024.01) for 'he ICS A & B High flow-Possible 8
Rupture Alarm identifies confirmatory operator actions to verify condenser E$
area high temperaturn alarms and to verify closure of the respective isolation
,J M o g g'p'a,1ves. If a pipe break is verified, the procedure directs the operator to v
tace the control switches for the isolatien valves in the "Close" position.
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GPU Nuclear Coq >oraton s a subreaf y of Genera! PutAc Uttt es Co'poraSon V
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,Page 2 The Condenser A or B Vent Ili Alarm is also annunciated upon an upscale trip of the ICS A or B Vent radiation monitor.
The alarm response procedure similarly directs the operator to verify the high radiation level on redundant endicators, and provides a note that the alarm is not positive indicotion of a leak in the ICS.
The operator is further directed to check isolation condenser temperature and level for indications of a leak.
Operator training at OCNGS presently emphasizes the importance of the Isolation Condenser System as a decay heat removal system and that the operator is to confirm that a pipe rupture has i need occurred before the system should be isolated.
Therefore, the focus of the operator is not directed to immediate isolation of the ICS.
Present training and procedural guidance emphasizes that the pipe rupture is to be confirmed before isolation of the ICS No guidance or direction is given to override the 35 second delay to manually isolate on an immediate basis.
Therefore, we believe that the assumption of a 35 second delay in closure of the motor operated 105 condensate line isolation valves, for determination of the valve design basis differential pressure, accounts for the actual system and operator response to such a postulated scenario.
Based on the above, GPUN believes that adequate procedures and training guidance are presently provided such that it is unreasonable to postulate that the operator would take action within 35 seconds to isolate the ICS.
l
_S tricerely, k
N.
John J Barton T
Vice president and Directar Oyster Creek Nuclear Generating Station JJ8/DD:lga cc:
Administrator, Region 1 Oyster Creek NRC Project Manager Senior Resident NRC Inspector i
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