ML20153B039
| ML20153B039 | |
| Person / Time | |
|---|---|
| Site: | Oyster Creek |
| Issue date: | 07/01/1988 |
| From: | Fitzpatrick E GENERAL PUBLIC UTILITIES CORP. |
| To: | NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM) |
| References | |
| RTR-NUREG-0833, RTR-NUREG-833, TASK-05-05, TASK-5-5, TASK-RR NUDOCS 8807120694 | |
| Download: ML20153B039 (3) | |
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GPU Nuclear Corporation
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2al-316-7oco TELEX 136-482 Writer's Direct Dial Number:
July 1,1988 U.S. Nuclear Regulatory Commission Attention:
Document Control Desk Mail Station P1-127 Washington, D.C.
20555 Gentlemen:
Subject:
Oyster Creek Nuclear Generating Station (OCNGS)
Docket No. 50-219 SEP Topic Y-5, Reactor Coolant Pressure Boundary (RCPB) Leakage Detection IPSAR 4.16.1, Airborne Particulate and Gaseous Radioactivity fioni tors The purpose of this letter is to provide the Staff with our current activities and future plans associated with the drywell airborne particulate and gaseous radiation monitoring system ( APGRitS).
As docume ited in Section 4.16.1 of the NRC Staff's Integrated Plant Safety Assessment Report (IPSAR - NUREG 0833), for SEP Topic Y-5, Reactor Coolant Pressure Boundary (RCPE) Leakage Detection, GPUN comitted to identify the system modifications accessary to make the installed airborne particulate and gaseous radioactivity monitors operational.
Subsequently an attempt was made to restore the APGRitS, however it was determined that replacement rather than repair of the existing system was more cost effective.
In our letter dated July 8,1986 we requested cancellation of our commitment to restore the APGRMS.
The letter described the diversity and adequacy of the sump conitoring system available at Oyster Creek to detect RCPB leakage quantitatively and stated that the APGRitS would be of little use in quantifying leakage rates to meet Technical Specification limits.
It stated that the APGRMS would measure the leakage indirectly through released radioactivity and could only be used as a trending indication of the leakage which must be confirmed and quantified by other meant It also stated that there are other data available such as drywell pressure, humidity and temperature which can also provide qualitative or trending information concerning RCPB leakage comparable to that provided by the APGRMS.
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e' U.S. Nuclear Regulatory Commission Page Two four letter dated March 12, 1987 denied our request for cancellation on the basis that GPUN did not supply sufficient information such as the sensitivity of drywell pressure, humidity and temperature data and concluded that the
' APGRMS should be installed during the upcoming 12R outage.
GPdH proceeded with a detailed eval'uation which attempted to supply the additional information the Staff referred to. The evaluation pointed.out that-the interpretation of drywell atmosphere contamination in terms of reactor coolant leakage could lead to ambiguous results because different portions of the reactor coolant system contain different levels of radioactive contamination.
It also. indicated that pressure.and hunicity would respond well to leakage and could be better quantified. However, we have also recently concluded that these indications may be masked by operator action.
Because of this, we have decided to replace the APGRMS to provide the diversity required by the Staff..
We plan to accomplish the modification in two phases. The first phase, which will be completed during the upcoming 12R outage, consists of those activities which require the plant to be shutdown, i.e., rerouting the existing piping and relocating electrical controls for control of isolation valves.
To this end, GPUN has completed the engineering and installation specification and initiated the material procurement effort.
The second phase, installation of a new APGRMS, will be completed during the operating Cycle 12.
Our Integrated Schedule Project Listing will be revised to reflect this revised schedule commitment.
It must be noted that there are several leak detection methods available for unidentified leakage into the containment su'np at Oyster Creek which operate on diverse principals, The normal method of monitoring unidentified leak rate is to obtain flow 4
integrator readings from the containment sump pump discharge every four hour period and calculete average flow rate.
Approximately 1 gpm can be measured in a four hour interval. This methodology is identified in Oyster Creek Technical Specifications as the primary method of leakage measurement.
When the flow integrator is not available, tl.e average leakage rate can be calculated using the known volume between the high and the low level alarms for ti sump and the time required to fill the sump between these levels.
A recorder available in the control room also provides continuous indication of an estimated unidentified leak rate to the containment sump by utilizing a differential pressure signal as a result of the sump level change.
The sensitivity of the recorder is approximately 0.2 gom.
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Pace Three Additianally, a timer available in the 480 volt switch aear room orovides the run time of the containment sumo oumos.
This run time alona with the estimated. flow rate of the sumo oumos can orovide acoroximate leak rates. This methodolooy is' utilized every four hours during power operation.
Also, an annunciator will alarm in the control room if the time to fill-the containment sumo is too short an interval. The time associated with this alarm is set to brina in the alarm if unidentified leak rate equals or exceeds 4 aom.
These methods provid) quantitative indications of unidentified RCS 'aakaae inside containment and also orovide assurance that unidentified leai qe can be ietected and quantified durina Cycle 12 operation cendina operability of the new APGRMS which will orovide an additional diverse t.nd qualitative means of leak detection.
If you need any additional information reaardina our plan, clease contact Mr.
M. Lacqart, Manaaer, BWR Licensino at (201)316-7968.
Very truly yours, E.E.Fitzbitrick Vice President and Director Oystar Creek EEF/YN/pa(6863f) cc: Mr. Williau T. Russell Administrator Reaion I U.S. Nuclear Reaulatory Concission 475 Allendale Road Kina of Prussia PA.
19406 1
HRC Resident Inspector Oyster Creek Nuclear Gereratina Statirn Forked River, N.J.
08731 Mr. Alex Dromerick U.S. Nuclear Reaulatory Commission Mail Station P1-137 Washinaton, D.C.
20555 i
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