ML20084M866
| ML20084M866 | |
| Person / Time | |
|---|---|
| Site: | Byron, Braidwood, 05000000 |
| Issue date: | 05/02/1984 |
| From: | Tramm T COMMONWEALTH EDISON CO. |
| To: | Harold Denton Office of Nuclear Reactor Regulation |
| References | |
| 8315N, NUDOCS 8405160160 | |
| Download: ML20084M866 (7) | |
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[G Commonwealth Edison
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) One Fust N1tional Plaza. Chicigo. Illinois O
Address Reply to. Post Office Box 767 Chicago. Ilknois 60690 s
May 2, 1984 Mr. Harold R. Denton, Director Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission Washington, DC 20555
Subject:
Byron Generating Station Units 1 and 2 Braidwood Generating Station thits 1 and 2 Environmental Qualification of Equipment NRC Docket Nos. 50-454, 50-455, 50-456, and 50-457 Reference (a): January 5,1984 letter from T. R. Tramm to H. R. Denton.
Dear Mr. Denton:
This letter provides the justifications for interim operation (JIO) for two items of electrical equipment for which environmental testing may be incomplete at the time of fuel load for Byron Unit 1.
Reference (a) provided the other environmental qualification J10's.
Attachment A to this letter contains the justification for interim cperation of Barton Model 581A differential pressure indicating switches used in the residual heat removal " mini-flow" lines. As described in reference (a), these switches will also be installed to replace Barton Model 288A switches on the containment spray additive tanks. Justification for interim use in that applicatior was previously provided. Testing of the 581A switches is in progress but documentation may not be available by July 1, 1984.
Attachment B to this letter nontains the justification for interim operation of instrumentation for the detection of inadequate core cooling.
Generic testing is complete but the review of the test results _with respect to Byron and_Braidwood may not be available by July 1, 1984.
Attachment A to reference (a) provided the justification for interim operation for thirteen Limitorque valve operators. Approval for -
interim operation of twelve of the thirteen Limitorques is no longer needed because new valve operators have been installed. Approval for interim operation of valve of valve 1 CC 9416 is still-needed because the operator for that valve is not expected to be available until the end of July,1984.
Additiona1' justification for interim operation of that valve is contained in Attachment-A to this letter.
8405160160 840502 PDR ADOCK 05000454 A
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1 H. R. Denton 2-May 2, 1984 Please address questions regarding this matter to this. office.
One signed original and fifteen (15) copies of this letter and the attachments are provided for NRC review.
Very truly yours,
[ kef4tw-T. R. Tramm Nuclear Licensing Administrator 8315N t
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Attachment A Byron Interim Justification Position for the Seismic and Environmental Qualification of the Differential Pressure Indicating Switch Barton 581A (Group B)
(ESE-40)
Instruments FIS-610, FIS-611 Control of flow in residual head removal system " mini-flow" lines and resulting protection of RHR pumps is dependent on switch contact i
action in a differential pressure indicating switch. The Barton model 581A switch in this function is intended to be qualified for service i
during and after a design basis safe shutdown earthquake. Because of questions raised about switch operation, results from a complete seismic test program in 1977 were considered incdequate to demonstrate successful seismic performance. A description of the original tests and subsequent tests performed to establish seismic qualification and the basis for interim operation with existing DP switches is provided below.
In the original DP switch seismic test completed in 1977, switch contacts were monitored. A review of analog recordings of switch contact status revealed no intermittent contact status changes in either the normally open or normally closed contacts. No attempt was made to vary measured differential pressure and actuate switch contacts during actual seismic test runs.
The acceptance criteria at that time were no contact bounce in the deactivated switches and no affect on performance following seismic testing. Subsequent testing of another model switch revealed that susceptibility to contact bounce in switches of similar design was greater at or near the switch setpoints.
In December 1982 two model 288A switches were included in another test then being conducted. During this test, provisions were made to mechanically change the differential pressure and j
to control the switching of contacts. This test was not comprehensive enough to establish design limits for all switch ranges, however, confidence was provided that except at differential pressures near the switch setpoints, no intermittent contact action might be expected as the result of seismic testing. The switches tested had ranges of 30 psid and 60 inches of water. The 60 inch unit was one of those originally tested in 1977. During each seismic simulation using generic WRD seismic envelope inputs, the switches were either operated through their ranges or held '
near.setpoints. The 30 psid unit showed negligible tendencies for switch bounce, even at positions less than two percent full scale from a switch setpoint. The 60 inch unit from the original test was susceptible to switch (contact) bounce, showing decreasing sensitivity as the distance from the setpoint was increased. ~ At two percent from the setpoint,~.
contact bounce was extensive. However, less tendency for contact bounce was exhibited at 5% of full scale from the setpoint and during one run in which *he switch was held approximately 8%.from its setpoint, only two instances of intermittent switch action were observed, each lasting _less than two milliseconds.
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$ A minimum flow rate is maintained to prevent pump failure from cavitation or pumping against a dead head. If contact bounce of a switch occurred for long enough to initiate valve closure, flow through the pump would decrease until an actuator limit switch indicates full closure.
Provided the DP switch contacts are in the correct state, the valves would then begin to reopen. A partial or full restriction of flow to the pumps could thus occur for the duration of the seismic event but the valve would fully reopen within 10 seconds following the event.
Performance specifications and type test results of the Pacific RHR pumps demonstrate that the pumps can tolerate fully restricted flow at operating speed without failure for 30 seconds.
If contact bounce initiates valve closure at the beginning of a seismic event, flow restriction would occur only until limit switch actuation and subsequent ve3.ve reopening following such an event. Normal system performance would be insured provided no drift of the DP switch setpoints had occurred.
The original tests in 1977 demonstrated post seismic adequacy of switch performance.
The miniflow valve is also closed at high flow to assure adequate safety injection flow following a LOCA.
The peak clad temperature remains well below the limit even when a 30-second delay in valve closure is considered.
In summary, evaluation of pump performance and resultant peak clad temperature demonstrates that no detrimental effects will occur due to a 30-second delay-in the completion of either function. Following an SSE, i
normal switch and valve functions would be restored to assure adequate i
miniflow and SI flow.
8315N W
ATTACHENT 8 Inadequate Core Cooling Instrumentation Justification for Interim Operation Byron Unit 1 The Byron /Braidwood inadequate core cooling (ICC) instrumentation system provides an advanced warning of the approach to ICC by providing indication of:
- 1) the loss of subcooling and occurrence of saturation with a subcooled margin monitor
- 2) the loss of inventory in the reactor with the reactor vessel level monitoring system (RVLMS)
- 3) the increasing core coolant exit temperature with core exit thermocouples (CET).
At this time, the environmental and seismic qualification of some of the components of the RVLMS has not been demonstrated for the Byron /
Braidwood plant specific conditions. The generic qualification of the mineral insulated cable connector interface inside the containment was completed in March,1984, however a plant specific report will not be available until May, 1984.
To date, qualification of the mineral insulated cable and connector interface for use in a CET system at another plant has been successfully completed.
In addition, a plant specific qualification program for the mineral insulated cable and connector interface used in a-RVLMS at another plant has also been successfully completed. Therefore, based on Combustion Engineering's experience at other plants, we are confident that these components will be demonstrated to be qualified for the Byron /Braidwood plant specific conditions.
In the interim, we believe other means for monitoring ^the approach to ICC are available to the operator and justify operation without complete qualification of the ICC instrumentation system prior to fuel load.
As noted in past submittals in response to TMI item II.F.2,'the RVLMS does not provide the sole source of indication for the approach to ICC.
Its indication is used in combination with the subcooled margin monitor (SMM) and CET system and helps to provide a confirmation of the approach to ICC.
In the interim, reliance on indication from the SMM and CET system will provide sufficient indication for the approach to ICC conditions such that the accomplishment of any safety function will not be degraded.
Given the short time frame-within which qualification will be complete for Byron /Braidwood and the fact that the system has been.
successfully qualified for other plants, we believe' interim operation.
. pending completion of qualification for Byron /Braidwood is justified.
In addition,: this interim' mode of operation is consistent with what the NRC.
-has accepted on operating plants.
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Attachment C i
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Byron Interim Justification Position for the i
Seismic and Environmental Qualification of the Limitorque Motor Operator (SMB0010) for Valve 9416 (6GM62F3H) i l i
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Valve 9416, CCW return from the RCP oil cooler, utilizes Limitorque operator model S!!B0010 at the Byron site.
This valve, due to its high speed characteristics, has a electro-mechanical brake to prevent damage to the valve components during the closing sequence. Until recently it was believed that the brake need not be qualified to demonstrate the post-accident operability of the valve. Recent information has reversed that position. Byron has ordered a replacement high speed Limitorque motor operator (model SB-00510) that performs the required function without the use of a brake. However, this will not be available to support the anticipated fuel load date. Based upon review of the components involved the following is provided as a Justification for Interim Operation.
Valve 9416 is an active valve due to the application of a containment phase B (high containment pressure) isolation signal.
In the event of a P signal the valve is required to close; no other safety signals or safety requirements are associated with valve 9416. Valve 9414 provides a second isolation valve for this containment penetrations; 9414 being outside containment and 9416 inside containment.
In order for a breach of containment to occur all the following must happen: an adverse containment atmosphere must exist (i.e., LOCA or HELB), the CCW oil cooler piping must rupture and the line depressurize and valve 9414 must fail to shut on its P signal in order for a failure of valve 9416 to result in a release of radioactivity or steam outside of containment.
Based on the above, it is believed that the present operator on valve 9416 is adequate to perform its safety function until the scheduled first refueling outage for Byron Unit 1.
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