ML20045C685
| ML20045C685 | |
| Person / Time | |
|---|---|
| Site: | Cooper  |
| Issue date: | 06/07/1993 |
| From: | Horn G NEBRASKA PUBLIC POWER DISTRICT |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| RTR-REGGD-01.097, RTR-REGGD-1.097 NSD930697, TAC-M51082, NUDOCS 9306240177 | |
| Download: ML20045C685 (3) | |
Text
e GEWERAL OFFICE j]j Nebraska Public Power District
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P O. BOX 499. COLUMBUS. NEBRASKA 68602-0499
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z NSD930697 June 7, 1993 U. S. Nuclear Regulatory Commission Document Control Desk Washington, DC 20555
Subject:
Cooper Nuclear Station Compliance with NEDO-31558, " Position on NRC Regulatory Guide 1.97, Revision 3, Requirements for Post-Accident Neutron Monitoring System".
Reference:
Letter from Harry Rood (NRC) to Guy R.
Horn (.NPPD) dated April 4, 1993, " Regulatory Guide 1.97 - Boiling Water Reactor Neutron Flux Monitoring - Cooper Nuclear Station (TAC NO. M51082)"
Gentlemen:
The Boiling Water Reactor (BWR) Owners Group submitted NEDo-31558, " Position on NRC Regulatory Guide 1.97, Revision 3, Requirements for Post-Accident Neutron Monitoring System" to the staff for review.
NEDO-31558 proposed alternate criteria for neutron flux monitoring instrumentation in lieu of the Category 1 criteria stated in Regulatory Guide (RG) 1.97.
In the reference, the staff issued a safety evaluation which concluded that, for current BWR operating license holders, the criteria of NEDO-31558 are acceptable for post-accident neutron flux monitoring.
The staff further concluded that Category 1 neutron flux monitoring instrumentation is not needed for existing BWRs to cope with a loss-of-coolant accident, anticipated accident without scram, or other accidents that do not result in severe core damage conditions.
The reference also requested licensees to (1) review their neutron flux monitoring instrumentation against the criteria of NED0-31558 to determine whether it meets the criteria, and (2) provide a letter to the NRC documenting the results of this review, and if necessary make a commitment to meet the criteria and state when this commitment will be fulfilled. This letter documents the requested actions stipulated in the reference.
The Nebraska Public Power District (District) has completed a review of the existing neutron monitoring system at Cooper Nuclear Station (CNS) against the alternate functional design criteria for a post-accident neutron monitoring system listed in section 5 of NEDO-31558. In general, the CNS Neutron Monitoring System meets or exceeds the alternate post-accident functional design criteria defined by NEDO-31558 with the following exceptions:
(2)
Accuracy - NEDo-31558 Criteria:
( 2% of rated power)
CNS does not have formal loop accuracies for APRM's or LPRM's, however, NPPD setpoint calculations for the APRM's and RBM show loop accuracy for the APRM's to be better than 2% of rated power up to but not including either the local meters or recorders. Complete loop accuracies including
.I local meters and recorders would conform with vendor manual specifications n
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of 2.4% of rated power, or 2% of full scale.
Since the LPRM's provide input into the APRM system, their errors are accounted for in the APRM accuracy.
The District considers the CNS Neutron Monitoring System (NMS) accuracy of 2% of full scale to be acceptable in meeting the intent of NEDO-31558 for i
accuracy criteria.
The downscale trips are initiated from the APRM's prior to the local meters and recorders and therefore, are within the 2%
of rated power criteria.
Any APRM downscale trip will receive prompt operator attention and appropriate action. Furthermore, the lowest power level requiring E0P operator action is above the alternate criteria of 2%
rated power for APRM loop accuracy.
(4)
Equipment Qualification - NEDO-13558 Criteria:
(Operate in an ATUS Environment)
The CNS NMS equipment, as designed, will meet the generic abnormal environments that are listed in Table 5-1 of NEDO-31558.
However, a plant-specific evaluation of ATWS environments is needed to assure there are no unique features or configurations that would not conform to the BWR Owners Group assumptions used in generating NEDO-31558.
The plant-specific evaluation will be initiated and any modifications resulting from the plant-specific evaluation that are determined to be necessary will be scheduled for completion prior to startup from the next scheduled CNS refueling outage.
We will be discussing this issue with your staff in the near future.
(5)
Function Time - NEDO-31558 Criteria:
(1 Hour)
The function time is tied to the event in which the equipment must survive. The CNS NMS equipment is designed for function times that exceed this criteria as listed in Table 5-1 of NEDO-31558.
However, a plant-specific evaluation of ATWS environments as discussed above is needed to assure that this criteria can be met.
The plant-specific evaluation will be initiated and any modifications resulting from the plant-specific evaluation that are determined to be necessary will be scheduled for completion prior to startup from the next scheduled CNS refueling outage.
We will be discussing this issue with your staff in the near future.
(8)
Power Source - NEDO Criteria:
(Uninterruptable and Reliable Power Sources)
The CNS design powers the APRM's, IRM's, and SRM's recorders from the No Break Power Panel (NBPP circuit 2).
However, the APRM and LPRM cards are powered from RPS power panels RPSPP1A and RPSPPlB which would be lost during some plant design basis events by load shedding logics.
A plant modification will be required to relocate the APRM and LPRM card power sources to two redundant uninterruptable power sources to conform
with the guidance of NEDO-31558.
This modification will be completed prior to startup from the next scheduled CNS refueling out' age.
In conclus' ion, the CNS NMS meets the appropriate post-accident des,ign criteria defined by NEDO-31558 with the exceptions listed above. The alterni 3 accuracy criteria is considered to be met by the existing CNS design of 2% of full scale.
The alternate criteria of Equipment Qualification and Function Time are dependent on site specific evaluations of AWS environment survivability of the CNS NMS.
No modifications for the ATWS environment are currently expected, but if the evaluation should indicate otherwise, any modifications determined to be necessary would be implemented prior to startup from tha next scheduled CNS i
refueling oucage. The power source for the APRM and LPRM cards will require a plant modification to meet the alternate criteria of NEDO-31558.
This modification will be completed prior to startup from the next CNS refueling outage.
The District will infor.n the NRC when the exceptions to the alternate criteria defined by NED0-31558 described herein have been resolved.
Should you have any questions concerning this m?.tter, please contact my office.
Sinc rely, w
Horn Nuc ear Power Group Manager GRH/tj a : 31558.nre cc:
Regional Administrator USNRC - Region IV Arlington, TX NRC Resident Inspector Cooper Nuclear Station 1
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