ML20212J031

Informs of Actions Taken to Close Remaining Open Items in .Attachment Provides Detailed Justification for Closure of Open Items in Sections 5.2.2 & 5.2.8

ML20212J031
Person / Time
Site:	LaSalle
Issue date:	06/21/1999
From:	Jamie Benjamin COMMONWEALTH EDISON CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
NUDOCS 9906280299
Download: ML20212J031 (7)

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Cannmonwealth labon Company laSalle Generating Station ,

, ,2N)1 North'2ist Road Marwilles. II,61341-9757 f

Tcl 815-3574761 i

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June 21,1999 United States Nuclear Regulatory Commission Attention: Document Control Desk Washington, D.C. 20555 LaSalle County Station, Units 1 and 2 Facility Operating License Nos. NPF-11 and NPF-18 NRC Docket Nos. 50-373 and 50-374

Subject:

Compliance with Regulatory Guide 1.97-Boiling Water Reactor Neutron Flux Monitoring

References:

(1) Letter dated June 3,1993 from C. P. Patel (U.S. NRC Office of NRR) to D. L. Farrar (Comed), " Regulatory Guide 1.97 - Boiling Water

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Reactor Neutron Flux Monitoring (TAC No. M77660)

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(2) Letter dated August 17,1993 from D. J. Chrzanowski (Comed) to the U.S. NRC Document Control Desk / 00 1 (3) Letter dated November 12,1993 from M. J. Vonk (Comed) to the U. S. NRC Document Control Desk l

The purpose of this letter is to inform you of our actions taken to close the remaining open items in Reference 3. Reference 3 provided LaSalle's conformance to NEDO 31558-A, March 1993, related to compliance with Regulatory Guide 1.97 for ileutron flux monitoring. The attachment to this letter provides detailed justification for the closure of the open items in Sections 5.2.2 nnd 5.2.8. '

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9906200299 990621 PDR ADOCK 05000373 P PDR m A l'nimm Company ,

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'U S Nuclear Regulatory Commission Page 2 Should you have any questions concerning this letter, please contact Mr. Frank Spangenberg Ill, Regulatory Assurance Manager, at (815) 357-6761, extension 2383.

Respectfully, )

b$lfAIW Q  !

t Jeffrey A. Benjamin l Site Vice President j LeSialle County Station Attachment l cc: Regional Administrator - NRC Region ll! I NRC Senior Resident inspector - LaSalle County Station i

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ATTACHMENT LASALLE COUNTY STATION NEUTRON MONITORING SYSTEM DESIGN COMPLIANCE WITH NEDO 31558-A, MARCH 1993 SUPPLEMENTAL INFORMATION SECTION 5.2.2 Requirements ACCURACY Alternate Requirement i 2% of rated power R.G.1.97 Requirement: None Specified Qr[ginal Commitment:

In the response to NEDO-31558, LaSalle County Station (LaSalle) committe,d to evaluate the APRM loop error analysis. If the error analysis could not support the specified loop accuracy, the results of the analysis would be incorporated into the appropriate station procedures.

Response

LaSalle is changing its commitment related to this action, so an APRM loop error analysis has not been completed; however, justification consistent with the BWROG position on this topic is provided as follows:

LaSalle procedures LIS-NR-111 A/111B(211), Locai Power Range Monitor (LPRM) Flux Amplifier Gain Adjustmen't, and LIS-NR-103AA/103BA (203AA/203BA), Average Power Range Monitor (APRM), Rod Block ar,d SCRAM Calibration, provide for LPRM and APRM channel calibration in accordance with the LaSalle Technical Specifications. In addition, LaSalle procedure LIS-NR .09 (209), APRM Gain Adjustment, provides guidance for a weekly APRM gain adjustment, also in accordance with LaSalle Technical Specifications. The weekly adjustment verifies the APRMs are accurate to i 2% rated thermal power based on the power values calculated by a heat balance during Run Mode (Operational Condition 1),

when thermal power is greater than or equal to 25% of rated thermal power.

The pre-accident APRM accuracy, therefore, meets the alternate criteria with the existing equipment. However, APRM system will NOT meet the NEDO post-accident accuracy requirement of 2% of rated power.

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NEDO-31558, Section 5.2.2, specifies an accuracy requirement of 2% of rated power. This requirement is more restrictive than Regulatory Guide (R.G.) 1.97, which is silent on instrumentation accuracy. LaSalle has determined that the APRM system will NOT meet the NEDO post-accident accuracy requirement of 2% of rated power. This judgment is based on evaluations performed for other stations with similar design features, and based on the effects of the anticipated off-normal core conditions following an Anticipated Transient Without Scram (ATWS) event (control rod pattern, xenon, etc.). Therefore, the total APRM power measurement uncertainties are expected to be in excess of 2% during an ATWS event.

LaSalle has evaluated the impact of not conforming to NEDO-31558 Section 5.2.2 and concludes the deviation is acceptable. The justification for this conclus!on is provided below and is consistent with the BWROG position on this subject.

LaSalle uses the Emergency Procedure Guidelines (EPGs) to achieve shutdown during an ATWS event. When the ATWS condition potentially threatens containment, shutdown is accomplished by injecting boron via the Standby Liquid Control system. The decision to inject boron is independent of the APRM indications and is predicated on degrading containment conditions (such as rising suppression pool temperature). As a result, an APRM system uncertainty beyond that specified in NEDO-31558 is acceptable and does not compromise plant safety. Comed l considers this item closed. l This position was accepted by the NRC for Quad Cities Nuclear Power l

Station Units 1 and 2 by Letter dated December 31,1998 from R. M. I Pulsifer to O. D. Kingsley, Regulatory Guide 1.97 - Boiling Water Reactor Neutron Flux Monitoring - Quad Cities Nuclear Power Station, Units 1 and 2 (TAC Nos. M51124 and M51125). The letter dated April 24,1998, from J. P. Dimmette, Jr. to U. S. NRC, concerning Quad Cities Nuclear Power Station Units 1 and 2 Regulatory Guide 1.07 Closeout, provided the final Quad Cities responses for paragraph 5.2.2 of NEDO31558-A.

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SECTION 5.2.8 Reauirements POWER SOURCES Alternate Requirement Uninterruptible and Reliable Power Sources R.G.1.97 Requirement: Standby Power Source Oriainal Commitment:

1. The power supply for the APRM recorders will be upgraded to provide redundancy and improve reliability. Comed will modify the power supply for the recorders to ESF power sources during outages L1R07 and L1R08.

2. The power supplies for the APRMs deviate from the alternate requirements because both RPS power sources will be lost for the Loss of Offsite Power event. LaSalle deferred a response to this issue because it was under review by the BWROG. LaSalle committed to provide a response when the BWROG evaluation was completed.

Response

1. The power supplies for the NMS recorders were upgraded to provide redundancy and improve reliability. Comed modified the power supply for the recorders during refueling outages L1R07 and L2R07 to power the recorders from ESF power sources. This was met for Unit 1 upon startup from L1R07 on April 11,1996 and for Unit 2 upon startup from L2R07 on April 9,1999.

2. The LaSalle Neutron Monitoring System (NMS) is fed from highly reliable Diesel Generator (DG) backed power sources. The LPRM/APRM is powered from redundant 480/120 Volt AC motor-generator (MG) sets configured in two Reactor Protection System (RPS) divisional buses (A and B) and fed from redundant and separate divisional (ESF Divisions 1 and 2) 480 Volt AC buses in separate motor control centers in Auxiliary Building. Either RPS Division Bus A or B can be energized by a reserve feed from a non-divisional source via main control room operator action.

Two Electrical Protection Assemblies (EPAs) are installed in series between each of the two RPS MG sets and RPS buses and between the reserve feed and the RPS buses. EPAs provide redundant protection to the RPS buses by acting to disconnect the RPS from the power circuits.

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Each MG set is equipped with a high inertia flywheel which is sufficient to maintain voltage and frequency within 5% of rated values for at least one second following a total loss of power to drive the MG set.

The MG set power sources are reliable and uninterrupted as required during a NMS design defining event (i.e., a stuck open relief valve with partial scram failure), to assure continuous neutron flux monitoring.

It has been determine,d that during this event, the NMS power monitoring will not be lost due to load shedding logic or a single failure that would cause loss of redundant RPS buses powering the NMS instrumentation.

In the unlikely event of the loss of one RPS Division, the power level j indication will be provided on the redundant Division of the NMS.  !

The power sources for the NMS meet the altemate requirement for uninterruptibility, because they are reliable and capable of providing continuous power to the NMS during the design basis event.

However, for the scenario of an ATWS condition concurrent with a Loss of Offsite Power (LOOP) event, Comed deviates from the alternate requirements because both RPS power sources will be lost temporarily during this event. For this event, restoration of power to the APRM system (Power from Reactor Protection System) is dependent upon the DG startup time plus manual restart of the RPS MG sets and reset of the EPAs. In accordance with station procedures for loss of RPS power, immediate operator actions are to verify that automatic actions have occurred which include verifying reactor SCRAM. The subsequent operator action following verification of automatic actions is to restart the RPS MG setc upon determination that the cause was from LOOP and conditionally that the 4 kV and 480-Volt AC ESF buses are energized by the DGs. In accordance with the design, the DGs are up and running in approximately 13 seconds. Reset of the EPAs and manual restart of the RPS MG set are in the same location, however, this location is remote from the main control room and an operator dispatch is required.

During this period of time, the control room operator can determine reactor criticality with the use of the Source Range Monitor (SRM) and intermediate Range Monitor (IRM) systems. These systems, which can be used below 15% power, utilize detectors that are withdrawn from the core during normal power operation. The drive motors for the SRM/lRM detectors are powered from a 120/208 Volt AC ESF divisional source, which will be energized upon DG startup. The SRM and IRM systems have redundant channel capability. The system sensors and associated 4 of 5

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equipment are powered by a 24-Volt DC battery / charger system. The battery chargers for this system receive their power source from ESF l divisional sources.

in summary, the present design of the LaSalle NMS meets the intent of Section 5.2.8 of NEDO 31558-A in that the system is reliable and j uninterruptible for the NMS design basis event. It should be noted that '

with a concurrent LOOP the RPS MG set would be interrupted, but can be manually restored as described above. The operator still has information available as described above to determine reactor status during RPS MG Set restoration. Comed considers this item closed.

Comed has verified that LaSalle meets the BWROG Reg. Guide 1.97 Neutron Monitoring System subcommittee positions on NMS Post- l Accident Monitoring Functional Criteria from NMS Committee Workshop, September 22-23,1993. This subcommittee for the RG 1.97 NMS -

Power Supplies determined that the existing MG set power supplies meet the intent of the BWROG post-accident monitoring functional criteria as l

described in paragraph 5.2.8 of NEDO 31558-A. This position was accepted by the NRC for Quad Cities Nuclear Power Station Units 1 and 2 by Letter dated December 31,1998 from R. M. Pulsifer to O. D. Kingsley ,

Regulatory Guide 1.97 - Boiling Water Reactor Neutron Flux Monitoring -  !

Quad Cities Nuclear Power Station, Units 1 and 2 (TAC Nos. M51124 and M51125). The letter dated April 24,1998, from J. P. Dimmette, Jr. to U.

l S.. NRC, concerning Quad Cities Nuclear Power Station Units 1 and 2 l

Regulatory Guide 1.97 Closeout, provided the final Quad Cities responses for paragraph 5.2.8 of NEDO31558-A.

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