ML20217D816

Safety Evaluation Supporting Amend 224 to License DPR-56

ML20217D816
Person / Time
Site:	Peach Bottom
Issue date:	09/30/1997
From:	NRC (Affiliation Not Assigned)
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ML20217D770	List: ML20217D768 ML20217D810 ML20217D816
References
NUDOCS 9710060139
Download: ML20217D816 (7)

Text

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NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 30 6 0001 g * . . . + ,$j SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR RECULATION--

RELATtD TO AMENDMENT NO. 224 TO FACILITY OPERATING LICENS: NO. DPR-56 PECO ENERGY COMPANY PUBLIC SERVICE ELECTRIC AND GAS COMPANY DELMARVA POWER AND LIGHT COMPANY ATLANTIC CITY ELECTRIC COMPANY PEACH BOTTOM ATOMIC POWER STATION. UNIT NO. 3 DOCKET NO. 50-278

1.0 INTRODUCTION

By letter dated January 17, 1995, as supplemented by letters dated March 30, 1995, July 2,1996, February 28, 1997, and September 22, 1997, PECO Energy Company (PECO Energy, the licensee) submitted License Change Request (LCR) 93-18, in accordance with 10 CFR 50.90, requesting changer to Ap>endix A of the Peach Bottom Atomic Power Station (PBAPS), Units 2 and 3. Tecinicel Specifications (TSs). PECO Energy submitted this LCR to support PBAPS Modification P00271, which proposes to replace the existing Source Range (SRM) and Intermediate Range Neutron Monitors (IRM) with the Wide Range Neutron Monitoring System (WRNMS). The licensee's September 22, 1997, letter indicated that PECO Energy intended to install modification P00271 on Unit 3 during the fall 1997 refueling outage, and on Unit 2 during the fall 1998 refueling outage. The licensee further requested that the NRC not issue the Unit 2 WRNMS amendment earlier than September 1,1998. The March 30, 1995, July 2, 1996, February 28, 1997, and September 22, 1997, letters provided clarifying information that did not change the initial proposed no significant hazards consideration determination.

2.0 EVALVATION 2.1 Evaluation of WRNMS Modification Design In its January 17, 1995 application, PECO Energy stated that the PBAPS WRNMS is effectively identical with the staff-a) proved generic system documented in Licensing Topical Report NEDO-31439-A, "T1e Nuclear Measurement Analysis and Control Wide Range Neutron Monitoring System (NUMAC-WRNMS)." The staff's safety evaluation report (SER) approving the generic NUMAC-WRNMS in NED0-31439-A was transmitted to General Electric (GE) Nuc1 car Energy by letter dated October 3, 1990.

The PECO Energy submittal included the GE Nuclear Energy Licensing Report, NED0-32368, " Nuclear Measurement Analysis and Control Wide Range Neutron Monitoring System Licensing Report for Peach Bottom Atomic Power Station, Units 2 and 3." NE00-32368 summarizes the analyses and evaluations performed 9710060139 970930 PDR ADOCK 05000270 P PDR \

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to justify installing and operating a NUMAC-WRNMS at PBAPS, Units 2 and 3, and

! also addresses plant-specific differences betwou the PBAPS WRNMS and the

' generic WRNMS. The staff's SER approving NED0-32368, except for the review of the pro)osed changes to the technical specifications, was transmitted to PECO

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Energy )y letter dated June 9, 1995.

{ 2.2 Evaluation of WRNMS Technical Specifications (TSs)

Because the licensee proposed to convert to improved TSs between the date of the January 17, 1995, WRNMS application and the planned date for installation of the WRNMS, the staff elected to review the proposed WRNMS TSs after the completion of the PBAPS improved TS conversion. PECO Energy implemented license amendments 210 and 214, which approved PBAPS improved TSs, in Janaury 1996. The following is the staff's evaluation of the proposed TS changes in NEDO-32368 associated with the installation of the WRNMS at PBAPS, Unit 3.

, The WRNHS replaces all of the hardware and performs all of the functions

' formerly connected to both the SRMs and the IRMs. This replacement results in extensive changes to the TSs. Table 4-4 in NED0-32368 documents each of the

proposed changes to the TSs. The staff has grouped the proposed changes to the TSs into three categories, as follows:

{ (1) TS changes that replace each reference to SRM and IRM and their

functions, ranges, or modes of operation with WRNM and its equivalent j functions, ranges, or modes of operation. This includes changes to the

, TS definition of core alterations, limiting conditions for operation t

(LCOs)3.3.1.1,3.3.1.2,3.6.2.1,3.9.3,3.9.4,3.9.5,3.10.2,3.10.8, and their associated bases.'

i (2) TS changes that revise TS Table 3.3.;.1-1 (Reactor Protection System Instrumentation) and associated allowable values, surveillance requirements (SRs) and bases to reflect the implemar.tation of the WRNMS operating in the intermediate range mode, i (3) TS changes that revise TS Table 3.3.1.?-l (formerly Source Range Monitor Instrumentation, now Wide Range Neutron Monitor Instrumentation) and i associated SRs and bases to reflect the implementation of the WRNMS operating in the startup range mode.

The following documents the staff's evaluation of the above three types of proposed TS changes.

2.3 Replace References to SRM or IRM with WRNM l

In the submittal, the licensee changed each reference to IRM and SRM and their

- associated functions, ranges, or modes of operation with WRNM and its equivalent functions, ranges, and modes of operation as appropriate. This includes the definition of equivalent power levels for conditions that were previously defined in terms of meter readings and IRM range settings. This

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also includer changes to the TS definition of core alteration and changes to LCOs 3.3.1.1, 3.3.1.2, 3.6.2.1, 3.9.3, 3.9.4, 3.9.5, 3.10.2, 3.10.8, and their associated bases.

The staff finds that the replacement of the references to SRM and IRM with WRNM in the TS definition of core alterations is consistent with the existing definition and results in no other changes to the TS definition of core alteration.

The staff has reviewed each replacement of the references to SRM and IRM with WRNii and finds that each his been appropriately adjusted to reflect the implementation of the WRNMS and that each is consistent with the TS changes approved in the staff's SER of generic topical report NED0-31439-A. The staff has checked each reference to equivalent power levels and finds that each is consistent with the existing TS requirement. The staff, therefore, finds these TS changes in NEDO-32368 to be acceptable.

2.4 Changes to TS Table 3.3.1.1-1 and Associated SRs and Bases The licensee proposed to change TS Table 3.3.1.1-1 and associateo SRs and bases to reflect the implementation of the WRNMS operating in the intermediate-range mode as follows:

(1) The licensee proposed to delete existing SR 3.3.1.1.5, which requires the verification of overlap between the SRMs and IRMs in MODE 2. This SR is not needed because the neutron detectors used in the WRNMS are not retracted and do not require re-insertion. The deletion of this SR is consistent with TS changes approved in the staff's review of NED0-31439-A, in which this SR is deleted. The staff, therefore, finds deletion of SR 3.3.1.1.5 to be acceptable.

(2) The licensee proposed to delete existing SR 3.3.1.1.6, which requires the verification of overlap between the IRMs and average power range monitors (APRMs) in MODE 2. In the existing system this surveillance performs several functions. It confirms that the IRM gains, ranges, pre-amplifier, etc., are set up correctly. It also confirms -that the IRM detectors are inserted into the core. Together with normal operator -

procedures, this assures that neutron flux monitoring and scram trip protection are in effect when entering MODE 2.

The proposed replacement WRNMS uses fixed in-core detectors, therefore, existing SR 3.3.1.1.6 is no longer required to usure that the detectors are inserted. The upscale, level-based IRM scran, trip is eliminated for the WRNM and replaced with the rate-based "short-teriod" trip. The-IRM range switches and the two-range pre-amplifier e e also eliminated.

Consequently, no set-up selections or adjustment.s are required to assure that the WRNMS monitoring functions are active. The trip calculation and

period extraction are performed diettally. The period extraction depends only upon proportional change in the WRNM signal relative to neutron flux, a characteristic that is independent of WRNM gain adjustments. "

Therefore, no WRNM calibration is required.

With the above neutron monitoring system changes, no specific surveillance test is required to assure that neutron monitoring is available. Normal operator procedures exercised start-up mode assure that the WRNMS is omrable. prior to entering theOperator panel are presented in a manner that pemits tte operator to easily conclude that the WRNMS channel is operating, and that signal outputs are reasonable. This is all that is required to assure that the WRNMS channels are functioning properly when entering MODE 2. Based on the above, the staff finds that the deletion of existing SR 3.3.1.1.6 is acceptable.

(3) The licensee proposed to replace the tixisting neutron flux high function having an allowable value of 120/125 divisions of full scale with the period short function having an allowable value of equal-to-or-greater-than 13 seconds. This change was included in the licensee's analysis of the rod withdrawal error event, which was previously reviewed and approved by the staff in the SER for NED0-32368. That analysis was based on a short period of 10 seconds. The proposed 13-second allowable value is conservative by 30 percent. The licensee stated that the basic methodology used to calculate the WRNM setpoints is unchanged from the existing RM and SRM systems. The staff, therefore, finds that the proposed allowable value of 13 seconds is acceptable.

(4) The licensee proposed to change the surveillance interval as it applies to the WRNM period short function for SRs 3.3.1.1.3 and 3.3.1.1.4 from 7 days to 31 days, while keeping the 7-day interval as it applies to APRM functions. This is accomplished by replicating these two SRs, changing the interval to 31 days for WRNM, and assigning to then SR numbers 3.3.1.1.5 and 3.3.1.1.6, which were not used, as is discussed above.

The licensee based the extensioi of the surveillance interval from 7 to 31-days on the WRNMS having (1) fixed in-core detectors, (2) greater reliability than the SRMs and 1RMs, and (3) self-test features (including the fact that the WRNMS self-test automatically perfoms the CHANNEL FUNCTIONAL TEST at least every half hour). The only portions of the WRNMS trip circuit that are not monitored continuously by the self tests are the initial signal processing and the relay logic. The initial signal processing is covered by a channel check every 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> (SR 3.3.1.1.1 .

test interval)should be 31 days, as is used for other relay logicThe licensee proposed, t circuitry. Based on the above, the staff finds that the surve'11ance p interval of 31 days for these WRNM functions is acceptable.

(5) The licensee proposed to extend the surveillance interval for existing SR 3.3.1.1.11 (Channel Calibration) from 6 months to 24 months. The licensee based the extension request upon the WRNMS setpoint analysis.

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The licensee also proposed to reverse the order of SRs 3.3.1.1.11 and 3.3.1.1.12 in order to keep the :,borter intervals listed before the longer intervals, consistent with the format of the PBAPS improved TS.

Existing SR 3.3.1.1.11 becomes new SR 3.3.1.1.12, and vice versa.

The licensee stated that the basic methodology used to calculate WRNMS setpoints is unchanged from that used for the existing IRM and SRM systems. The significant difference between the systems is the reduced effect of drift on the WRNMS.

The existing IRM and SRM systems both use analog components for initial signal processing, mean-square-voltage (MSV) calculation (IRM), period s

extraction (SRM) and trip processing. The IRM and SRM use individual pre-amplifiers. The IRM pre-amplifier has two ranges and the IRM instrument has 10, each of which require calibration.

The replacement WRNMS uses a single, improved, pre-amplifier. This pre-amplifier is a simplified digital design, which has eliminated all adjustable components. Therefore, no hardware calibration is required.

The HSV calculation is performed with fully integrated highly stable components. As a result of these simplifications in processing hardware design, and the improvement in component quality, term drift of component values that affect signal processing is virtually eliminated. All trip calculations are performed digitally, therefore, trip unit drift is not a concern. In addition, the change in the WRNM from level-based trips (for IRM) and digital extraction of the period makes the safety trips and I indication of increasing rea:tivity insensitive to any residual drift in I the processing. The licensee stated that since the calibration frequency is influenced primarily by drift, the virtual elimination of drift in the WRNMS justifies the factor of 4 reduction in calibration frequency. This is confirmed by using the WRNMS estimated drift effects for 30 months (24 months plus the TS-allowed 25 percent grace period) in the normal, NRC-approved, setpoint calculation methodology when calculating WRNM setpoints. The licensee states that because the setpoint calculations yield adequate margins, the necessary TS surveillance interval is determined to be 24 months. The staff has reviewed the above justification and agrees with the licensee that setpoint drift for the WRNMS will be negligible over a 24-month interval.

In addition, the licensee has established a program for monitoring and i assessing the effects of increased calibration intervals on instrument drift. The purpose of this monitoring program is to provide a means to verify the assumptions made in the setpoint methodology with regards to instrument drift. This monitoring also provides a method to determine the adequacy of a surveillance interval. The licensee's drift trending program commits to evaluate a reduction in surveillance interval for any calibration surveillance that fails to meet the specified leave-alone criteria (procedure drift allowance) for that instrument, l

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Based on the above, the staff finds that the proposed extension of the ,

surveillance interval to 24 months for existing SR 3.3.1.1.11 (new SR3.3.1.1.12) will not have a significant effect on safety margins, is consistent with the guidance of Generic Letter 91-04 and is, therefore, acceptable.

2.5 Changes Related to Table 3.3.1.2-1 The licensee proposed the following changes to Table 3.3.1.2-1.

(1) Note (d) is added. The existing requirement is that a minimum of three of four total SRM channels be operational. This is considered adequate indication of core activity during shutdown. Note (d) is needed to requf re that there be at least three of eight WRNM channels operational to monitor activity in the core, and that at least three of the four quadrants of core have at least ono operational WRNM channel. The staff finds that this is consistent with the current TS and is, therefore, acceptable.

G) The licensee proposed to delete existing SR 3.3.1.2.5, which requires a channel functional test and determination of signal-to-noise ratio (SNR) ,

every 7 days when in Mode 5. The purpose of the SNR determination was to assure that the SRM detectors were inserted into the core to an acceptable level. Since the WRNM detectors cannot be retra ".ed, there is no longer a need to assure that they are inserted to an acceptable level.

The licensee also proposed to substitute existing SR 3.3.1.2.6 in pla<:e of existing SR 3.3.1.2.5, thus, combining all of the requirements of the two existing SRs, except that the surveillance interval is extended from 7 to 31 days. The licensee justified the proposed surveillance interval extension on the basis that the normal WRNMS channel check will confirm that t::e count rate indication is still reasonable, and that the channel check in combination with The WRNMS self-test feature will confirm that the total signal processing path and central processing unit operations are still being performed. The channel check and self-test confirm operability of all hardware required to indicate a short or decreasing period, which is the indication of unexpected reactivity changes in the core. The staff agrees that the above sureeillances are sufficient to justify a surveillance interval of 31 days. Based on the above, the staff finds that the proposed combination of existing SRs 3.3.1.2.5 and 3.3.1.2.6 into the new SR 3.3.1.2.5 is acceptatle.

(3) The licensee proposed to extend the surveillance interval for existing SR 3.3.1.2.7 from 6 months to 24 months, and to assign the vacated number 3.3.1.2.6 to this SR. The licensee's justification for this surveillance interval extension is the same as for the extension from 6 to 24 months for existing SR 3.3.1.1.11 discussed in Section 2.4, item (5), above.

The staff agrees that this justification is applicable to this SR, and therefore, finds that the proposed extension of the surveillance interval to 24 months for existing SR 3.3.1.2.7 (new SR 3.3.1.2.6) is acceptable.

3.0 STATE CONSULTATION

In accordance with the Commission's regulations, the Pennsylvania State official was notified of the proposed issuance of the amendments. The State official had no comments.

4.0 ENVIRONMENTAL CONSIDERATION

The amendment changes a requirement with respect to installation or use of a facility component located within the restricted area as defined in 10 CFR Part 20 and change surveillance requirements. The NRC staff F Jetermined that the amendment involves no significant increase in the ame' cs, and no significant change in the types, of any effluents that may be released offsite, and that there is no significant increase in individual or cumulative occupational radiation exposure. The Commission has previously issued a proposed finding that the amendment involves no significant hazards consideration, and there has been no public comment on such finding (60 FR 29885). Accordingly, the amendment meets the eligibility criteria for categorical exclusion set forth in 10 CFR 51.22(c)(9). Pursuant to 10 CFR 51.22(b) ?> environmental impact statement or environmental assessment need be prepared in connection with the issuance of the amendment.

5.0 CONCLUSION

Based on the above, the staff concludes that the licensee's proposed changes in NED0-32368 to the PBAPS, Unit 3 TSs, to incorporate the WRNMS are a consistent with the TS changes approved in the staff's SER of NEDO-31439-A, dated October 3, 1990. The staff further concludes that the proposed extension to surveillance intervals for certain WRNMS surveillance requirements will not have a significant effect on safety margins and are consistent with the guidance of Generic Letter 91-04. The staff therefore concludes that the TS changes proposed for the PBAPS, Unit 3 WRNMS associated with LCR 93-18 are acceptable.

The Commission has concluded, based on the considerations discussed above, that: (1) there is reasonable assurance that the health and safety of the public will not be endangered by operation in the proposed manner, (2) such activities will be conducted in compliance with the Commission's regulations, and (3) the issuance of the amendments will not be inimical to the common defense and security or to the health and safety of the public.

Principal Contributor: W. K. Mortensen Date: September 30, 1997

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