ML20238F266
| ML20238F266 | |
| Person / Time | |
|---|---|
| Site: | Peach Bottom  |
| Issue date: | 08/24/1998 |
| From: | NRC (Affiliation Not Assigned) |
| To: | |
| Shared Package | |
| ML20238F255 | List: |
| References | |
| NUDOCS 9809030233 | |
| Download: ML20238F266 (7) | |
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?L UNITED STATES
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NUCLEAR REGULATORY COMMISSION 2
WASHINGTON, D.C. - anat s...../
SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NO2??TO FACILITY OPERATING LICENSE NO. DPR-44 PECO ENERGY COMPANY PUBLIC SERVICE Fl FCTRIC AND GAS COMPANY DFt MARVA POWER AND LIGHT COMPANY ATLANTIC CITY FI FCTRIC COMPANY PEACH BOTTOM ATOMIC POWER STATION UNIT NO. 2 DOCKET NO. 50-27'T l
1.0 INTRODUCTION
By letter dated January 17,1995, as supplemented March 30,1995; July 2,1996; February 28 and September 22,1997; and January 23, July 9, and July 29,1998, PECO Energy Company (the licensee) submitted License Change Request (LCR) 93-18, in accordance with 10 CFR 50.90, requesting changes to Appendix A of the Peach Bottom Atomic Power Station (PBAPS),
Units 2 and 3, Facility Operating Licenses. PECO Energy submitted this LCR to support PBAPS Modification P00271, to replace the existing Source Range (SRM) and Intermediate Range Neutron Monitors (IRM) with the Wide Range Neutron Monitoring System (WRNMS). The March 30,1995; July 2,1996; February 28 and September 22,1997; and January 23, July 9, and July 29,1998, letters provided clarifying information that did not change the June 6,1995 initial proposed no significant hazards consideration determination (60 FR 29885).
2.0 EVALUATION h
2.1 Evaluation of WRNMS Modification Design
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in its January 17,1995 application, PECO Energy stated that the PBAPS WRNMS is effectively identical with the staff-approved generic system documented in Licensing Topical Report NEDO-1 31439-A,"The Nuclear Measurement Analysis and Control Wide Range Neutron Monitoring System (NUMAC WRNMS)." The staff's safety evaluation (SE) approving the generic NUMAC-,
WRNMS in NEDO-31439-A was transmitted to General Electric (GE) Nuclear Energy by letter dated October 3,1990.
The licensee's submittalincluded the GE Nuclear Energy Licensing Report, NEDO-32368,
" Nuclear Measurement Analysis and Control Wide Range Neutron Monitoring System Licensing Report For Peach Bottom Atomic Power Station, Units 2 and 3." NEDO-32368 summarizes the 9809030233 980824 y
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analyses and evaluations performed to justify installing and operating a NUMAC-WRNMS at PBAPS, Units 2 and 3, and also addresses plant-specific differences between the PBAPS WRNMS and the generic WRNMS. The staffs SE approving NEDO-32368, except for the review of the proposed changes to the technical specifications, was transmitted to PECO Energy by j
letter dated June 9,1995.
2.2 Evaluation of WRNMS Technical Specircations (TSs)
I The licensee implemented license amendments 210 and 214, which approved PBAPS improved TSs, in January 1996. The followng is the staffs evaluation of the proposed improved TS changes assoaated with the installation of the WRNMS at PBAPS, Unit 2. The TS changes
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associated wi*h the installation of the WRNMS at PBAPS, Unit 3 were previously approved in Amendment No. 224, issued on September 30,1997. The TS changes associated with the l
installation of WRNMS at PBAPS, Unit 2 were deferred pending the forthcoming refueling outage 2R12 scheduled for early October 1998.
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The WRNMS 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 NEDO-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, cr modes of operation with WRNM and its equivalent functions, ranges, or modes of o,Deration. This includes changes to the TS definition of core alterations, limiting conditions for operation (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.
(2)
TS changes that revise TS Table 3.3.1.1-1 (Reactor Protection System instrumentation) and associated allowable values, surveillance requirements (SRs) and bases to reflect the implementation of the WRNMS operating in the intermediate range mode.
(3)
TS changes that revise TS Table 3.3.1.2-1 (formerly Source Range Monitor instrumentation, now Wuie Range Neutron Monitor instrumentation) and associated SRs l'
and bases to reflect the implementation of the WRNMS operating in the startup range mode.
The following documents the staffs evaluation of the above three types of proposed TS changes.
2.3 Replace References to SRM or IRM with WRNM 1
in the submittal, the licensee changed each reference to IRM and SRM and their associated j
functions, ranges, or modes of operation with WRNM and its equivalent functions, ranges, and modes of operation as appropriate. This includes the defirution of equivalent power levels for conditions that were previously defined in terms of meter readings and IRM range settir'gs. This also includes 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.
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4 i 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 defitution of core alteration.
The staff has reviewed each replacement of the references to SRM and IRM with WRNM and finds that each has been appropriately adjusted to reflect the implementation of the WRNMS and j
that each is consistent with the TS changes approved in the staffs SER of generic topical report NEDO-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.
i 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 associated 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.
3 The deletion of this SR is consistent with TS changes approved in the staffs review of NEDO 31439-A, in which this SR is deleted. The staff, therefore, fods 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 overiap between the IRMs and average power range monitors (APRMs) in MODE 2. In the existing system this surveillance performs several funchons. It confwms that the IRM gains, ranges, pro-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.
l The proposed replacement WRNMS uses fixed in-core detectors, therefore, existing SR 3.3.1.1.6 is no longer required to assure that the detectors are inserted. The upscale, i
level-based IRM scram trip is eliminated for the WRNM and replaced with the rate-based l
"short-period" trip. The IRM range switches and the two-range pro-amplifier are also l
alimmated. Consequently, no set-up selec ions or adjustments are required to assure that the WRNMS monitoring functions are active. The trip calculation and period extraction are l
performed digitally. The period extraction depends only upon proportional change in the l
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 specirc surveillance test is required to assure that neutron monitoring is available. Normal operator procedures exercisec' prior to entering the start-up mode assure that the WRNMS is operable.
Operator panel displays are presented in a manner that permits the operator to easily J
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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 funchoning property
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when entenng 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 existing neutron flux high funcbon having an sliowable 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 NEDO-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 IRM 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 them 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 extension 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 IRMs, and (3) self-test features (including the fact that the WRNMS self-test automatically performs the CHANNEL FUNCTIONAL TEST at least every half hour). The only portions of the WRNMS trip circust 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). The licensee proposed, therefore, that the funchonal test interval should be 31 days, as is used for other relay logic circuitry. Based on the above, the staff finds that the surveillance interval of 31 days for these WRNM funchons is acceptable.
1 (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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1 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 shorter 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.
a 5-The existing IRM and SRM systems both use analog components for initial signal processing, mean-square-voltage (MSV) calculation (IRM), period extraction (SRM) and trip processing. The IRM and SRM use individual pre-amplifers. The IRM pro-amplifer has two ranges and the IRM instrument has 10, each of which require calibration.
The replacement WRNMS uses a single, improved, preamplifier. This pre-amphfieris a simplifed digital design, which has eliminated all adjustable components. Therefore, no hardware calibration is required. The MSV calculation is performed with fully integrated highly stable components. As a result of these simphfications in processing hardware design, and the improvement in component qualsty, 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 concem. In addition, the change in the WRNM from level-based trips (for IRM) and digital extraction of the period makes the safety trips and indication of increasing reactivity insensitive to any residual drift in the processing The hcensee stated that since the calibration frequency is influenced pnmarily by drift, the virtual ehmination of drift in the WRNMS justifes the factor of 4 reduction in cahbration 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 hcensee 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 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 trendog program commsts to evaluate a reduchon in surveillance interval for any calibration surveillance that fails to meet the specifed leave-alone criteria (procedure drift allowance) for that instrument.
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 SR 3.3.1.1.12) 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 followng 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 indecation of core actsvity during shutdown. Note (d) is needed to require 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 one operational WRNM charmel. The staff finds that this is ceasistent with the current TS and is, therefore, acceptable.
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(2)
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) overy 7 days when in Mode 5. The l
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 retracted, there is no longer a need to assure that they are inserted to an acceptable level.
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The licensee also proposed to substitute existing SR 3.3.1.2.6 in place of existing SR I
3.3.1.2.5, thus, cc,mtAW,g 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 the 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 I
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 i
agrees that the above surveillance are sufficient to justify a surveillance interval of 31
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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 acceptable.
(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 (now 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
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the proposed issuance of the amendments. The State official had no comments.
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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 changes surveillance l
requirements. The NRC staff has determined that the amendment involves no signifmant increase in the amounts, and no signifcant 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) no environmental impact statement or environmental assessment need be prepared in connection with the issuance of the amendment.
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5.0 CONCLUSION
Based on the above, the staff concludes that the licensee's proposed changes in NEDO-32368 to the PBAPS, Unit 2 TSs, to incorporate the WRNMS are consistent with the TS changes approved in the staffs 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 NRC Generic Letter 91-04. The staff therefore concludes that the TS changes proposed for the PBAPS, Unit 2 WRNMS assocasted 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: August 24, 1998 f
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