ML20207E242
| ML20207E242 | |
| Person / Time | |
|---|---|
| Site: | Peach Bottom  |
| Issue date: | 03/01/1999 |
| From: | Geoffrey Edwards PECO ENERGY CO., (FORMERLY PHILADELPHIA ELECTRIC |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| Shared Package | |
| ML20207E246 | List: |
| References | |
| GL-94-02, GL-94-2, NUDOCS 9903100202 | |
| Download: ML20207E242 (15) | |
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J 10CFR50.59(c) 10CFR50.90 GL 94-02 PECO NUCLEAR eeco % c -.,
A Unit of PECO Ene gy N5 cke [e roo$ BoSNa Wayre PA 19087 5691 o
March 1,1999 Cocket Nos. 50-277
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50-278 License Nos. DPR-44 DPR-56 U.S. Nuclear Reguistory Commission ATTN: Document Control Desk Washington, DC 20555
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Subject.
Peach Bottom Atomic Power Stations, Units 2 and 3 License Cnange Request ECR 98-01802
Reference:
Letter from Garrett D. Edwards, PECO Energy Company to USNRC, dated March 2,1998.
Dear Sir:
PECO Energy Company (PECO Energy) hereby submits License Change Request 5
ECR 98-01802 in accordan,e with the requirements of 10CFR50.59 and 10CFR50.90, requesting changes to the Peach Bottom Atomic Powf.,r Station (PBAPS), Units 2 and E. Facility Operating Licenses.
The proposed changes are necessary to support PBAPS Modification P00507 which will inst &ll a digital Power Range Neutron Monitoring (PRNM) system and incorporate long-term thermal-hydraulic stability solution hardware.
in response to Ger eric Letter 94-02, "Long-Term Solutions and Upgrade of Interim Operating Recommendations for Thermal-Hydraulic Instablities in Boiling Water Reactors," PECO Energy submitted the reference letter informing you of our selection of Option 1.1 as the long-term solution. We have deci(*.ed to install General Electric (GE) Option ill as described in NEDO-31960-A (including Supplement I), "BWR Owners' Group Long-Term Stability Solutions Licensing Methodology." The Option lli stability solution will be installed as part cf PBAPS Modification P00507 PBAPS Modification P00507 consists of replacing the existing Power Range Monitor system, including the Average Power Range Monitor system, the Rod Block Monitor system, and tne Local Power Range Monitor system, excluding the detectors and signal cables, with GE's Nuclear Measurement Analysis and Control (NUMAC) PRNM system. The Option 111 stability solution is integrated into PRNM system electronics.
9903100202 990301 PDR ADOCK 05000277 P
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March 1,1999 Page 2 The PRNM system is scheduled for installation at PBAPS Unit 3 during Refueling Outage 3R12 scheduled to begin in October 1999. The PRNM system is scheduled for installation at PBAPS Unit 2 during Refueling Outage 2R13, scheduled to begin in October 2000. to the lottar describes the proposed changes and provides justification for the changes. Attachment 2 to the letter provided marked-up Technical Specifications pages. The proposed Technical Specifications changes are consistent with GE Licensing Topical Report NEDC-32410P-A,
- Nuclear Measurement Analysis and Control Power Range Neutron Monitor (NUMAC-PRNM) Retrofit Plus Option ill Stability Trip Function," with some minor deviations. Attachment 3 to this letter prevides plant-specific responses required for NUMAC-PRNM Retrofit in the form of a table. It lists the required utility actions delineated in the Topical Report and PECO Energy's response.
e The 10CFR50.59 Review prepared for this niodification concluded that the proposed change may create the possibility of a malfunction of equipment of a different type than any evaluated previously in the safety analysis report. Because this conclusion constitutes an unreviewed safety question,10CFR;0.59 requires NRC approval of the proposed change and submission of this application for amendment of the PBAPS Units 2 and 3 licenses.
We request that the NRC review and approve this application by September 30,1999, to support installation of PRNM in PBAPS Unit 3 during Refueling Outage 3R12. This it, the same stability option previously approved and installed on Hatch Units 1 and 2, Nico Mile Point Unit 2, Browns Ferry Units 2 and 3, and Fermi Unit 2.
Pursuant to 10CFR50.91(b)(1), PECO Eriergy has provided a copy of this license change request with enclosures to the appropriate State Official.
if you have any questions or require additional information, please do not hesitate to contact us.
i Ve truly yours, arrett D. Edwards l
Director-Licensing l
Enclosures:
Affidavit, Attachments 1,2 and 3 i,
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H. J. Miller, Administrator, Region I, USNRC A. C. McMurtray, Senior Resident inspector, PBAPS, USNRC j
R. R. Janati-Commonwealth of Pennsylvania l
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1 COMMONWEALTH OF PEN %YLVANIA l
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C0UNTY OF CHESTER J. J. Hagan, being first duly swom, deposes and says:
That he is Senior Vice President of PECO Energy Company, the Appicant hereen; that he has read l
the attadwd License Change Request (ECR 9601802) for Peach Bottom Atomic Power Stabon, l
Units 2 and 3, Facility Operating Loonse Nos. DPR-44 and DPR-56, and knows the contents thereof; and that the statements and matters set forth therein are true and correct to the best of his 1'
i knowledge,information and belief.
i Subsenbod and swom to before me thisby of 1999.
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Notary Public NOTARIAL SEAL CAROL A, wALTON. Notary Putsils 3
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- c-adelphia. Pula.
City of Phil e w,e - av a l
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i Peach Bottom Atoniic Power Station Units 2 and 3 i
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Docket Nos. 50-277 50-278 License Nos. DPR-44 DPR-56 License Change Request ECR 98-01802
" Thermal Hydraulic Stability Solution Option lil"
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Supporting information for changes - 9 pages l
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i Docket Nos. 50-277 50-278 License Nos. DPR-44 DPR-56 PECO Energy Company (PECO Energy) requests that the facility operating licenses for Peach i
Bottom Atomic Power Station (PBAPS) Units 2 and 3 be amended for installation of a digital Power Range Neutron Monitoring (PRNM) system to replace the existing Power Range Monitor system. Prior NRC approval is required for this modification, PBAPS Modification P00507, because the 10CFR50.59 Review prepared for this modification concluded that the proposed modification constitutes an unreviewed safety question. PECO Energy also requests approval of proposed Technical Specifications (TS) changes regarding the installation of long-term thermal-hydraulic stability solution hardware.
Provided below is a discussion and description of the propc::ed changes, a safety assessment, information supporting a finding of No Significant Hazards Consideration, and information on supporting an Environmental Assessment.
The PBAPS Unit 3 marked-up TS pages indicating the proposed changes are provided in.
We request that, if approved, the changes be effective by September 30,1999. The PRNM system will be installed in PBAPS Unit 3 during Refueling Outage 3R12 scheduled to begin in October 1999. The PRNM system will be installed in PBAPS Unit 2 during Refueling Outage 2R13 scheduled to begin in October 2000.
1 Discussion and Description of the Proposed Channes:
PBAPS Modification P00507 replaces the existing Power Range Monitor system, including the Average Power Range Monitor (APRM) system, the Rod Block Monitor (RBM) system, and the Local Power Range Monitor (LPRM) system, excluding the detectors and signal cables, with General Electric's Nuclear Measurement Analysis and Control (NUMAC) PRNM system. The long-term thermal-hydraulic stability solution is integrated into the PRNM system electronics.
l The NUMAC PRNM system utilizes the Oscillation Power Range Monitor (OPRM) detect-and-
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suppress function to implement the Option lil stability solution. During the first operating cycle following installation of the PRNM system, the OPRM will be fully operational except for the trip functions. These OPRM trip functions will not be connected to the Reactor Protection System (RPS)in order to evaluate the performance of the OPRM algorithms. During the first operating i
cycle following instellation of the PRNM system, PECO Energy will continue to implement the l.
Interim Corrective Actions specified in NRC Bulletin 88-07 Supplement I to detect and suppress l
power oscillations as committed to in PECO Energy letter from G. A. Hunger to USNRC dated l
September 9,1994.
After one cycle of operation, the OPRM performance will be evaluated, any changes tc the l
OPRM setup or tuning will be implemented, the OPRM trip function will be connected to the RPS, the TS will be updated with the OPRM-related functions under a separate license amendment, and appropriate operator training and procedures will be modified.
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h TS Table 3.3.1.1-1 Channes to Functions:
The "APRM Startup High Flux Scram" will be retained but the name will be changed to "APRM Neutron Flux-High (Setdown)." The "APRM Flow Biased High Scram" and " Scram Clamp" will be replaced with "APRM Simulatea Thermal Power (STP) High" and *APRM Neutron Flux.
4 High."
The "APRM Downscale Scram" will be eliminated.
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The "APRM Inop" trip will be retained, but will be changed to reflect the new NUMAC PRNM system equipment ano to delete the minimum LPRM detector count from this trip. The minimum LPRM detector count will be retained in the Inop alarm.
A new function entitled "2-Out Of-4 Voter" will be added. The six APRM channel configuration I
of the current system will be replaced with a four channel configuration. In this configuration, four new 2-out-of-4 trip output voter channels will be added as an interface between the APRM functions and the RPS. The ouputs from all four APRM channels will go to each of these four independent 2-out-of-4 voter channels. Two of the 2-out-of-4 voter channels will provide inputs to one RPS trip system and the other two 2-out-of-4 voter enannels will provide inputs to the i
other RPS trip system. As such, each of the inputs to the RPS is a voted result of all four APRM channels. Additionally, only one APRM channel out of the four can be bypassed, while none of the voter channels can be bypassed. This assures at least two APRM channels to i
each of the 2-out-of-4 voter channels in the event of a single APRM channel failure and one APRM channel bypassed. This will in turn result in trip signals to each RPS trip system (full scram).
TS Table 3.3.1.1-1 Channes to Reauired Number of APRM Channels:
l The required minimum number of operable APRM channels will change from four to three
- channels, A new requirement for minimum number of 2-out-of-4 voter channels will be added; all four 2-out-of-4 voter channels must be operable.
The minimum number of cperable LPRMs per APRM channel required for APRM channel operability will increase from 14 to 20 per APRM channel and from 2 to 3 for each of the four LPRM axiallevels.
A new requirement for the maximum number of LPRMs per APRM channel that may become inoperable (and bypassed) between APRM calibrations will be added; the new limit is 10 LPRMs per APRM channel.
TS Table 3.3.1.1-1 Channes to ADDlicable Modes of ODeration:
The new "APRM Simulated Thermal Power High Scram" and "APRM Neutron Flux-High Scram" will be required to be operable in Mode 1 only.
The new "APRM 2-Out-of-4 Voter Scram" will be required to be operable in Modes 1 and 2.
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TS Table 3.3.1.1-1 Channes to APRM Surveillance Recuirements (SRs):
The new "APRM 2-Out of 4 Voter Scram" will have a channel check requirement of once per 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />.
The "APRM Neutron Flux-High (Setdown)" channel functional test SR frequency will be changed from every 7 days to every 184 days, but with a note allowing operation for up to 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> prior to test after entering Mode 2 from Mode 1. This SR will include both the APRM channels and the 2-out-of-4 voter channels.
The "APRM Simulated Thermal Power-High" channel functional test frequency will be every 184 days (without any specific requirement related to startup or shutdown). This SR will include the APRM channels, the 2-out-of-4 voter channels, and the flow input function excluding the flow transmitters.
The "APRM Neutron Flux-High" channel functional test frequency will be every 184 days (without any specific requirement related to startup or shutdown). This SR will loclude both the APRM channels and the 2-out-of-4 voter channels.
1 The "APRM Inop" channel functional test frequency will be changed from every 92 days to 184 days (without any specific requirement related to startup or shutdown). This SR will include both the APRM channels and the 2-out-of-4 voter channels.
The "APRM Neutron Flux-High (Setdown)" channel calibration frequency will be changed from every 18 months to every 24 months.
The "APRM Simulated Thermal Power-High" channel calibration frequency will be every 24 months. The existing surveillance requirement for monthly adjustment of flow hardware will be deleted. Calibration of the flow hardware will be included in overall channel calibration of this function at 24-month intervals.
The "APRM Neutron Flux-High" channel calibration frequency will be every 24 months.
The "APRM 2-Out-of-4 Voter Scram" will have a logic system functional test frequency of 24 months. The logic system functional test requirement for all other APRM functions will be deleted.
APRM Setoolnts and Allowable Values:
Setpoints and Allowable Values have been changed where justified by the setpoint calculations and the improved equipment performance specifications.
TS Teble 3.3.2.1-1 Channes:
l The thermal power range surveillance limits associated with each RBM upscale function (Low Power, Intermediate Power, and High Power Ranges) will be modified to make them "one-sided" limits to reduce the risk of potential surveillance compliance problems in the future. The i
precision required to transition between Power Ranges as currentif prescribed is difficult to achieve.
The *RBM Downscale" rod block will be deleted.
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I The 'RBM Bypass Time Delay" rod block will be deleted.
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TS 3.4.1. " Recirculation Loops Operatina":
The reference to the "APRM Flow Biased High Scram" will be replaced with "APRM Simulated Thermal Power-High."
TS 3.10.8. " Shutdown Marain Test-Refuelina":
The *APRM 2-Out-of-4 Voter Scram" will be added to SR 3.10.8.1 because it is required to be operable in Mode 2.
Bases for the TS Chanaes:
The bases for the above listed TS changes are documented in Section 8.0 of the NUMAC PRNM Licensing Topical Report (LTR) NEDC-32410P-A, including Supplement 1 with the following exceptions:
References to SRM and IRM in the LTR are replaced with corresponding references to WRNM.
The LTR discusses in detail the aspects of the PRNM equipment that are improved and the justification for elimination of SR 3.3.1.1.7 due to drift of the PRNM equipment. However, the justification included in the LTR does not address the potential impact of changes in the core flow / recirculation flow ratio, either as a result of changes in power distribution over the cycle or due to the potential for operating at a higher rod line than that used for flow calibration. SR 3.3.1.1.7 only applies to flow as an input to the STP High (flow biased) scram. No safety credit is assumed in any analysis for the STP flow biased scram function. To the extent that flow biased scram is included in analysis, it is included as drive flow. Therefore, deletion of SR 3.3.1.1.7 and ' te potential increased difference between indicated drive flow and core flow have no safety impact on the STP flow biased scram function.
The LTR describes response time testing, including the APRM " sensors." PBAPS is committed only to response time testing of the RPS logics. Therefore, the changes included in the LTR that relate to response time testing of the PRNM electronics and logic are not applicable to PBAPS.
The improved performance specifications for the PRNM equipment compared to the current equipment provide additional margin between the setpoints or allowable values and the corresponding analytical limits or design basis values. Part of that margin wil' be used to offset the effect of increased surveillance intervals. The remaining margin, whare available, is used to justify relaxing the Allowable Values. The LTR does not address how to determine the Allowable Value for the STP-High or Neutron Flux-High functions when they replace the APRM Flow Biased Scram and Scram Clamp function as part of the modification. The PBAPS modification will retain the Analytical Limit for the Scram Clamp function as the APRM Neutron Flux-High Analytical Limit since those two functions are equivalent. Based on the Analytical Limit, the Allowable Value for the APRM Neutron Flux-High function has been calculated based on the improved specifications of the PRNM system. The value is shown in the TS markups.
There is no specific safety credit taken for the "APRM Flow Biased High Scram" in the original design, nor any safety credit taken for the "APRM Simulated Thermal Power-High" function in the re7 acement PRNM. Therefore, the Allowable Value for the "APRM Simulated Thermal 1
Power-High" function is based on engineering judgment to balance the be afits of providing additional margin for transients initiated at reduced flow conditions with the potential for inadvertent trips. Based on engineering judgment, a design bases " analytical limit" of 2% lower 5
than the value of the "APRM Neutron Flux-High" function (120%) has been established. The design bases for the STP flow biased scram equation has been established to provide the same " flow intercept" (approximately 81% rated flow) as the current equation for the "APRM Flow Biased High Scram." With these limits, the Allowable Values for the clamp and flow biased portions of the "APRM Simulated Thermal Power-High" have been calculated using t%e improved performance specifications of the PRNM system. The calculated values are included
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The thermal power ranges associated with each RBM upscale function " Low Power, intermediate Power, and High Power Ranges) have been modified to be "one-sided" to reduce the risk of non-compliance with performing SR in the future. As revised, the TS SR still accomplishes the same technical objective without the literal compliance problem at the transition point between Power Ranges in the current TS.
Deletion of the "RBM Downscale" trip from the TS is not discussed in the LTR. The RBM downscale trip function will detect substantial reductions in the RBM local flux after a
- null" is completed (a " null" occurs after a new rod selection). This function, in combination with the "RBM Inop" function, is intended to detect problems or abnormal conditions in the RBM equipment and system. However, no credit is taken for the RBM downscale trip function in the establishment of the RBM upscale trip analyticallimits or setpoint values. In the original analog RBM, the inclusion of a "downscale" function in addition to the "inop" function had some merit because the analog equipment had some failure modes that could result in a reduction of signal, but not a full failure. Unlike other neutron monitoring system downscale functions (e.g.,
the APRM downscale), there are no normal operating conditions whicn are intended to be detected by the RBM downscale function. Therefore. the RBM downscale function was in fact part of the overall RBM "inop" function. The replacement of the original analog RBM with the NUMAC digital RBM results in all of the original anniog processing being replaced by digital processing. One effect of this is to eliminate the types of failures that can reasonably be detected by the downscale trip function. In addition, the "inop" function is enhanced in the NUMAC RBM by the use'of automatic self-test and intemal logic to increase the detectability of abnormal conditions and to directly include these in the "RBM Inop" function. Therefore, in the NUMAC RBM, there is no incremental value or benefit provided by the "RBM Downscale" trip function. Consistent with the criteria of 10CFR50.36(c)(2)(ii), the *RBM Downscale" trip function is removed from TS while the "RBM INOP" function will be retained in TS.
The LTR did not include any discussion of the Recirculation loops Operating TS changes. The changes to the Recirculation Loops Operating are for consistency with the changes being made to TS 3.3.1.1.
Safety Assessment P9APS Modification P00507 and associated TS changes will not adversely affect the ability of the RPS and RBM systems to perform their intended function. The replacement system has improved channel trip accuracy and channelindicated accuracy. The proposed changes do not cause a plant parameter for any analyzed event to fall outside of acceptable limits. The SRs and their frequency of performance will assure reliability of the RPS and RBM systems.
Consequently, the proposed modifications and associated TS changes will not adversely affect the health and safety of the public and will not be inimical to the common defense or safety of the public.
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l Information SuDDortina a Findina of No Slanificant Hazards Consideration The changes proposed in this application do not constitute a Significant Hazards Consideration in that:
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- 1) The proposed chanaes do not involve a slanificant increase in the probability or consecuences of an accident previousiv evaluated.
As discussed in the LTR, the NUMAC PRNM modification and associated changes to the TS involve equipment that is designed to detect the symptoms of certain events or accidents and initiate mitigating actions. The worst case failure of the equipment involved in the modification is a failure to initiate mitigating action (scram or rod block), but no failure can cause an accident.
j The PRNM replacement system is designed to perform the same operations as the existing Power Range Monitor system and meets or exceeds all operational requirements. Therefore, it is concluded that the probability of an accident previously evaluated is not increased as a result l
of replacing the existing equipment with the PRNM equipment.
The PRNM system reduces the need for tedious operator actions during normal conditions and l
allows the operator to focus more on overall plant conditions. The automatic self-test and increased operator information provided with the replacement system are likely to reduce the burden during off-normal conda ons as well. The replacement equipment qualifications fully l
envelope the environmental conditions, including electromagnetic interference, in the PBAPS control room.
The replacement equipment has been specifically designed to assure that it fully meets the
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response time requitements in the worst case. As a result, due to statistical variations resulting l
from the sampling and update cycles, the response time is typically faster than required in order to assure that the required response time is always met. Setpoints are changed only when justified by the improved equipment performance specifications and by setpoint calculations which show that safety margins are maintained. There is no impact to the Control Rod Drop accident analysis because the PRNM system maintains all existing system functions with a reliability equal to or better than the existing Power Range Monitor system.
The replacement equipment includes up to 5 LPRM inputs on a single module compared to one per module on the current system. Up to 17 LPRM signals are processed through one l
preprocessor. The recirculation flow signals are processed in the same hardware as the LPRM
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processing. The net effect of these architectural aspects is that there are some single failures that can cause a greater loss of "sub-functionality" than in the current system. Other architectural and functional aspects, however, have an offsetting effect. Redundant power s,upplies are used so that a single failure of AC power has no effect on the overall PRNM system functions while still resulting in a half scram as does the current system. Continuous automatic self-test also assures that if a 1; ingle failure does occur, it is much more likely to be detected immediately. The net effect is that from a total system level, unavailability of the safety-related functions in the replacement system is equal to or better than the current Power Range Monitor system.
Based on the extensive and through verification and validation program used in the PRNM i
design and field operating experience, common cause failures in software controlled functior,
are judged to not be a significant failure rnode, lowever, in spite of that conclusion, means are provided within the system to mitigate the effects of such a failure and alert the operator.
Therefore, such a failure, even if it occurred, w,Il not increase the consequences of a previously evaluated accident.
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To reduce the likelihood of common cause failure of software controlled functions, thorough and careful verification and validation (V8V) activities are performed both for the requirements and the implementing software design. In addition, the software is designed to !!mit the loading that external systems or equipment can place on the system, thus significar.tly reducing the risk that some abnormal dynamic condition external to the system can cause system functional performance problems due to processing " overload" (i.e., " slowing down" or stopping the processing).
As a conservatism, however, despite these V&V activities, common cause failures of software controlled functions due to residual software design faults are assumed to occur. Both the software and hardware are designed to manage the consequences of such failure (and also cover potential common cause hardware failures). Safety outputs are designed to be fail safe by requiring dynamic update of output modules or data signals, where failure to update the information is detected by simple receiving hardware, which, in turn, forces a trip. This aspect covers all but rather complex failures where the software or hardware executes a portion of the overall logic but fails to process some portion of new information (inputs
- freeze") or some portion of the logic (outputs " freeze").
To help reduce the likelihood of complex failures, a watchdog timer is used which is updated by a very simple software routine that in turn monitors the operational cycle time of all tasks in the system. The software design is such that as long as all tasks are updated at the design rate, it is likely that software controlled functions are executing as intended. Conversely, if any task fails to update at the design rate, that is a strong indication of at least some unanticipated condition. If such a condition occurs, the watchdog timer will not be updated, the computer will be automatically restarted, and the system will detect an abnormal condition and provide an alarm and trip.
The information available to the operator is at least the same as with the current system and, in many cases, improved. No actions are required by the operator to obtain information normally used and equivalent to that available with the current equipment. Hnwever, the replacement system does provide more directly accessible information regarding the condition of the equipment, including automatic self-test, which can aid the operator in diagnosing unusual situations beyond those defined in the licensing basis.
In summary, the reliability of the new PRNM system and its ability to detect and mitigate abnormal flux transients have either remained the same or improved over the existing Power Range Monitor system. Since these postulated reactivity transients are mitigated by the new system as effectively and reliability as the existing system, the consequences of these transients have not changed. Therefore, the proposed changes do not involve a significant increase in the probability or consequences of an accident previously evaluated.
II) The proposed chanaes do not create the possibility of a new or different kind of accident from any accident previousIV evaluated.
PBAPS Modification P00507 uses digital processing with software (firmware) control for the main signal processing part of the modification. The remainder of the equipment in the modification uses conventional equipment similar to the current system (e.g., penetrations, cables, interface panels).
The digital equipment has " control" processing points and software controlled digital processing where the current system has analog and discrete component processing. The result is that 8
1 the specific failures of hardware and potential software common cause failure are different from the current system. The effects of software common cause failure are mitigated by hardware design and system architecture, but are of a "different type" of failure than those evaluated in the PBAPS Updated Final Safety Analysis Report (UFSAR). In general, the PBAPS UFSAR assumes simplistic failure modes (relays for example) but does not specifically evaluate such effects as self-test detection and automatic trip or alarm. Therefore, the replacement system may have a malfunction of a different type from those evaluated in the PBAPS UFSAR and constitutes an unreviewed safety question. However, when these PRNM failures are evaluated at the system level, there are no new effects.
PBAPS Modification P00507 involves equipment that is intended to detect the symptoms of certain transients and accidents and initiate mitigating action. The worst case failure of the equipment involved in the modification is a failure to initiate mitigating action (scram), but no failure can cause an accident. This is unchanged from the current system. Software common cause failures could cause the system to fail to perform its safety function, but this possibility is addressed in Section i) above. In that case, it might fail to initiate action to mitigate the consequences of an accident, but would not cause one. No new system level failure modes are created with the PRNM system.
Therefore, PBAPS Modification P00507 does not create the possibility of a new or different kind of accident from any accident previously evaluated.
iii) The proposed channes do not involve a slanificant reduction in a marain of safety.
The PRNM system response time and operator information is either maintained or improved over the current Power Range Monitor system.
The PRNM system has improved channel trip accuracy compared to the current system and meets or exceeds system requirements assumed in setpoint analysis. The channel response time exceeds the requirements. The channel indicated accuracy is improved over the current system and meets or exceeds all of the system requirements.
The PRNM system was developed to detect the presence of thermal-hydraulic instabilities and automatically initiate the necessary actions to suppress the oscillations prior to violating the MCPR Safety Limit. The NRC has reviewed and approved the LTR concluding that the PRNM system will provide the intended protection.
Therefore, PBAPS Modification P00507 does not result in a significant reduction in a margin of safety.
Information SuDoortina and Environmental Assessment An environmental impact assessment is not required for the changes proposed by this appl; cation because the changes conform to the criteria for " actions eligible for categorical exclusion," as provided for under 10CFR51.22(c)(9). The requested changes have no impact on the environment. The proposed changes do not involve a Significant Hazards Consideration as discussed in the preceding section. The proposed changes do not involve a significant change in the types or significant increase in the amounts of any effluents that may be released offsite. The proposed changes do not authorize any change in the authorized power level of the facility. In addition, the proposed changes do not involve a significant increase in individual or cumulative occupation radiation exposure.
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Conclusion The Plant Operations Review Committee and the Nuclear Review Board have reviewed PBAPS Modification P00507 and have concluded that the changes involve an unreviewed safety question and the proposed changes will not endanger the public health and safety.
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