ML20294A063
| ML20294A063 | |
| Person / Time | |
|---|---|
| Site: | Hope Creek  |
| Issue date: | 10/20/2020 |
| From: | Public Service Enterprise Group |
| To: | Office of Nuclear Reactor Regulation |
| Kim J | |
| References | |
| Download: ML20294A063 (14) | |
Text
Application of RIS 2002-22 Supplement 1 Qualitative Assessment Approach to Install Digital WRNMS Upgrade Under 10CFR50.59 NRC Public Meeting October 27, 2020 Hope Creek Replacement of SRMs and IRMs with Digital NUMAC Wide Range Neutron Monitor System
Agenda Introduction Purpose of meeting Scope of Project Rationale for use of RIS-2002-22 Supplement-1 for WRNM RWE During Startup Startup of Idle Recirc Pump at Low Power Plant / System Attributes Supporting Qualitative Assessment Elements Supporting Qualitative Assessment Proposed Scope of LAR Next Steps Adjourn 2
Purpose of Meeting Hope Creek is pursuing replacement of the Source and Intermediate Range Neutron Monitors (SRMs/IRMs) with the GE NUMAC Wide Range Neutron Monitor System (WRNMS)
Pursue implementation of digital upgrade under 10 CFR 50.59
50.59 supported by a Qualitative Assessment prepared using the criteria and guidance described in Regulatory Information Summary (RIS) 2002-22 Supplement 1 QA to support conclusion that Likelihood of Failure of digital SSC sufficiently low
Standard LAR to address required Tech Spec changes
Licensing approach informs project costs and schedule This meeting seeks to gather staff feedback on this approach
Assessment of SRM / IRM / WRNM replacement falling within the scope of 50.59 and the RIS in lieu of submittal under ISG-06 review process
Use of Qualitative Assessment via RIS guidance to address 50.59 questions 3
Scope of Project Project replaces the 4 SRM channels and 8 IRM channels with 8 WRNM channels
Improved reliability and dose reduction over SRMs / IRMs
Installed at Peach Bottom and international plants Hope Creek Source Range Monitors
Four non-safety related SRM channels Flux monitoring during refueling and startup through critical Detectors withdrawn below core once IRMs on scale Provides alarm on short reactor period and rod block on count rate Not credited for mitigating any UFSAR Chapter 15 event Non-coincident scram function on high count rate used during initial fuel load and startup and if shutdown margin test performed in lieu of SDM calculation WRNMS doubles number of channels for refuel monitoring 4
Scope of Project cont.
Hope Creek Intermediate Range Monitors
Eight safety related IRM channels Flux monitoring during startup up to the low power range (~10%)
Channel manually ranged up through 10 ranges during startup to maintain indication on scale as reactor flux increases Detectors withdrawn below core once APRMs on scale and Mode-1 entered Provides rod block on HI setpoint (<108% of scale) and scram on HI-HI setpoint (<120% of scale)
Provides protection against prompt reactivity additions Rod block and scram logic bypassed when mode switch in Run Identified as redundant mitigation for the Rod Withdrawal Error -
Startup transient in UFSAR Section 15.4.1 and Appendix 15B Described to mitigate startup of idle recirc pump at low power in UFSAR Section 15.9 5
Scope of Project cont.
NUMAC Wide Range Neutron Monitor System Eight safety related WRNM channels
Covers flux monitoring from shutdown through full power operation
No manual range switching Automatically ranges from Range 0 (S/D Refuel) through Range 6 (Power Ops)
Breeder detectors fixed in core at similar elevation as SRM/IRM
Provides rod block and scram trip outputs based on reactor period in lieu of percent of scale RPS input logic 1-out-of-4 twice - Same as IRM logic Rod block and scram logic bypassed with mode switch in Run Provides indication only during power ops - no trip function Fulfills same role as IRM trip for Chapter 15 AOOs Change to period-based rod block & scram function and conversion of SRM to WRNM requires TS changes 6
Applicability RIS-2002-22 Supplement-1 for WRNM
- NRC/Industry guidance on digital upgrades via 50.59
RIS 2002-22 Supplement-1
Reg Guide 1.187 Rev. 2 / NEI 96-07 Appendix D
Qualitatively assess likelihood of failure for safety related digital SSCs
- Draft BTP 7-19 Rev. 8 acknowledges qualitative assessment and plant diversity can be used to address software CCF
- SRM / IRM can be considered within the scope of the RIS WRNMS is a replacement of an RPS input (IRMs) and not a wholesale replacement of the RPS logic system WRNM design attributes align with the guidance in the RIS IRM / WRNM only used for brief period in the operating cycle (startup) and is bypassed during power ops IRM trip is only protective function from SRM/IRM in Chapter 15 events Two Anticipated Operational Transients 7
Continuous Rod Withdrawal Error During Startup
- Non-limiting event in UFSAR Sec 15.4 - Reactivity and Power Distribution Anomalies Not required to be re-analyzed as part of reload licensing
- Continuous withdrawal of out of sequence, high worth rod Event is precluded by Rod Worth Minimizer Contingent upon failure of RWM and failure of rod blocks and operational procedures and verifications for rod withdrawal No radiological release or consequences from event
- Transient analysis performed to demonstrate large margin to licensing basis criterion for fuel failure (<< 170 cal/g-UO2)
Described in UFSAR Appendix 15B Evaluated using conservative point kinetics model 8
RWE During Startup cont.
Event is terminated by either IRM scram or by APRM 15% power Setdown scram in startup Appendix 15B analysis assumes IRM system in worst case bypass condition APRM 15% scram assumed in analysis for event termination Analysis shows APRM scram likely to be reached as soon as (worst case bypassed) IRM scram IRM trip backed by diversity of protection against RWE Operational procedures and peer check verifications Rod block from RWM APRM setdown rod block and scram 9
Startup of Idle Recirc Pump at Low Power Anticipated Operational Transient in UFSAR 15.9 - Nuclear Safety Operational Analysis Non-limiting event NSOA intended to ensure limiting transients analyzed in UFSAR Secs.15.1 - 15.8 remain bounding for all possible transients Evaluates event at a reactor power between 5% and 10%
Resulting flux transient may produce a high flux trip from IRM Although not specifically stated, the APRM 15% setdown scram provides a diverse backup to the IRM scram during this transient NUREG-1433 Bases identifies that at IRM Range 9 or 10, it is possible that the APRM 15% power setdown scram will possibly provide the primary trip signal for a core wide increase in power Startup of an idle recirc pump would produce a core wide increase in power 10
Plant /System Attributes that Support a Qualitative Assessment IRM / WRNM system falls outside the scope of an ISG-06 / BTP 7-19 based License Application
System provides redundant & diverse protection for impacted transients
Impacted transients are non-limiting and do not result in any release of radioactive material
RWE contingent on failure of multiple barriers Operational Procedures and Peer Checks Rod Worth Minimizer IRM / APRM Control Rod Blocks
Limited reliance on IRM protection for idle recirc pump start in startup
Both Chap 15 events terminated by either IRM or APRM scram
IRMs are not relied upon to initiate and complete control actions essential to maintain plant parameters within acceptable limits established for a DBE
Minimal window of time in operating cycle when IRM trip is relied upon for transient protection 11
Design Elements Supporting Qualitative Assessment WRNM based on NUMAC digital platform
Long operational history of Class 1E platform
WRNM processor/design updates to be performed via GEH Appendix-B development program Same process as NUMAC PRNM - recently evaluated by NRC (ML17216A022)
Continuous self diagnostics built into the channel with trip on critical faults No cross-divisional or cross-channel communication or shared resources
Each WRNM channel self-contained No change to active RPS logic Dedicated, simple routine program resides on internal firmware Independent SW and HW watchdog timers that generate a trip on timeout Even in event of worst case software CCF, RWE & idle recirc pump start events terminated by diverse APRM trip Diversity among NUMAC WRNM, PRNM and RWM designs can be established These and other design attributes will support a qualitative assessment via the RIS 12
Proposed Scope of LAR
- LAR would describe required TS changes to reflect the design of the WRNM system
Conventional (Non ISG-06) License Change per 10 CFR 50.92 Licensing action limited to required TS changes Similar to LAR for Salem analog wide range NI replacement of SR/IR channels (Amendment Nos. 313 / 294, ML16096A419)
Replace references to SRM / IRM with WRNM Replace RPS TS percent of scale IRM trip with WRNM period based trip Eliminate SRM and drive related rod blocks and replace TS percent of scale IRM rod block with period based rod block 13
Hope Creek WRNM Installation under 10 CFR 50.59 Next Steps 14