ML063330288
| ML063330288 | |
| Person / Time | |
|---|---|
| Site: | LaSalle  |
| Issue date: | 09/19/2006 |
| From: | Exelon Nuclear |
| To: | Office of Nuclear Reactor Regulation |
| Sands S,NRR/DORL, 415-3154 | |
| Shared Package | |
| ML063330299 | List: |
| References | |
| TAC MD0360, TAC MD0361 | |
| Download: ML063330288 (47) | |
Text
LaSalle County Station Ganged Rod Drive Capability as part of Rod Control Management System (RCMS)
Introduction Objective of Meeting 3/4 Identify the specific scope and level of detail of information needed to complete a review of a resubmitted License Amendment Request (LAR) for Ganged Rod Drive Capability at LaSalle County Station.
3/4 Provide an overview of the Rod Control Management System (RCMS).
3/4 Provide a summary of Ganged Rod Drive Capability as part of RCMS, including the basis for acceptability.
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Introduction Topics and Presenters 3/4 Installation of Rod Control Management System (RCMS) -
Alan McLaughlin, Operations Shift Manager 3/4 Description and Functionality of RCMS - Bob Fredricksen, Lead Design Engineer 3/4 RCMS Hardware and Software Development and Validation Process - Bob Fredricksen 3/4 Regulatory Analysis - Terry Simpkin, Regulatory Assurance Manager 3/4 Joint NRC/EGC Discussion: LAR Review Requirements 3
Introduction History of Issue 3/4 Late-2005 3/4 10 CFR 50.59 process identified need to submit LAR for optional design feature of a planned modification.
3/4 March 15, 2006 3/4 Submitted LAR requesting NRC review and approval of a change to the LSCS Licensing Basis.
3/4 April 11, 2006 Teleconference 3/4 NRC provided seven informal questions concerning LAR.
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Introduction History of Issue 3/4 May 10, 2006 Supplement 3/4 Provided response to four of seven NRC questions.
3/4 June 1, 2006 Supplement 3/4 Provided response to remaining NRC questions as part of SRP Section 7.7, Control Systems, review.
3/4 July 31, 2006 3/4 Withdrawal of LAR.
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Installation of RCMS Overview and Purpose of RCMS 3/4 General Electric control rods move in discrete six-inch steps by high-pressure water being sequentially ported to hydraulic drive units by four directional control valves.
3/4 Each rod has a separate Hydraulic Control Unit (HCU) that controls that rods motion.
3/4 Original design on all BWRs, except BWR/6s, would only move one rod at a time. BWR/6 units can move multiple rods (i.e., a gang of up to four rods).
3/4 The RCMS provides the control of the HCUs, indication of rod position, and sequence enforcement.
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Installation of RCMS Added Functionality of RCMS 3/4 Enhanced the implementation and documentation of control rod maintenance and surveillance activities.
3/4 Improved control rod movement operations that are required for control rod drive functionality.
3/4 Enhanced the confirmation of reactor shutdown following a scram.
3/4 Added the capability to move multiple rods (up to four) in a single gang (i.e., Ganged Rod Drive Capability).
The RCMS System is being installed in accordance with the requirements of 10 CFR 50.59, with the exception of Ganged Rod Drive Capability.
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Installation of RCMS Operational and Safety Benefits With Ganged Rod Drive Capability, the RCMS will:
3/4 Reduce operational challenges by reducing the amount of time that the reactor is in the Intermediate and Startup range power levels during startups. These power levels require a heightened level of reactivity management attention and resources.
3/4 Enhance SCRAM avoidance by allowing the rapid insertion of CRAM rods (rods specified in analyzed sequences for the purpose of significantly reducing reactor power rapidly) during plant transients.
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Installation of RCMS Four-Phased Installation Process 3/4 Phases 1 and 2 implemented on-line at the HCUs:
3/4 Programmable Logic Device (PLD) Transponder Cards 3/4 PLD Branch Amplifier Cards 3/4 Phase 3 implemented during refueling outages (L2R11 and L1R12) 3/4 Control Room Hardware (i.e., full core map, status and select displays, interface units, controllers, and controls) 3/4 Auxiliary Electric Equipment Room (AEER) Hardware (i.e.,
controllers, interface units, and maintenance display) 3/4 Implementation of Phase 4 (Ganged Rod Drive Capability) following NRC Review and Approval 9
Description and Functionality of RCMS Purpose of RCMS 3/4 The RCMS provides indication of rod position, enforcement of rod movement sequences, and rod movement control (i.e., the control of Hydraulic Control Units) during normal operation.
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Description and Functionality of RCMS Probe/MUX Cards RCMS RCMS FCP Controller A Controller B Individual Rod Position Switches Maintenance AEER Display MCR Field Branch HCU Transponders Junction Modules RCMS RCMS Interface Interface Branch Unit A Unit B HCU Transponders Junction Modules Plant Status Inputs 11
Description and Functionality of RCMS P603 Main Control Room LPRM Upscale &
Downscale Inputs 40 LCD AEER Full Core Map MCR MCR Interface Controller Unit B B 20 LCD Status Display Rod Block Monitors MCR MCR Controller Interface A 20 LCD Unit A Rod Select Display Rod Motion Push Buttons 12
Description and Functionality of RCMS 13
Description and Functionality of RCMS 14
Description and Functionality of RCMS Human System Interface 3/4 Main Control Room Reactor Control Panel P603 15
Description and Functionality of RCMS Human System Interface 3/4 Methodology defined in NUREG-0800, Section 18, Human Factor Engineering, Section B was used to develop graphical user interface screens.
3/4 Recommendations and design participation from LSCS personnel, and NUREG-0700, Human-System Interface Design Review Guideline were used to create consistency in the user interfaces.
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Description and Functionality of RCMS Human System Interface is made through the following displays 3/4 40-inch LCD Full Core Map 3/4 20-inch LCD Status Display 3/4 20-inch LCD Select Display 3/4 20-inch Maintenance Display 17
Description and Functionality of RCMS 40-inch LCD Full Core Map 3/4 General control room display of rod information.
3/4 All information that was displayed in old Core Map, with lights and rod position information.
3/4 No actions or screen changes can be made to or from this display.
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Description and Functionality of RCMS 19
Description and Functionality of RCMS 20-inch LCD Rod Select Display Screen 3/4 Used for selecting rods for movement, conducting rod surveillances, etc.
3/4 Touch screen select, with mouse backup.
3/4 Ten Primary Screen Types selected from Navigation Panel with sub-screens on several of the primary screens.
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Description and Functionality of RCMS 21
Description and Functionality of RCMS 20-inch Status Display Screen 3/4 Provides a second display screen for the operator and is the backup rod select screen.
3/4 Only one screen (status or rod select) can be used for control.
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Description and Functionality of RCMS 23
Description and Functionality of RCMS 24
Description and Functionality of RCMS 25
Description and Functionality of RCMS 26
Description and Functionality of RCMS 20-inch Maintenance Display 3/4 Same display as the control room, but located in AEER for technician use.
3/4 All logic functions for rod motion are blocked from this screen.
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Description and Functionality of RCMS 28
Description and Functionality of RCMS 29
Description and Functionality of RCMS Design Basis and Functions 3/4 No single failure can negate the effectiveness of a reactor scram.
3/4 Repair, replacement, or adjustment of any failed or malfunctioning component shall not require that any element needed for reactor scram be bypassed unless a bypass is normally allowed.
3/4 Inhibit control rod withdrawal following erroneous control rod manipulations so that RPS scram is not required.
3/4 Inhibit control rod withdrawal in time to prevent local fuel damage as a result of erroneous control rod manipulations.
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Description and Functionality of RCMS Design Basis and Functions 3/4 Inhibit control rod movement whenever such movement would result in operationally undesirable core reactivity conditions or whenever instrumentation is incapable of monitoring the core response to rod movement.
3/4 Deliberate operator action is required to effect a continuous rod withdrawal.
3/4 Provide the operator with the means to achieve prescribed control rod patterns. Enforce adherence to established startup, shutdown, and power level control rod patterns.
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Description and Functionality of RCMS Design Basis and Functions 3/4 Provide information pertinent to the position and motion of the control rods in the control room.
3/4 Provide interlocks that inhibit rod movement under specified conditions, including receipt of input signals from other systems and subsystems.
3/4 Control the solenoid operated valves that control the drive water path for each control rod.
3/4 Rod withdrawal is permitted only if the outputs from both rod-block logic circuits allow it.
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Description and Functionality of RCMS Safety Classification Non-Safety Related Control Function only No Protection Function However the system is designed for redundant channel operation of the RCMS Controllers and Interface units.
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Description and Functionality of RCMS Optional Design Feature: Ganged Rod Drive Capability 3/4 By individually controlling the existing CRD hydraulics, up to four rods can be moved at one time. Previous LSCS system did not consider this. BWR/6 design includes this capability.
3/4 Ganged Rod Drive Capability complies with RCMS Design Bases.
3/4 Insertion of rod gangs will enable faster negative reactivity insertion, thus providing increased power maneuverability.
3/4 Withdrawal of rod gangs will also increase positive reactivity insertion. Therefore, rigorous controls are necessary to prevent undesired reactivity excursions.
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Description and Functionality of RCMS RCMS Rod Motion Controls The following must be satisfied to withdraw a rod gang:
3/4 The rod movement sequence stored in the Rod Worth Minimizer (RWM) must specify the use of rod gangs.
3/4 The rod movement sequence that specifies the use of rod gangs must be selected, from a password protected control screen.
3/4 The RWM must be operational.
3/4 The operator must enable gang motion from a password protected control screen.
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Description and Functionality of RCMS RCMS Rod Motion Controls 3/4 The operator must select GANG mode on the rod SELECT screen.
3/4 Every selection of GANG mode will require positive verification by the operator 3/4 There are no Withdraw errors from the RWM present.
3/4 The core power is below that which will initiate the Rod Block Monitor.
3/4 All RCMS and Main Control Room Controllers and Interface Units are in operation and not bypassed.
3/4 A redundant cross-comparison check on all rod motion activities indicates agreement between channels.
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Description and Functionality of RCMS Equipment Redundancy and Cross-Comparison Function 3/4 With all equipment operational, a redundant, cross-comparison check on input and output signals between the RCMS Controllers and Interface Units prevents inadvertent single or gang rod motion.
3/4 Specific comparisons:
3/4 RCMS Controller A Output to RCMS Controller B Output.
3/4 Each RCMS Interface Unit comparing input from both controllers.
3/4 If either RCMS Controller or Interface Unit is inoperable or bypassed, gang withdrawal will be prevented.
3/4 Disagreement in any comparison will prevent rod withdrawal.
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Description and Functionality of RCMS Impact of RCMS on Analyzed Accidents 3/4 15.4.1.1 Control Rod Removal Error During Refueling Unaffected; RCMS continues to enforce Rod Withdraw Block in Shutdown and the One-Rod-Out-Interlock in Refuel.
3/4 15.4.1.2 Continuous Rod Withdrawal During Reactor Startup Unaffected for Single Rod Withdrawal; NRC review and approval required for potential accident associated with Ganged Rod Withdrawal Capability.
3/4 15.4.2 Rod Withdrawal Error - At Power Unaffected; RCMS continues to only allow Single Rod Withdrawal above the Rod Block Monitor Reactor Power Set Point.
3/4 15.4.9 Control Rod Drop Accident Unaffected; RCMS continues to enforce the RWM Rod pattern constraints required to mitigate this single control rod drop accident scenario.
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Development and Validation Process Initial Development 3/4 RCMS development was joint effort by GE and Exelon 3/4 Although RCMS is non-Safety-Related, the development process for RCMS hardware and software followed GEs safety-related processes.
3/4 GE used NUMAC process for development of software, following the Baseline approach.
3/4 Process addresses issues such as design control, change control, documentation, record keeping, independent verification, and software development requirements, as described in RG 1.152, "Criteria for Digital Computers in Safety Systems of Nuclear Power Plants.
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Development and Validation Process NUMAC Baseline Approach 3/4 Baseline 1 - Definition and Planning 3/4 Baseline 2 - Product Performance Definition 3/4 Baseline 3 - High Level Software Design 3/4 Baseline 4 - Coding and Module Test 3/4 Baseline 5 - Integration Test 3/4 Baseline 6 - Validation and Software Release 40
Development and Validation Process Exelon Participation 3/4 Approved all Baseline 1 and 2 documents 3/4 Developed matrix to track requirements of the Baseline documents (i.e., approximately 3800 entries).
3/4 Monitored the Factory Acceptance Testing (FAT) V&V testing (i.e.,
Baseline 6), and approved resolution of deviations identified in the testing.
3/4 Contracted an independent third party (i.e., Process Design Consultants, Inc. (ProDesConTM)) to ensure that the software development and V&V processes are not compromised.
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Regulatory Analysis Current Licensing Basis 3/4 UFSAR Section 15.4.1.2, Continuous Rod Withdrawal during Reactor Startup, for a single rod, evaluated as an infrequent incident.
3/4 UFSAR Section 15.4.1.2 does not address ganged rod motion.
3/4 The potential for multiple continuous rod withdrawal may be created by the addition of Ganged Rod Drive Capability, which has not been evaluated, and must be reviewed.
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Ganged Rod Drive Capability NUREG-0800, Section 15.4.1 3/4 NUREG-0800, Section 15.4.1, Uncontrolled Control Rod Assembly Withdrawal from a Subcritical or Low Power Startup Condition, evaluated this accident for ganged rod motion at BWR/6 designs.
3/4 In Section 15.4.1, the NRC concluded that the requirements of General Design Criteria (GDC) 10, 17, 20, and 25 had been met for ganged rod drive capability at BWR/6 designs:
These requirements have been met since the system design contains a Rod Pattern Control System. This system has been reviewed and found acceptable because single failures in the reactor control system which could result in uncontrolled withdrawal of control rods under low-power conditions have been precluded. The scope of this review has included the design features which act to prevent such withdrawals.
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Ganged Rod Drive Capability Applicability of NUREG-0800, Section 15.4.1 3/4 The purpose of the Rod Pattern Controller in a BWR/6 design is to ensure control rod patterns during startup are such that only specified control rod sequences and relative positions are allowed over the applicable operating range.
3/4 Exelon has evaluated the RCMS design against the acceptance criteria of Section 15.4.1 for ganged rod drive capability. The RCMS meets the acceptance criteria based upon:
3/4 The presence of a Rod Worth Minimizer; 3/4 Dual channel, redundant hardware; and 3/4 The Cross-Comparison verification function 44
Ganged Rod Drive Capability NUREG-0800, Section 7.7 Control Systems 3/4 Item II, Acceptance Criteria:
3/4 10 CFR 50.55a(a)(1), Quality Standards.
3/4 10 CFR 50.55a(h), Protection Systems, and ANSI/IEEE Std 279, Criteria for Protection Systems for Nuclear Power Generating Stations, Item 4.7.2, Isolation Devices.
3/4 GDC 1, Quality Standards and Records.
3/4 GDC 13, Instrumentation and Control.
3/4 GDC 24, Separation of Protection and Control Systems.
3/4 SECY-93-087, Policy, Technical, and Licensing Issues Pertaining to Evolutionary and Advanced Light-Water Reactor (ALWR) Designs, Item II.Q.
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Ganged Rod Drive Capability Conformance with NUREG-0800, Section 7.7 3/4 Exelon has evaluated the RCMS design against the acceptance criteria of Section 7.7 for ganged rod drive capability. The RCMS meets the acceptance criteria based upon:
3/4 The Exelon Quality Assurance Program (10 CFR 50.55a(a)(1) and GDC 1).
3/4 Electrical separation of RCMS from the Reactor Protection System (10 CFR 50.55a(h); ANSI/IEEE Std 279, Section 4.7.2; and GDC 24).
3/4 The RCMS Displays and Controls (GDC 13).
3/4 The RCMS Software Development and Validation Process and the Exelon assessment of RCMS failures affecting Ganged Rod Movement Capability (SECY-93-087, Item II-Q).
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Ganged Rod Drive Capability Analysis of Postulated Ganged Rod Withdrawal Error 3/4 Exelon has evaluated the impact of a postulated ganged rod withdrawal error upon fuel design limits.
3/4 Results indicate that in the event a gang is erroneously withdrawn out-of-sequence, the result will not challenge the fuel integrity (i.e., Section 15.4.1 Acceptance Criteria).
3/4 Minimum Critical Power Ratio (MCPR),
3/4 Linear Heat Generation Rate (LHGR),
3/4 Uniform Cladding Strain, and 3/4 Peak Pin Enthalpy.
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