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Non-Safety Related Digital Feedwaterand AMSAC/DSS Control Systems

Replacement Project

Xcel EnergyPrairie Island Nuclear Generating Plant

8-30-2017

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Agenda

• Introductions

• Meeting Purpose

• Project Overview

• 10 CFR 50.59 Assessment

• Future Actions

• Summary

• Feedback and Questions

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Meeting Purpose

• Outline project scope, design, and licensing basis supporting the digital FW and AMSAC/DSS control system change

• Discuss the preliminary 10 CFR 50.59 assessments and conclusions

• Discuss possible future interaction with the NRC staff

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Project Overview

• Current System– Westinghouse WDPF System

• Digital Technology• Installed WDPF FWCS and AMSAC in 1989/1990• Modified AMSAC and installed DSS Feature in 1998/1999• Non-Safety Related Distributed Control System (DCS)

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Project Overview

• Project Drivers– Obsolescence

• WDPF Systems are 28 years old– Parts not manufactured since 2002 – Vendor technical support ends in 2017

• Recent Hardware Issues• Current system not suitable for plant life

– Unit 1 operation to 2033 – Unit 2 operation to 2034

– Long term operating and maintenance strategy• Common platform with demonstrated history of reliable operation

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Project Overview

• Timeline– 2015-2016: Preliminary Engineering Phase

• Multidiscipline team • Many team members from original WDPF team

– 2017: 10 CFR 50.59 Assessment Phase– 2018: Detailed Design Phase– 2019–2020: Installation Phase

• In service dates:– Unit 2 – 2019– Unit 1 - 2020

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Project Overview

• Project Scope– Replace existing DCS

• Digital to digital - Ovation• WDPF to Ovation

– Next generation of platform– Same OEM

– Upgrade FW Reg Valve Controls• Analog to digital - DVC

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Project Overview

• Project Design Principles– Mitigate obsolescence– Improve equipment reliability – Eliminate SPVs and transient initiators– Use well vetted, common platform with demonstrated

history– Design system hardware and software within the bounds

of current design and licensing basis – Use industry standard methods for design and testing– Use a multi-layer testing approach through fabrication,

installation, and commissioning – Design, test, and install system to minimize outage

impact

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Project Overview

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Project Overview

• Project Scope Detail– Install Ovation DCS:

• FW Control System (SGWLC)• AMSAC/DSS System• Control System Infrastructure

– Modify Main Control Board Operator Interface:• Retain operator manual controls• Move some indications to new graphic display

– Modify FW Control Valve field devices:• Replace FW Reg valve controls with dual redundant digital

positioners on Main Control Valves and single digital positioner on Bypass Control Valves

– Modify Simulator

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Project Overview

• Project Scope Detail (cont’d)– Improve Equipment Reliability

• Increase redundancy • Eliminate at least 16 SPVs (8 per unit)

– Functional Control Enhancements• Reduce operator burden• More fault tolerant• Improve FW Control strategies• Improve time response

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10 CFR 50.59 Assessment

• FW Design & Licensing Basis• AMSAC/DSS Design & Licensing Basis• Assessment Approach• Qualitative Assessment• 10 CFR 50.59 Criteria• Preliminary 10 CFR 50.59 Overall Conclusion

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10 CFR 50.59 Assessment

• FW Design & Licensing Basis– USAR described FWCS & Control Valve Design

Functions:• Provide FW flow to SGs for RCS heat removal during normal

operation • Provide SG Program Level Control during normal operation• Prevent control and protection interaction with Median Signal

Select (MSS) for NR SG level• Valves provide isolation of FW flow to SGs

– Licensing• Steam Flow/FW Flow mismatch trip elimination

– USAR described Failures and Accident Analysis

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• AMSAC/DSS Design & Licensing Basis– Design Function: Satisfy 10 CFR 50.62

• AMSAC Actuation: Turbine Trip and AFW actuation• DSS Actuation: Remove power to the control rods

– Licensing• Installed WDPF AMSAC to meet requirements of 10 CFR 50.62• Modified AMSAC logic and added DSS feature

– USAR described Failures and Accident Analysis

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10 CFR 50.59 Assessment

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10 CFR 50.59 Assessment

• Assessment Approach– Use current regulatory requirements & guidance

• NEI 96-07, Rev 1, endorsed by NRC RG 1.187• NEI 01-01 (including Appendix A) endorsed by NRC RIS 2002-22• NRC IN 2010-10

– Monitoring ongoing NEI/NRC efforts– 10 CFR 50.59 screening considerations (NEI 01-01

Section 4.3):• Software considerations• Functional segmentation• Time response• Human System Interface• Safety to Non-Safety Interface

– NEI 01-01 drives conservative conclusion to “screen in”

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10 CFR 50.59 Assessment

• Assessment Approach (cont’d)– 10 CFR 50.59 Evaluation Considerations (NEI 01-01

Section 4.4)• Same as screening considerations• Qualitative Assessment is key to addressing Criterion 1, 2, 5,

and 6 of 10 CFR 50.59

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10 CFR 50.59 Assessment

• Assessment Approach (cont’d)– NEI 01-01, Section 5.3.1, “Factors that Affect

Dependability”• The ability to provide reasonable assurance that an upgrade will

exhibit sufficient dependability is a key element of 10 CFR 50.59 evaluations

– Qualitative Assessment characteristics:• System design features• System design development and quality processes • Operating history

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10 CFR 50.59 Assessment

• Qualitative Assessment – Design Features– Design Features to support low likelihood of failure

(examples):• Isolation Devices• Redundancy• Architectural assignments• Segmentation• Self Diagnostics• Failure states• Existing Manual Controls

– Susceptibility Analysis • Hardware Failures• Environmental• Design Defects • Operator or Maintenance Errors

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10 CFR 50.59 Assessment

• Qualitative Assessment – Design Development and Quality Processes

– Design specification provides requirements for design, fabrication, documentation, testing, and delivery

– Specification and Westinghouse design development processes based upon industry standards

– Specification requires multi-layer testing approach through fabrication, installation, and commissioning

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10 CFR 50.59 Assessment

• Qualitative Assessment – Operating History– Ovation Experience

• More than 100 Ovation nuclear systems deployed• Variety of nuclear applications worldwide• Greater than 500 Rx years of OE

– Fisher DVC Experience• Over 700,000 sold• Over 7 years

– OE Research

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10 CFR 50.59 Assessment

• Qualitative Assessment Preliminary Conclusions– Will demonstrate dependability and low likelihood of

failure:• Required design features maintained and no new failure results• Design development and quality processes being applied• Operating history is strong

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10 CFR 50.59 Assessment

• 10 CFR 50.59 Criteria– Expected 10 CFR 50.59 Criteria 1, 2, 5, and 6

conclusions based on preliminary Qualitative Assessment and preliminary design work:• No more than a minimal increase in frequency of an accident• No more than a minimal increase in likelihood of malfunction • No possibility of an accident of a different type• No possibility of a malfunction with a different result

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10 CFR 50.59 Assessment

• 10 CFR 50.59 Criteria (cont’d)– Other 10 CFR 50.59 Criteria:

• Criteria 3 & 4: – Systems do not initiate new failures or malfunctions– Radiological consequences are not evaluated for these events

• Criterion 7: – Systems do not impact any critical inputs credited in the Safety

Analysis for fission product barriers– Change will not exceed or alter a fission product barrier design

basis limit• Criterion 8:

– Change does not constitute, involve or modify a method of evaluation described in the USAR

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10 CFR 50.59 Assessment

• Preliminary 10 CFR 50.59 Overall Conclusion– Screens in for evaluation– Would not require prior NRC approval– Perform change under 10 CFR 50.59

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Future Actions

• Xcel Next Steps– Proceed with detailed design– 10 CFR 50.59 evaluation sufficiently complete in 3rd

Quarter 2018– Opportunity for additional learning with new guidance– Timing to accommodate project installation

• Unit 2 - 2019• Unit 1 - 2020

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Summary

• Described the project scope, design, and licensing basis supporting the digital FW and AMSAC/DSScontrol system change

• Discussed the preliminary 10 CFR 50.59 assessment and conclusions

• Outlined next steps and possible future interaction with the NRC staff

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Feedback and Questions

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Acronyms

• AFW – Auxiliary Feedwater• AMSAC – ATWS Mitigating System Actuation Circuitry• AOO – Anticipated Operational Occurrences• ATWS – Anticipated Transient Without SCRAM• BFRV – Bypass Feedwater Regulating Valve• CCF – Common Cause Failure • CFR - Code of Federal Regulations• CR – Control Room• DCS – Distributed Control System• DSS – Diverse Scram System• DVC – Digital Valve Controller• FW – Feedwater

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Acronyms

• FWCS – Feedwater Control System• HSI - Human System Interface• IN – Information Notice• I/O – Input/Output• I/P – Current to Pressure Converter• LVDT – Linear Variable Differential Transformer• MFRV – Main FW Regulating Valve• M/A - Manual/Automatic Control Station• M/L – Manual Loading Station• M/P – Motor to Pressure Converter• MSS - Median Signal Select • NEI – Nuclear Energy Institute

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Acronyms

• NR – Narrow Range• NRC – Nuclear Regulatory Commission• NRR – Nuclear Reactor Regulation (Office of) • OE – Operating Experience• OEM – Original Equipment Manufacturer• P/I – Pressure to Current Converter• RCP – Reactor Coolant Pump• RCS – Reactor Coolant System• RG – Regulatory Guide• RIS – Regulatory Issue Summary• Rx - Reactor• SF/FF – Steam Flow/Feedwater Flow

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Acronyms

• SG – Steam Generator• SGWLC – Steam Generator Water Level Control• SLIM – Small Loop Interface Module• SME – Subject Matter Expert• SPV – Single Point Vulnerability• SWIL – Software In Loop• USAR – Updated Safety Analysis Report• WDPF – Westinghouse Distributed Processing Family• WR – Wide Range

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