Operational Reactor Safety

22.091 /22.903

Professor Andrew C. Kadak Professor of the Practice

Integration of Safety Analysis into Operational Requirements

Lecture 13

Department of Nuclea r S c ien ce & Engineering

Prof. Andrew C. Kadak, 2008 Page 1

How is Nuclear Plant Safety Managed?

• T here is a close link between:

• C ore Design

• P l a n t D e s i g n

• S afety Analysis

• NRC Requirements

• O perating Requirements

• O rganizational Structure

• M anagement

• S afety Culture

Plant Design to Licensing to Operations

• Vendor proposes reactor plant design

• Vendor performs core and plant design analysis demonstrating power and safety

• Vendor summarizes all analyses in a Safety Analysis report which demonstrates compliance to NRC regulatory requirements – 1 0 CFR Part 50.

• Utility submits Safety Analysis and Environmental Report to NRC for review and acceptance.

• Possible adjudicatory licensing hearings before the Atomic Safety and Licensing Board

NRC Regulations - Examples

• 10 CFR Parts

http://www.nrc.gov/reading-rm/doc-collections/cfr /

• 10 CFR Part 50

http://www.nrc.gov/reading-rm/doc-collections/cfr/part050/

Department of Nuclea r S c ien ce & Engineering

Prof. Andrew C. Kadak, 2008 Page 3

Chapter 15 Accident Analyses

• B ased on Requirements of 10CFR Part 50 and all appendices – A ppendix K – LOCA

• Includes:

– N ormal Operation and Operational Transients

• L oss of feedwater

– Infrequent Faults

• Small pipe breaks

– Limiting Faults

• L oss of Coolant Accidents

Contents of Safety Analysis Report

• G eneral Description

• Site Characteristics

• D esign Criteria SSC

• R eactor Design

• R eactor Coolant Sys.

• Engineered Safety Features.

• I nstrumentation & Controls

• Electric Power

• Auxiliary Systems

• Steam & Power Conversion System

• R adioactive Waste Management

• R adiation Protection

• C onduct of Operations

• I nitial Tests and Operations

• Accident Analyses

• T echnical Specifications

• Q uality Assurance

Roughly 15 - 3 inch thick Notebooks

Design Basis Accidents

• O vercooling – i ncrease in secondary side heat removal – steam line break – Pressurized thermal shock

• U ndercooling –decrease in above

• O verfilling – r eactor water

• L oss of flow

• L oss of cooling – L OCA (large and small) STGR

• R eactivity – r od ejection, power anomalies

• Anticipated Transients Without Scram (ATWS)

• External events – tornadoes, earthquakes, floods, etc.

• Beyond Design Basis – Class 9 > leading to meltdown

NRC Requirements

• D eterministic and prescriptive as to how to analyze accidents and allowed assumptions.

• N RC reviews and licenses computer codes used in analysis.

• T he results of the analyses identify operational limits, limiting conditions for operation, test and surveillance requirements - all of which are contained in the Technical Specifications

Key NRC Appendices to 10 CFR 50

• A – G eneral Design Criteria

• B – Q uality Assurance

• G – RV Fracture Toughness Requirements

• H – Reactor Vessel Surveillance Requiremts

• I – A llowed release limits from plant

• J – C ontainment leak rate testing

• K – E CCS rule

• R – F ire Protection

Other Requirements on Licenses

• G eneric Letters

• B ulletins and Orders

• Information Notices

• Maintaining Plant Design Basis current

• C onfirmatory Action Letters

• C ommitments made in response to the above

Design Basis – Licensing Basis

• Design Basis

– H ow the plant is actually designed and works.

• Licensing Basis

– A ll the collected commitments of the licensee to the NRC including the safety analysis reports, technical specifications, etc.

NRC Oversight

• NRC requires compliance to licensing basis:

– T wo resident inspectors per site (plant)

– S pecial inspections on key regulatory issues

– Licensee event reports (LERs)

– E nforcement actions based on performance

– R eactor Oversight Process – “risk informed – performance based”

– H ighly transparent – w eb based

Reactor Oversight Process

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Reactor Oversight Process

• NRC’s p rocess to monitor reactor performance

http://www.nrc.gov/NRR/OVERSIGHT/ASSESS/index.html

Department of Nuclea r S c ien ce & Engineering

Prof. Andrew C. Kadak, 2008 Page 4

Requires Balance

Skills

Rules Knowledge

Objective

• Maintain Compliance to all NRC Regulations

• O perate within safety envelope

• Maintain Critical Safety Functions

– R eactivity Control

– C ore Heat Removal

– S econdary Heat Removal

– C ontainment Integrity

• Make Electricity !

Managing Safety

• T echnical Specifications are the key operational criteria

• P rocedure Based

– O p e r a t i n g

– Abnormal Operating Procedures

– Emergency Operating Procedures

– M aintenance

– E ngineering

– S e c u r i t y

– R adiation Protection (As Low As Reasonably Achievable)

Safety Envelope

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Control Room

• T ools include

– A utomatic Trips

– S afety Parameter Display System of Critical Safety Functions

– Risk Monitors

– Key Process and control parameters

Risk Monitor

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Organizational Structure

A Typical Non-Outage Day

• M orning call – w hat happened yesterday, overnight – i ssues – operability status – days since last human error - LCOs

• Risk monitor status – P lant vulnerabilities

• P lan for the day shift – maintenance, tests surveillances

• E lectric Generation

Plant Oversight Processes

• Corrective Action Program

– C orrective Action Review Board

• Q uality Assurance Department Plant Operations Review Committee

• Nuclear Safety Advisory Review Com.

• External Review Boards

• Institute of Nuclear Power Operations

Key Success Safety and Performance Factors

• S afety Culture

• B asic Design of Plant – F ault tolerant

• T raining – O perations, Engineering, Mgt.

• Q uality Assurance – S elf Assessment

• O rganizational Factors – S ustain Safety

• Regulations – Motivate Safety (Risk Informed Regulations)

Homework Assignment

1. Use the Reactor Oversight Process site and identify the key safety issues in the last 2 quarters of the reactor nearest your home.

2. Based on the review of the performance indicators, identify the particular NRC inspection reports upon which the finding is based.

3. Summarize your review in a two page memo to me about the condition of this plant and the corrective actions being taken.

4. Are you satisfied with the safety of this plant?

Department of Nuclea r S c ien ce & Engineering

Prof. Andrew C. Kadak, 2008 Page 2

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22.091 Nuclear Reactor Safety

Spring 200 8

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