Design Bases

From 1957 to 2003June 18, 2007

Chuck Casto

Region II NRC

HISTORY OF DESIGN BASES

• Atomic Energy Act of 1954 – (1957 Thru 1962)

• Section 182

• Technical Specifications are part of license

• Implemented in 10CFR50.34 & 50.36

• Hazards Summary Report– Safety Analysis Report

HISTORY OF DESIGN BASES (cont’d)

• Two approaches for Tech Specs– Vallecitos –Include entire

Hazard Summary Report

– Yankee Atomic – TS culled from Hazard Summary Report

• Section 189 – Mandatory hearing for issuance of license or license amendment

HISTORY OF DESIGN BASES (cont’d)

• Results were unworkable– Diminishing return –

Mandatory Hearing– Need recognized for

discriminating significant and insignificant changes

• The Vallecitos Decision (1960)– Concept of Unreviewed

Safety Question (10CFR50.59)

– No significant hazards consideration (10CFR50.92)

HISTORY OF DESIGN BASES (cont’d)

• Regulations to manage changes– 10CFR50.59

– 10CFR50.91

– 10CFR50.92

Early History of 50.59

• “Clarifies” the extent which the licensee may make changes, conduct tests & experiments not specifically provided in the license

• Changes:– 1. Explicit license authority

– 2. Credible probability by possibility

– 3. Licensee can conduct test & experiments in HAR approved by NRC

• April 8, 1961 (AEC) NRC issues proposed Rule

• June 9, 1962 50.59 issued

Early History of 50.59

• Changed reference to Safety Analysis Report from HAR (HSR)

• Tech Specs could serve purpose with less content. The PSAR & SAR explicitly specified and Bases for TS were required

• Final Rule change brought in– 1. Consideration of “malfunctions”

– 2. Inclusions of the “margin of safety” as defined in the bases for any TS

• 1966

• August 16, 1986 Proposed Rule change

• December 17, 1988 Rule Revised

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Public Impact of 50.59

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Historical Definitions and Assumptions

• No undue risk to health safety

• No unreviewed safety questions remain

• Licensee’s have freedom to control the plant

• Drew a line across which the licensee could not step without NRC approval

• Permitted the license to determine if line crossed

Historical Definitions and Assumptions (cont’d)

• Consequences equal dose

• 50.2 defines design basis as..”That information which identifies the specific functions to be performed by a SSC of a facility, and the specific values or ranges of values chosen for controlling parameters as reference bounds for design.”

Historical Definitions and Assumptions (cont’d)

• Experiment – an operation carried out under controlled conditions in order to discover an unknown effect.

• Test – the procedure of submitting a statement to such conditions or operations as will lead to its proof or disproof to its acceptance or rejection.

Historical Definitions and Assumptions (cont’d)

• Malfunction – Failure, breakdown, or inaccurate operation. In 50.59, the term malfunction is more component or equipment oriented, e.g., single failure.

• Margin of safety – the difference between the acceptable limit and the design failure point.

Historical Definitions and Assumptions (cont’d)

• Unreviewed safety question – If the probability of occurrence or consequences of an accident or malfunction or equipment important to safety previously evaluated in the SAR may be increased; or

• If a possibility for an accident of malfunction of a different type than any evaluated previously in the SAR may be created; or

Historical Definitions and Assumptions (cont’d)

• USQ (cont’d)

• If the margin of safety as defined in the basis for any TS is reduced.– Seven questions were used to determine if a

change was a USQ– USQ did not mean unsafe

Regulatory Significance of the FSAR

• Tech Specs are incorporated into the license (50.36)– Commission approval to

change (50.90/91)

• Descriptive information– Controlled under 50.59

• Descriptive information not controlled under 50.59– Subject to 50.9

History of Design Basis Configuration

• Davis Besse incident

• NUMARC 90-12

• NUREG 1327 Assessment of DBR

• 1990 FSAR update Rule

• GL 91-18

• 1992 Commission Policy Statement

• 1992 Regulatory Review Group

History of Design Basis Configuration (cont’d)

• 1993/1995 National Performance Review

• August 1995 plant events

• July 1996 Commission Policy on Voluntary Industry Initiatives

• Risk Informed Regulation

• Special Treatment

P rin c ip a l " le s s o n s le a rn ed " fo cu s a rea s o f S E C Y -97-205

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Design Bases Interpretation

• Appendix B of NEI 97-04 proves guidance for interpreting 10 CFR 50.2 design bases

• Commission endorsement through RG 1.186

• 10 CFR 50.2 design bases includes:– Design bases functions

– Design bases values

Design Bases Functions

• SSC functions required by, or otherwise necessary to comply with, regulations, license conditions, tech specs or orders; or

• SSC functions credited in licensee safety analyses to meet NRC requirements

Design Bases Values

• Design bases values:– Values or ranges of values

of controlling parameters established as reference bounds for design to meet design bases functional requirements

• Established by NRC requirement

• Derived from or confirmed by safety analyses

• Chosen by licensees from an applicable code, standard, guidance document

Why are these definitions important?

• Common understanding of 10 CFR 50.2 “design bases” supports:– UFSAR updates– 10 CFR 50.59 implementation– Proper characterization of design discrepancies

Simplified Relationship

UFS A R

1 0 C FR 5 0 .2D e s ig n B a s e s

S u ppo rt in g D e s ig n I n fo rm a t io n

1 0 C FR 5 0 .5 9

L ic e n s in g B a s is

10 CFR 50.59

• Establishes criteria for making changes to the licensing/design bases

• Guideline for implementation NEI 96-07

• Endorsement of NEI 96-07 through RG 1.187

10 CFR 50.59

• Objectives of guidelines:– Update existing guidance and provide guidance

on new provisions– Provide guidance on when to apply processes

other than 10CFR50.59– Promote more consistent, effective

implementation

10 CFR 50.59

• Final Rule changes:– Eliminated “zero standard”– Established “minimal”

standard– Enhanced screening process– Replaced problematic

“margin of safety”– Clarified role of

overlapping requirements– Affirmed purpose as a

“regulatory threshold”• No more “unreviewed

safety questions”

10 CFR 50.59

• Key changes in implementation:– Broad scope of “design functions” as used in

“change” definition– Only adverse changes “screen in”

• Determination based on effects on design functions

• Change is not adverse if effects are within the bounds of existing safety analysis

10 CFR 50.59

– Always consider adverse and screen in:• Any change to barrier design basis limits

• Fundamental changes in how required functions are performed (e.g., manual vs. automatic action)

– Other clarifications:• Applicability of MR(a)(4) to installation and post-

mod testing of plant changes

• Minimal increase in malfunction in likelihood

• Use of alternative methodologies

10 CFR 50.59

– Control of maintenance procedures– Definition of “design functions”– Consideration of human factors– Analog-digital upgrades

UFSAR Updates

• 10CFR50.71e• RG 1.181, Sept 1999,

endorses NEI 98-03• UFSAR updates must

reflect:– New Commission

Requirements– Effects on USFAR info of:

• Changes made to facility and procedures

• Evaluations in support of changes

• Requested analysis of new safety issues

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Commitment Management

• RIS 2000-17 endorses NEI 99-04, Guideline for Managing NRC Commitment changes

Licensing Basis Today!!!

• Hierarchical approach to licensing basis– Obligations – legally binding requirements

imposed by rule, reg, order and licenses.– Mandated documents – documents for which

the NRC has established required content, e.g, UFSAR, security, EP, QA plans.

– Regulatory Commitments – explicit statements agreed to and submitted on the docket.

Configuration Control Insights

• Great job! <5% of NRC findings CC all green• Big hitters:

– Human Performance (~20%)– Failure to follow procedures (~20%)– Decision making (~20%)– Outside design basis (~15%)– Less than adequate procedures (~10%)– Tagging (~8%)

Design Control Insights

• ~13% of NRC findings related to DC– Design control (~30%)– Awareness of criteria (~22%)– Calculation error (~15%)– Configuration control (~15%)– Corrective action (~6%)– Other (Op Evals, FSAR, OE, vendor, materials)

• ~(12%)

Human Performance in IndustryJanuary 2005 – Present Reference NRC Human Factors Information System

• Human Performance Cause Codes in LER’s & Inspection Reports – “Work Practices” – Problem identification & resolution– Procedures

Human Performance in EngineeringJanuary 2005 – Present Reference NRC Human Factors Information System

• Human Performance Cause Codes in LER’s & Inspection Reports– Work Practices 20%

• Design work– Skill– Non-conservative decisions– Implementation of action less than adequate

– PI&R 18%• Problem Identification• Problem Resolution• Problem Evaluation

Human Performance in EngineeringJanuary 2005 – Present Reference NRC Human Factors Information System

• Human Performance Cause Codes in LER’s & Inspection Reports– Procedures 16%

• Design

• Content of procedures

• Maintenance/surveillance

Questions????