Overview of the IAEA TECDOC on Integrated Risk Informed Decision Making

Dr Abdallah AMRI, Nuclear Safety ConsultantSafety Assessment SectionDivision of Nuclear Installation SafetyDepartment of Nuclear Safety and SecurityInternational Atomic Energy Agency

Joint seminar on Integrated Risk Informed Decision making organised byRisk Science and Technology Division of AESJ (Japan) in co-operation with

Safety Assessment Section of IAEA, 4 December 2020 (8AM-10AM Vienna time)

Presentation outline

1- What are the bases of the TECDOC?

• General considerations on IRIDM

• IRIDM in INSAG-25

– “A Framework for Risk-Informed Decisions Making Process”

2- How these bases have been reflected in the TECDOC?

• IAEA TECDOC-1909

– “Considerations on Performing Integrated Risk Informed Decision Making ”

GENERAL CONSIDERATIONS ON IRIDM

Integrated Risk Informed Decisions Making (IRIDM)

a systematic decision-making process that

takes account of all relevant safety aspects in making a safety decision

risk considerations are explicitly taken into account in integrating and balancing the decision

It can be used for a wide range of licensee or regulatory issues that have safety and/or security implications– IRIDM process is also used to establish requirements that better focus licensee and

regulatory attention on design and operational issues commensurate with their importance to safety and public health

IRIDM Process

IRIDM Applications

• An integrated approach can be applied to making decisions on operational and safety issues of a nuclear power plant

– Hardware Modifications & Procedural Changes• Plant modifications and backfittings• Emergency operating procedures• Accident management measures, etc.

– Changes to Tech Specs (Operation Limits and Conditions)• Optimization of on-line maintenance practices• Changes to allowed outage times• Optimization of testing intervals & arrangements• Plant configuration management, etc.

– Exemptions from Tech Specs, etc.

Advantages of IRIDM Process

Transparent on the way the decision was made Balanced

If all important elements are considered and weighted properly

Logical If carried out in a structured way

Consistent If weightings developed appropriately

Accountable If documented properly so the process can be reconstructedThe result is expected to be a good safety decision

INSAG-25

A FRAMEWORK FOR AN INTEGRATED RISK-INFORMED DECISION MAKING PROCESS

INSAG 25: What is it Intended to Do?

• Identifies the basic framework

• Sets out the principles for application

• Defines the key elements of

IRIDM

INSAG 25 – published in 2011

The International Nuclear Safety Group (INSAG) is a group of experts with high professional competence in the field of safety

INSAG is convened under the auspices of the IAEA with the objective to provide authoritative advice and guidance on nuclear safety approaches, policies and principles

Recommendations and opinions on current and emerging nuclear safety issues to the IAEA, the nuclear community and the public

INSAG 25: IRIDM Objectives The main objectives of IRIDM

To achieve efficient and safe operation of NPP AND To ensure that any decision affecting safety is optimized

The outcome of IRIDM should Maintain Defence-in-Depth Maintain Safety Margins Take engineering and operational good practices into

account Make use of relevant OEF, R&D and state-of-the-art

methodologies Consider adequate integration of safety and security

requirements Ensure relevant regulations are met

If the revision of regulations is not the main subject of the IRIDM application

Regulatory Considerations

• Existing and new regulations

• Safety level• Inspection findings• OEF• R&D

Utility Considerations• Improved performance• Safety level • Financial savings• OEF• New knowledge

Defined Options

Evaluationof all factors and selecting

the best option

Defining the Issue and Possible Solutions

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INSAG 25: The Basic Framework and Key Elements of IRIDM• Existing and new

regulations• Safety level• Inspection findings• OEF• R&D

• Improved performance• Safety level • Financial savings• New knowledge

What are the possible safety measures?

Which is the preferred safety measure(s)?

Decisions need to be put into place

Has the level of safety desired been achieved?

If NOT - back to “Defined Options”

Logical, reproducible, verifiable, uncertainties addressed

Key Elements: Standards and Good Practices Major considerations in IRIDM

Laws and regulations Standards and codes produced by a range of organizations

e.g. Government agencies, engineering organizations, QA bodies Good practices

e.g. IAEA Safety Standards, ASME/ANS Standards, IAEA Mission Reports

Key Elements: Deterministic Considerations Basic deterministic safety principles are fundamental

in IRIDM Defence-in-depth philosophy “Adequate” safety margins Fault tolerant design Emphasis on prevention Mitigation of accidents’ consequences

Key Elements: Probabilistic Considerations

Complements deterministic and other considerations Aims to identify unanalysed failure sequences

Probabilistic considerations Can range from evaluation of data on simple events e.g.

maintenance failures through analysis of system reliability, to complex analyses such as PSA

Both quantitative and qualitative outputs should be considered within IRIDM Information from the logic structure shows weaknesses and

lack of balance in design or operation Quantitative measures allow evaluation of effects of changes

and comparison with safety target

Probabilistic considerations are essential in IRIDM

Key Elements: Organizational Considerations

IRIDM gives organizational and management issues adequate attention Preparedness for implementation of the decision

option Management for safety

Leadership, control, competence, communication and co-operation among staff

Comprehensive training of all parties involved in the process, etc.

Key Elements: Security Considerations

Security or physical protection of nuclear material are important issues which must be considered within the IRIDM process

Selected decision must ensure proper integration of safety and security requirements

Key Elements: Other Considerations

• Radiation effects on people and the environment• Inspection Findings• R&D results • Operational experience • Remaining Lifetime• Costs• Potential effects on future operation, etc.

Concept of Integration Process (1/2)

The process of decision-making should be • Logical and Comprehensive: e.g. give explicit consideration to the possible

adverse effects in other areas

• Transparent : e.g. the weighting of elements is clear

• Reproducible in the form of adequate documentation • Verifiable by using a formal process

The IRIDM process must be able to combine different forms of input from its various elements

There is no single, simple IRIDM integration process The precise process and the relevant importance of each element

depend on the issue under consideration Quantitative and qualitative aspects are both important in IRIDM

process Decision-making process should be clear on how the balancing of different

risks is achieved The uncertainties of the numerical results of analyses, deterministic and

probabilistic need to be addressed

• Establish appropriate IRIDM process management– Performance monitoring:

• The consequences of IRIDM decisions affecting safety should be monitored

– Feedback:• Feedback on the effectiveness of IRIDM decisions should be

monitored, documented and communicated in a clear and consistent manner to all relevant stakeholders at the earliest opportunity

• Training in IRIDM– Sufficient budget and staff need to be allocated and– Staff need to be trained in the IRIDM process tasks

• Documentation & Communication– IRIDM decisions should be documented, reviewed,

approved, and communicated in a clear and consistent manner

IRIDM: Other Important Issues

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TECDOC“Considerations on Performing Integrated Risk Informed Decision

Making”

Objectives of the TECDOC

• To provide principles and suggest approaches to integrate the results of DSA and PSA as well as other important aspects to make sound, optimum, and safe decisions

– Follows main principles listed in INSAG-25 report “A Framework for Integrated Risk-informed Decision Making Process”

– Provides detailed information/insights on the key elements of IRIDM and their integration

– Provides several examples illustrating how the decisions can be made or have been made using structured IRIDM process

– Addresses issues not elaborated in the INSAG-25• Establishment of the IRIDM process

• Integration of inputs,

• Treatment of uncertainties , etc.

Structure of the TECDOC

1 INTRODUCTION

2 GENERAL OVERVIEW OF THE IRIDM PROCESS3 DESCRIPTION OF THE IRIDM WORKFLOW4 PREPARATION FOR THE ASSESSMENT5 ASSESSMENT, INTEGRATION AND DOCUMENTATION

6 SELECTION OF THE OPTION, IMPLEMENTATION AND PERFORMANCE MONITORING

7 SETTING UP A FORMAL IRIDM CAPABILITY8 CHALLENGES OF THE IRIDM PROCESS

ABBREVIATIONSTERMS AND DEFINITIONSREFERENCES

ANNEXES I to VIII

Section 1: Introduction

• Purpose of the TECDOC, scope, structure

• Areas of IRIDM Applications Addressed in the Document

– All types of nuclear facilities and activities listed in the General Safety Requirements (GSR) Part 4 with graded approach

– Application of the IRIDM process to regulatory activities

• In relation to safety and security issues at nuclear facilities not to risk informed regulation

– Application of the IRIDM process to security issues– Application of the IRIDM process in different

regulatory regimes

Section 2: General Overview of the IRIDM Process

• Gives an overview of the integrated risk informed decision making approach

– Definition and objectives of IRIDM– Applicability of IRIDM– Uses of IRIDM

• Use of IRIDM in discussions between regulatory bodies and licensees• Use of IRIDM within a regulatory body• Use of IRIDM by plant operators/ licensees

– decisions aimed at enhancing safety or security; and– decisions aimed at increasing revenue.

• Use of IRIDM by design organizations

– General description of IRIDM framework• Follows INSAG-25

Section 2: General Overview of the IRIDM Process (cont.)

Section 3: Description of the IRIDM Workflow

• Principles Applicable to the IRIDM Process

– Clear definition of the problem, issue and objective

– Identification of all challenges and hazards associated with the issue

– Assessment of all sources of uncertainty

– Consideration of both short- and long-term implications / consequences

• Applicability of IRIDM for the Issue (see next slides)

• Framework for the IRIDM Process

– Five stages are outlined (See next slides)

Applicability of IRIDM for the Issue

IRIDM Process

Section 3: Description of the IRIDM Workflow (cont.)

Clear and unambiguous definition of the problem or issue that needs to be resolved

The characterization of the issue should include• Description of physical impact on the facility and the potential impact on safe

operation, including possible impact on human actions• Identification of regulations or requirements (e.g., design basis, TSs), organizational

factors, and/or security arrangements that may be challenged by this issue

Initial set of decision options are defined A multi-disciplinary team of specialists established

• The IRIDM core team expanded with other experts when the issue under consideration and options defined require specific expertise

Review of initially drafted decision options• Reason to discard options could be if an option falls short of fundamental requirements,

complexity of implementation or limited time schedule or non-economic feasibility, etc.

Preparation of all the necessary information needed to perform the IRIDM assessments• Step 1: Identification of Constituent Factors (CFs) relevant to the issue under consideration

and to decision options identified• The list of inputs for key elements and details on these inputs are given in Annex I

• Step 2 : Gathering the detailed technical information• For the same input, each option may have different technical information requirements

• Step 3: Information Quality Checking • The tools and models used for the development of the information should be validated to ensure that

they appropriately represent the issue, configuration, or decision• Quality and scope of the technical information are essential

Section 4: Preparation for the Assessment

The CFs of IRIDM are assessed for each decision option and the IRIDM team recommends one of the decision options for implementation (6 basic steps)o Step 5: Recommendation of Options

• To present to the DM(s) the list of acceptable options and option which is considered optimal in relation to addressing the issue and the safety requirements

• The DM(s) should then select the option for implementation.

o Step 6: Final documentation of IRIDM process and results • The assessment process in reaching the decision for each option should be documented,

reviewed, and approved in a clear and consistent manner

Section 5: Assessment, Integration and Documentation (cont.)

Issues Important for the Administration of the IRIDM Processo Conduct of the process

• Is best achieved using a meeting or a series of meetings involving the experts from each relevant discipline

o Managing participants• Strong characters should not dominate • It may be beneficial to utilise a trained facilitator

o Maintaining thorough records• Thorough records should be maintained at each stage of the IRIDM process

Section 5: Assessment, Integration and Documentation (cont.)

Those decisions that require regulatory approval should be submitted to the regulatory body

o The decision options of regulatory body and utility could be influenced by different factors for the same issue

• Utility options could be very much influenced by economic factors, which is not the case with regulatory decision options

o Possible decisions for the IRIDM option chosen by licensee• Accepted• Accepted with additional conditions being imposed• Rejected

• IRIDM option could be deferred by the regulator until additional information is provided and reviewed to allow regulatory body to approve or reject the proposed option

Section 6: Selection of the Option, Implementation and QA

o The approved option should be implemented according to the details outlined in the IRIDM documentation

• IRIDM team needs to periodically review the implementation of the approved option as it progresses. If implementation is found not to be satisfactory, appropriate actions according to the management systems in place should be taken.

o Monitoring Programme: • Specific monitoring programmes, structured to gather performance information and feedback

concerning the implemented option, need to be developed• To ensure that it produces the intended results in relation to the issue and that there are no

unintended effects

Section 6: Selection of the Option, Implementation and QA (cont.)

Section 7: Setting Up a Formal IRIDM Capability

Section 7: Setting Up Formal IRIDM Capability (cont.)

• Safety goals must be set, which requires a safety policy that is tied to basic acceptance of concept of risk in a country– The policy should clearly state that an IRIDM process is

encouraged and decisions that are derived in accordance with this process will be considered and accepted if the IRIDM process is correctly applied

• Establishing acceptance criteria– Once the safety goals have been determined and safety

policy is stated, acceptance criteria need to be developed for use in the IRIDM processes

• Define the area of applicability of IRIDM – The range of decisions where the IRIDM process could be

applied and accepted by regulators

Section 7: Setting Up Formal IRIDM Capability (cont.)

• Establishing regulatory and/or utility infrastructures in relation to IRIDM

• Mechanisms for changing existing requirements and regulations

– Risk-informed decisions might be in conflict with mandatory requirements or other deterministic regulations

• A mechanism should exist inside the regulatory body to process requests for exemptions from such regulation and to grant them where feasible– Regulatory body may also decide to develop new regulation

that replaces the former one

Section 8: Limitations of the IRIDM Process

• Legal implications in different countries – With different laws and different regulatory systems

• Definition/use/acceptability of risk criteria• Quality and limitations of PSA• Bulk of regulations to be considered for a change• Resources needed• Organizational issues

– Regulatory body infrastructure – Cultural differences between the staff of regulatory bodies and NPPs – Training of non-PSA staff to understand the inputs from the PSA

• Technical issues– Difficulties to combine the insights from different inputs of different nature– Difficulties in applying a new approach– Formation of multi-disciplinary teams

• Communication/Documentation issues– Risk communication/incorporating risk information into the process– Communication of the results of the risk informed process– Documentation of the results of the risk informed process.

• Annex I detailed discussion of the various IRIDM inputs that may be considered

– Added value – regulations

• Annex II description of some decisions – That have been made using the IRIDM process or – which have been considered against the IRIDM process

• Annex III suggestion on how the assessment of the impacts of the decision options on the inputs could be performed

• Annex IV possible approaches for integration of the inputs while making a decision

• Annex V illustrative examples on how the IRIDM process described in the document can be applied to a particular issue in a formal way

• Annex VI suggestions on how uncertainties of the IRIDM process could be considered

• Annex VII proposed structure for documenting the IRIDM process and the results

• Annex VIII example on the use of methods of IRIDM to consider non-radiological hazards in IRIDM process

Annexes to the TECDOC

• Two types of uncertainty:- Aleatory uncertainty (variability): associated to the natural randomness in a process (e.g. timing and

nature of accidents); in principle, cannot be reduced by additional knowledge or data;

considered e.g. by constructing explicit probabilistic models for the random processes

- Epistemic uncertainty: associated to limitations in the collective knowledge; in principle, can be reduced by obtaining additional information Sources of epistemic uncertainty are:

Parameter uncertainty (e.g. parameter values to quantify probabilities of basic events in a PSA)

Model uncertainty (e.g. HRA models) Completeness uncertainty (known unknowns and unknown unknowns)

Uncertainty dealing with information from expert judgement belongs to epistemic uncertainty type Important in the IRIDM process; It is due to the incompleteness of information available to the experts

Annex VI: Suggestions on how to address uncertainties of the IRIDM process

• Main sources of uncertainty in KE of IRIDM process:- Uncertainty in the assessment of the importance (e.g. weights) of the constituent factors (CFs)

mainly caused by the different opinions of the experts involved in IRIDM;

- Uncertainty in the assessment of the level of compliance of the decision options with the CFs

Typically dealing with the uncertainty in the results of the assessment and the different opinions of the experts;

• Uncertainty in the assessment of importance of the CFs:- Calculation of uncertainty range based on expert judgement

Main value for the importance of CFs of the key element can be assessed by averaging opinion of the IRIDM team members

Uncertainty range defined based on the lowest and highest weights assigned for the CF

Annex VI: Suggestions on how to address uncertainties of the IRIDM process (Cont.)

• Uncertainty in the assessment of the compliance with the CFs:

- Mainly due to Uncertainty in the information; Different opinions of IRIDM team members on the level of

compliance with the CFs

- Evaluation of the uncertainty in the level of compliance with CFs Averaging opinion of the IRIDM team members about compliance

with CFs Uncertainty range defined based on the lowest and highest scores for

the options regarding the CFs

• Treatment of uncertainty in IRIDM process:- Through sensitivity studies to ensure robustness of the preferred option;- Using Monte-Carlo simulations (see Section VI-4-2 of Annex VI)

Annex VI: Suggestions on how to address uncertainties of the IRIDM process (Cont.)

Summary• Integrated decision-making process combines the insights from different

inputs aimed at reaching a balanced and optimized decision• In spite of some challenges in applying IRIDM, it is a very useful approach

that– Facilitates dialog between regulators and licensees;– Can be applied in many areas: in discussion between regulators and licensees, within the regulatory bodies, within the licensees of nuclear installations, in discussions with different stakeholders and communications with the public

• The IAEA TECDOC-1909 on “Considerations on Performing Integrated Risk Informed Decision Making” provides useful insights and detailed examples on how to establish and apply IRIDM

• It also attempts to deepen some topics e.g. uncertainties related to the application of IRIDM

• There is a potential for IRIDM application, e.g. advanced reactors (including SMR) design

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