Safety Assessment Methodologies and Implementation of Monitoring and Control Programmes Dr. Japie van Blerk AquiSim Consulting (Pty) Ltd Wednesday, 24.

Safety Assessment Methodologies and Implementation of Monitoring and Control Programmes

Dr. Japie van BlerkAquiSim Consulting (Pty) Ltd

Wednesday, 24 March 2010

Leriba Lodge

Centurion, Gauteng

Introduction

Application of Safety Assessment Process (IAEA Glossary, 2007)

Facilities and activities (existing and new, utilized for peaceful purposes) General term encompassing any human activity that may cause people to be exposed to

radiation risks arising from naturally occurring or artificial sources

Nuclear facilities Irradiation installations Mining and raw material processing facilities; Radioactive waste management facilities; and Any other places where radioactive material is produced, processed, used, handled, stored or

disposed of — or where radiation generators are installed

…on such a scale that consideration of protection and safety is required…

Occupational (worker ) and public safety assessments

Operational and post closure phases

Introduction









Introduction









Introduction

Safety Assessment (IAEA Glossary, 2007)

Assessment of all aspects of a practice that are relevant to protection and safety; for an authorized facility, this includes siting, design and operation of the facility

Analysis to predict the performance of an overall system and its impact, where the performance measure is the radiological impact or some other global measure of the impact on safety

Safety Standards (Regulation No. 388)

Systematic process to ensure that all the relevant safety requirements are met by the proposed (or actual) design. Safety assessment includes, but is not limited to, the formal safety analysis

Introduction

The Scientific Committee 87-3 established by the National Council on Radiation Protection (NRCP) (Kennedy, 1997)

Portrayed a post-closure safety assessment as a multidisciplinary, iterative process focussed on regulatory compliance rather than an analysis of a disposal system for the purpose of predicting its actual behaviour

With this in mind, they defined a post-closure safety assessment as: ‘the iterative process involving site-specific, prospective evaluations of the post-

closure phase of the system’ with the primary objectives to

determine whether reasonable assurance of compliance with quantitative performance objectives can be demonstrated,

identify data, design and other needs to reach defensible decisions about regulatory compliance

Introduction

The NRCP Scientific Committee 87-3 Definition

Iterative process: expect that a safety assessment will have to be repeated two or more consecutive times

Site-specific prospective evaluations: include data from the actual system assessed

Not with the intent to predict its actual behaviour in the future, but rather to understand the behaviour of the system better and to reflect on the importance of specific components with respect to the compliance criteria

Reasonable assurance: emphasizes the inexact nature of the procedure Reach defensible decisions on the extent to which the disposal system may comply with

the regulatory criteria

A decision tool to determine the conditions for which reasonable assurance of compliance with safety objectives can be provided; not a method to predict the actual behaviour of a disposal system into the future

Introduction

Safety Assessment in the Context of a Safety Case

Definition of Safety Case (IAEA Glossary, 2007) A collection of arguments and evidence in support of the safety of a facility or

activity

This will normally include the findings of a safety assessment and a statement of confidence in these findings

For a repository, the safety case may relate to a given stage of development. In such cases, the safety case should acknowledge the existence of any unresolved issues and should provide guidance for work to resolve these issues in future development stages

IAEA PRISM and GEOSAF Projects

Safety Assessment and Exact Sciences

An exact science is any field of science capable of accurate, quantitative expression or precise predictions and rigorous methods of testing

hypotheses, especially reproducible experiments involving quantifiable predictions and measurements

Unlike purely scientific areas of study, the radiological public safety assessment process cannot be considered what one would describe as an exact science

The assessment process draws from the fundamental principles of exact sciences, and parts of the assessment methodology are sometimes amenable to normal scientific approaches

The time scales, space scales, uncertainties in boundary conditions, and uncertainties in future human behaviour make it impossible to test and verify (or falsify) the overall assessment

Safety Assessment and Exact Sciences

The inherent nature of the assessment methodology - from the release of radioactive contaminants, the migration of these contaminants into the environment, the subsequent uptake of radionuclides into the human body to pose a radiological exposure - in itself is not an exact science

Safety assessment is a process to develop an understanding of the limits of potential radiological exposure to members of the public for an assumed set of conditions and parameter values

By examining a range of potential conditions of concern, it is possible to develop confidence that the public will be protected from radiation, even though exact statements about future exposures cannot be made

Safety Assessment Methodologies

Developed and improved significantly since 1980s

Radioactive waste management Geological disposal Near surface disposal

Mining and mineral processing facilities Difference in characteristics and timescales

IAEA Coordinated Research Projects NSARS ISAM, ASAM PRISM GEOSAF

Safety Assessment MethodologiesAssessment Context

(Regulatory Framework)

System Description(Process, Site, Waste, Facility, Human Behavior)

Mathematical Model Development(All Features, Events, Process and Interacting Media)

Definition and Justification of Exposure Conditions

Interpretation of Results(Comparison with Regulatory Requirements and Exclusions)

Source Pathway Receptor

Exposure Condition

Perform Consequence Analysis(For Each Exposure Condition)

Review andModify

Conceptual Model

Effective to Improve Assessment

Components

Yes

Yes

No

No

AdequateSafety Assessment?

AcceptanceMake Decision

RejectionMake Decision

Effective to Improve Assessment

Components

Yes

Yes

No

No

AdequateSafety Assessment?

Assessment Context

Run Analysis

Formulate and ImplementModels

Develop and JustifyScenarios

Describe System

Interpret Results Review andModification

Compare AgainstAssessment Criteria

AcceptanceMake Decision

RejectionMake Decision


Regulatory Framework

System Description Process, site, waste, facilities and human behavior

Incremental contribution to radiation exposure (historical perspective)

Source identification and description Primary and secondary sources

Pathway analysis Atmospheric pathway Aquatic (groundwater and surface water) pathways

Definition and justification of exposure conditions and scenarios


Model Development Conceptual and mathematical models Comprehensive and transparent

Approach to System Modeling Complex systems

Introduce simplifying assumptions Decouple system processes Combination of above

Compartmental approach Coupled modeling approach

Sensitivity and uncertainty analysis Improve confidence in the assessment

Scenario 1

ConceptualModel 1A

ConceptualModel 1B

ConceptualModel 1C

Parameter Set 1Parameter Set 2Parameter Set 3Parameter Set 4

.

.

.Parameter Set n


.

.

.Parameter Set n


.

.

.Parameter Set n

Scenario 2

ConceptualModel 2A

ConceptualModel 2B


.

.

.Parameter Set n


.

.

.Parameter Set n

Decision

Treatmentof Model

Uncertainties

Treatmentof Future

Uncertainties

Treatmentof ParameterUncertainties

LLα Release

Residence

Upper Soil

Deposition

Radon GasExhalation

CropConcentration

AtmospherePathwaySource

External I rradiation I ngestion I nhalation

Root Uptake

Elsewhere

Resuspension

Atmosphere

Biodegradation

Elsewhere

Elsewhere

Deposition

Monitoring and Control Programme

What is the Purpose of a Monitoring Programme?

Environmental monitoring (IAEA Glossary, 2007) The measurement of external dose rates due to sources in the environment or

of radionuclide concentrations in environmental media

Safety Standards (Regulation No. 388) An appropriate environmental monitoring and surveillance programme must be

established, implemented and maintained to verify that the storage, disposal or effluent discharge of radioactive waste complies with the conditions of the nuclear authorization

Source monitoring (IAEA Glossary, 2007) The measurement of activity in radioactive material being released to the

environment or of external dose rates due to sources within a facility or activity


What is the purpose of a monitoring programme?

Demonstrate compliance with the conditions of the nuclear authorization System behave as designed

Determine the current status of the system

System characterization

Input data for the safety assessment process

Validation of system models used in safety assessment

Develop stakeholder confidence


Use safety assessment as a tool to developed the monitoring programme

Safety assessment helps to understanding system behavior Understand environmental pathways of concern (Historical perspective)

Atmospheric pathway Aquatic (surface water and groundwater) pathways Requirements for the atmospheric pathway monitoring different from the groundwater pathway

Recognize the differences between a radioactive waste disposal facility and a mining and mineral processing operation

Different pathway of concern Slow migration processes

Contribution from facilities and activities, but also natural background radiation

Background reference site

Safety Case and Safety Assessment

The Safety Case and Safety Assessment for Radioactive Waste Disposal (IAEA Draft Safety Guide DS355)

Safety case ...is the collection of scientific and technical arguments and evidence in support of the

safety of a disposal facility covering the suitability of the site and the design, construction and operation of the facility, the assessment of radiation risk and assurance of the quality of all the safety related work associated with the disposal facility

Safety assessment ...a systematic assessment of radiation hazards, is an important component of the safety

case. It involves the quantification of radiation dose and risk that may arise from the disposal facility for comparison with dose and risk criteria, and provides an understanding of the behaviour of the disposal facility under normal and disruptive conditions, considering the timeframes over which the radioactive waste remains hazardous


Stakeholder Confidence in Facilities and Activities

The NEA (NEA, 1999) defines confidence as

“…to have reached a positive judgement that a given set of conclusions are well-supported…”


Stakeholder Confidence in Facilities and Activities

Stakeholders (target audience) Regulatory authorities, local, regional and national government Public and environmental interest groups Management

Confidence in the safety assessment Confidence in the safety assessment methodology, approach and results Identification and handling of unresolved issues

Confidence in the management and performance of the facilities or activities

Monitoring and surveillance programme Supporting arguments


PRISM Proposal for DiscussionPurposes ONLY

Safety assessment is part of aprocess

Monitoring programme in supportof confidence building and safetyarguments

Integration of safety arguments in support of the safety case for the facilities and activities

Conclusion

Safety Assessment Process is not an Exact Science

Integration and Assessment of the Environmental Pathway into the Assessment Process

Focus on the Safety Case and not on the Safety Assessment

Monitoring programme in support of safety arguments Stakeholder confidence

Thank You for Your Attention!

Safety Assessment Methodologies and Implementation of Monitoring and Control Programmes Dr. Japie van Blerk AquiSim Consulting (Pty) Ltd Wednesday, 24.

Documents

relevant safety requirements

formal safety analysis

radioactive material

radiation risks

radiation generators

post closure phases

gauteng slide

consideration of protection