Transcript THE MISSION OF THE IAEA

Safety Assessment Methodologies and
Implementation of Monitoring and Control
Programmes
Dr. Japie van Blerk
AquiSim Consulting (Pty) Ltd
Wednesday, 24 March 2010
Leriba Lodge
Centurion, Gauteng
Introduction

Application of Safety Assessment Process (IAEA Glossary, 2007)
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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
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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
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

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…on such a scale that consideration of protection and safety is required…
Occupational (worker ) and public safety assessments
Operational and post closure phases
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

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

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)
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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
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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
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Iterative process: expect that a safety assessment will have to be repeated
two or more consecutive times
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Site-specific prospective evaluations: include data from the actual system
assessed
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Reasonable assurance: emphasizes the inexact nature of the procedure
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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
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
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
Definition of Safety Case (IAEA Glossary, 2007)
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A collection of arguments and evidence in support of the safety of a facility
or activity
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This will normally include the findings of a safety assessment and a
statement of confidence in these findings
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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
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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
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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
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Developed and improved significantly since 1980s
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Radioactive waste management
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Mining and mineral processing facilities
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Geological disposal
Near surface disposal
Difference in characteristics and timescales
IAEA Coordinated Research Projects
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NSARS
ISAM, ASAM
PRISM
GEOSAF
Safety Assessment Methodologies
Assessment Context
(Regulatory Framework)
Assessment Context
System Description
(Process, Site, Waste, Facility, Human Behavior)
Describe System
Definition and Justification of Exposure Conditions
Source
Develop and Justify
Scenarios
Pathway
Receptor
Exposure Condition
Formulate and Implement
Models
Conceptual Model
Mathematical Model Development
(All Features, Events, Process and Interacting Media)
Run Analysis
Compare Against
Assessment Criteria
Perform Consequence Analysis
(For Each Exposure Condition)
Review and
Modification
Interpret Results
Yes
Interpretation of Results
(Comparison with Regulatory Requirements and Exclusions)
Review and
Modify
Yes
Adequate
Safety Assessment?
Yes
Acceptance
Make Decision
No
Effective to
Improve Assessment
Components
No
Rejection
Make Decision
Adequate
Safety Assessment?
Yes
Acceptance
Make Decision
No
Effective to
Improve Assessment
Components
No
Rejection
Make Decision
Safety Assessment Methodologies
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Regulatory Framework
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System Description
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Process, site, waste, facilities and human behavior
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Incremental contribution to radiation exposure (historical perspective)
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Source identification and description
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Pathway analysis
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Primary and secondary sources
Atmospheric pathway
Aquatic (groundwater and surface water) pathways
Definition and justification of exposure conditions and scenarios
Safety Assessment Methodologies
Elsewhere
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Atmosphere
Pathway
Source
Model Development
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LLα Release
Atmosphere
Radon Gas
Exhalation
Resuspension
Deposition
Elsewhere
Conceptual and mathematical models
Comprehensive and transparent
Upper Soil
Root
Uptake
Crop
Concentration
Deposition
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Approach to System Modeling
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External Irradiation
Introduce simplifying assumptions
Decouple system processes
Combination of above
Compartmental approach
Coupled modeling approach
1
2
3
4
n
Parameter Set
Parameter Set
Parameter Set
Parameter Set
.
.
.
Parameter Set
Improve confidence in the assessment
Inhalation
Treatment
of Future
Uncertainties
Scenario 2
Conceptual
Model 1B
Sensitivity and uncertainty analysis

Ingestion
Scenario 1
Conceptual
Model 1A
Parameter Set
Parameter Set
Parameter Set
Parameter Set
.
.
.
Parameter Set
Residence
Elsewhere
Complex systems
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Biodegradation
Conceptual
Model 1C
1
2
3
4
n
Parameter Set
Parameter Set
Parameter Set
Parameter Set
.
.
.
Parameter Set
Decision
Conceptual
Model 2A
1
2
3
4
n
Parameter Set
Parameter Set
Parameter Set
Parameter Set
.
.
.
Parameter Set
Treatment
of Model
Uncertainties
Conceptual
Model 2B
1
2
3
4
n
Parameter Set
Parameter Set
Parameter Set
Parameter Set
.
.
.
Parameter Set
1
2
3
4
n
Treatment
of Parameter
Uncertainties
Monitoring and Control Programme
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What is the Purpose of a Monitoring Programme?
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Environmental monitoring (IAEA Glossary, 2007)
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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
Monitoring and Control Programme

What is the purpose of a monitoring programme?

Demonstrate compliance with the conditions of the nuclear authorization
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System behave as designed
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Determine the current status of the system
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System characterization
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Input data for the safety assessment process
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Validation of system models used in safety assessment
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Develop stakeholder confidence
Monitoring and Control Programme
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Use safety assessment as a tool to developed the monitoring
programme
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Safety assessment helps to understanding system behavior
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Understand environmental pathways of concern (Historical perspective)
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Recognize the differences between a radioactive waste disposal facility and
a mining and mineral processing operation
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Atmospheric pathway
Aquatic (surface water and groundwater) pathways
Requirements for the atmospheric pathway monitoring different from the groundwater
pathway
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

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...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
Safety Case and Safety Assessment

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…”
Safety Case and Safety Assessment
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Stakeholder Confidence in Facilities and Activities
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Stakeholders (target audience)
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Confidence in the safety assessment
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Regulatory authorities, local, regional and national government
Public and environmental interest groups
Management
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
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Monitoring and surveillance programme
Supporting arguments
Safety Case and Safety Assessment
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PRISM Proposal for Discussion
Purposes ONLY

Safety assessment is part of a
process

Monitoring programme in support
of confidence building and safety
arguments

Integration of safety arguments in
support of the safety case for the
facilities and activities
Conclusion
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Safety Assessment Process is not an Exact Science
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Integration and Assessment of the Environmental Pathway into
the Assessment Process
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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!