radioactive waste management limited protective marking uk geological disposal safety case early...

Radioactive Waste Management Limited Protective marking

UK Geological Disposal Safety Case

Early design stage operational safety case structure

GEOSAF Meeting26 – 30 May 2014

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UK Regulatory Position

• Nuclear Regulation in the UK is based upon the Nuclear Installations Act 1965 (NIA)

• This Act sets out those activities which require a Nuclear Licence• The Nuclear Installations Regulations 1971 set out those Activities

other than reactors which require a License by “prescribing” them.• Currently “disposal” is not “prescribed” and consequently is not

yet a licensable activity in the UK


Current work

• Work is currently underway to make disposal licensable (probably by prescribing it).

• However the NIA also relates to insurance liability and is therefore inextricably linked with the Paris Convention.

• There is a requirement in the UK that regulation be proportionate. Therefore in whatever changes take place we want to avoid putting an undue burden upon installations which we consider do not need the full regulatory force of a license, i.e. There is other health and safety and environmental regulations which could be more appropriate for existing and future very low level disposal sites.

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Radioactive Waste Management Ltd

Radioactive Waste Management Limited:

•Previously a Directorate of Nuclear Decommissioning Authority. Since 1 April a wholly owned subsidiary.

•RWM is the NDA’s GDF delivery body

•RWM is implementing policy being developed by Government

•Expect new Government policy (“White Paper”) to be issued in July 2014

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Disposal System Safety Case

Launched February 2011, comprising 28 individual documents, including:

• Disposal System Specification• Engineering Designs• Transport, Operational and

Post-Closure Safety Assessment

• Off-site operational Environmental Assessment

• Suite of status reports setting out current understanding of underpinning science


Disposal System Safety Case

• A suite of documents collating analyses and scientific and engineering evidence to support our confidence in the safety of a geological disposal facility.

• The generic Disposal System Safety Case addresses:– transport of waste to the facility– construction and operation of the facility– long-term environmental safety after facility has been closed.

• The DSSC presents for the first time an integrated assessment for all higher activity wastes and materials defined in the MRWS Baseline inventory.

• The DSSC at this stage is generic – no site identified and decisions on disposal concepts not yet been made. Based on illustrative concept examples for 3 different geological settings– Early stage, not recognised in UK regulator guidance


Scope and structure


Operational Safety Case


Generic v site-specific

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Purpose of Generic OSC

• Intended to demonstrate:

– That a safety case can be produced that is soundly constructed by a auditable process and which gives a reliable indication of the safety of geological disposal

– There is a clear understanding of what needs to be done to put in place the infrastructure necessary for the production of a future safety case that meets modern standards

• What it does:

– Explains key elements of a nuclear safety case

– Describes expectations for the management of safety, how we meet them now and will do in the future

– Explains legislative requirements

– Describes RWM safety principles

– Describes safety methodologies

– Sets out an early stage s.c. based on illustrative disposal concepts

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Design Principles

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Based on• IAEA Safety

Fundamentals SF-1• IAEA Safety

Requirements WS-R-4

Benchmarked against• HSE Safety Assessment

Principles• Environment Agency

Guidance on Requirements (GRA)


UK nuclear regulatory guidance

• Safety Assessment Principles for Nuclear Facilities 2006 edition– Ca 300 principles with supporting guidance and numerical criteria – Basis of assessment of nuclear facilities in the UK– Relevant (but not mandatory) to geological disposal safety case– Not all principles will be applicable to all facilities

• Technical Assessment Guides (TAGs)– Designed for ONR assessors but useful to safety case developers– Ca 65 in total, ones we found particularly useful:

• Demonstration of ALARP (005)• Criticality (041)• Purpose, scope and content of nuclear safety cases (051)• Design safety assurance (057)

• The Tolerability of Risk (1992)• Reducing Risks, Protecting People (2001)

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Safety Approach

• Built on defined design principles, including– Eliminate hazards and consequences rather than controlling– Hierarchy of safety measures – passive safety measures,

automatically initiated active, active manual– Defence in depth– Design to withstand design basis events

• Normal operating conditions – dose to workers and public• Analysis of faults – design basis analysis used to define

appropriate safety measures. Too early to apply PSA• Claims are supported by the ‘evidence base’• Hierarchical structure with top-tier summary document allowing

readers to ‘drill-down’ for more detail• Presumption of publication – but some aspects of the safety

analysis are protected on account of security considerations

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Radiological protection policy

Initiating fault frequency

BSL (mSv) BSO (mSv)

Off-site

> 10-3 1

0.01 mSv per yr10-3 – 10-4 10

< 10-4 100

On-site

> 10-3 20

0.1 mSv per yr10-3 – 10-4 200

< 10-4 500

RWM Dose Criteria for Design Basis Fault Sequences

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Operational Safety Case Structure

• Volume 1: Construction and non-radiological safety• Volume 2: Normal operations – operator dose• Volume 3: Accident safety assessment

– Radiological faults– Design basis accident analysis– Probabilistic assessment– Severe accident assessment

• Volume 4: Criticality safety assessment• Consideration given to:

– Implications for different geologies– Baseline inventory with implications for “upper inventory”– ALARP discussion– Post emplacement operations – retrievability, decommissioning,

closure

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Fault schedule

Fault ID Waste type Fault description Initiating event IEF

1.3.2.1 UILW Exposure to bare UILW package during On or Off-site maintenance of transport container believed empty but containing UILW waste package.

Receipt of a transport container believed to be empty but which has been accidentally despatched containing a waste package.

7E-2

1.6.2.1 UILW Exposure to bare package during man-entry to UILW Crane Maintenance Area when package in crane cradle.

Attempted entry to Crane Maintenance Area with package on crane.

2E-5

3.2.5.3 HLW, SF, Pu or HEU

Impact on transport package in the Drift due to runaway locomotive or derailment.

Train runs away while carrying package.

6E-3

4.3.3.1 UILW Sustained fire affecting bare UILW package at the Inlet Cell (including Lid Removal Station, Package Removal Station, Package Monitoring Station, Stillage Transfer Station).

Sustained fire in an active area of a GDF process facility.

1E-2

6.2.4.5 SILWCollapse of Drift Top Building structure onto transport package.

Extreme Weather 1E-4

6.2.5.2 SILWImpact on transport package in the Drift due to runaway locomotive or derailment.

Seismic event. 1E-4

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Examples from the fault schedule


Accident Safety Assessment

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• To inform the development of the design regarding the design features and safety systems required for safe operation.

• For design basis faults – single failure criterion (SAP EDR.4) must be met


Design Basis Analysis

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Purpose:• To inform the development

of the design regarding the design features and safety systems required for safe operation.

• For design basis faults – single failure criterion (SAP EDR.4) must be met


Probabilistic Safety Assessment

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Purpose:• To provide an integrated,

structured safety analysis that combines engineering and operational features in a consistent overall framework.

• We were able to conduct only a limited PSA due to early stage of our design.


Normal operational discharges

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Para 4.1 of T/AST/051: Purpose of a safety case is to establish and demonstrate in written form that plant, process, activity, modification etc. being proposed:

1. Are soundly assessed and meet required safety principles

2. Conform to good nuclear engineering practice and to appropriate criteria, standards and codes of practice

3. Are adequately safe during both normal operation and fault conditions

4. Are and will remain fit for purpose

5. Give rise to a level of nuclear risk to both public and workers which is ALARP

6. Have a defined and acceptable operating envelope, with defined limits and conditions, and the means to keep within it

Purpose of a Nuclear Safety Case


Conclusion

• DSSC documents downloadable from NDA website

• http://www.nda.gov.uk/aboutus/geological-disposal/rwmd-work/dssc/index.cfm

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