Safety Integrated Design Development

Inlet cell design development for the safe handling of radioactive waste underground (2018)

In collaboration with Arup, MCM delivered a (3 year, £300,000) project for RWM to design an Unshielded Intermediate Level Waste handling facility for a future UK Geological Disposal Facility.  MCM managed the project and provided technical quality assurance throughout.

Project Context

The UK has accumulated a legacy of radioactive waste and continues to produce radioactive wastes from various industries and programmes.  UK government policy for management of these wastes is safe and secure interim storage, followed by geological disposal, as set out in the 2014 Implementing Geological Disposal White Paper (https://www.gov.uk/government/publications/implementing-geological-disposal).  Radioactive Waste Management Limited (RWM),  a wholly owned subsidiary of the Nuclear Decommissioning Authority (NDA), is responsible for delivering a Geological Disposal Facility (GDF) and managing the UK’s higher activity radioactive waste inventory.

Waste Disposal Units (DUs) containing Unshielded Intermediate Level Waste (UILW) are currently planned to be transported to a GDF and transferred underground in Standard Waste Transport Containers (SWTC). Waste Disposal Units would be removed from SWTCs and transferred to the ‘inlet cell’.  The inlet cell, a key part of the GDF, is assumed by (RWM)  to be located underground and would be a shielded facility which would allow the remote unpacking and handling of waste DUs from SWTCs.  From the inlet cell, the waste DUs would then be transferred to disposal areas for emplacement.

During 2016, RWM prepared an updated generic design for the UK GDF.  The design includes several options flexible to a range of geological environments (higher strength rock, lower strength sedimentary rock and evaporite rock) and suitable for a range of higher-activity wastes, including UILW.

The generic GDF inlet cell design has a planned receipt capacity (2,500 SWTCs per annum) which will remain for the UILW emplacement period of the GDF programme.  The throughput for some periods will be modified to match the SWTC receipt rate by changing the operational shift pattern, for example going from a three-shift (24 hour) working pattern to two-shift operations.  The GDF generic design waste receipt schedule has a planned capacity of 2,300 SWTCs per annum for approximately 24 years, followed by 1,500 per year for about 44 years.

The generic design was classified by RWM using the NDA’s Technology Readiness Level (TRL) methodology, which comprises three components:

  • Technology; refers to a technological process, method, or technique such as machinery, equipment or software needed for the plant, facility or process to achieve its purpose
  • Readiness; refers to time. Specifically it means ready for operations at the present time
  • Level; refers to the level of maturity of equipment. Equipment that is already being used for the same function in the same environment has a higher level of maturity than equipment that is still being developed. The levels are a nine-point scale based on a qualitative assessment of maturity

The inlet cell of the generic design was estimated to have a TRL of two, at the ‘invention and research’ stage.  The aim of our project was to enhance this TRL to three, ‘proof of concept’ or ‘demonstration’. This would provide confidence that an inlet cell could be constructed and operated to meet the throughput target for UILW waste packages and be decommissioned in the range of geological environments suitable for hosting a UK GDF.  The approach to the design utilised existing proven engineering, knowledge sharing and systems engineering all fully integrated with Building Information Modelling (BIM) technology.

Project deliverables

The project deliverables included:

  • Development of a Functional Specification, including User and System Requirements and an assumptions register
  • Derivation of Nuclear Safety Functions
  • Development of Process Flow Diagrams in support of both Nuclear Safety and requirements development
  • A detailed optioneering study
  • Development of an integrated technical specification (covering construction, mechanical, EC&I, civil, structural and maintenance)
    • Demonstration of ERICPD principles throughout the design
    • Calculations to modern standards and value engineering
    • Codes and Standards (equipment maintenance)
  • Development of a 3-D model (see below);

  • Derivation of facility throughput capability
  • Concept Design report
  • Impact analysis to assess the design in RWM’s three generic host rock environments

Papers published in Nuclear Future Volume 14, Issue 1 (January/February 2018) https://www.nuclearinst.com/CoreCode/Admin/ContentManagement/MediaHub/Assets/FileDownload.ashx?fid=324704&pid=66158&loc=en-GB&fd=False and Nuclear Engineering International

Design principles and approaches for radioactive waste repositories (2018)

Dr Ally Clark (MCM) provided consultancy support to the IAEA to take part in consulting activity, providing expert opinion and developing an IAEA document entitled Design Principles and Approaches for Radioactive Waste Repositories.

Given the number of Member States with plans to construct a repository for radioactive waste is increasing, the IAEA sought expert input to their draft document which outlines the basic design features of typical disposal facilities for low and intermediate-level radioactive waste, including process and auxiliary buildings and systems. Generic disposal options with increasing depth of containment are shown below.

As an expert in the field, Ally was able to support the IAEA in documenting a generic approach to facility design, communicating essential design principles, outlining key design stages and summarising a wealth of international experience. A generic design process is outlined below.

The final document specifies the scope of design works for selected types of facilities, to facilitate better understanding of how to implement requirements related to nuclear safety, radiation protection, physical protection and emergency preparedness.

GDF ventilation concept design (2017)

MCM, with their partners in ARUP, were contracted to support RWM in addressing their need to provide airflow in sufficient quantity and quality to the underground areas of a Geological Disposal Facility to maintain acceptable working conditions for operators and equipment, and to contribute to the isolation and containment of radioactive waste.

MCM defined a set of traceable user requirements, capturing their justification, a measure of effectiveness and method of validation. Following this, system requirements were similarly defined and mapped back to their respective user requirements. The ARUP team continued to define functions to be met by the ventilation system, thus providing a foundation for the design criteria. These design criteria were defined, establishing the ventilation and air flow in every room, space, tunnel and vault of the underground system, for both emplacement & construction ventilations circuits. The ventilation flow diagram at a point 130 years into the construction of the GDF in Higher Strength Rock (HSR) is shown below.

With a ventilation concept design for each of the three rock types, based on certain assumptions about the GDF and its contents, RWM is in a position to refine the GDF ventilation system design as other decisions are made with regards to the wider GDF design.

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