Wednesday, 18 May 2016

Don't waste our future!


Here are some salient extracts from the UK Nuclear Decommissioning Authority (NDA)’s new High Activity Waste (HAW) strategy, published on 16 May.


“Current UK policy classifies radioactive waste into categories depending on the nature and quantity of radioactivity they contain and whether they generate heat or not. The NDA (with support from the nuclear site regulators) advocates an approach where wastes are managed based on their best means of disposal rather than what waste category they fall into. The NDA is now moving towards a single radioactive waste strategy for its estate that will need to demonstrate how it will support all relevant policies in the UK. Our radioactive waste strategy will not replace the use of existing waste categories (e.g. ILW, LLW). It will also need to take into account the nature of wastes (radiological, chemical and physical properties) and the most appropriate waste management route while recognising the challenges posed by waste classification boundaries. Considerable stakeholder engagement will be required as the strategy develops over the next few years.


“The total lifetime packaged volume of the NDA’s HAW is 404,000 m3 (~87% of all UK HAW). About 75% of all the NDA’s HAW is from the Sellafield site and about 20% from the Magnox sites.


“The UK policy position recognises that some radioactive materials not currently classified as waste, including spent nuclear fuel, uranium and plutonium, may be managed as HAW if it is decided at some future time they are of no further use.

“It should be noted that transport of HAW is a particularly significant enabling step within the waste management lifecycle. The safe and secure movement of waste requires significant planning and specialised reusable transport containers.

“An interim store for packaged HAW is a robust engineered facility with a design life of typically 100 years that is resistant to foreseeable incidents such as seismic events and severe weather. Furthermore, an interim store system should provide protection for waste packages from potential external corrosion caused by ambient conditions including atmospheric salts, temperature and humidity levels which could have a long-term impact on the integrity of the package


“As the UK’s nuclear clean-up mission progresses, more and more packaged HAW will be held within interim storage facilities reflecting the current status of the waste retrievals, waste processing and indeed, the disposal programmes. Hence, the packaged HAW is of high intrinsic value in terms of environmental, safety and security benefit and cost and programme investment. Therefore it is highly appropriate that the industry takes the right precautions in managing the storage system and ensuring the waste packages remain in good condition to minimise the potential need for future rework

“the NDA will explore in more detail alternative management options for wastes at the ILW/LLW boundary including opportunities for HAW disposal to near-surface facilities, e.g. in support of integrated radioactive waste management

“As HAW is a complex management area the NDA evaluates the inventory as broken down into four distinct types of waste:

• Wet ILW

• Solid ILW

• Graphite

• HLW


“Although at face value the objective of the HAW strategy is very simple it is not always possible to achieve this objective in a single step, direct approach. On occasions other complicating factors mean that the approach to achieving the objective needs to be undertaken in a staged manner. Some of the reasons for this include:

• The complex nature of some poorly characterised heterogeneous waste streams

• The condition of some raw waste storage facilities (and the need to make swift progress with retrieval operations)

• An evaluation of programme deliverability and prioritisation, which will include affordability considerations

“Therefore the NDA’s HAW strategy recognises the importance of supporting the required progress on managing legacy facilities, e.g. Sellafield legacy ponds and silos.


“Although at face value the objective of the HAW strategy is very simple it is not always possible to achieve this objective in a single step, direct approach. On occasions other complicating factors mean that the approach to achieving the objective needs to be undertaken in a staged manner. Some of the reasons for this include:

• The complex nature of some poorly characterised heterogeneous waste streams

• The condition of some raw waste storage facilities (and the need to make swift progress with retrieval operations)

• An evaluation of programme deliverability and prioritisation, which will include affordability considerations

“Therefore the NDA’s HAW strategy recognises the importance of supporting the required progress on managing legacy facilities, e.g. Sellafield legacy ponds and silos.


“Overall, the NDA believes there are opportunities at a strategic level to reduce risk (programme uncertainties, cost, etc.) in the HAW management programme for the NDA sites and also the potential to provide a step change in benefit. Most of the opportunities are likely to centre on improvements within the reference strategy, with an emphasis on effective use of the waste hierarchy.

“Areas for strategic improvement are targeted at significant risks such as Sellafield legacy plants, and of significant opportunity, for example, wastes that are close to the boundary between ILW and LLW specific activity level (boundary wastes) and sharing waste management infrastructure although in this case it is acknowledged that many waste streams will continue to follow a reference strategy with tactical opportunities at a specific waste,

“The NDA recognises that waste categorisation is a useful simplification for planning purposes although it is ultimately the safety case that determines the actual route utilised. Recent work has initiated the evaluation of opportunities for the management of boundary waste and disposal using a risk-based approach. The NDA is now seeking optimisation and a risk-based approach throughout the waste management lifecycle rather than relying on early categorisation and subsequent distinct and separate ILW and LLW planning.

 

“Decontamination techniques to treat waste, particularly surface-contaminated material, allowing the leftover bulk material to be managed:

o As a lower category of radioactive waste


o As Directive waste

o For reuse or recycling


“The volume of HAW to be managed will have a significant impact on the lifecycle cost and, just as important, will also have an impact on safety, security and the environment. Investigating opportunities for waste volume reduction is a principle that the NDA expects all of its SLCs to closely consider as part of any waste management programme.

“Significant waste volume reduction may be achieved by mechanical means, e.g. supercompaction, chemical dissolution, or by chemical conversion that separates volatile species from a non-volatile residue. For example, high temperature processing of ILW could result in a low volume concentrated waste form that could exist as a glass or ceramic material and an off-gas waste stream, which will require some form of aerial discharge abatement.

 




e) Chemical conversion


Chemical conversion of ILW streams will result in more passive products especially when dealing with wastes containing relatively high concentrations of reactive metals, e.g. aluminium, magnesium alloys (Magnox) and uranium. The conversion of metal to its corresponding oxide may also aid long-term product performance in terms of storage and subsequent disposal. It should also be recognised, that for certain high hazard wastes a multi-step approach to disposal could support the implementation of more novel approaches to waste conditioning.



f) Storage and disposal

 “
The principles of the waste hierarchy equally apply to HAW interim storage and disposal. HAW stores are large robust facilities that require considerable resource in the construction, operations and decommissioning. It is important that waste should be minimised as a result of a store build programme and where appropriate recycled materials could be used. Likewise, the build, operations and closure of HAW disposal facilities needs careful planning to minimise waste production. Reducing the overall volumes of HAW to be managed will have a significant impact on the number of stores to be built (when compared to the baseline plan) and the number of disposal vaults to be constructed in a disposal facility. While reducing waste volumes is beneficial overall it is also appropriate to ensure that storage capacity is used efficiently. The NDA will continue to encourage industry to investigate the sharing of storage solutions and in particular, maximise the utilisation of storage capacity in existing stores.

 


b) Spent fuel and HLW


“The current baseline position for spent fuel (that is destined for disposal) and for the UK’s HLW, is a planning assumption that they are included in the inventory for disposal in a GDF and they are considered as part of the implementation of geological disposal. Provision is made for its management through inclusion in the Derived Inventory and the Disposal System Technical Specification  that defines the requirements that the disposal system must satisfy (see the Spent Fuel strategic theme of the NDA Strategy for more detail).

c) Plutonium and uranics


“Plutonium and uranics are nuclear materials that are not declared as wastes but are included in the inventory for disposal in the Implementing Geological Disposal White Paper as a planning assumption. If in the future a proportion of these nuclear materials are deemed to have no further use then they will be managed as wastes through geological

“Plutonium and Uranics are topic strategies within the Nuclear Materials strategic theme of the NDA Strategy.

“In line with government policy, the NDA is developing options for the reuse of plutonium . Some of the options under consideration may offer opportunities in terms of co-disposal of wasteforms such that other wastes or uranium, for example, could potentially be co-disposed of. These opportunities will be explored further in the future to determine whether there is benefit in pursuing this approach.

Transport and logistics


“Transport is an integral part of the waste management lifecycle. The availability of transport routes is an essential part of treatment, storage and disposal especially when dealing with UK-wide or multi-site solutions. At a tactical level, programme logistics will also allow the NDA to optimise its waste export scheduling (the programme for transferring waste from storage to a GDF) with respect to road and rail travel and potentially consideration of sea transport around the UK.
the NDA encourages involvement in international collaboration programmes with its counterpart organisations in other countries. This takes place either bilaterally or through international organisations such as the Club of Agencies and the International

“Association for Environmentally Safe Disposal of Radioactive Materials (EDRAM). This again ensures that the NDA takes account of international good practice, both technological and sociological, in delivering the UK government’s geological disposal programme”.


 

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