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”.
