Nuclear Waste Management & Decontamination

A PLANNED APPROACH TO NUCLEAR WASTE MANAGEMENT

The safe and secure management of nuclear waste is a highly regulated area. The main focus of nuclear waste disposal, particularly in the eyes of the general public, is the disposal of spent fuel rods. However, tiny amounts of radioactive waste are produced by a nuclear power plant every day – from cooling pond water to used protective clothing. As such, operators should plan the treatment and disposal of any radioactive material as part of a defined, approved and documented strategy.

Nuclear waste management involves four distinct phases:

• Avoid and plan: Naturally, trying to reduce the amount of any possible waste is an ideal solution, and will save money. But not all waste can be avoided so having a plan for its safe disposal is a must.

• Treat: When waste arises, it is advisable to treat it immediately. Depending on its type and classification, this could include decontaminating, shredding, compacting, drying or vitrifying the waste.

• Pack: Some radioactive waste needs to be packed and stored in bespoke, approved containers so it can be handled and transported easily.

• Store and dispose: Packed in suitable containers, waste can be stored for several years or even decades at approved waste storage facilities before it is permanently disposed of at a long-term storage site.

DEALING WITH ALL LEVELS OF NUCLEAR WASTE

The vast majority of nuclear waste (around 90% according to the World Nuclear Association) is classed as Low Level Waste (LLW) and arises from day-to-day operation of a nuclear power plant and, to a lesser extent, from hospitals, research facilities and laboratories. Such waste typically comprises of scrap metal, paper and plastics exhibiting low levels of radioactivity – not exceeding 4 Giga-Becquerel (GBq) per tonne of alpha activity, or 12 GBq per tonne of beta/gamma activity. A lot of LLW, in the form of rubble, machine parts, etc, is also created during decommissioning and dismantling of a nuclear power plant.

Intermediate Level Waste (ILW) exceeds LLW’s upper boundaries. ILW usually comprises of nuclear reactor components, graphite from reactor cores as well as sludge, ion exchange resins and flocculants. ILW may need treatment such as compacting, cutting or drying, before being packed and stored.

High Level Waste (HLW) can arise from different sources. It can be produced as a by-product from reprocessing spent fuel rods from nuclear reactors.  HLW from this source is typically a liquid which, when mixed with crushed glass and heated can be poured into stainless steel canisters. The molten waste then turns into a stable, solid form when cooled (a process called vitrification) and the canisters can then be transported, stored and disposed of safely.

Another HLW is the spent fuel itself. The process of the safe handling of spent fuel from the reactor core over the spent fuel pool to the dry interim storage in a cask is very important for the decommissioning, because the first goal for a NPP in decommissioning is to be free from fuel rods.

TÜV SÜD’s experts can call on their experience to support operators in developing an effective, safe, and compliant waste management strategy, including waste minimization and waste pre-treatment options. Our experts use an array of tools to better understand the entire waste cycle, such as “waste led” decommissioning diagrams based on IAEA guidelines.

CHOOSING THE RIGHT NUCLEAR WASTE PACKAGING

Some LLW may not require packaging as it may be possible to treat the waste away from Low Level Waste Repositories (LLWR); options include incineration, metals recycling and alternative disposal via licensed landfill for Very Low Level Waste (VLLW). Otherwise, there is a wide choice of standardized packaging for LLW on the market – from bulk bags, liners, to canisters and shielded containers – that are approved by local regulatory authorities.

TÜV SÜD provides expertise when identifying and selecting packaging options, encapsulation techniques and packaging processes that are suitable for the waste produced. We also offer waste package management covering various forms of radioactive waste that arise during decommissioning.

SAFE AND SECURE NUCLEAR WASTE TRANSPORT

During its lifecycle, nuclear waste needs to be transported for treatment, storage, and disposal. And every day, radioactive material is transported safely and securely by road and rail thanks to strict licensing and conditions in place.

Before moving any nuclear waste, operators need to obtain packaging and shipping approval so TÜV SÜD will support you with waste process and throughput modelling as well as criticality and shielding assessments to ensure waste is transported safely.

SELECTING INTERIM AND LONG-TERM NUCLEAR WASTE STORAGE

At the end of its life, nuclear fuel is usually bundled into fuel assemblies and transferred to cooling pools for around five years. This allows the fuel to cool down in an interim storage facility while its radioactivity decays. Afterwards, operators can put the waste into long-term storage packed in dry casks filled with inert gas. These concrete and steel casks are built to withstand natural and man-made disasters.

Many countries have specially designed interim surface or sub-surface storage waste facilities. In the long term, the preferred option is “geological disposal”, where packed radioactive waste is stored in an underground repository. These locations are carefully chosen so that the surrounding rock formations form a barrier against any possible radioactive escape.

DECONTAMINATING WASTE DURING DECOMMISSIONING

During decommissioning of a nuclear power plant, several decontamination techniques can be used to reduce radiation exposure, to salvage and reuse components, materials, and equipment and to facilitate waste management. Techniques such as washing, heating, mechanical cleaning or even leveraging chemical or electrochemical reactions help reduce the amount of material requiring specialist storage or disposal and can contribute to restoring the site to its previous state.

TÜV SÜD’s experts can support operators during decommissioning by analyzing that your nuclear waste decommissioning options meet safety, environmental, practicality and cost criteria. For example, removing contamination from environments and components reduces dosage levels so manual dismantling can be undertaken avoiding the use of more expensive robots. We can also advise you on possible techniques to reduce the contamination of systems and facilities to levels that allow for more economical waste treatment options or even reuse or recycling.