Over a period of years the radioactivity and heat generation declines, until the spent fuel can be removed from the water and stored in casks for burial.
This process is often completed using robots, which are able to access the difficult to reach areas deemed too radioactive for human workers.
The first step is to cover the area with a protective shield which is usually made up of radioactive-resistant materials - this allows workers to continue working with a significantly lower radioactive environment.
Once established, entombment structures cannot practically be transported or modified, making disposal sites effectively permanent for their intended lifespan often up to 1,000 years.
[11] In addition, the intended permanence of such structures raises the concern of leak integrity over long periods of time.
Should a leak occur, the nuclear waste contents could potentially radioactively contaminate nearby water sources, posing a serious health risk to surrounding inhabitants and the biosphere, possibly violating the polluter pays principle.
[12] Public perception plays an important role in the development of nuclear entombment sites and it can be difficult to ensure a steady supply of both funding and willing workers.
[17] In addition to reducing cost, it also minimizes public interaction with the project and the amount of nuclear radiation emitted from the waste.
Entombment is also preferable in instances of time sensitive scenarios, in which the deferred dismantling of a nuclear power plant could potentially increase financial burden and/or the hazardous radioactive decay.
The NRC has decided in order for nuclear entombment to be possible, a long-term structure must be created specifically for the encasing of the radioactive waste.
If states have also agreed to follow §274 of the Atomic Energy Act they may take on the responsibility of disposing of low-level waste and receive facilities from the federal government for this purpose.
[19] Other commissions in the pursuit of improving nuclear entombment as a solution include the Cementitious Barriers Partnership (CBP)[8] and the U.S. Department of Energy (DOE).
[10] Research facilities such as those at the Savannah River[20] and Lawrence Livermore Laboratory have contributed to the understanding of safe nuclear entombment.
In El Cabril, Spain a multi-concrete barrier concept was used wherein the radioactive waste drums are placed inside concrete boxes.
Those boxes are then placed inside a reinforced concrete vault sealed with a waterproof coating to prevent any hazardous liquid from escaping the drums.
[21] In the Hallam Nuclear Power Facility, expanding concrete, seal-welding at penetrations, sand, waterproof polyvinyl membranes, and earth were all used to envelop radioactive residuals.
The main arch is composed of triple-layered radiation resistant panels made up of stainless steel coated in polycarbonate, which will provide the shielding necessary for radioactive containment.
This new tomb is designed to last over 100 years, and has special ventilation and temperature systems to prevent condensation of radioactive fluids on the inside which could result in a compromised containment.
The new containment structure is still intended to be temporary, with the goal of allowing the Ukrainian Government and the EU time to develop ways of properly decommissioning the plant and cleaning up the site.