Technology of immobilization of tritium-containing liquid radioactive waste

Scientists and engineers of our company have developed a technology for handling large volumes of tritium LRW.
The technology is applicable for the immobilization of the accumulated tritium water at the Fukushima-1 NPP and for the neutralization of the tritium waste generated by heavy water reactors of the CANDU type.
The technology uses widely available reagents, it is economical and has no performance limitations.

1. In March 2011, a 9-point earthquake occurred in the Pacific Ocean

The tectonic shift of the ocean floor provoked a tsunami that struck the northeastern coast of Japan. The Fukushima-1 nuclear power plant, the first four blocks of which were built using technologies of the 60s of the last century, was under the blow. A giant wave came ashore and flooded the territory of the NPP. Although the blocks were designed with the account of seismic and tsunami hazards of the region, the unfortunate design decision to place the backup diesel engines on the lower floors of the block buildings became fatal. The NPP automation reacted properly, and stopped the fuel cycle, however, the absence of power supply to the cooling circuit led to the melting of the reactor cores, thermal explosions of three power units and the leakage of radiation outside the station – into the atmosphere, the water area, the ground surface and underground aquifers.

10 years have passed since the disaster. More than 1.2 million cubic meters of LRW have been accumulated together with over 200 thousand tons of low- and intermediate-level SRW.

The major problem of the LRW is that it is contaminated with tritium which has to be neutralized.

All this time, scientists and engineers from all over the world kept trying to offer an adequate technology for neutralizing the accumulated tritium LRW. All of these proposals were based on traditional approach. It is:

The traditional approach is caused by the traditional goal of reducing the final volume. However, practically, standard technologies are capable of producing 100 l / h, which in no way corresponds to the actual volumes of LRW.

2. Our approach:

In the case of a bulk accumulation of a large amount of radioactive waste (for example, an emergency or decommissioning of NPP units), it is important not to reduce the final volume, but to ensure the safety of the final packages. In fact, in 3 years from 1 million cubic meters of hazardous waste we can make 2 million cubic meters of garbage, which will not require monitoring efforts, special storage conditions, and which can be transported for storage at various landfills; this solves the problem. And if the technology allows making 100 cubic meters from 1 million, but this takes 1000 years, so it does not solve the problem.
Thus, the criteria for choosing the technology are productivity and economy.

Our goal is making the waste safe, not just reducing the volume.

Physically and chemically, tritium and protium waters are completely identical. For others, it is a problem, but for us, it is an advantage.

We have selected a solid reagent – a special crystalline hydrate, of which water is a large integral part. Our technology is that first water is removed from this reagent, and then tritium water is placed in its place. Our task was that at removing the water, the reagent would not be destroyed, being capable of regeneration/rehydration. In addition, it is important that the energy of the separation of water from the reagent is high. Then we are guaranteed that tritium is firmly fixed under normal conditions.
The resulting technology is in which:

  • no new facilities to be built,
  • no new energy capacities are needed – neither power plants, nor boilers,
  • the original tritium water is not to be purified, and tritium is not separated from hydrogen,
  • no bulky and seismically hazardous rectification columns that are mandatory in all the other methods, to separate hydrogen and tritium by weight,
  • no hazardous processes associated with the production and use of pure hydrogen,
  • secondary radioactive waste is not generated.

The technology has no scale limitations.

  • 130 liters of LRW are poured into this tank from the tank where tritium water is currently stored
  • 217 kg of pre-dehydrated reagent is added to it
  • The reagent is added through a special opening in the lid of the container at constant stirring
  • To do this, at the lower side of the lid polymer blades are attached to a rod running to the upper side of the lid, and connected to a removable electric motor. After 5-7 minutes, the reagent hardens, the blades are automatically unfastened and stay in the container. The electric motor is transferred to the next container.
    As a result, 350 kg of solid waste are formed in the container, wherein tritium is reliably fixed; the walls of the container reliably shield the β – radiation

The hardening occurs without energy consumption.
To carry out this procedure on the station territory, we must have a prepared reagent.
IMPORTANT: the reagent dehydration can be performed anywhere in the world where electric power is available.
For example, it can be nuclear power plants thousands of kilometers away from Fukushima.
For greater efficiency, the electric power needed for the dehydration may be consumed at night when there is a natural drop in the nominal consumption.

This is why we say that the technology has no performance limits.
In all other methods, to scale the speed of the process, it is compulsory to increase the number of installations and of capital buildings for their placement, and to build new power facilities. And all this has to be done on the territory of the plant.
That is, the whole idea of freeing the site from the stored tanks, to start work on the decommissioning of damaged units, becomes senseless.
In our case, to increase the speed of the process with a sufficient amount of prepared reagent we just have to increase the manpower.

The processing cost is estimated at $ 600 / m³.
This includes the cost of raw materials, costs of dehydration, manufacture of containers and special lids with additional devices. (Note that as a result of R&D and optimization of the dewatering technology, the price can be significantly reduced).
This does NOT include:

  • the cost of dewatering plants,
  • staff salary,
  • transportation costs (delivery of the prepared reagent and delivery of finished packages to the place of storage),
  • the cost of storage.
  • As the reagent is a quite sought-after commodity, it can be assumed that after the decay of the tritium (100 years), it can be brought back into circulation. This means that the cost of the reagent can be deducted from the total cost of the disposal. Also, various dehydration procedures are part of many technological processes. Therefore, after the completion of the work for Fukushima, the installations can also be returned to circulation.