Japan's Nuclear Fuel Cycle

Nuclear Fuel Cycle diagram

Uranium fuel (spent fuel) once used in nuclear power generation contains unburned uranium and plutonium produced in the nuclear reactor. If these are reprocessed and removed, they can be reused as fuel, in other words, recycled. This series of recycling and utilization of fuel is called "nuclear fuel cycle".

Japan relies on imports for more than 90% of its energy resources. Although all uranium is imported, it is imported from countries with relatively stable political situations. And because uranium production is spread all over the world, it can be said to be an energy source with a more stable supply than oil.
Furthermore, uranium and plutonium recovered through the nuclear fuel cycle can be considered "semi-domestic energy resources."

What is a cask?

Spent fuel transportion cask

The special container used for transportation and storage of spent fuel in the nuclear fuel cycle stream is called a "cask".

Casks play an important role in recycling nuclear fuel, and we believe that our cask-related technology can contribute to the establishment of the nuclear fuel cycle and ultimately to a stable energy supply in Japan.

Cask Functions

Spent fuel removed from the reactor is cooled in the spent fuel pool in the power plant, and then transported or stored using a cask. The cask have to have the following functions.

1

Secure containment of radioactive materials (Primary Lid, Secondary Lid)

Radioactive materials are contained by using a double lid structure with metal gaskets (metal packing).

2

Radiation shielding (Neutron Shield, Body)

The body is made of heavy materials such as iron or lead that block gamma rays and of neutron shielding materials such as synthetic resin, to sufficiently reduce the amount of radiation.

3

Subcriticality (Basket)

Baskets (dividers) keep the spent fuel spaced apart to prevent criticality (a chain reaction of nuclear fission) from occurring.

4

Heat removal (Heat Transfer Fins)

The heat generated by the spent fuel is transferred to the surface of the cask using heat transfer fins with excellent thermal conduction, and cooled by the outside air.

Cask structure and safety functions

These functions ensure that the radiation levels and temperatures outside the cask are kept at levels that are safe enough for people to approach and work.
Advanced technology is required to design casks that can transport and storage efficiently while maintaining the necessary functions.