QSE

Energy Physics Engineering
Neutron Device Engineering

Front Line Research
An accelerator + "sub" critical reactor = a hybrid nuclear system pursuing safety. Creation of the future energy figure.

Exploration of advanced nuclear systems which researchers around the world compete to develop.

As the best combination of energy sources for the mid-and-long term in our nation, nuclear system (nuclear reactors) is considered as one viable option. The key to further research and development is improvement of long-term safety, and many researchers from Japan and around the world have been promoting various attempts. In which "accelerator driven system (:hereinafter called ADS)" is the center of attention. This is a type of hybrid energy system consisting of the combination of accelerator and nuclear reactor in subcritical states (where nuclear fission chain reaction is less persistent and decrease over time). In this nuclear reactor, high-energy protons accelerated by high-intensity accelerator are injected into a target such as lead-bismuth (Pb-Bi) to induce nuclear spallation reaction, and by irradiating high-energy neutrons produced from this reaction to nuclear reactor care in sub-critical state, nuclear fission reaction is occurred and energy is produced.

ADS relies its sustention of nuclear fission chain reaction on the external accelerator-driven neutron source. If the accelerator is stopped, the nuclear reactor will shut down inevitably without going out of control, making it possible to operate more safely. ADS is also called "nuclear waste incinerator" since it is possible to "transmute (annihilate) nuclear waste".

Reduce toxicity of radioactive waste and shorten the length of their half-life.

The disposal of high-level radioactive waste generated from used nuclear fuel of nuclear power plants are being discussed to be placed in a stable, geological layer deeper than 300 meters after they are vitrified. Wastes are roughly divided into fission products and minor actinoids (MA), and includes long-lived radionuclide whose half-life (time required to decay half of radioisotope into another nuclides. A rough estimate of its radioactive life duration) is tens of thousands of years. If we can convert these substances into short-lived or stable nuclides, it may contribute greatly to the decrease of environmental load. A typical method for this is the nuclear transmutation (annihilation) described above, which destroys the nucleus by artificially irradiating the neutron using accelerators and nuclear reactors that will convert long-lived radionuclide into low-radiotoxic nuclides or short-lived nuclides.

Aizawa Laboratory promotes experiments by comparing numerical analysis results and experiment data such as assessment of safety and characteristic of ADS reactor core, measurement of sub-criticality, development of characteristic analysis of nuclear transmutation (annihilation) by numerical simulation, as well as basic experiments using Critical Assembly (Kyoto University). We　are accumulating steady efforts and unique challenges for a safe and secure usage of nuclear energy and development of future technologies that will generate new values.

Front Line Research

The concept of accelerator driven system

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