The results of the international joint tests have proven the safety of the high-temperature gas-cooled reactor (HTGR).
Tests conducted by the Japan Atomic Energy Agency (JAEA) on January 28 on the High Temperature Test Reactor (HTTR) in Oarai, Ibaraki Prefecture (thermal output of 30,000 kW) proved that it would not melt even in the event of a total power failure.
The experiment was conducted under severe conditions corresponding to a total loss of electrical power and included stopping the circulation of coolant and helium gas.
The HTTR’s response was flawless. With only the built-in safety devices with which HTGRs are fitted, the HTTR reactor shut down automatically without the use of control rods and natural core cooling continued.
In the accident at TEPCO’s Fukushima Daiichi nuclear power plant in 2011, a complete power failure caused the core to melt, spreading radioactive contamination over a wide area. However, even in the event of an accident identical to that of Fukushima Daiichi, such a situation would not occur in an HTGR. This is true not only in theory, but has been confirmed by tests using the HTTR.
Japan is at the forefront of HTGR development in the world. While China is developing a different type of HTGR, the Japanese HTTR is the first in the world to undergo safety demonstration tests at this level. The tests were conducted as part of a joint project with the Nuclear Energy Agency of the Organization for Economic Co-operation and Development.
The next demonstration test will take place in March 2022, when the reactor’s power output will be increased to 100% from the 30% of this most recent test. In addition to increasing the amount of data, the tests aim to increase the understanding among Japanese and overseas that the HTGR is a reactor not associated with major accidents.
In 2022, JAEA will begin designing hydrogen production equipment that will utilize the nearly 1,000 degree Celsius high temperature of the HTTR. The plan is to first produce hydrogen from natural gas, and the next step would be to move to a hydrogen mass production technology that uses only iodine, sulfur and water, and does not emit carbon dioxide.
The HTGR at the practical use stage would be the ultimate decarbonized energy source as it would produce green hydrogen while generating electricity.
In addition, the HTGR is endowed with the capacity to absorb fluctuations in production, which are the fatal weakness of renewable energy sources like solar energy. Therefore, it could help to reduce the thermal power generation ratio.
Although conventional nuclear power generation is very convenient, concerns about the risk of a major accident occurring have been a factor in delaying the restart of operations in Japan.
It is in this context that the unprecedented safety of the HTGR has been demonstrated. The government should now focus its efforts on accelerating the development of commercial reactors. This would also lead to the development of human resources in the field of nuclear energy.
(Read the editorial in Japanese on this link.)
Author: editorial board, The Sankei Shimbun