The goal is to protect people and the environment from the harmful effects of radionuclides, even if an accident leads to the loss of reactor safety systems. This goal can be achieved by utilizing physical phenomena to suppress the progression of any loss or degradation of the confinement function of fuel-coating layers, thereby retaining radionuclides within coated fuel particles. (^*1 topic 9-2, ^*2 topic 9-3)