Safety

JT-60SA requires sophisticated provision especially for radiation shielding and radioactive waste management in order to comply with the related law and regulations defined by the local governments, including Ibaraki prefecture and Naka city, and QST as the Implementing Agency.

The device has the following additional safety features beyond those previously provided for JT-60U:

(1) For radiation shielding, the vacuum vessel is designed so that water with boric acid added is circulated between shells. The boron helps keep doses below the regulation limits. Openings, including the clearances between the doors and the walls of the assembly hall, have required additional shielding.

(2) Gaseous effluent, including activated air from the torus hall and/or the vacuum vessel, is removed from the ventilation system. Some modification of the pre-existing heating, ventilation and air conditioning system of the experimental building has been made to achieve this.

(3) The liquid waste drain system that treats borated water and tritiated water has also required some modification of the drain line and an additional disposal tank for dilution.

(4) Radiation monitoring systems have been expanded into the extended controlled areas of the plant.

(5) Additional neutron and gamma radiation detectors have been added.

(6) The cobalt content of steels facing significant neutron doses has been kept to low levels in the system specifications, to aid in their eventual disposal.