Stacking of the concrete blocks surrounding a treatment room in the new megavoltage irradiation facility, 1972. NB click to enlarge
Around 1970, the development of equipment for megavoltage irradiation is still in its infancy and it is difficult to predict what the size of new equipment would be and what type of shielding and additional devices would be required. It was decided to build a universal type of bunker for 4 large treatment units. This concrete building becomes about 66 m long, 11 m wide and 8 m high. The roof is 110 cm thick and the walls 70 cm. The ground floor at working level is situated 3 m above the basement floor. The basement is intended for the installation of auxiliary tools and systems and the storage of technical equipment.
The walls of the 4 treatment rooms are built up from the floor of the basement using separate concrete blocks without using cement. In this way the plan could be adapted to new requirements. The two new accelerators and the neutron generator which have been ordered, generate radiation of 8, 16 and 14 megavolt, respectively, thus requiring heavy shielding of this high energy. The wall thickness varies between 50 and 200 cm of concrete. Physicist Herbert Marcuse, who has designed the treatment rooms, consulted with his colleagues Wijker (KEMA, before also NKI-AVL) and Julius (Ministry of Health). The architects (Duintjer-Istha), advised on the dimensions of the concrete blocks to be 25x25x50 cm. Each block weighs about 75 kg and can be moved by two persons. In between the blocks 5 cm wide lead strips were placed to fill any small gap. When building these concrete walls, use was made of a fork lift truck with vacuum suction cups that could lift four blocks simultaneously.
The still empty megavoltage irradiation facility with openings in the roof through which the irradiation equipment could be lowered into the building.
These openings are later closed with concrete beams. At the left hand side the concrete edge of the ground floor that connects to the Radiotherapy Department is just visible.
Design of treatment room 7 (now A2) for the neutron generator.
Top view and longitudinal section of the megavolt irradiation facility with the cobalt unit and two linear accelerators. NB click to enlarge and find more information.
In 1975 the neutron generator was installed in the fourth shielded room.
It can be seen that the irradiation units in the treatment rooms were mounted on a separate sturdy support. Surrounding this support a lighter floor was placed on a steel construction, which was connected to the ground floor level of the radiotherapy department. In the basement auxiliary instrumentation of the irradiation equipment was installed.