Careful design of a concrete structure to surround a new proton beam radiation therapy equipment for cancer sufferers helped reduce costs during construction and minimises radioactive debris requiring processing at the end of the structure’s useful life.

Proton beam therapy is a promising new treatment for cancer. Irradiation with the proton beam enables a higher dose of radiation to be used against cancer cells while avoiding damage to the healthy tissue surrounding the tumour. The first clinic to offer this treatment to cancer sufferers in Denmark was planned at Aarhus Hospital.

Demolition costs factored into the design

The equipment is mounted within a specially-designed bunker which fits tightly around the device. The bunker must offer good dimensional stability and provide necessary radiation shielding for the environment and staff. A further consideration is that, due to the fast-changing nature of medical equipment, the building’s lifespan could be as short as 10-15 years. Demolition costs are highly relevant in the design of the building because processing radioactive debris is up to 100 times more expensive than processing non-radioactive debris.

Royal HaskoningDHV undertook the structural design of the building and worked closely with partners to identify the ideal solution. Physicists from Aarhus University determined the required level of shielding which we incorporated within our design. We worked with the contractor to determine the appropriate building method and with the concrete supplier to determine the composition of the concrete.

Cost-effective measures applied to avoid cracks in concrete

Two features stood out in our solution. The first was the use of a particular marble from Norway to provide shielding. By using finely ground marble in place of sand in concrete for areas directly exposed to the beam, we avoided contamination in a solution which significantly lowers future demolition costs.

It was also very important to avoid cracks in the concrete. This could have been avoided by distributing reinforcement over the thickness of the wall, but in our solution only the outsides of the walls were reinforced. This had the advantage of reducing construction costs and meant the equipment inside was accessible. To avoid cracks on internal walls, we used a combination of measures, including as little cement as possible and placement of a cover and temporary insulation just after casting. Our methods were successful as no cracks appeared requiring repair.

The team completed the building on schedule and the first patients were treated in 2018.