For the past three years (the fourth is ongoing), I have been involved in the demolition project of nuclear power plants. The target has been the so-called biological shield, which in this case is a steel-reinforced concrete cylinder approximately 15 meters high, with wall thickness of 1.5 meters and a diameter of 9 meters, protecting the environment from radiation from the nuclear reactor. Each cylinder weighs about 1,500 tons. The demolition contractor is Lodab Demolering AB, and I am subcontracted by them, handling the HSE coordinator duties. In practice, we have shared project leadership with Lodab’s Site Manager, Mika Myntti.

The project involves the same work at four units: BKAB 1 and 2, and OKG 1 and 2. Three of these are already completed, and the fourth, OKG 1, is currently ongoing and will be completed by the end of this year. The first three have been structurally identical, but this last one was built first and is smaller than the others but more challenging to dismantle structurally, with higher radiation levels.

Safety is, as always in demolition work, of the utmost importance. The risks associated with the demolition work itself, lifting operations, working at heights, and similar tasks are addressed as usual. However, naturally, radiation safety is a factor not typically considered on regular demolition sites. In addition to radiation safety, dust control is slightly more precise than on other demolition sites due to the plant's controlled ventilation. All air is directed through a stack where filters analyze both radiation and impurities. The maximum allowed personal radiation dose per year is 20 mSv, but the plants themselves have set internal limits at about 25% of this. Although it is to be avoided, the demolition work involves operating in close proximity to the bioshield, where the inside and mid-height of the cylinder are the most heavily radiated areas. As work has progressed, we have developed methods to significantly reduce work in these areas. This has been necessary not only for personal safety but also for practical reasons, as exceeding the set personal radiation dose removes the worker from the site for the remainder of the year.

The demolition has been carried out using wire sawing. Before sawing, hundreds of holes are drilled through the cylinder according to the cutting plan for both lifting chains and the wire. Depending on the location, 5–35 ton segments are cut from the concrete cylinder, which are then further cut into various waste categories based on radiation levels according to customer specifications. Our contract boundary is the packaging of these segments into shipping containers for final disposal by the client.

This has been a very interesting project, which has taught me a lot not only about radiation safety but also about working on an international job site, lift safety, and dust control. Now the final unit is progressing well, and I am already looking forward to upcoming projects. Where and what kind – that I do not know yet.