Radiation from the radioactive interim storage facility is negligible

The original article can be read as “Schlumpfs graphic 120” in the online Nebelspalter of 22 July 2024.

Sworn opponents of nuclear power repeatedly claim that the disposal of radioactive waste is unresolved. They imply that the radiation from this waste is dangerous for humans and the environment for hundreds of thousands of years. In the following, I will show that the measured radiation exposure from Switzerland’s centralised interim storage facility, where this waste is currently stored with less protection than in a deep geological repository, is completely negligible.

What is important:

• The total radiation dose for a person in Switzerland averages just under six millisieverts per year. Most of this comes from natural sources.
• The average annual dose per Swiss person from the interim storage facility for radioactive waste is only 0.000004 millisieverts.
• The radiation exposure from radioactive waste in the interim storage facility is therefore totally negligible – this applies all the more in an even better protected deep geological repository.

The Swiss Energy Foundation (SES), which sees itself explicitly as an anti-nuclear organisation, writes on the Internet about nuclear waste (see here) that the problems for deep storage of this waste are unique and have not been solved, particularly because the high-level waste radiates for hundreds of thousands of years. Not a word is said about the place where the radiation from this waste can be directly measured and analysed: the Central Interim Storage Facility (Zwilag) for radioactive waste in Würenlingen (see here). The waste will remain there until it can be transferred to a deep geological repository in a few decades’ time, where the radiation will be less intense than in the interim storage facility.

Melting, reducing, decontaminating

All radioactive waste from Switzerland has been collected in the Zwilag since 1999. This includes high-level waste from the operation of nuclear power plants and, until 2016, from the reprocessing of fuel elements. It also includes intermediate and low-level waste from nuclear power plants and from industry, research and medicine.

There is a special plasma furnace for the low and medium-level waste, in which this waste is melted at very high temperatures. This reduces their volume without changing the radiation. The residual materials are packaged in special drums ready for final disposal with the addition of glass-forming substances. Low-level waste is also decontaminated in a so-called conditioning plant, allowing certain materials to be recycled as conventional waste.

Open storage facility for high-level radioactive waste

The process is completely different for high-level waste: This comes from the nuclear power plants to the Zwilag by rail in special transport containers. There, the incoming inspection merely checks whether the containers are leak-proof. The containers are then placed in a special storage hall in which the so-called dry storage principle is applied. This means that the great heat that these containers radiate is dissipated by the natural circulation of air: The air flows in through openings in the side walls of the hall. The waste heat from the containers heats the air, which rises and leaves the hall through further openings in the roof.

These special steel containers for the high-level waste are over six metres high and weigh up to 140 tonnes. They protect the waste against all possible external impacts such as earthquakes, aeroplane crashes, flooding and terrorism. The containers also shield the environment from radiation.

Main sources of radiation: radon and medical applications

Let’s now take a look at the level of radiation exposure from the Zwilag. All radioactivity measurements in Switzerland are collected and analysed by the Radiation Protection Division of the Federal Office of Public Health (FOPH) (see here). The latest report compiled there, “Radiation Protection and Monitoring of Radioactivity in Switzerland – Results 2022”, calculated the radiation exposure balance of the Swiss population for the year 2022 – the decisive reference value for Zwilag radiation.

The following graph from this report shows the contribution of the various sources of exposure to the average effective dose per year and inhabitant:

As can be seen from the legend of the graph, radioactivity comes from everywhere: from outer space, from the ground, from food, from radon in living spaces, from air travel, from smoking, from industry, research and contaminated sites, and from medical imaging. The clear main causes of this total radiation exposure are radon (violet), which penetrates buildings from the ground, and medical applications (dark green) such as X-ray examinations, with shares of 56 and 25 per cent respectively.

The Swiss annual dose is six millisieverts

All figures in the graph are given in millisieverts (mSv) per year. The sum of all the sources of exposure indicated amounts to just under six millisieverts – that is the total effective dose that a person in the Swiss population receives on average per year.

And where is the contribution from Zwilag? It belongs in the “Industry, research, contaminated sites” area, for which the graph shows a total value of 0.02 mSv. Using information provided to me by Zwilag, I was able to estimate the Zwilag annual dose using conservative assumptions from two components: on the one hand from an average value for the emissions from the chimney of the plasma furnace, and on the other hand from an assumed dose that one would receive from direct radiation if one were to camp right next to the Zwilag fence for a week – which of course nobody does.

The Zwilag dose is 0.000004 millisieverts

Calculated in this way, a person in the vicinity of Zwilag receives an annual dose of 0.000004 mSv. This is such a small number that it no longer makes sense to calculate it. Nevertheless, I will try to illustrate this figure with a few comparisons.

As comparative figures, I have chosen the three prescribed limits for an annual dose per person and year, which are set differently for different population groups in Switzerland. For the entire Swiss population, a maximum of one millisievert per year is permitted. For people living in the vicinity of a nuclear power plant, an additional maximum of 0.3 mSv is permitted, and for people living in the vicinity of the Zwilag, an additional maximum of 0.05 mSv is permitted. The next graph shows how much the tiny Zwilag annual dose utilises these limits in percentage terms:

Please note the scale of the y-axis, which ranges from zero only to 0.01 per cent: all the figures shown in the graph are therefore below one 10,000th of the corresponding limit values! For the strictest limit value for the plant itself (far right), the Zwilag dose accounts for one 12,500th or 0.008 per cent. And for the limit value for the entire population it is one 250,000th or 0.0004 per cent.

The Zwilag dose plays no role at all

Even crazier, however, is what the first bar shows: Here, the Zwilag dose of 0.000004 mSv is shown as a percentage of the total dose for the Swiss population of six mSv shown in the first graph: Zwilag emissions account for one 1,500,000th or 0.00007 per cent of the real radiation dose to which the Swiss population is exposed on average per year.

To cut a long story short: Zwilag emissions do not play the slightest role in radiation exposure in Switzerland. Smoking, flying or eating is much more “dangerous” – let alone undergoing medical treatment or having radon in the house.

The false fears fuelled by the SES and other nuclear critics about radiation from radioactive waste turn out to be completely unfounded as soon as the actual situation at the Zwilag is analysed. However, because radioactive shielding will be improved with a deep geological repository, the fears of nuclear opponents are even less valid – especially as the situation is constantly improving because the radiation exposure of the waste is constantly decreasing with radioactive decay.