BfS presents result of Comparison of Options for decommissioning Asse

According to the present state of knowledge, the best variant of how to further deal with the radioactive waste emplaced in the Asse II mine is retrieving the waste. This is the result of the comparison of options for decommissioning Asse. "Not only do we confront a great scientific-technical challenge, but we will only be able to walk this road to permanent safety together with the people living in the area," Wolfram König, President of the Federal Office for Radiation Protection (BfS), said today in Hanover when the result was presented. Apart from the retrieval of the waste, the complete backfilling of the mine and the relocation of the waste to deeper parts of Asse were examined, too. According to the present state of knowledge, proof of long-term safety can be furnished regarding the option of retrieving the waste.

Three special challenges had to be taken into account in the examination of the options:

• On account of the instable state of the mine, the time frame for each solution is probably very limited.
• The conditions prevailing in the 1960ies and 1970ies when the radioactive waste was emplaced have led to the fact that there is only insufficient knowledge of the actually emplaced radioactive inventory and the state of the containers and waste packages.
• The state of the mine into which approximately 12,000 litres of saline solution enter daily and whose development is very difficult to predict, complicates the proof of long-term safety which is required according to nuclear law.

All three decommissioning options have been evaluated with the help of previously established evaluation parameters and criteria.

The result of this comparison is that on the basis of today’s state of knowledge one must aim at completely retrieving the waste from the Asse mine.

One argument against choosing the option of complete backfilling is the fact that it is currently not known whether it will be possible to furnish proof of long-term safety for this option. The relocation of the waste additionally involves the risk of not finding an appropriate emplacement area. Besides, this decommissioning option requires by far the most time.

None of the three variants is optimal, all of them involve uncertainties as to their realisation. The stability of the mine, in particular, is not predictable. In case of a considerable increase in influent saline solution, BfS has therefore been preparing emergency measures. If the state of the emplaced waste were considerably worse than expected, this would lead to an unjustifiable radiation exposure to the staff recovering the waste, or one would need too much time for retrieval, which cannot be accounted for in view of the dangerous situation. In this case, the preference of retrieval would have to be re-evaluated. However, since the long-term safety - and thus the safety for future generations – is vitally important and can currently only be ensured through retrieving the waste, this option has been identified as the best variant.

The weighting of the existing uncertainties leads to the following action plan which BfS will now efficiently pursue in coordination with the Federal Ministry for the Environment, Nature Conservation and Nuclear Safety (BMU):

1. The plans for retrieval need to be completed until they are ripe for implementation.
2. By examining the content of the emplacement chambers, comprehensive possibilities are to be created for a systematic evaluation of the aforementioned critical uncertainties.
3. Parallel to this, all technically feasible measures to stabilise the mine need to be carried on.
4. At the same time, emergency measures to limit the effects of an uncontrollable fall of rock pieces from the roof need to be taken. This should include a determination of its consequences for long-term safety.

In order to clarify the existing uncertainties as soon as possible, BfS will shortly present a concept of how to proceed further regarding the opening of the chambers and the examination of the waste packages.

BfS takes care that all interested people can reproduce the professional evaluation by publishing the comparison of options in text-only format and as an interactive screen version at its website.