Federal Office for Radiation Protection implements new radiation protection rules for Asse

The Federal Office for Radiation Protection (BfS) has developed the nuclear law boundary conditions for the safe operation of Asse up to decommissioning, has made essential modifications to the operating procedure and thus implemented basic radiation protection requirements. This was necessary as the state of the facility was not in compliance with the stipulations of the Atomic Energy Act and the Radiation Protection Ordinance. "With this step essential deficiencies that had been the key cause for the change of operator were remedied," BfS President Wolfram König said on Thursday in Salzgitter.

BfS has already filed an application for the safe operation of Asse until the start of decommissioning according to the provisions set out in § 7 Radiation Protection Ordinance at the licensing authority, the Lower Saxony Environment Ministry. The proofs that have now been submitted are the basis for the decision about the application. Thus, for the first time, complete and verifiable data are available on how the Asse mine is to be operated as a nuclear facility according to the strict specifications of the Atomic Energy Act and the Radiation Protection Ordinance.

Among others, radiation protection directives were developed as a result of the safety assessments for normal operation and radiation prone areas were identified that may be radioactively contaminated. A contamination control is mandatory for persons staying in these areas or in newly identified radiation protection areas. Staff members and also visitors are monitored with dosimeters.

"On behalf of safety and since I am the radiation protection supervisor, I have already given order to Asse GmbH who is operating the mine on behalf of BfS to apply the newly established radiation protection rules with immediate effect," König said. Thus, BfS committed itself to applying the stricter rules already before a licence will be granted.

The additional safety assessments for incidents carried out for the application according to § 7 Radiation Protection Ordinance show that no reliable prediction can be made regarding the amount of the influent saline solution. As a precaution, the inflow of so-called design-exceeding amounts must therefore be assumed. In that case, according to estimations of the charged expert, larger amounts of saline solutions could be contaminated and the radiation protection objectives could not be complied with.

For the Federal Office for Radiation Protection, these results give reason to implement two packages of measures. On the one hand, they serve to reduce the probability that the mine will drown in an uncontrolled way. On the other hand, the radiological consequences for the case of an unexpected, large inflow of saline solutions must be limited.

Reducing the current deformation of cavities in the salt mine is one possibility to avoid this. One has already started implementing the preparation works for the backfilling of the clefts having formed between the roofs of the chambers and the loose salt.

As a part of the documents on the application according to § 7 StrlSchV, BfS has therefore developed strategies with the help of which negative impacts on the environment can be minimised, even in the worst case which would be a massive increase in saline solutions flowing into Asse.

The concept includes concrete technical measures and provisions to secure the facility which are to prevent a radiological dispersion of the emplaced waste. Measures to control higher rates of influent saline solution are of priority here. Among others, it is planned to install large reservoirs and to maintain more powerful pumps in order to be able in case of emergency to collect large amounts of influent saline solution in these reservoirs and to remove them. In order not to lose time, BfS has already started to carry out security works that need not be licensed.

The last step of the gradual approach is the minimisation of release of radioactive substances in case of emergency, when all other measures are not successful. The purpose is here to limit the release of harmful substances, to impede the movement of the solution in the mine, and to delay the transport of radioactive substances. It is of particular importance to avoid direct connections between the chambers where radioactive waste has been emplaced and the surrounding overlying rock and that radioactively contaminated solution is squeezed out of the rock into the environment. The necessary measures would include, among others, backfilling of residual cavities in emplacement chambers or flooding of parts of the mine with a saturated saline solution to counteract dissolution processes of the rock. Pipelines will be installed in certain emplacement chambers, so that concrete could be pumped into them in case of emergency.

Contrary to other measures according to Atomic Energy Act, all these options for future action must be pursued in parallel, examined for their feasibility, maintained, or even implemented by way of precaution. The reason for this time pressure is that Asse is not a designed repository but a mine that has been operated under different conditions for more than 40 years.

Attention will have to be paid that the measures to be carried out now are in compliance with the currently examined decommissioning options for Asse. This includes the retrieval of all or part of the waste, the relocation into another part of the mine, and the complete backfilling of Asse with salt concrete.