Summarised comments of the BfS on the report of Helmholtz Zentrum München, PG Jüclih "AG Asse Inventory – Final Report"

On 10 September 2010, the Federal Office for Radiation Protection received the report of the Working Group Asse Inventory of Helmholtz Zentrum München. The BfS had supported the HMGU project group with the reporting. The aim of the HMGU report commissioned by the Federal Minis-try for Education and Research, was to research as to whether there were new findings relating to the inventory emplaced between 1967 and 1978 according to the state of the art of science and technology. Likewise, the reports by the press and the survey results of the 21st parliamentary in-quiry committee were to be investigated. The data was collected especially by inquiring former waste producers and deliverers to the Asse mine and re-evaluating old documents. This report is of special importance to the BfS in particular because of the plans for the safe decommissioning of the Asse mine. According to the present state of knowledge, the safety case required by the Atomic Energy Act can only be ensured if the radioactive waste is retrieved. Correspondingly, the infor-mation about the inventory and the state of concrete waste packages to be recovered is relevant.

Basically, the HMGU report does not provide new findings about the general state of the wastes or the radionuclide inventory of the Asse II mine and mainly confirms the assumptions and estima-tions regarding the waste inventory that have so far been available to the BfS. However, it contrib-utes to taking safety measures that are necessary for the protection of the staff and the population in the retrieval process.

In detail it should be pointed out:

Waste acceptance requirements

In the HMGU report, the development and updating of the waste acceptance requirements for the Asse mine are represented in a misleading way. For example, for the emplacement phases 1 to 4 (1967-1971), waste acceptance requirements in the current sense did not yet exist. Instead there were requirements contained in the emplacement licences about which the waste deliverers were informed, too. The actual waste acceptance requirements only came into existence in 1971. There were special requirements for low-level and intermediate-level radioactive waste, which were up-dated later on.

Statement of the Jülich Research Center

Regarding the statement of the Jülich Research Centre it should be noted that with respect to the radionuclide inventory of the graphite and absorber balls, in addition to the tritium inventory, also the inventory of carbon-14 and, if necessary, further nuclides needs to be checked and revised. The carbon-14 inventory in the emplaced graphite and absorber balls needs to be supplemented according to the available information; this corresponds to an increase in the beta and gamma activ-ity inventory of ca. 0.02%. The summary of the HMGU report, however, deals only with the tritium inventory. Compared with tritium, the increase in the carbon-14 inventory is of greater importance with respect to radiation protection and long-term safety.

Chapter 6 on the radionuclide inventory contains activity calculations on single waste packages, which show that deviations of the declared package content must be expected. This was also con-firmed by the examination of packages originating from Braunschweig and conditioned for the Asse mine (but not emplaced there) that are stored intermediately in Geesthacht.

Activity calculations

The activity calculations conducted with the help of MICROSHIELD at three containers are basically a method for plausibility checks of the data on dose rate and activity inventory. With the calculation method it also be checked in the future to see whether plausible information is available about other containers than the ones examined in the context of the HMGU reporting. However, in the accompanying lists frequently only data was found that had been averaged over batches of several drums; therefore subsequent calculations could provide no information about the inventory of concrete individual packages, either. This information would be helpful for the decommissioning planning for the Asse mine, however. More information can be gathered during the careful exami-nation of all accompanying lists. This examination is carried out by TÜV Süd in the scope of the in-ventory examination commissioned by the BfS.

Waste classification

The activity concentration is used for the former classification as low-level, intermediate-level and high-level radioactive wastes (cf. Fig. 1, HMGU report). In contradiction with this, but technically true, it is stated at the same time that the wastes were formerly classified according to the "level of radiation" – that meant the gamma dose rate, which was the major classification criterion for low-level and intermediate-level radioactive wastes in the Asse II mine. Actually, and this was stated in the report, in particular the "levels on the outer surface of the packages were relevant". That was essential for the handling of the wastes, i.e. the wastes were classified as low-level and intermedi-ate-level radioactive wastes under the aspect of handling.

At the national and international level there was no generally valid classification of radioactive wastes at that time. Only at the beginning of the 1980s did the International Atomic Energy Agency suggest a qualitative classification of radioactive wastes. The Figure on waste classification quoted by R Odoj in the HMGU report is only a rough orientation in terms of the relation between activity inventory and classification.

Wastes whose handling required special shielding, were emplaced on the 511-m level as intermediate-level radioactive wastes. No special shielding was necessary to handle the residual wastes un-derground that were classified as low-level radioactive wastes. On account of the shielding, these wastes including the drums in "lost concrete shielding (VBA)", that originally contained intermediate-level radioactive wastes, are emplaced as low-level radioactive wastes on the 750-m level and in a chamber on the 725-m level. So far nothing has been found that points to the emplacement of high-level radioactive wastes.

Old documents

The old documents (meeting notes, telephone notes, minutes) thus available to the parliamentary inquiry committee in the Lower Saxon Landtag were not completely evaluated by the HMGU work-ing group. More documents and correspondence are available for many of the listed files. A first comparison, however, did not indicate significant findings going beyond what was said in the report, in particular with respect to the safe decommissioning of the Asse repository.

Conclusions

The HMGU report mainly confirms the assumptions and estimations on the waste inventory availa-ble to the BfS so far. In the year 2009, there were supplementations regarding the tritium and plu-tonium inventory that have already been taken into account in the BfS safety considerations. The statement made in the HMGU report that further findings regarding the nuclide specific activity inventory have not resulted, is widely confirmed by the BfS. The report provides another basis for supplementing research and examinations in particular on the nuclear fuel inventory, that are cur-rently being carried out.