Architecture and management of a geological repository - Andra

11 – Operational SafetyIn all cases, the primary packages taken from the demonstration models after the drop test show slightdeformation to the upper part of their envelopes (which impacted the lid when hitting the ground), butno evidence of rupture. These observations are consistent with the results of the simulations (cf. Figure11.8.3).The studies and tests carried out show that a disposal package that falls during emplacement in the cellis not liable to result in a loss of primary package containment.11.8.2 Assessment of the radiological consequences of a fall of B waste disposal packages in adisposal cellThe results of the studies and tests on the mechanical consequences of B packages falling in thedisposal cell gives grounds for believing that there would be no loss of containment of radioactivematerial should such an event occur.However, scenarios involving the release of radioactive materials in the case of B2 disposal packageshave been envisaged, assuming that the package lid comes off at the moment of impact. Thishypothesis was not considered in the case of B5 disposal packages given its different designcomprising cast individual lids fully integral with the container body.11.8.2.1 Retained assumptionsFollowing the detachment of the lid from the disposal package at the moment of impact, a primarypackage (or primary packages) could be damaged to some extent which could result in a release ofradioactive material which would be suspended in the atmosphere of the repository cell. Thecontaminated air would circulate in the return air circuit before being rejected into the atmosphere atthe exhaust shaft.Various assumptions were retained concerning the quantities of radionuclides liable to be released inthe cell. In one case, one single package shows a local tear and, in another case, it is supposed that thelid of the four primary packages is detached. The nature of the matrix of bituminised sludges was alsotaken into consideration, because it has a good ability to immobilise the radioactive wastes.11.8.2.2 Radiological consequences of a fall of B2 packages in a cellThe simulation studies show that the phenomenon of an instantaneous placement in suspension at themoment of the impact appears preponderant compared to the phenomenon of a continuous placementin suspension by the leaching of the radioactive materials through ventilation in the cell.The preponderant ways of exposing the public would be the inhalation due to the passing by of theradionuclide plume and, to a lesser extent, food ingestion.Simulations show that the dose received at 500 m from the rejection outlet would be less than0.001 mSv, regardless of the scenario retained. This negligible dose would not generate consequencesto people or to the environment.11.8.3 ConclusionDuring the transfer and handling operations of the B waste packages in the disposal cells, no fallshould occur because of the recommended preventive measures. Nevertheless, if it should happen thatthe package would flip over and fall on the cell floor in spite of these arrangements, this fall wouldcause mechanical deteriorations of the disposal package. Simulations show that the primary packageshould not suffer a loss of containment and should not release radioactive particles. However, for thepackages of bituminised sludge (B2), scenarios were studied where particles are released in thedisposal cell and then in the environment via the ventilation circuits. The radiological consequenceswere then estimated, and construed to be negligible for the public.DOSSIER 2005 ARGILE -ARCHITECTURE AND MANAGEMENT OF A GEOLOGICAL DISPOSAL SYSTEM481/495