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| Home > Publications database > Evaluation of LILW degradation processes and products in a geological repository for radioactive waste in Boom Clay in the Netherlands |
| Home > Publications database > Evaluation of LILW degradation processes and products in a geological repository for radioactive waste in Boom Clay in the Netherlands |
| Poster (Other) | FZJ-2015-02875 |
; ;
2015
Abstract: OPERA is the Dutch acronym for research programme for geological disposal of radioactive waste which focusses on the development of initial conditional safety cases for generic repositories for high-level and low-intermediate level (LILW) radioactive waste in the Boom Clay and Zechstein rocksalt formations in the Netherlands. In the disposal concept aspired in this context, cementitious materials are extensively used, e.g. as buffer within the waste containers, as backfill material and also as construction material. Thus, highly alkaline conditions are expected in the vicinity of the emplaced wastes.LILW arises mainly from activities with radioactive materials or radioisotopes in the industry, research institutions and hospitals. It includes lowly contaminated materials, such as plastics, cellulose or metal and is stored in containers with volumes of 200, 400, 600, 1.000 or 1.500 litres at COVRA. According to [1],o the waste is likely to contain a significant fraction of solid organic/degradable material,o the waste may contain a significant fraction of NaOH/KOH and is processed by COVRA into a stable solid cementitious waste form for storage.In this study, the initial results of the evaluation of degradation processes and products (e.g. gas generation) of the LILW matrix are presented. Several chemical and physical processes relevant for the LILW degradation and the formation of degradation products are investigated, whereas focussing on the investigation of the chemical and physical behaviour of the degradation products and their interaction with the host rock and the engineered barrier system, respectively. Due to the expected high amount of organic materials in the LILW, emphasis is laid in this paper on the degradation processes of cellulose and hemicellulose under alkaline (repository) conditions, rate and extent of degradation with time and the identification of degradation products (e.g. isosaccharinic acid, xylosaccharinic acid and small chain fatty acids [2]) under near-field conditions. Furthermore, the results regarding the investigation on the degradation processes and degradation products of plastics, polystyerene and PVC under repository conditions are discussed. Due to the variability of the porewater composition encountered in the Boom Clay in the Netherlands and the generic nature of the OPERA safety case (i.e. without selection of even a potential repository site), various scenarios regarding the composition of the near-field water resulting from the interaction of Boom Clay porewater with the cementitious materials and their evolution with time will also be discussed.References[1] Meeussen, J.C.L., Rosca-Bocancea, E. 2014. Determination of the inventory, Part B: Matrix composition. OPERA-IR-NRG1112B. COVRA, Vlissingen.[2] Humphreys, P. N., Laws, A., Swanton, S.W. 2010. A Review of Cellulose Degradation and the Fate of Degradation Products Under Repository Conditions. Serco/TAS/002274/001, Issue 2. SERCO, Oxfordshire, UK.
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