LILW degradation processes and products OPERA-PU-IBR512 Ionising radiation and radioactive substances are used in various fields: e.g., medicine, industry, agriculture, research. However, radioactive waste is produced by using radiation. In the Netherlands, this waste is collected, treated and stored by COVRA (Centrale Organisatie Voor Radioactief Afval). After the waste is stored for at least 100 years it is intended for disposal in a geological repository. There is world-wide scientific and technical consensus that this approach represents the safest long-term option for radioactive waste disposal. The geological waste disposal is understood as the emplacement of radioactive waste in deep underground geological formations. The objective is to isolate the radioactive waste from the biosphere in order to avoid the exposure of future generations to ionising radiation from the waste. The Dutch research programme focussing on the geological disposal of radioactive waste is called OPERA (OnderzoeksProgramme Eindberging Radioactief Afval). In the framework of OPERA, researchers of different institutions and scientific areas cooperate on the initial, conditional Safety Cases for the host rock formations Boom Clay and Zechstein rock salt. OPERA is a preliminary or initial safety case and will be developed to set up the research necessary for the eventual development of a repository in the Netherlands. OPERA is financed by the Dutch Ministry of Economic Affairs and the public limited liability company Electriciteits-Produktiemaatschappij Zuid-Nederland (EPZ) and coordinated by COVRA. Further details on OPERA and its outcomes can be accessed at www.covra.nl. This report concerns a study conducted in the framework of OPERA. The conclusions and viewpoints presented in the report are those of the author(s). COVRA may draw modified conclusions, based on additional literature sources and expert opinions. A .pdf version of this document can be downloaded from www.covra.nl OPERA-PU-IBR512 Title LILW degradation processes and products Authors: A. Filby, G. Deissmann, R. Wiegers Date of publication 26 October 2016 Keywords: LILW, degradation, Cellulose, Plastics, Metals, Source-Term COVRA N.V. Summary ................................................................................................1 Samenvatting.............................................................................................1 1. Introduction.................................................................................2 1.1. Background ....................................................................................2 1.2. Objectives......................................................................................2 1.3. Realization .....................................................................................2 1.4. Explanation contents .........................................................................2 2. OPERA waste disposal concept in Boom Clay...........................................3 3. LILW in OPERA ..............................................................................5 3.1. LILW inventory and matrix composition ...................................................5 3.1.1. Compacted waste........................................................................6 3.1.2. Processed liquid Molybdenum waste and spent ion exchangers ..................8 3.1.2.1. Processed liquid molybdenum waste ....................................................9 3.1.2.2. Processed liquid waste with spent ion exchangers .................................. 11 3.1.3. Depleted Uranium ..................................................................... 12 3.2. Radionuclide inventory..................................................................... 13 4. Evolution of the Repository Near-Field ............................................... 13 4.1. Evolution of pH and pore water composition ........................................... 13 4.2. Evolution of redox conditions ............................................................. 15 4.2.1. Aerobic phase .......................................................................... 15 4.2.2. Anaerobic phase ....................................................................... 16 5. LILW degradation processes and products............................................ 16 5.1. Introduction to cellulose chemistry ...................................................... 16 5.2. Cellulose degradation processes.......................................................... 18 5.2.1. Chemical degradation of cellulose.................................................. 18 5.2.1.1. Cellulose degradation products ........................................................ 21 5.3. Cellulose degradation kinetics ............................................................ 25 5.3.1. Microbial degradation of cellulose .................................................. 28 5.3.2. Radiolytic degradation of cellulose ................................................. 30 5.3.3. Cellulose degradation kinetics: determining factors ............................. 31 5.4. Degradation processes of ISA.............................................................. 32 5.4.1. Chemical Degradation ................................................................ 32 5.4.2. Microbial degradation................................................................. 33 5.4.3. Radiolytic degradation................................................................ 34 5.5. Plastics ....................................................................................... 35 5.5.1. Non-aqueous phase liquids ........................................................... 35 5.5.2. Non-halogenated plastics............................................................. 36 5.5.2.1. Chemical degradation of polyethylene................................................ 37 5.5.2.2. Radiolytic degradation of polyethylene............................................... 37 5.5.2.3. Microbial degradation of polyethylene................................................ 43 5.5.3. Halogenated plastics .................................................................. 44 5.5.3.1. General information on PVC ............................................................ 44 5.5.3.2. Specific additives: Plasticisers ......................................................... 46 5.5.3.3. Specific additives: Stabilisers .......................................................... 47 5.5.3.4. Chemical Degradation of PVC .......................................................... 48 5.5.3.5. Microbial Degradation of PVC........................................................... 51 5.5.3.6. Radiolytic degradation of PVC.......................................................... 52 5.5.4. Degradation processes of PVC plasticisers ......................................... 57 5.5.4.1. Chemical and radiolytic degradation.................................................. 58 5.5.4.2. Microbial degradation ................................................................... 62 5.6. Rubbers....................................................................................... 63 5.6.1. General information................................................................... 63 5.6.2. Chemical degradation................................................................. 65 5.6.3. Radiolytic degradation................................................................ 65 5.6.4. Microbial degradation................................................................. 68 5.7. Ion exchangers .............................................................................. 69 5.7.1. General information................................................................... 69 5.7.2. Chemical degradation of ion exchangers........................................... 70 5.7.3. Radiolytic degradation of ion exchangers.......................................... 70 5.7.4. Microbial degradation of polystyrene............................................... 76 5.8. Varnish........................................................................................ 77 5.9. Cement admixtures......................................................................... 77 5.9.1. Chemical degradation................................................................. 80 5.9.2. Microbial degradation................................................................. 81 5.9.3. Radiolytic degradation................................................................ 81 5.10. Metal corrosion processes and products .............................................. 82 5.10.1. Carbon Steel......................................................................... 82 5.10.2. Zinc ................................................................................... 87 5.10.3. Aluminium ........................................................................... 88 5.11. Behaviour of U3O8 ........................................................................ 90 5.12. Degradation of processed liquid molybdenum waste ............................... 92 5.13. Gas generation............................................................................ 93 5.13.1. Gas generation processes.......................................................... 93 5.13.1.1. Gas generation due to metal corrosion ............................................... 93 5.13.1.2. Gas generation due to microbial activity ............................................. 95 5.13.1.1. Volatile radioisotopes ..................................................................