On Alteration Rate Renewal Stage of Nuclear Waste Glass Corrosion
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MRS Advances © 2020 Materials Research Society DOI: 10.1557/adv.2020.36
On Alteration Rate Renewal Stage of Nuclear Waste Glass Corrosion Michael I. Ojovan1 1
Department of Materials Science and Engineering, The University of Sheffield, UK; [email protected]
Abstract:
The three generically accepted stages of glass corrosion are reviewed with
focus on final stage termed alteration rate renewal (or resumption) stage when the glass may re-start corroding with the rate similar to that at the initial stage. It is emphasized that physical state and physical changes that occur in the near-surface layers can readily lead to an effective increase of leaching rate which is similar to alteration rate renewals. Experimental data on long-term (during few decades) corrosion of radioactive borosilicate glass K26 designed to immobilize high-sodium operational NPP radioactive waste evidence on resumption-like effects of radionuclides (137,134Cs) leaching. The cause of that was however related not to chemical changes in the leaching environment but rather to physical state of glass surface due to formation of small cracks and new pristine glass areas in contact with water.
INTRODUCTION: Vitrification is one of the best solutions in providing safety of nuclear waste storage, transportation and final disposal [1-3]. France, India, Japan, Russia, Slovakia, South Korea, the UK and USA have currently vitrification facilities in operation for the immobilisation of high level nuclear waste (HLW) and low and intermediate level nuclear waste (LILW), with Germany having recently completed their HLW vitrification program [2-6]. Table 1 gives data on HLW vitrification programs (see [2] for details). Except for alkali-aluminophosphate glass used in Russia, borosilicate glass has been universally selected as the vitreous wasteform to immobilize HLW [5, 6] whereas some LILW waste streams such as legacy waste accumulated from various nuclear development programs are preferable immobilized using bespoke selected silicate or phosphate systems better suited for particular waste compositions.
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Table 1 Operational data of HLW vitrification programmes Country (Facilities)
Performance
France (R7/T7, AVM)
8252, 291106 TBq to 2019
USA (DWPF, WVDP, WTP)
7870 tonnes, 2.7106 TBq to 2012
Russia (EP-500)
6200 tonnes, 23.8106 TBq to 2010
UK (WVP)
2200 tonnes, 33106 TBq to 2012
Belgium (Pamela)
500 tonnes, 0.5106 TBq. Completed.
Japan, Tokai
70 tonnes, 0.4106 Ci* to 2007
Germany (Karlsruhe)
55 tonnes, 0.8106 TBq. Completed.
India (WIP, AVS, WIP)
28 tonnes, 0.26106 Ci to 2012
Slovakia (Bohunice)
1.53 m3 to 2012
*1 Ci = 0.037 TBq
The long-term behaviour of nuclear waste glass in disposal environment is an important input feature in safety assessment programs and models used to assess the u
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