Solidification treatment is planned for filter sludge and spent resin waste generated from nuclear power plants. Ordinary cement is used to solidify waste. However, when cement is used for solidification, it has been confirmed that radioactive substances are easily eluted due to the influence of cellulose and resin contained in filter sludge and the like.
If the solidification treatment is performed using chemical treatment or heat treatment, secondary waste is generated or a dedicated treatment facility is required, which complicates the solidification treatment.
We conducted a test using a geopolymer (SIAL®) that has been used to treat radioactive waste from nuclear power plants in other countries.
From 2018 to 2019, We have conducted laboratory-scale experiments using SIAL® to solidify filter sludge and spent resin. The unconfined compressive strength was 6.4 MPa or more, satisfying the unconfined compressive strength of 1.47 MPa, which is the burial standard. In addition, most of the distribution coefficients of major nuclides satisfied the set values for burial. Based on the above, we have confirmed that there is no problem with the solidification and the ability to contain radioactive materials. we are planning to consider the formulation adjustment of the solidification material and the addition of additives.
In 2020, we conducted a cold test simulating filter sludge and used resin in order to investigate whether even drum-sized waste can be solidified. The unconfined compressive strength is 4.2 MPa or more, and we have confirmed that there is no problem in solidifying even drum-sized waste.
Based on the results of solidification of filter sludge and spent resin, we thought that it could be applied to other wastes, and in 2021, we conducted a solidification test on incinerated ash. As a result of conducting a full-scale test using general incineration ash, it was confirmed that drum-sized waste could be solidified. However, when the incineration ash contains a large amount of amphoteric metals such as aluminum, the reaction between the amphoteric metals and alkalis generates air bubbles, which lowers the strength of the waste. We are planning to consider pretreatment before incineration.
In the future, we plan to investigate the applicability of SIAL® technology to hot tests of incineration ash and sulfate (concentrated waste liquid). We will continue to collect data to confirm that the solidification method is suitable for burial.
