Nuclear Techniques ›› 2018, Vol. 41 ›› Issue (2): 20603-020603.

• NUCLEAR ENERGY SCIENCE AND ENGINEERING •

### Thermal stability of geological cement waste forms containing Cs, Sr and U simulated nuclide

SANG Peilun1, XIE Hua2, SU Wei1, WANG Lielin2, WANG Wenwen2, FENG Zhiqiang2

1. 1. Institute of Materials Science, China Academy of Engineering Physics, Mianyang 621907, China;
2. Key Laboratory of Defensive Discipline on Nuclear Wastes and Environmental Safety, Mianyang 621900, China
• Received:2017-10-24 Revised:2017-12-03 Online:2018-02-10 Published:2018-02-06
• Supported by:
Supported by State Administration of Science Technology and Industry for National Defence Research Project (No.FKY201402), China Academy of Engineering Physics Horizontal Project (No.16zx7127)

Abstract: [Background] The thermal stability of geological cement waste forms containing high pyrolysis products such as Sr and Cs, is an important index for performance evaluation of the nuclear waste solidified body. [Purpose] This paper aims to evaluate the thermal stability of geological cement waste forms. [Methods] Cement waste forms containing Sr, Cs and U were prepared. The changes of mass, volume, compressive strength and other parameters for cement waste forms were observed after heat treatment at different temperatures, and the phase and structure of the samples were analyzed by means of X-ray diffraction (XRD) and scanning electron microscope (SEM). [Results] The experimental results showed that when T ≤ 300 degree Celsius, the appearance of the three kinds of cement waste forms had no obvious change; volume shrinkage and the compressive strength loss rate were less than 3% and 25%, respectively. Only part of the hydration product dehydration caused a greater weight loss, corresponding to the decrease of the needle, reticular characteristic organization and the increase of porosity in microstructure. When T > 700 degree Celsius, the cement surfaces had many significant cracks and hydration products had complete phase change, but the structure had not yet collapsed; the microstructure became more dense and had ceramic structural features, which resulted in a compressive strength increasing inversely with temperature, exhibiting good thermal stability at high temperature. The formation of the newly wollastonite phase Ca3Si3O9 was the main reason for the surface cracking of the geological cement waste forms. [Conclusion] Compared with ordinary Portland cement (OPC) and alkali activated cement (AAC) cement waste forms, the geological cement waste forms have better thermal stability.

CLC Number:

• TL941+.111