A computer code, CONTAIN-LMR, has been developed in Japan Atomic Energy Agency (JAEA) for application to a probabilistic risk assessment (PRA) of liquid metal fast reactors (LMFRs) since the original CONTAIN code had been introduced from Sandia National Laboratories (SNL) of U.S. in 1982. The CONTAIN-LMR code is a best-estimate, integrated analysis tool for predicting the physical, chemical and radiological conditions inside a containment building of LMFRs following a severe accident with reactor vessel melt-through. The code is also able to predict the source term to the environment in the accident. This code can treat many important phenomena consistently such as sodium fire, radioactive aerosol behavior, a water release from heated concrete, hydrogen burn, sodium-concrete reaction and core debris-concrete interaction occurred in the accident with inter-cell heat and mass flow under the multiple cell geometry. This paper describes the chronology of the code development in JAEA briefly as an introduction, and after that, the outline of computational models in the code, the examples of the code validation, and the future plan of the code application are described.