[en] One of the most important safety design issues for a High Temperature Gas-cooled Reactor (HTGR) hydrogen production system is to ensure reactor safety against fire and explosion at the hydrogen production plant. One of the authors has already proposed safety evaluation methods, safety criteria, and countermeasures against fire and explosion. While the proposed safety evaluation method is based on the most conservative assumptions, it is necessary to make its quantitative degree of conservativeness clear and to re-construct a safety evaluation method with moderately reasonable safety margins, from the view point of rationalization of safety design. In this report, we considered and mapped out our concrete course to develop a new code system which can analyze event sequences and consequences in detail, on assumed fire and explosion accidents in the HTGR hydrogen production system. As a result of consideration on analytical functions required for the code system and of review on commercial analysis codes, it is concluded that it can be easily achieved to couple and cooperate three existing codes (one wide-use thermo-hydrodynamic analysis code, one gas explosion/blast simulation code and one high explosive/blast simulation code), with the help of newly developing interfaces between each code. Although as one of choices we considered to develop a new code corresponding to the three codes, on the basis of a wide-use thermo-hydrodynamic analysis code of which we can obtain the source code, it is difficult to develop such a short time period of three years. We selected Phoenics code as a wide-use thermo-hydrodynamic analysis code, AutoReaGas code as a gas explosion/blast simulation code and AUTODYN code as a high explosive/blast simulation code, as a result of the consideration and the review. (author)