[en] In the introduction the general design features of a high temperature gas cooled nuclear power reactor are given. Some of the main chemical problems connected with a high temperature gas cooled graphite moderated reactor are mentioned. In particular, attention i s given to the corrosion of graphite by the oxidizing impurities of the coolant and to fission product control, The introduction is closed by mentioning briefly those design details of the Dragon reactor and the General Atomic reactor which are connected with these chemical problems. In Section 2 the removal on a technical scale of the impurities introduced in the coolant during reactor operation and of the fission products by delay and trapping i s discussed. In particular, attention is given to the use of low temperature adsorption techniques. In Section 3 the main chemical problems are again considered, but now, from a point of view of further reactor development. The use of BeO as a substitute for graphite in certain vital parts of the reactor is discussed. It is concluded that even when further reactor development is taken into account additional chemical engineering effort is still needed for the economical optimisation of a fission product removal plant. (author)