Experience in the operation and maintenance of the FiR 1 reactor

The Finnish TRIGA Mkll reactor FiR1 has been in operation from the year 1962 and its maximum steady-state power level was raised from 100 kW to 250 kW in the summer of 1967. The effect of electrical defects such as instrument failures and instrument shut-downs on the use of the reactor has been usually negligible. The reliability of the electrical and mechanical systems from this point of view can be examined generally with the aid of shut-down statistics. The rotary specimen rack has until now been the most important reliability problem of the FiR1 reactor. The neutron flux values and distribution in the reactor core and its vicinity has been determined by activation and absolute (4πβ-γ) counting of gold foils and with copper foils and wires which have been compared with the gold foil measurements. The reactivity values of core elements, specimens, research devices, etc. and the influence of a black absorber in the specimen ring on the reactor power have been measured. (author)