Operating experience with the Agesta Nuclear Power Plant

Agesta is a pressure vessel PHWR used for production of electricity (12 MW) and district heat (68 MW). The reactor achieved criticality in July 1963. Power operation began in March 1964. The reactor has been in operation for 32 880 hours up to and including December 1970. The availability figures (not accounting for the routine summer outage) have been very high for four of the seven years (average 94%). A low value in the 1964 - 65 season was due to repair of a heavy water leak through inspection pipes in the reactor vessel lid, and in 1968 due to extensive damage of the first fuel charge as a result of fretting corrosion. This was probably initiated by unscheduled power cycling during a lengthy shut off period of the cooling tower. An extensive clean up operation was necessary before the reactor was recommissioned. An interesting fault in 1969 was failure of a non-return valve causing a flood so that cooling tower water reaching a relay curbicle triggered some undesirable pump and motor valve operations. Heavy water losses have been extremely low - 1100 kg total noncollectable in seven years, averaging about 0.25% of he inventory per year. The total recollected amount was 2040 kg. Acceptance of the reactor by the public has been good, resulting indeed in complaints about smoke during reactor shut down periods when the load is taken over by the standby oil fired boiler. The paper gives a detailed account of the operating history with particular accent on the analysis of the causes of the various forced outages and the reason for and methods of dealing with the above mentioned fuel damage. (author)