RFNC-VNIIEF pulse reactors design and operation experience

Abstract only, full text of publication follows: Since the early 60's VNIIEF had started works on creation of powerful lab pulse neutron sources capable to simulate the penetrating radiation of nuclear explosion, which resulted in development of a unique fleet of nuclear pulse reactors (NPR). Operation of pulse reactors was started in 1964 since start-up of the VIR-1 reactor that used a solution of high enriched uranium salt in water as a fuel. Nearly at the same time, the BIR-1 pulse reactor with metal core was put into operation. Both these reactors were being improved constantly. Besides the above reactors, VNIIEF created reactors BIGR, TIBR, RIR, BR-1, BR-K1, GIR [1,2]. Pulse reactors are rather specific facilities. They are a variation of research reactors, which provide controllable and repeatable nuclear fission bursts. The common feature of all pulse reactors is creation within a short period of conditions for prompt-power excursion. The pulse reactors developed at VNIIEF have some peculiar features. They are as follows: - 'Zero' energy release (fuel burn-out during operation doesn't exceed several grams); - Absence of a coolant (the core cooling is effected, as a rule, via natural convection); - Core small sizes; - Small amount of control units, which perform simultaneously the functions of emergency protection units; - High enrichment of the fuel (as a rule, ∼90% of ²³⁵U); - Precise prediction of pulse parameters (the error makes up ±10%); - Each pulse is a specially arranged experiment, and intervals between the pulses are determined by the period of experiment arrangement. The pulse reactor core design, a special calibration procedure before each burst, a remote control system and a powerful biological shielding, as well as highly qualified personnel, constant actions on improvement and control of the reactor state provide the operation safety. During over 40 years of pulse reactor operation, no nuclear accident has been happened while generating over 11000 pulses. Nuclear pulse reactors are unique facilities for conducting a great variety of experiments of high interest. During NPR lots and lots of different researches have been carried out including radiation hardness testing of different devices, specimens and materials, nuclear pumping lasers investigation, testing of NPP fuel during RIA accident, ultra-cold neutrons production etc. [1,2]. (author)