Thermal mode of ultracold neutron source at WWR-M reactor

• Published in: Nauchno-tekhnicheskiĭ vestnik informat͡s︡ionnykh tekhnologiĭ, mekhaniki i optiki mekhaniki i optiki, 2019-06, Vol.19 (3), p.538-545
• Main Authors: Serebrov, A.P., Lyamkin, V.A., Koptyukhov, A.O., Onegin, M.S.
• Format: Article
• Language: English
• Subjects: BWR-M reactor; Comsol Multiphysics; natural convection; reactor radiation; ultracold neutron source
• ISSN: 2226-1494; 2500-0373
• DOI: 10.17586/2226-1494-2019-19-3-538-545

The paper presents the results on creation of a source of ultracold neutrons in the National Research Center “Kurchatov Institute” — PNPI. The source has three temperature zones: a helium chamber with superfluid helium at the temperature of 1.3 K, a deuterium chamber with liquid deuterium at the temperature of 20 K, a vacuum case with a lead screen and graphite blocks at room temperature. All these parts are exposed to cooling under the conditions of the reactor heat load. Calculations associated with the design of cooling circuits are presented. Analytically, a mass flow rate of 0.56 kg/s was obtained for cooling of the lead screen with a volumetric heat flow of 27 kW. A pump and a heat exchanger were selected for an autonomous cooling circuit on the basis of this flow. At this thermal mode, the radiant heat gain from the nose part of the vacuum module to the deuterium capsule was 24 watts. The total heat flux to the deuterium capsule and liquid deuterium, taking into account the reactor radiation, was 0.3 kW. To maintain the phase state of deuterium, temperature control is required in the temperature range 18.73–24.122. The finite-square method proved the possibility of safely maintaining the phase state of liquid deuterium in a 60-liter capsule with a flow of helium gas of 50 g/s.