Abstract
A fundamental consideration of a closed-thermosiphon type cold neutron source (CNS) has been presented on the basis of the non-equilibrium thermodynamics. In order to simplify the treatment, a discontinuous thermodynamic model consisting of two large sub-systems connected by a small transport sub-system is employed. The analyses are especially concentrated in the self-regulation property, that is, the amount of liquid hydrogen in the moderator cell can be kept almost constant against thermal disturbances from reactor output fluctuations. It is shown that this property results from a thermodynamic process producing an entropy of a total system by a temperature increment in which an evaporation in one sub-system is compensated by a liquefaction in the other sub-system linked together by a common quantity of latent heat.
