Concept and salient design features of a high-temperature nuclear reactor with solid coolant

Abstract

The salient features of using a solid substance to cool the core of a nuclear reactor and the associated advantages and limitations are examined. Conceptual proposals concerning the core design and the arrangement of the in-reactor space of a high-temperature nuclear reactor with a solid coolant are presented. Evaluated data and some results for a model reactor are presented.The development of nuclear power requires an examination and development of innovative reactor designs which have enhanced safety due to the inherent properties of a reactor and are highly cost-effective. One interesting and promising proposal is to use a solid substance as the coolant [1].There are substantial advantages to using a solid coolant to cool the core of a nuclear reactor. These include the possibility of the coolant moving in the core under gravity and the absence of any need for excess pressure in the vessel. In turn, this means that the metal content of the system is low, the risk of accidents is lower, and the scale of the consequences of accidents is smaller. The core of a reactor can be cooled with a solid substance when certain conditions associated with the characteristic features of the solid coolant are satisfied. The most important requirements are uniform continuous motion of the coolant with minimum density fluctuations in all sections of the core, high mechanical strength and durability of the particles, and good heat-transfer indicators, i.e., the coolant material must have a high thermal conductivity and heat capacity under the working conditions characteristic for the core of a nuclear reactor.Studies of the possibility of using a solid coolant based on finely dispersed particles of graphite for cooling the core of a thermal reactor have revealed concrete conditions which are necessary in order to satisfy the main requirements for a solid coolant. A brief report on the results of such investigations is given in [2]. To prove that the proposed coolant can move under gravity as a dense layer with a high velocity and to study the durability of the particles, a complex of experimental works was conducted at the Research Institute and Scientific-Industrial Association Luch. The results of these investigations confirmed that a solid coolant consisting of spherical graphite particles with average diameter 1 mm coated with a pyrolytic carbon coating can move uniformly under gravity. When such a coolant is used, coolant velocities and heat-transfer coefficients which make it possible to obtain energy release density characteristic for high-temperature gas-cooled reactors can be

Investigation of the thermal inertia and thermal stresses of heat-transferring elements in a solid-coolant nuclear reactor

“…The basic ideas of the reactor design and assessment of the actually attainable technological parameters are presented in [2][3][4], and the experimental results of a study of the thermophysical characteristics of the flow of heat-carrying particles are presented in [5]. The particulars of the proposed nuclear reactor are as follows:…”

Evaluation of the technological parameters of a high-temperature reactor with solid coolant in the electricity generating regime

“…Microfuel and fuel compacts based on microfuel and graphite with dimensions adopted in the GT-MGR design (12.5 mm diameter, 50 mm height) were chosen as fuel at the first stage of the investigations. The conceptual questions concerning the engineering arrangement of the reactor setup, which make it possible to implement the advantages of solid coolant in the form of small heat-carrying particles moving through the core without special orientation, including passive cooldown, are presented in [2,3].It should be noted that using a solid coolant in reactors with coarse-elemental graphite coolant was studied in 1974-1988. The conceptual ideas presented in [4][5][6][7] proposed reactors constructed with massive elements which move along a circle in a horizontal plane on special rollers and cyclically heated in the core followed by heat transferred to a secondary coolant by means of radiation.…”

“…Microfuel and fuel compacts based on microfuel and graphite with dimensions adopted in the GT-MGR design (12.5 mm diameter, 50 mm height) were chosen as fuel at the first stage of the investigations. The conceptual questions concerning the engineering arrangement of the reactor setup, which make it possible to implement the advantages of solid coolant in the form of small heat-carrying particles moving through the core without special orientation, including passive cooldown, are presented in [2,3].…”

“…In the conceptual scheme proposed for HRSC [3], the first-loop coolant with the gas pressure below the atmospheric level, moves on the outside of the heat-exchanging tubes of the heat exchanger and the second-loop coolant moves inside tubes. This scheme makes it possible to have a large heat-exchange surface area with moderate metal content and high pressure in the second loop.…”

“…The fact that in accordance with the conceptual solutions [3] the heat exchangers are located beneath the core and the coolant moves through them under gravity and is collected in the bottom hoppers, from which lifts raise the cooled coolant in to the top feeding copper, was taken into account when the computational model was developed. The bottom hoppers in the normal operating regime contained only a small quantity of coolant, which is necessary for interruption-free operation of the lifts.…”