Intermediate Heat Transport Loop

The AHTR will use an intermediate heat transport loop containing molten salt to transfer heat generated in the reactor system to the hydrogen production plant. The salt composition has not been selected yet and may be different from the salt used as the primary coolant. A comparison was performed of the performance of low-pressure molten salt vs high-pressure helium for the intermediate loop. 

If the AHTR is used to produce hydrogen, a key issue is the coupling of the two plants via the intermediate heat transport loop. The intermediate heat transfer system has two sets of safety-related functional requirements (1) protect the reactor and chemical plant from transients and accidents in either facility and (2) protect the reactor and chemical plant from transients and accidents within the intermediate heat transfer system. Molten salts may offer major safety advantages compared to helium for this application. 

Loss of primary pump power and loss of all cooling by the intermediate heat transport loop without scram (improtected loss of flow/loss of cooling)... 

First off, the balance of plant (BOP) would have no nuclear safety function. Moreover, the STAR-H2 heat source reactor is being designed not only for passive safety response to Anticipated transients without scram (ATWS) initiators but also for passive load follow. The only information flow path from the BOP to the reactor would be the fused salt intermediate heat transport loop, which will convey the BOP heat request to the reactor by means of its flow rate and return temperature (see Fig. XXIV-3). In this way, the reactor could passively adjust its power to match heat demand while remaining in a safe operating regime. The safety implication of passive load follow is that the reactor would safety respond to all possible combinations and timing of ATWS initiators taken more than one at a time it would also safety respond to all conceivable human errors of the maintenance crew and the operator. In summary, all faults exterior to the reactor vessel might be safely accommodated on the basis of passive thermo-structural feedbacks. 

A forced circulation, ambient pressure fused salt (flibe) intermediate heat transport loop carries the heat from the in-vessel intermediate heat exchanger (IHX) to the balance of plant (BOP). Figure XXIV-4 shows the overall heat flow for the reactor and BOP at full power of 400 MW(th). 

The STAR-H2 reactor heat source drives a balance of plant through an ambient pressure, forced circulation, fused salt (flibe) intermediate heat transport loop. 

For hydrogen production, an intermediate heat transport loop will be used to isolate the reactor from the hydrogen production facility. As shown earlier, molten salts (liquids) have superior heat transfer characteristics compared with those for helium (gases). As a consequence, the temperature drops across intermediate heat exchangers will be less and thus the peak reactor temperature will be lower for heat delivered at any given temperature to a thermochemical hydrogen production plant or power cycle. 

The intermediate heat transport system (IHTS) is located within the reactor vessel. The IHTS consists of piping and components required to transport the reactor heat from the primary system, through the IHX, to the SG system (SGS). The IHTS is shown schematically in Figure 6.10. The IHTS is a closed loop system with an expansion plenum in the SG top head and an argon cover gas space to accommodate thermally induced system volume changes. 

The secondary sodium loop acts as an intermediate heat transport system and consists of the MX, piping, dump tank, EM pump, and SG. Secondary sodium coolant heated in the MX flows inside the piping to the SG where heat is transferred to water/steam of the power circuit to be supplied to the steam turbine generator. 

The rated thermal output of MONJU [5.63, 5.64] is transported through the primary heat transport system (PHTS) and intermediate heat transport system (IHTS) loops to the steam generators. Shutdown heat removal is normally by forced circulation (FC) provided by pony motors associated with each of the loop pumps. Heat is rejected to air at the air blast heat exchanger of the intermediate reactor auxiliary cooling system (ACS) which branches off from each IHTS loop. Thus the auxiliary cooling system (ACS) of the Monju reactor is coupled with the secondary system which also has the role as decay heat removal system. 

Roy, P., and Licina, G.J., Carbon Activity Determinations in a Bimetallic Sodium Loop Mock-up of the Intermediate Heat Transport System of a Liquid Metal Fast Breeder Reactor. Proceedings of the Third International Conference on Liquid Metal Engineering and Technology in Energy Production, Oxford, USA, April 1984,3,207. 

Reactor style Loop type no intermediate heat transport system Tank-type, modular, no intermediate heat transport system... 

Korea has been actively engaged in international collaborative research activities. As part of this effort, Korea has been actively participating in collaborative research and development (R D) activities of the Gen-IV International Forum (GIF). Large experimental facihties have been constmcted to conduct various experiments to validate thermal—hydrauhc phenomena and a large sodium loop, called Sodium Test Loop for Safety Simulation and Assessment (STELLA)-1, for the test of key decay heat removal system (DHRS) components, started its operation in 2014. Design work started in early 2015 for STELLA-2, which is an integral test loop for a simulation of the thermal—hydraulic characteristics of the PGSFR primary and intermediate heat transport systems. 

Secondary cooling system One sodium loop heat transport from intermediate heat exchanger (IHX) to steam generator (SG) ... 

Figure XXI-6 shows the heat transport path from the core to the ultimate sink during normal operation and under emergency conditions. The normal heat removal system is based on a three-circuit design and includes a loopless (pool type) primary circuit in the reactor module, two equivalent loops of the intermediate sodium circuit, two loops of the steam-water circuit and a turbogenerator facility. During normal operation, heat released in the core, including residual heat release of the shutdown reactor is transferred to the steam-water circuit. Steam can be taken off from the third (steam-water) circuit for industrial applications and district heating. The steam-water circuit is designed to supply steam to the turbine generators of 500 or 800 MW power, taking the heat from three or five BMN-170 reactors.

The heat can he removed from the main transport system and the special air cooling system connected with three loops of the intermediate circuit. The air cooling system can ensure that the residual heat is removed by natural circulation under station blackout accident. 

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