Reactor cooling system

Reactor Cooling System - The coolant and fission products are confined within the piping and vessels of the reactor cooling system. This boundary may fail by high pressure relief,... 

The methanation reaction is a highly exothermic process (AH = —49.2 kcal/ mol). The high reaction heat does not cause problems in the purification of hydrogen for ammonia synthesis since only low amounts of residual CO is involved. In methanation of synthesis gas, however, specially designed reactors, cooling systems and highly diluted reactants must be applied. In adiabatic operation less than 3% of CO is allowed in the feed.214 Temperature control is also important to prevent carbon deposition and catalyst sintering. The mechanism of methanation is believed to follow the same pathway as that of Fischer-Tropsch synthesis. 

Such a weak adiabatic temperature rise cannot lead to a thermal explosion. The severity is low. In case of malfunction of the reactor cooling system, the reaction, providing it is not stopped, will lead to an immediate temperature rise by 6 K reaching the MTSR of 36 °C. The thermal risk linked to this hydrogenation reaction is low. 

Figure 2. Schematic diagram of the reactor cooling systems consisting the main cooling system, auxiliary cooling system and vessel cooling system of the HTTR...

Figure 12.11 Magnitude of transfer functions for reactor cooling system, and disturbances (1- reactor inlet temperature, 2- reactor inlet concentration) vs. frequency...

In the nuclear field, an additional reason for recleaning results from the possibility of radioactive contamination of that part of the system external to the nuclear reactor. Such contamination can occur either by fission-product release or by corrosion of the reactor and subsequent redeposition of the corrosion products in the pumps, heat exchangers, or other parts of the reactor-cooling system. 

Hydrogen Transport Membranes in Nuclear Reactor Cooling Systems... 

In case off-site power is available, the decay heat is removed through normal heat transport path of secondary sodium and water/steam circuits. Additionally, an independent safety grade passive direct reactor cooling system consisting of 4 independent circuits of 6 MWt nominal capacity each has been provided. Each of these circuits comprises of one sodium to sodium heat exchanger dipped in reactor hot pool, one sodium to air heat... 

Fig. 5 Reactor cooling system with decay heat removal system...

COSTES, J.R., ANTOINE, P., GAUCHON, J.P., Decontamination before dismantling a fast breeder reactor cooling system, paper presented in the IAEA Specialists Meeting on Sodium Removal and Disposal from LMFRs in Normal Operations and in the Framework of Decommissioning, Aix-en-Provence, France, 1997. 

The reactor cooling system is composed of the MCS, ACS and VCS as schematically shown in Fig. 1. The MCS is operated in normal operation condition to remove heat from the core and send it into the environment. The ACS and VCS have incorporated safety features. The ACS is initiated to operate in case of a reactor scram. Besides one out of two components of VCS has sufficient capacity to remove residual heat, the ACS is provided to cool down the core and core support structure. A helically coiled intermediate heat exchanger (IHX) whose heat-resistant material is Hastelloy-XR developed by the JAERI has been installed in S tember 1994. Nuclear heat application tests using the HTTR, are planned to be carried out, and accordingly a heat utilizaticxi system will be connected to the IHX. The fuel fabricaticm started in June 1995 and will complete in 1997. 

A functional test operation of the reactor cooling system will be performed from May 1996 to September 1997. Fuel will be loaded into the core around in September 1997 and the first criticality is expected in December 1997. 

The maximum rate of addition that the reactor cooling system can handle should be identified, and precautions taken to ensure that this limit cannot be exceeded. One way of doing this is to install a restricting orifice in the feed line. (See also case histories Al 39-49. pages 179-182.)... 

It is not considered economically convenient to place the turbine with the reactor in a containment building (although in the past, small reactors with this characteristic have been buUt). Isolation of the reactor cooling system from the outside is by means of quick isolation valves. Inherent in this feature are the problems of their rehabdity in closure and their leakproof characteristics (to the point that some experts say, but without sufficient reason, that BWRs have to be considered substantially open towards the outside environment). On the other hand, no problems have been attributed to the steam generators. 

In the ideal IPWR system, all the primary reactor cooling system components including the pumps (if required) and pressurizer are incorporated within the single primary reactor pressure vessel. A simplified drawing of a generic low-power IPWR concept that uses natural circulation without any primary pumps is shown in Figure 2. 

Chapter 22 "Heat Transfer, Thermal Hydraulic, and Safety Analysis" and Chapter 23 "Thermodynamics and Power Cycles" are analytical tools used by engineers to evaluate reactor and power-producing systems. Heat transfer and thermal hydraulics are not only important in the operation of nuclear reactors, they are also critical in the evaluation of how the systems will respond under upset conditions. The chapter on thermodynamics is included to show how the energy generated by the reactor is transferred by the reactor cooling system to the turbine power generating system used to produce electricity. 

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