Coolant system

Fig. 1. Pressurized water reactor (PWR) coolant system having U-tube steam generators typical of the 3—4 loops in nuclear power plants. PWR plants having once-through steam generators contain two reactor coolant pump-steam generator loops. CVCS = chemical and volume-control system.

Fig. 21. Schematic of a pressurized-water-loop reactor coolant system.

In some BWR transient scenarios, the high pressure injection systems are postulated to fail. To make use of the low pressure injection system, it is necessary to depressurize the reactor coolant system, a function performed by the automatic depressurization system (ADS). In the scenario considered, ADS actuation is manual because the signals for automatic initiation of the system are not present. 

A first attempt to estimate the potential consequences from severe LWRs accidents was the BNL report WASH-740 (1957). The authors of WASH-740, to overcome the lack of information and methods, estimated "Hazard States based on the core state, radioactive inventory, fuel cladding, reactor coolant system, and containment conditions. 

The assumed form of iodine is not substantially retained in early containment failure, but may be retained in the reactor coolant system, where cesium iodide is more strongly retained than the elemental iodine assumed by the RSS. 

An accident sequence source term requires calculating temperatures, pressures, and fluid flow rates in the reactor coolant system and the containment to determine the chemical environment to which fission products are exposed to determine the rates of fission product release and deposition and to assess the performance of the containment. All of these features are addressed in the... 

Overall behav<4 of reactor coolant system, mrilten core, and containmerf... 

Initial blowdown of the coolant from the reactor coolant system. 

Many manufacturers, users, and compressor applications still require that compressor cylinders be supplied with liquid-cooled cylinders. Figure 11-21 includes schematics of several types of liquid coolant systems. 

Forced coolant systems using a mixture of glycol and water are the most common for natural gas compressors. Normally, the compressor cylinder cooling system and compressor frame lube oil cooling system is combined. A single pump is used to circulate the coolant through the cylinders and the lube oil heat exchanger and then to an aerial cooler where the heat is dissipated. 

When forced coolant systems are used, care must be taken to provide the coolant at the proper temperature. If the cylinder is too cool, liquids could condense from the suction gas stream. Thus, it is desirable to keep the coolant temperature 10°F higher than that of the suction gas. If the cylinder is too hot, gas throughput capacity is lost due to the gas heating and expanding. Therefore, it is desirable to limit the coolant temperature to less than 30°F above that of the suction gas. 

Premature disk failure Operator error Pump motor failure Reaction inliibitor system failure Coolant system failure Outlet piping obstruction Motor alann failure Pressure sensor failure... 

Pressurizer The pressurizer maintains and controls both the temperature and the pressure in the primary coolant system. It contains a cold water spray and electric heater bank as a means of providing the necessary control. 

Boric acid [B(OH)3] is employed in primary coolant systems as a soluble, core reactivity controlling agent (moderator). It has a high capture cross-section for neutrons and is typically present to the extent of perhaps 300 to 1,000 ppm (down from perhaps 500 to 2,500 ppm 25 years ago), depending on nuclear reactor plant design and the equilibrium concentration reached with lithium hydroxide. However, boric acid may be present to a maximum extent of 1,200 ppm product in hot power nuclear operations. 

Nuclear power plants in the United States are supposed to be designed well enough to prevent accidents as serious as the one at Chernobyl. Nevertheless, the Three Mile Island plant in Pennsylvania, an aerial view of which is shown in Figure 22-14Z). experienced a partial meltdown in 1979. This accident was caused by a malfunctioning coolant system. A small amount of radioactivity was released into the environment, but because there was no explosion, the extent of contamination was minimal. 

Ethylene glycol is not as active in depression of the freezing point as methanol, but it has a very low vapor pressure evaporation loss in a coolant system is due more to the evaporation of water than to the evaporazation of ethylene glycol. Furthermore, the flammability problem is literally eliminated. 1 1 mixtures of ethylene glycol and water do not exhibit a flash point at all. 

The fuel cell coolant system uses a liquid fluorinated hydrocarbon and transfers the waste heat from the cell stack through the fuel cell heat exchanger of the fuel cell power plant to the Freon-21 coolant loop system in the midfuselage. Internal control of the circulating fluid keeps the cell stack at an operating temperature of approximately 200°F. 

Coolant systems are an integral part of container formation and serve to cool the molds and, if applicable, the parison clamp assembly. Coolant, although not in direct contact with product pathways, is in close proximity to the containers, and maintenance should be carried out to prevent leakage. Coolant systems are prone to microbiological contamination and should be routinely treated to keep the bioburden imder eontrol. They should be regularly sampled and tested for bioburden to ensure continuous compliance to a predefined specification. 

Mass Transport at Very Low Concentrations. Heavy Water Plants. The phenomenon of mass transport at very low concentrations is not unique to the reactor coolant systems. It can occur also in the heavy water production plants. Table III compares iron transport in a reactor primary circuit and a GS plant dehumidifier circuit and illustrates the quantities of iron that can be transported each day. While the concentrations in the reactors are typically two orders of magnitude lower, the flow rates are an order of magnitude higher. The lower concentration in the reactors gives a lower driving force for deposition and the efficiency of deposition is considerably lower. 

Performance is also a consideration and in some instances favors polymers over steel. DuPont developed a nylon water jacket spacer for the 2006 Toyota Crown and Lexus GS-300. It did not reduce weight, but did increase the heat-transfer efficiency between the engine coolant system and the cylinders lowering the fuel consumption by 1% or an equivalence of over 50 lb. 

Automobile engine coolant systems properly protected by engine coolant meeting specification ASTM D 3306 do not require use of supplemental additives. Major coolant manufacturers discourage use of these supplements with their coolant in automobile cooling systems. 

LMFBR Design Principles. There are many design differences among the reactor designs, including (1) primary coolant system arrangement ... 

---