Secondary coolant

It has developed a real time method to compare successive non-destructive inspections of the steam generator tubes in nuclear power plants. Each tube provides a safety barrier between the primary and secondary coolant circuits. Each steam generator contains several thousands of tubes whose structural integrity must be ensured through the lifetime of the plant, Therefore, Laborelec performs extensive nondestructive tests after each plant outage. 

Secondary coolants frequently are called brines because such fluids originally were mixtures of salts and water. Common refrigeration brines are water solutions of calcium chloride or sodium chloride. These brines must be inhibited against corrosion. 

Organic fluids also are mixed with water to serve as secondary coolants. The most commonly used fluid is ethylene glycol. Others include propjiene glycol, methanol (qv), ethanol, glycerol (qv), and 2-propanol (see Propyl alcohols, isopropyl alcohol). These solutions must also be inhibited against corrosion. Some of these, particularly methanol, may form flammable vapor concentrations at high temperatures. 

For large motors, which use water as the secondary coolant in a closed circuit, the temperature of the cooling air, i.e. of the primary coolant, varies with the temperature of the cooling water inlet temperature and its rate of flow. For the performance of the motor output, this primary coolant, temperature has the same significance as the ambient temperature for an air-cooled motor. The motor output is unaffected by the ambient temperature. For such motors the output graph is shown in Figure 1.13 at different coolant temperatures and altitudes. The rating at 25°C inlet water temperature for water-cooled machines is the same as for air-cooled machines at an ambient temperature of 40°C. 

Separately mounted heat exchanger The primary coolant is circulated in a closed circuit and dissipates heat to the secondary coolant. It can be a heat exchanger as an independent uni separately mounted 9 This numeral is used for circulation by any means other than stated above... 

Readily peroxidises in air, and explosions have occurred during large-scale distillations [1], particularly towards the end when sufficiently concentrated [2], Use of tetralin as secondary coolant in a molten sodium heat transfer system led to an explosion due to peroxide formation [3],... 

The PWR is more expensive to build because the reactor vessel must be stronger to withstand the higher water pressure, and there is a secondary coolant loop with pumps and so on. The BWR, while less expensive to build, is more complicated to service since the turbines are part of the primary coolant loop. The details of the core design are different as well. Approximately twice as many PWRs have been constructed as BWRs. 

Pressurized Water Reactor (PWR) A type of nuclear power reactor that uses ordinary water as both the coolant and the neutron moderator. The heat produced is transferred to a secondary coolant which is subsequently boiled to produce steam for power generation. 

One is the secondary- coolant reduction test by partial secondary loss of coolant flow in order to simulate the load change of the nuclear heat utilization system. This test will demonstrate that the both of negative reactivity feedback effect and the reactor power control system brings the reactor power safely to a stable level without a reactor scram, and that the temperature transient of the reactor core is slow in a decrease of the secondary coolant flow rate. The test will be perfonned at a rated operation and parallel-loaded operation mode. The maximum reactor power during the test will limit within 30 MW (100%). In this test, the rotation rate of the secondary helium circulator will be changed to simulate a temperature transient of the heat utilisation system in addition to cutting off the reactor-inlet temperature control system. This test will be performed under anticipated transients without reactor scram (ATWS). 

High energy and economic efficiency due fo reduced investment, maintenance and power costs, high throughput, and cost efficiency. Environmenfal friendliness due fo fhe use of environmentally friendly secondary coolants (syrup-type solutions or ice slurries) and primary refrigerant in a small isolated system. The use of product-friendly refrigerant... 

Any process heat plant design implies piping through the containment to connect the reactor vessel with the chemical plant. The fracture of a pipe could result in the accumulation of a flammable gas mixture in the containment. Precautions must be taken to minimize the risk of a fire or gas explosion such as avoidance of explosive gas ingress, proper detection devices, inerting, sufficient safety distances, appropriate layout of secondary coolant boundary, explosion-proofed wall, plant isolation valve. For the PNP-500, the use of two concentric pipes for the process gas carrying lines were recommended. Alternatives are concrete channels around the gas lines or inerting of the containment [10]. 

As motioned in Chapter 19, the name implies that a pressurized water reactor is cooled by hot high pressure water, either H2O (PWR, VVER) or DjO (PHWR). In the PWR and VVER types the coolant is also us as moderator whereas a separate D2O containing moderator tank is normally used in the PHWR type. These power reactor types have several things in common primary — secondary coolant circuits separated by heat exchangers (steam generators), a pressurizer to adjust primary system pressure and often diemical shim control for adjustment of the excess reactivity with fresh fuel. 

Corrosion mechanisms can become very damaging if not controlled. They are identified in Module 2, Properties of Metals. High corrosion resistance is desirable in reactor systems because low corrosion resistance leads to increased production of corrosion products that may be transported through the core. These products become irradiated and contaminate the entire system. This contamination contributes to high radiation levels after shutdown. For these reasons, corrosion resistant materials are specially chosen for use in the primary and secondary coolant systems. 

Reactor vessel height / diameter Primary coolant systems Primary coolant sodium mass Inlet / outlet reactor temperature Primary coolant flow rate Primary coolant flow velocity Secondary coolant systems Secondary coolant sodium mass Inlet / outlet IHX temperature Secondary coolant flow rate Secondary coolant flow velocity Water - steam systems Feed water flow rate Steam temperature (turbine inlet) Steam pressure (turbine inlet) Type of steam generator Refueling system... 

In the 4S, following the loss of off-site power, the primary loop shifts to natural circulation. The pump in the secondary loop of the decay heat removal system does not work assuming the loss of emergency power following loss of off-site power. Under such conditions, the secondary coolant operates in natural circulation mode and natural air-cooling operates in the air cooler. Thus, a passive heat removal circuit is established. 

The above 1-131 release limits were derived from the 0-2 hr limits given in Section 4.1.3 with the assumption that the core release would be attenuated by a factor of 100 by plateout and washout in the primary and secondary coolant circuits prior to environmental release. This assumption will be validated by the Regulatory Technology Development Plan. 

I Heat is transferred to an external source of water, condensing the secondary coolant, which is pumped back to the heat exchanger... 

Figure 21.19 Because large quantities of water are needed to condense the secondary coolant once it passes through the turbine...

In January 1959, BR-5 reactor having 5 MW rated power was put into operation at the IPPE. There are three heat removal circuits in the BR-10 facility (sodium in the primary circuit, originally sodium-potassium and then sodium — in the secondary circuit, and air in the third circuit) with two parallel loops. Initial parameters of the primary and secondary coolants were respectively 430/500°C and 380/450°C, i.e. close to those of power FR. Now sodium temperatures in the primary and secondary circuits are respectively equal to 330/450°C and 270/370°C. There is a wide range of experimental devices in the reactor, namely test channels and irradiation devices and beams of thermal and fast neutrons. There are 5 dry instrumented channels in the reactor. Fast neutron flux in the central loop channel is up to 8.4x lO " n/cm -s. 

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