Primary cooling system

Methods utilized for leak detection and measures for minimizing the loss of the primary coolant shall be described. The potential consequences of the loss of the primary coolant shall be discussed. 

Secondary coolii system (ultimate heat sink) 

If the reactor uses a closed intermediate cooling system between the primary and the secondary cooling systems, this shall also be described. 

The design and operation of the moderator system shall be described in detail. The calculation of the heat generated in the moderator shall be presented. The design and the performance characteristics of the main components of the moderator cooling system should be tabulated. A flow and instrumentation diagram of this system should be included as well as drawings of the main components. The materials of which the components are made should be specified the effects of irradiation and corrosion should be discussed. Material ageing should also be discussed. 

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In MLO, the reactor is shutdown, and the coolant is drained until it is level with the center of the hot leg of the primary cooling system... 

Primary cooling system Reactor outlet temperature 950°C... 

During the IHXTR, helium flows through the rupture point from the secondary to the primary cooling system until the pressure of both balances. In the meanwhile, pressure control systems try to maintain the set pressures of cooling systems. The following parameters would vary sensitively ... 

Reactors operating today all have closed primary cooling systems that do not allow for this type of contamination. Therefore, under normal conditions production of electricity from nuclear reactors does not create significant amounts of operational discharges of radionuclides. However, the 434 energy-producing nuclear plants of the world in 1998 created radioactive waste in the form of utilized fuel. Utilized fuel is either stored or reprocessed. 

The CP behavior analysis code PSYCHE [13] has been developed and verified with the measured radiation data to analyze the distribution of corrosion product in the primary cooling system. A radiation dose calculation code has been developed by INC, to analyze the CP deposition distribution along the piping and components of the primary cooling system. The build-up of CPs is shown in Fig. 19 together with the reactor operation time. The PSYCHE calculations agree with the measured values. 

A Plastic Scintillation Fiber (PSF) measured the dose rate distribution in the primary cooling system of JOYO [14], Figure 20 shows the schematic diagram of the PSF system. 

AOYAMA, T, et al.. Application of Optical Fiber for Radiation Measurement in Fast Reactor Primary Cooling System, Proc. 12 Pacific Basin Nuclear Conference, Seoul, Korea, 29 October - 2 November 2000, Vol. 2, Korea Atomic Industrial Forum and Korea Nuclear Society (KAIF-KNS) (2000) pp. 095-1105. 

A heterogeneous deboration is characterized by the formation of a slug of non-borated water or of water with a low boric acid concentration in the primary cooling system. Formation of such a slug is only possible if no circulation, natural or forced, is present, i.e. heterogeneous deboration is only possible if the MCPs and natural circulation are stopped. 

Plateout distributions in die parallel loaded operation at rated power operation, i.e. 850 °C of outlet coolant temperature, are shown in Fig, 5. It is predicted that both l and Cs plateout mainly on die heat transfer tubes of PWC where temperature is relatively low in the primary cooling system of the HTTR. On the other hand, there are very small amounts of plateout FPs on the inner pipe of co-axial double pipe where temperature is very high and therefore, desorption rate is large by its high lattice excitation frequency. From the calculation results, it is predicted that... 

Table 4 Main calculation parameter of primary cooling system of HTTR... 

It is predicted that both and Cs plateout mainly on the heat transfer tubes where temperature is relatively low in the primary cooling system of HTGR. The measured data show... 

The Intermediate Heat Exchanger (IHX) [2] which can be used over900°C condition is an essential component for process heat applications. The Helically coiled IHX (HCIHX) of 10MW has been developed and installed in a primary cooling system (PCS) in the HTTR. Various R D tests and design works were carried out to develop materials and component structures in the HCIHX. The HCIHX will be tested in high temperature... 

The system of vessels, pipes and pressure components which form the primary cooling system of a PWR (reactor vessel obviously included) is in Class 1, the highest one, as the failure (break) of the system constitutes a serious LOCA. 

A solid system , in the jargon of PWR operators, is a primary cooling system completely filled with water, that is without the steam bubble in the pressurizer. 

An initial release of a steam water mixture with a high internal energy into the containment takes place in many water reactor accident scenarios. Typically, it is the water of the primary cooling system which causes an initial overpressure and a subsequent pressure transient in the containment itself. The following paragraphs describe some simple methods, with essential data, for calculating the pressure with time in these two phases. 

A flooding system is provided with two systems containing pressurized borated water, which automatically inject water when the pressure goes below a preset value. This system has the objective of protecting the core in cases of intermediate and large breaks in the primary cooling system. 

The utilisation of specific codes (modelling tools) is required to obtain design parameters of some important systems (e g. primary cooling system, reactor core, etc.). In some cases these codes must be developed and/or validated with experimental data to build confidence on their results. 

A High Pressure Natural Circulation Loop (CAPCN) was constructed and operated to produce data in order to verify the thermal hydraulic tools used to design CAREM reactor. The CAPCN reproduces the dynamics phenomena of the CAREM primary cooling system, except for the three-dimensional effects. Dynamical experiment data are being used to test our numerical procedures and codes [1]. 

The primary cooling system provides significant retention of fission products released from the fuel. 

The confinement prevents release of radioactive gases which escape from the primary cooling system in both normal operation and an accident. In general accidents do not pressurize the confinement. 

Strong negative temperature coefBcient limits consequences High primary cooling system thermal inertia limits consequences... 

In the development of the MARS design, well-proven technological features of most experienced PWR s were extensively maintained for all components of the primary circuit (geometry of fuel rods lay-out of the primary cooling system type of control rods and of control rod drive mechanisms most core internals etc.). 

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