Reactor auxiliary systems system control

The reactor auxiliary systems are similar to those found on other PWRs and typically include a primary water volume control and inventory system, a primary water purification system, radioactive liquid and gaseous effluent treatment systems, and a ventilation system. At low power levels, many of these systems may be required only on an intermittent basis and would be valved out during periods of autonomous operation. 

Because the reactor is basically a water boiler, process systems are required which clean and control the chemistry of the water in the reactor vessel as well as protect the reactor core. Called the reactor auxiliary systems, these systems may be divided into two general... 

S has several safety systems active, passive, and inherent (IAEA, 2003) (see Fig. 20.22). Active shutdown systems are (1) inserting reflectors by using gravitational force and (2) inserting black control rods. The passive safety system of 4S uses natural circulation in RVACS and Intermediate Reactor Auxiliary Cooling System (IRACS). In addition, inherent safety system uses Doppler effect via metallic fuel and large inventory of coolant. 

In this approach accident cases and design recommendations can be analysed level by level. In the database the knowledge of known processes is divided into categories of process, subprocess, system, subsystem, equipment and detail (Fig. 6). Process is an independent processing unit (e.g. hydrogenation unit). Subprocess is an independent part of a process such as reactor or separation section. System is an independent part of a subprocess such as a distillation column with its all auxiliary systems. Subsystem is a functional part of a system such as a reactor heat recovery system or a column overhead system including their control systems. Equipment is an unit operation or an unit process such as a heat exchanger, a reactor or a distillation column. Detail is an item in a pipe or a piece of equipment (e.g. a tray in a column, a control valve in a pipe). 

The control performance of the heat-integrated reactor-column system shown in Fig.. 5.9 deteriorates as the auxiliary rehoiler provides less and less heat to the column. The reason is that uncontrolled variations in the steam pressure of the waste heat boiler affect the heat supplied to the column. When these variations are of the same order of magnitude as the total heat supplied by the auxiliary reboiler, the latter cannot compensate properly for the variations. Part of the prob-... 

The safety concept considers two nuclear shutdown systems, a set of six reflector rods for reactor scram and power control and a KLAK system of small absorber balls for cold and long-term shutdown. Decay heat removal is made via the heat exchanger, an auxiliary cooling system, and the panel cooling system inside the concrete cavern, or, in case of a failure of these systems, passively by heat transfer via the surface of the reactor vessel. 

Besides it was required to develop and modify core components (fuel sub-assemblies, control rod guide tubes and control rods), to explore and modify electrical drives of sodium pumps, to modify a reactor refuelling system, to construct advanced failed fuel detection systems, to design and construct advanced reactor vessel integrity inspection systems, reactor vessel and auxiliary primary sodium pipeline displacement measurement systems, to remarkably improve water-sodium reaction detection systems of the water-sodium steam... 

All systems and components which must fulfill, with a high level of confidence, their lOCFRlOO-related radionuclide control functions under design basis conditions are located inside buildings or structures which are designed to withstand the impact from tornado-generated missiles. The major portions of the Reactor Buildings, Reactor Auxiliary Buildings, and Reactor... 

Six-control rod subassemblies made of 90% enriched B4C were used in JOYO MK-II and were located symmetrically in the third row. In 1994, one control rod was moved to the fifth row to provide a position for irradiation test assemblies with on-line instrumentation. Since then, the control rod subassemblies have been loaded asymmetrically. The JOYO cooling system has two primary sodium loops, two secondary loops and an auxiliary cooling system. The cooling system uses approximately 200 tons of sodium. In the MK-II core, sodium enters the core at 370°C at a flow rate of 1 100 tons/h/loop and exits the reactor vessel at 500°C. The maximum outlet temperature of a fuel subassembly is about 570 C. An intermediate heat exchanger (IHX) separates radioactive sodium in the primary system from non-radioactive... 

Indications are that the reactor, PCU, secondary systems, etc., most of the auxiliary control and instrumentation systems could be housed within a concrete stmcture of size 40mx20mx40m. The primary components could be housed in a protective reactor pit. One of the design packages should include the finalization of design criteria for these components and housing. 

The performance of reactor systems, sodium systems, control rod drive mechanisms and other safety related systems and auxiliary system were generally satisfactory. The primary and secondary sodium purity was maintained below the plugging temperature of 105 C. The four sodium pumps and Aeir drives are operating well and have logged 83,293 h, 70,615 h, 88,878 h 69,201 h. 

A wide range of auxiliary equipment has been developed for gas-cooled reactors, including appropriate control and instrumentation systems, control rods and drives, and coolant handling and purification systems. The developments in these areas are too varied to report in detail here. However, it may be of interest to note some of the principal developments in control equipment and coolant purification equipment for the magnox, AGR, HTGR, and related plants. 

The reactor facility of pool design, which incorporates the core with reflectors and control rods, the lead coolant circulation circuit with steam generators, pumps, equipment of the fuel reloading system, as well as safety and auxiliary systems, is arranged in a steel-lined thermally insulated concrete vault O Fig. 58.16). The concrete temperature is maintained within the permissible limits by natural circulation of air. 

The System 80+ Standard Design incorporates pressurizer equipment that is different from current operating plant designs. For example, the Safety Depressurization System (SDS) performs rapid venting and depressurization of the Reactor Coolant System (RCS) when the Auxiliary Spray System is not available (see CESSAR-DC, Section 6.7.1.1 for a description of the SDS). Reliable pressurizer level indication is provided in the Nuplex 80+ Advanced Control Complex consistent with the guidance given in NUREG-0737. 

Much of the nuclear temperature-monitoring> flow-monitoring and other instrumentation which are in the safety clrc ts will ve useful functions for process control. Auxiliary Instrumentation systems which will be provided for N Reactor which a-e not In the safety circuit are described below. 

The 105-N and 109-N Buildings house the reactor, the heat dissipation system, reactor controls and other auxiliary systems and functions. These buildings are divided Into zone which provide for confinement and control of radioactive contamination. 

The main and auxiliary cooling systems are based on natural circulation of water coolant. The containment vessel (CV) is water-filled, preventing activity release to the environment and acting as a radiation shield. The control rod drive mechanism (CRDM) is in-vessel type, with no penetrations in the reactor pressure vessel (RPV). No chemical and volume control system is used during reactor power operation. The PSRD has a passive reactor shutdown system. 

A simple scheme of the reactor module and the fact that all modules installed are of the same type make it possible to reduce the number of personnel for operation and maintenance of the modular NPP as compared with the NPP unit comprising one large-power reactor that incorporates many safety systems, such as protection systems, localizing accident systems, and control and auxiliary systems. For example, the safety systems of the AP-1000 reactor [XIX-16] have 184 pumps, 1400 valves, and 40 km of pipelines and cables [XIX-16]. 

Installation of the disassembling area with the facilities of the remote controlled dismantling, connecting the disassembling area to the outer reactor vessel, commissioning of auxiliary systems (e.g. vent systems)... 

The instrumentation and control systems important to safety fall into the following categories reactor protection systems, engineered safety features control systems, safe shutdovwi control systems and other information systems, control systems, and essential auxiliary systems important to safety. Appropriate surveillance procedures and setpoint methodology for instrumentation and control systems important to safety are required to ensure the system operability. 

The reactor coolant system interfaces with a number of auxiliary systems, principally the ehemical and volume control system, the normal residual heat removal system, the steam generators, the primary sampling system, the liquid radwaste system and the eomponent cooling water system. 

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