Reactor auxiliary systems function

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). 

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... 

In the operation of nuclear power plants a number of additional systems are needed to support the regular functioning of the main systems. These systems, which are mainly located in the reactor auxiliary building, essentially have to fulfil the following functions ... 

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. 

Figure 1-2 shows the simplified schematic diagram of the SMART nuclear steam supply system (NSSS) and exhibits the safety systems and the primary system as well as auxiliary systems. The engineered safety systems designed to function passively on demand consist of a reactor shutdown system, passive residual heat removal system, emergency core cooling system, safeguard vessel and reactor overpressure protection system. 

The major auxiliary systems of SMART consist of a component cooling system (CCS), purification system and make-up system. The function of the CCS is to remove heat generated in the main coolant pumps (MCPs), control element drive mechanisms (CEDMs), pressurizer (PZR), and the internal shielding tank. Feedwater supplied from the condensate pump of the turbo-generator is used as the coolant to remove heat. The purification system purifies the primary coolant and controls water chemistry to provide reliable and safe operation of the reactor core and all equipment in any mode of operation. The make-up system fills and makes-up the primary coolant in case of a primary system leak and supplies water to the compensating tanks for the PRHRS it consists of two independent trains, each with one positive displacement makeup pump, a makeup tank, and piping and valves. 

A detailed treatment of the axial power distribution local heat transfer, two-phase mixture dynamics, and coupling with the rest of the reactor coolant system requires the use of complex computer models. Figure 3.2-1 compares the predictions based on Eq. (3.2-1) with code calculations for a Zion station blackout scenario compounded by failure of turbine-driven auxiliary feedwater (the so-called TMLB scenario). As indicated by the comparison, the exponentially decreasing function defined by Equations 3.2-1 and 3.3-2 is a reasonable approximation for the water level in the core region during this stage of the accident. 

Example 4.3 represents the simplest possible example of a variable-density CSTR. The reaction is isothermal, first-order, irreversible, and the density is a linear function of reactant concentration. This simplest system is about the most complicated one for which an analytical solution is possible. Realistic variable-density problems, whether in liquid or gas systems, require numerical solutions. These numerical solutions use the method of false transients and involve sets of first-order ODEs with various auxiliary functions. The solution methodology is similar to but simpler than that used for piston flow reactors in Chapter 3. Temperature is known and constant in the reactors described in this chapter. An ODE for temperature wiU be added in Chapter 5. Its addition does not change the basic methodology. 

Accompany with the RVCS, a shutdown cooling system(SCS) is proposed in the paper to provide a simple and reliable decay heat removal during normal shutdown period. The system is shown in Fig 3. It consists of an auxiliary blower, a cooler as well as a recuperator. Because the cooler and recuperator are also the parts of the RPV cooling system(RVCS), SCS is simple and its equipments have multi-function. The decay heat removal under the accidental conditions is depends on the passive reactor cavity cooling system. The SCS proposed in this paper therefore is not safety concerned. 

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 uncontrolled loss of heat sink also terminates safely if the SGAHRS holds the safety passive function. The reactor vessel auxiliary coolant system (RVACS), which removes heat through the reactor wall to the chimney, serves as a passive system to back up the function of the SGAHRS in accident conditions. 

Heat removal from PWR plants following reactor trip and a loss of off-site power is accomplished by the operation of several systems, including the secondary system via the steam relief to the atmosphere. The auxiliary (emergency) feedwater system (AFW) functions as a safety system because it is the only source of makeup water to the steam generators for decay heat removal when the main feedwater systems becomes inoperable. 

In this work, a Motor-Operated Valve (MOV) of the Auxiliary Feed Water System (AFWS) has been selected based on several arguments. First, the basic event representing MOV fails to remain open is one of the most important contributors to the CDF based on the standard PSA available. Second, equipment aging, preventive maintenance and surveillance requirements are meaningful for this MOV. This basic event is modelled as a standby-related failure. This valve is normally open and its function is to control the flow from AFWS until Steam Generators on the secondary of a typical Pressurized Water Reactor (PWR) NPP. 

Startup heating switch gear, gas heating and cooling systems for the reactor and dump tanks, inert gas storage systems, control rooms, and other auxiliaries are located relative to the above systems as logically as possible in the light of their functional requirements. 

In BWRs, the auxiliary feedwater system is usually termed the reactor core isolation cooling system. This system is used to maintain the water level in the reactor vessel in the event of a loss of feedwater in hot shutdown conditions (in such an event residual heat is removed from the reactor core by means of the release of steam through safety relief valves to a suppression pool). Another function of this system is to supply the necessary inventory of reactor coolant in the event of a small loss of coolant during normal operation. 

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