Isolation cooling system

RCIC - Reactor Core Isolation Cooling System... 

Figure 14.11 The mixed spectrum supercritical water-cooled reactor safety system. ICS, isolation cooling system GDCS, gravity-driven cooling system ACC, accumulators ADS, automatic depressurization system PCCS, passive cote cooling system SLCS, standby liquid control system. 

Coolant Inventory Control and Core Heat Removal High Pressure Coolant Injection System Reactor Core Isolation Cooling System Low Pressure Coolant Injection System Low Pressure Core Spray System Control Rod Drive Cooling System Condensate System High Pressure Service Water System... 

The reactor core-isolation cooling system (RCICS) could have been made available by installing a special short piece of pipe that was stored nearby. 

The cable spreading room below the control room is significant but not dominant in the fire analysis. The scenario of interest is a fire-induced transient coupled with fire-related failures of the control power for the high-pressure coolant injection system, the reactor core isolation cooling system, the automatic depressurization system, and the control rod drive hydraulic system. The analysis gave credit to the automatic CO2 fire-suppression system in this area. 

The Reactor Core Isolation Cooling System cools the core in the event that the main steam condenser and the main feedwater system are not available. This process can be initiated automatically by an emergency actuation signal, or can be... 

Fig. 7.5 Reactor Core Isolation Cooling System (US Nuclear Regulatory Commission, n.d.b)...

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. 

The reactor core isolation cooling system should be designed ... 

Perform functional test of cooling system prior to batch reaction addition Ensure automatic isolation of feed on detection of loss of cooling... 

A fire in either of two critical areas would disable all front line and emergency core cooling systems, but not affect confinement isolation and effluent filtration. 

Widespread practice has always existed, unfortunately, by owners and operators of cooling systems, or their general contractors and consultants, to specify chemical treatment operating standards in isolation, with little or no actual contact with prospective vendors of water treatment service companies before the issuance of such standards. There is now a growing tendency for particularly low corrosion rates to be specified as a part measure of the quality of water treatment and technical services to be provided in water management contracts (say below 1 mpy for steel in closed-loop systems and below 2 mpy for steel in open-recirculating systems). These low rates are often unattainable in practice. 

Fig. 6.20 Sensor Sr 2 and cooling system faults detection and isolation residuals for the sensor fault...

H. Sato (JAEA) presented a paper discussing detection methods and system behaviour assessments for a tube rupture of the intermediate heat exchanger (IHX) for a sulphur-iodine based nuclear hydrogen plant. A rupture could be detected by monitoring the secondary helium gas supply using a control system that monitors the differential pressure between the primary and secondary helium gas supply. Isolation valves would be used to reduce the helium flow between the primary and secondary cooling systems. The study showed that the maximum temperature of the reactor core does not exceed its initial value and that system behaviour did not exceed acceptance criteria. 

In order to reduce radionuclide transportation from the primary to the secondary cooling system, containment isolation valves should be installed. These valves will be automatically closed by the signal detecting the heat transfer tube rupture of IHX. Meanwhile, the current engineered safety features actuating system is not designed to detect the rupture since the scenario did not impact on the reactor safety of the original HTTR. Therefore, a detection method of heat transfer tube rupture of IHX should be established. 

Monitoring differential pressure between the primary and secondary cooling systems would be one of the candidates for detecting the heat transfer tube rupture. Meanwhile, the pressure varies even at normal operation and therefore there is a concern of malfunction of CV isolation valves. In case of primary helium gas recovery flow rate, primary helium pressure control system only covers the rated operation since the system activates when the primary coolant pressure reaches about 3.95 MPa. On the other hand, the primary-secondary differential pressure control system covers start-up, shutdown and rated operations. The control system keeps supplying helium gas to the secondary cooling system during the scenario. Thus, monitoring the entire secondary helium gas supply would be an effective way to detect the tube rupture. 

Detection method evaluations are conducted using the HTTR-IS system model. CV isolation valves are set to actuate when the integral of secondary helium gas supply exceeds the actuation conditions. In this calculation, the value 0.2% of secondary cooling system mass is selected as a reference case. Regarding the actuation time of the isolation valves, we selected the previous design value of 30 seconds for the high temperature isolation valve (HTIV) (Nishihara, 1999) and 5 seconds, which is feasible in the utilised temperature range (Tanaka, 1999), for the actuation time of low temperature isolation valve (LTIV) as a reference. 

Based on the reference case, parametric calculations were conducted specifying the actuation condition and time of isolation valves as a parameter. Table 2 shows the actuation times of isolation valves, calculation results of secondary cooling system isolation time and amount of helium gas transportation from primary to secondary. 

Run no. Actuation time of isolation valves (s) (HTIV/LTIV) Detection time of rupture (s) Secondary cooling system isolation time (s) Amount of helium gas transportation from primary to secondary cooling systems (kg)... 

Interfacing isolation valves simultaneously could reduce the helium gas transportation from the primary to the secondary cooling system. 

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