Coolant inventory

Heatup of the reactor coolant inventory and pressure rise to the relief or safety valve settings with subsequent boiloff. 

The world-wide production of Bi is -4000 t/a at a cost of 12 per kg, its explored reserves as of 1972 being -160 000 tons (coolant inventory of IGW(e) reactor is 15.000 tons). Respective data for lead is 4 xlO t/a and -100x10 tons. Bismuth is expensive, its resources being limited. It is possible that its use could be confined to a limited number of reactors. 

Fuel Storage and Handling Systems Heat Removal Capability. The fuel storage and radioactive waste storage systems shall be provided with systems to protect coolant inventory and remove residual heat under normal operation, AOEs and DBAs with a high degree of reliability. 

A system to provide RCS and core cooling following any loss of coolant event up to and including the rupture of the largest diameter piping system. This system should provide adequate coolant inventory to the RCS such that the following conditions are met ... 

Anticipated operational occurrences are off-normal events, usually plant transients, which can be coped with by the plant protection systems and normal plant systems but which could have the potential to damage the reactor if some additional malfunction should happen. Their typical frequency of occurrence may be more than 10 year Some of the anticipated occurrences (PIEs - postulated initiating events) are due to the increase of reactor heat removal (as might occur for an inadvertent opening of a steam relief valve, malfunctions in control systems, etc.). Some are due to the decrease of reactor heat removal (such as for feed-water pumps tripping, loss of condenser vacuum and control systems malfunctions). Some are due to a decrease in reactor coolant system flow rate, as in the case of a trip of one or more coolant pumps. Some are connected with reactivity and power distribution anomalies, such as for an inadvertent control rod withdrawal or unwanted boron dilution due to a malfunction of the volume control system for a PWR. Events entailing the increase or decrease of the reactor coolant inventory may also happen, due to malfunctions of the volume control system or small leaks. Finally, releases of radioactive substances from components may occur. 

The initiating event occurs at an unfavourable time as regards initial reactor conditions (e.g. power level, residual heat level, reactivity and reactivity coefficients conditions, system temperatures, pressures and coolant inventory). 

Inadvertent Operation of ECCS and Chemical and Volume Control System Malfunction that Increases Reactor Coolant Inventory... 

The vessel extension allows also to reduce the neutron irradiation intensity of critical weld between the supporting shell and the shell of nozzles zone. Owing to this, the margin is increased for the vessel integrity under pressurised thermal shock. The vessel extension allowed to increase the coolant inventory between the core top and the lower generant of the inlet nozzle, that is, to improve the core cooling conditions under loss-of-coolant accidents. 

The safety function fuel cooling during transients and accidents)) is ensured by provision of sufficient coolant inventory, by coolant injection, sufficient heat transfer, by circulation of the coolant, and by provision of an ultimate heat sink. Depending on the type of transient/accident, a subset of these function or all of them may be required. Various passive systems and components are proposed in V-392 design to fulfill these functions. 

Increase of core coolant inventory Spurious ECCS actuation T... 

The IPWR has a large inventory of primary coolant that is contained entirely widiin the RPV and, thus, is immediately accessible to the core fuel. A large coolant inventory provides a large heat sink and a correspondingly long response time during accident events to initiate protective measures. 

An additional advantage of a large primary coolant inventory coupled with a smaller secondary coolant inventory is that the magnitude of a cold water reactivity insertion event on primary pump start-up is greatly diminished. 

Steam line breaks are generally not serious accidents since the small amount of secondary water boils off rapidly. The resulting reactivity transient induced by the temporarily enhanced cooling is minor because the primary coolant inventory is large. 

Increased primary coolant inventory, natural primary coolant circulation and negative reactivity feedback slow down accident progression and ensures rather long grace period for engineered safety systems actuation. 

Second line of defence is to ensure that core xmcovery does not take place, the main feature is to avoid any penetrations in the RPV well above die core level by several meters to provide coolant inventory for boil off and relax the need for fast makeup water in the large quantity. 

Increase in reactor coolant inventory malfunctions of the chemical and volume control system. 

Decrease in reactor coolant inventory very small loss of coolant accident (LOCA) due to the failure of an instrument line. 

Decrease in reactor coolant inventory a spectrum of possible LOCAs inadvertent opening of the primary system relief valves leaks of primary coolant into the secondary system. 

A large negative MTC can lead to difficulty with cool-down accidents such as steam line break or inadvertent operation of emergency primary make-up systems. The problem can be handled by ensuring a large coolant inventory, which slows any temperature drop, and by limiting the maximum rate at which cool make-up water can be admitted. 

Coolant inventory Water losses are made up by coolant injection systems active Water is drawn from condensation pool, pool water can be replenished from outside. 

Coolant inventory Passive Safety Injection System (PSIS) Passive Fourteen times coolant system inventory... 

Coolant inventory Safety injection system (SIS) Active ... 

Coolant inventory Guard vessel Isolation valves Passive Passive GV integrates primary systems except clean-up. Quick-acting (5s closure time) valves,... 

The control and shutdown devices are in the low-pressure moderator, not the high pressure coolant, so are not subject to large hydraulic forces. Natural coolant circulation will remove decay heat fi-om the fiiel if pumping power is lost. This is effective even if, following a small loss-of-coolant accident, the heat transport system coolant inventory is somewhat depleted. 

This is effective even if, following a small loss-of-coolant accident, the heat transport system coolant inventory is somewhat depleted. 

Coolant inventory a) Feed and bleed b) ECCS c) Feed water make-up to SG Active Passive/Active Active a and c for normal operation and accidents without loss of coolant b is for LOCA... 

The design also features a large coolant inventory inside the RPV (about 200T) which provide for a lower total neutron fluence to the RPV (<10 n/cm for 40 Y lifetime of the reactor). 

Coolant inventory Integrated primary circuit Passive... 

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