Containment spray system

Prevent containment ova-pressure Residual heat removal system Shutdown cooling system Containment spray system... 

These plants generally have separate shutdown cooling and containment spray systems and a multi-loop core spray system. With the exception of Big Rock Point, which is housed in a large dry containment, these plants use an i,solation condenser... 

A disadvantage of filter system for the removal of fission products from large containment volumes is that the flow rates the systems can accept are generally relatively small by comparison with the containment volume, and some time must therefore elapse before the entire containment atmosphere can be treated. The containment spray system, which drenches the whole of the containment volume with a fine spray of water, does not suffer from this disadvantage. They also perform the double task of condensing steam and so reducing containment pressure and removing fission products. 

As far as possible effects of operator actions are concerned, if electric power is recovered before the core is uncovered, cooling is re-established and the accident is terminated without damage, or with only modest damage, to the core. The operator has also to open the PORV in order to decrease the pressure in the primary system and to allow the use of the low pressure injection pumps for cooling the core. If the power is recovered after vessel break, flooding of the cavity will take place as an effect of the containment spray system and consequently the end of the accident destructive processes will occur. 

This scenario assumes a break in the cold leg of the primary circuit with operation of the ECCS in the injection phase (although it could also faU in the recirculation phase). It is assumed that the auxiliary feed-water of the steam generators operates correctly, as well as the fan coolers of the containment. Additionally, it is assumed that one train of the containment spray system operates in the ECCS injection phase. 

The report on the new source terms (USNRC, 1992a) also gives guidance on the removal factors by filters, containment spray systems and water pools. Typical values for these factors are ... 

The acceptance criteria for the fission product cleanup function of the containment spray system are based on meeting the relevant requirements of the following regulations ... 

The containment spray system should be designed in accordance with the requirements of ANSI/ANS 56.5 (Reference...), except that requirements for any spray additive or other pH control system in this reference need not be followed. 

The containment spray system should be designed to be initiated automatically by an... 

Because the effectiveness of the containment spray system depends on a well-mixed containment atmosphere, all design features enhancing post-accident mixing should be considered. 

The nozzles used in the containment spray system should be of a design that minimizes the possibility of clogging while producing drop sizes effective for iodine absorption. 

The active safety systems consist of the safety injection system (SIS), safety depressurization and vent system (SDVS), in-containment refueling water storage system (IRWST), auxiliary feedwater system (AFWS), and containment spray system (CSS). 

The pressure suppression function is supported by a four train containment spray system that is continuously in service, with one train supplying spray water from the condensation pool to the gas compression chamber in accident situations the system will start operation at full capacity. Spraying is also possible for the upper drywell - after rerouting, on operator action. The drywell spray is generally initiated only in the event of "small" LOG As to "depressurize" the containment. 

Safety injection system Containment spray system Containment hydrogen recombiner system Containment isolation system Auxiliary feedwater system... 

The large containment is designed so as to enlarge the capacity of the hot well, The containment spray system may remove heat from the containment atmosphere to reduce contunment pressure and temperature following a LOCA or MSLB, and remove the airborne iodine. 

Design Basis Fission Product containment Clad Primary Circuit Containment/Containment Spray System Passive Passive Passive/Active ... 

Compared with current commercial LWR designs a number of safety-grade systems have been eliminated the control rods and the safety injection boron system are replaced by the density locks, the automatic depressurization system is not required, the auxiliary feedwater supply system for RHR is replaced by the reactor pool, the containment heat removal and containment spray systems are replaced by the passive cooling of the reactor pool. The safety-grade closed cooling water stem, HVAC sterns, and a.c. power supply systems have been replaced by non-safety-grade systems, allowing major simplification of the plant. 

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