Pressurized water reactors high-pressure injection

A high pressure injection system (HPI) with three pumps for the injection of borated water in the reactor. In emergency operation, which is automatically activated by low pressure of the primary system or by high pressure in the containment building, two pumps activate. Analyses show that only one pump is necessary to prevent core damage in cases of small breaks in the cooling system. 

Gravity driven injection system of borated water at high pressure makes up the Second Shutdown System. It actuates automatically when the Reactor Protection System detects the failure of the First Shutdown System or in case of LOCA. The system consists of tanks connected to the reactor vessel by two piping lines which valves are opened automatically when the system is triggered. Then one of the pipes -from the steam dome to the upper part of the tank- equalizes pressures, and the other -from a position below the reactor water level to the lower part of the tank- discharges the borated water into the primary system by gravity. 

The test system depicts a high-pressure injection system (HPIS) of a pressurized water reactor (PWR). 

The data obtained in the measurements showed that about 1% of the iodine inventory of the central fuel module reached the blowdown suppression tank, while only 0.23% of the cesium inventory appeared there. These data and those taken from the simulated broken line indicated that cesium deposited in this line more readily than iodine the reverse situation occurred in the upper plenum of the reactor pressure vessel. Here, almost no cesium was detected on the deposition coupons while iodine was present in amounts similar to those in the line of the low-pressure injection system. Besides iodine, silver was found on the upper plenum coupons in equivalent amoimts in addition, the iodine deposited on these coupons could not be leached by water, indicating that it was present there as an insoluble compound. From these data it was concluded that fission product iodine was transported out of the reactor core as Agl, rather than as Csl. Formation of Agl as the main iodine compound deposited in the upper plenum of the reactor pressure vessel is a behavior markedly different from that observed in other in-pile experiments and in the TMI-2 post-accident investigations. The reason for this behavior was assumed to be the low concentrations of both cesium and iodine present in the low-bumup fuel, which resulted in a very high stoichiometric excess... 

Both makeup pumps (lA and 1C) tripped at 258 min (4 h 18 min). Two unsuccessful attempts were made to restart pump lA. The control switch was then put in the "pull-to-lock" position. This completely defeated automatic starts of the pump. The pressurizer indicated full, and the operators were concerned about full high pressure injection flow coming on with an apparently solid primary system. Actually, a very large part of the reactor coolant system was filled with steam and hydrogen gas, and the system was far from being water solid. This condition could have been recognized from the fact that the temperatures in the hot legs were consistent with superheated steam. 

Figure 5.28 Schematic of the experimental set-up. Water/ethylene glycol/SDS reservoir (a) high-pressure liquid pumps (b) catalyst/ substrate HPLC injection valve with 200 pi sample loop (c) hydrogen supply, equipped with mass flow controller (d) micro mixer (e) heating jacket (f) tubular glass or quartz reactor (g) back-pressure regulator (h) [64],...

The presence of water, or water vapour, affects the chemistry of thermal modification and heat transfer within the wood (Burmester, 1981). Under dry treatment conditions, the wood is dried prior to thermal modification, or water is removed by the use of an open system, or a recirculating system equipped with a condenser. In closed systems, water evaporated from the wood remains as high-pressure steam during the process. Steam can also be injected into the reactor to act as a heat-transfer medium, and can additionally act as an inert blanket to limit oxidative processes. Such steam treatment processes are referred to as hygrothermal treatments. Where the wood is heated in water, this is known as a hydrothermal process. Hydrothermal treatments have been extensively studied as a... 

Two accumulators provide die high make-up flows initially required by a large LOCA. These tanks contain 1700 cubic feet (about 48 cubic meters) of borated water pressurized with 300 cubic feet (about 8.5 cubic meters) of nitrogen at 700 psi (4.8 x 106 Pa). The accumulators are isolated from the RCS by check valves. Each accumulator is paired with a core make-up tank, the pair sharing an injection line to the reactor vessel downcomer. 

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