Reactor vessel primary tank

PFBR (India) M centrifugal, single stage, free surface, top suction 

ALMR(USA) E submersible, double statar, self cooled 

BREST-OD-300 (Russian Federation) M axial single section 

---

MAIN COMPONENTS OF HEAT TRANSPORT SYSTEM (cont.) 7.1. Reactor vessel (primary tank)... 

The system s AHp should tall within the pump s primary or. secondary sweet zone. At the beginning of the operation, with the cold reactor vessel, the pump operates to the right of the BEP but within the. sweet zone, and as the reactor ve.s.sel is heated, the pump migrates on its curve toward the left, crossing the BEP, to the other extreme of its sweet zone. When the reaction is completed and the tank cools, the pump... 

The reactor vessel is surrounded by several physical barriers. These barriers protect the surroundings from a core accident and protect the core from damage caused by external effects. In a PWR these barriers are the reactor tank (about 15—25 cm steel), the biological shield (1.5—3 m of concrete), and the outer containment. The whole primary circuit, including pressurizer dome, steam generator, and connecting pipes, is surrounded by concrete. 

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. 

During normal operation, the EBR-II reactor was enclosed within an inner vessel that caused hot coolant to flow from the reactor outlet plenum through a pipe to the IHX, where heat was transferred to the secondary coolant. Cold primary coolant exiting the IHX flowed into the primary tank, which held all the primary coolant, the reactor, the IHX, and two primary coolant pumps, as well as provide short-term SNF storage. 

For the EBR-II, shaft penetrations through the primary tank cover are equipped with packing-gland seals to minimize escape of argon cover gas and prevent air in-leakage. For the FFTF and the CRBRP, vessel head ports are mated to special removable valves to control leakage. Similar methods will be required for salt-cooled reactors. 

Concentric holes in both plates accept the circular nose pieces of the subassemblies. The weight of the subassemblies is supported at a conical seal face on the top grid plate. This grid structure is the coolant inlet plenum, coolant entering side holes in the nose pieces. Close fits of the nose pieces in the lower grid plate provide a hydraulic hold-down, the area between the lower grid plate and the reactor vessel being opened to the primary tank. 

Shielding is provided between the reactor vessel and the moderating reflector subassemblies to attenuate the neutron flux on the vessel wall and to provide thermal shielding between the outlet sodium and the primary tank sodium. 

Consequently, the reactor must be cooled even after shutdown and even in case of an accident. Therefore several independent cooling systems are incorporated. The worst accident that is considered (maximum credible accident MCA ) is the complete shearing off of the primary circuit line. If this should occur, then a mixture of steam and air would be blown into the containment for a time span of 12 s (blowdown phase). When the pressure falls below 26 bar, water tanks maintained at this pressure automatically would empty into the reactor vessel from both sides (high and low temperature) of the circuit. If this water should evaporate or leak out again, at a pressure of 10 bar, a pump would provide water from other reservoirs. Water leaking out from the primary circuit will have to accumulate on the bottom of the... 

The PSRD is an indirect cycle light water cooled tank-type small reactor with an integral design of the primary circuit. Steam generator is located inside the reactor vessel. The PSRD is designed to achieve system simplification, resulting in the reduction of costs for construction, operation and maintenance. The assessments of the plant economy are... 

The primary, secondary and tertiary (steam-water) circuits each have three loops. Each secondary circuit loop includes two intermediate heat exchangers (enclosed in the reactor vessel), steam generator, sodium expansion tank, main circulating pump and pipes. The once-through steam generator consists of eight sections, each comprising three modules evaporator, superheater and reheater. Every section can be isolated (if necessary) by valves. 

The reactor vessel is a vertical cylindrical tank 17 m in inner diameter and of total height 20.4 m with a toroidal-spherical bottom. The external guard vessel is identical in shape and encloses the reactor vessel. The annular gap between the vessels in chosen so as to ensure continuous circulation of the primary coolant through the heat exchangers if the integrity of the reactor vessel should be lost. The outer surface of the guard vessel is covered with steel foil thermal insulation. 

The system is connected to the primary circuit by pipes and can be isolated by two stop valves. With this system the primary sodium can be kept below following impurity concentrations oxygen 10 ppm, hydrogen 0.5 ppm and carbon 20 ppm. The primary cover gas system serves as an isolation between the atmosphere and the sodium, and as a buffer for the reactor vessel, reactor roof and mechanism seals. The system is composed of a vapour trap, filters, decay tank, cesium trap, and compressor. The sodium purification and argon cover gas systems for the secondary sodium are similar to those for the primary sodium, but there is no cesium trap in the purification system or decay tank in the cover gas system. 

The compartment of the primary circuit contains the reactor vessel, the drywell, the wet well with water pools, the safety injection system and the surge tanks of the RRP loops. 

---