Main circulation pumps

Failure of the integrity of the DjO system in sequence 5 resulted from a small leak in the DjO system and failure of the operating personnel to isolate the leak which dominated the sequence. The probability of the small leak that challenges of the tank used to pressurize seals for the main circulating pumps was estimated to be 0.5 0.21 g. 

Corrosion in these areas is sometimes effectively controlled by cathodic protection with zinc- or aluminium-alloy sacrificial anodes in the form of a ring fixed in good electrical contact with the steel adjacent to the non-ferrous component. This often proves only partially successful, however, and it also presents a possible danger since the corrosion of the anode may allow pieces to become detached which can damage the main circulating-pump impeller. Cladding by corrosion-resistant overlays such as cupronickel or nickel-base alloys may be an effective solution in difficult installational circumstances. 

The design of RI SVBR-75 have two-circuit scheme of LBC heat removal for the primary circuit and steam-water for the secondary circuit. The integral design of the pool type is used for the RI primary circuit (see Fig. 2). It enables to mount die primary circuit equipment inside the one vessel. RI SVBR-75 includes the removable part with the core (the reactor itself), 12 SG modules with compulsory circulation over the primary circuit and natural circulation over the secondary circuit, 2 main circulation pumps (MCP) for LBC circulation over die primary circuit, devices for controlling the LBC quality, the in-vessel radiation protection qrstem and buffer reservoir which are the parts of the main circulation circuit (MCC). 

The BN-350 is a fast breeder reactor located in Aktau, Kazakstan on the eastern shore of the Caspian Sea. The reactor began operation in 1972. It operated on an open uranium fuel cycle optimized to produce plutonium for the USSR weapons complex and generated steam for electricity, heat and seawater desalination. The reactor was in operation until April 1999 when decision for final shutdown had been taken by Government. In this report the operational experience is considered for the following equipment that directly contacts the liquid metal coolant The main circulation pumps of primary circuit ... 

Leakage hold-up tank for the main circulation pump of loop No 4 ... 

The main circulation pump (pump) is intended for providing the sodium circulation in primary circuit. The pump is centrifugal, vertical arrangement, single-stage, console, sealed, electrically driven type. Motor — asynchronous, double-speed, vertical arrangement with squirrel-cage rotor. 

Self-induced vibrations of sodium level in the pump leakage drain tank during operation of the main circulation pump (pump) at 1000 rpm in the loop No 4 of primary circuit. The self-induced vibrations eliminated by the cutting off the loop No 4 via the gas communications from primary circuit and by maintaining the gas pressure in the loop No 4 higher than that in all the rest primary circuit gas volume. 

Graphite stack 20 Overhead crane of main circulation pump room... 

Main circulation pump 23 Controlled leakage tank... 

Main circulation pump electric motor 24 Controlled leakage heat exchanger... 

Reactor 2, Steam separators 3. Inlet header 4. Main circulation pump 5. Outlet header 6. Pressure suppression pool 7, ECCS vessels 8, ECCS pumps for cooling damaged half of reactor 9. Heat exchangers 10. Clean condensate container 11. ECCS pumps for cooling undamaged half of reactor 12. De-aerator 13. Feed pump,... 

Fig. 2.7. Schematic arrangement of part of the containment system (from Ref. 2, by permission of the IAEA) 1, reactor space 2, compartments (downcomer pipes and main circulation pump outlet headers) 3, compartments (distribution group header and...

The results of the SEPRA study have been used for implementing several improvements and for initiating some actions. The low equipment hatch of the containment must now be closed for a certain time period during the main circulation pump overhaul. In addition, procedures and technical specifications have been modified. Altogether, various modifications have resulted in a decrease in CDF by a factor of 10. 

The circulation circuit of the reactor is divided into two loops, each including a group of the main circulation pumps (MCPs), the suction, pressure and distribution group headers (DGHs), drum separators, as well as the downcomers between the drum separators and the MCP suction header. Each of the two circuit loops has half of the fuel channels connected to it. 

Main circulation pump seizure or trip leads to coolant flow reduction. The reactor CPS should restrict the degree and duration of the flow-power imbalance. The system will respond by reducing the reactor power or by shutting it down, depending on the power level at which the initiating event occurs. Analysis should explore the implications of the imbalance for the thermal conditions of fuel channels, i.e. the possibility of violating the safe operating limit in terms of the critical power ratio of the fuel channels. 

Main circulation pump trip in the group of pumps serving the common pressure header results in overloading of the pumps remaining in operation. Assessment of the possibility of failure of these pumps due to cavitation is an essential component of the analysis to be made for these initiating events. 

Possibility of 0[x ratioii without one or two pumps, transition to iiatuial circulation at simttmg down main circulating pumps Secondary transient... 

The main circulation pump must be of sufficient size to ensure necessary flow and pressure as specified on the tube data sheet. A filter screen of at least 60 mesh is usually installed in the pump outlet line to trap any circulating debris that might clog coolant passages within the tube. 

Both VBER-150 and VBER-300 use the same unified main equipment (reactor vessel and internals, steam generators (SG), main circulation pumps (MCP), control and protection system (CPS), etc. Using a two-loop modification of die VBER-300, the VBER-150 could be used to create floating nuclear power plants (NPPs) of various power output with a long refuelling interval tailored to the needs of a customer. 

The vessel system consists of a reactor vessel and two units (steam generator + main circulation pump (MCP)) connected with the reactor vessel by load-bearing nozzles of the coaxial type. 

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