Primary coolant pumps

The four primary coolant pumps are connected to the secondary shield wall by three-link snubbers designed to be flexible under static applied loads (thus, allowing thermal expansion) but become stiff under dynamic loads that might occur during an earthquake. Accordingly, the system is coupled to the wall under seismic loading. 

Prior to placing in dock, Lenin NIB reactors were defueled, and shielding assembly was imloaded from Reactor 1. Electromotors of the primary coolant pump were made dead, automatic power supply was cut off and sealed, drives of control rod groups and actuators of emergency protection system were dismantled and removed from both reactors. The primary circuit was filled with bi-distilled water under a pressure of 15 kgf/cm (reactors 1) and 9 kgf/cm (reactor 2). The third-circuit system was filled with atmospheric-pressme water. 

Since excitation of the alternators of the pump drive sets, compound type, can be interrupted by circuit breakers RCP 03 JA and straps had been installed so that these circuit breakers could open as soon as the 6 6 kV supply of RCP 01 MO tripped out, the system for progressive coast-down of the primary coolant pumps was not operational (common mode defect)... 

Two-circuit reactor plant (RP) with a vessel-type pressurized water reactor is used for floating power unit of nuclear head and power station. Basic RP components reactor, steam generators and primary coolant pumps are incorporated by pressure nozzles in a compact steam-generating block. KLT-40C RP characteristics are given in Table 1. 

A cross-section of the reactor pressure vessel together with that of the containment vessel is shown in Fig. 3. Effective layout of the primary components makes the reactor compact by installing the most of components inside the vessel The core locates in the lower part, the steam generator in the middle part, the CRDMs and pressurizer in the upper part inside of the reactor pressure vessel, and the primary coolant pumps are connected directly to the flange of this vessel. Major specifications of the core, the CRDMs, the SGs, the pressurizer, and the primary coolant pumps are shown in Table 1. 

The primary coolant pumps of a caimed motor fype, the double piped suction and delivery model is set horizontally at the upper part of the SGs. The JRR.-2 (Japan research reactor No.2) and the Lenin had the experiences on Ae pump of horizontal carmed motor type which revealed to have two problems ... 

The primary stem pipes coimected to the RPV are of small sized diameters, and the largest one is SOmm of diameter for those of the safety valve and the emergency decay heat removal system. A large LOCA over SOmm diameter, therefore, is not necessary to be postulated. The elevations of the all pipes connected to the RPV are near the primary coolant pumps as a result of possible upper part of Ae RPV. 

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. 

At low power ratings additional savings may result from the elimination of some components or systems through design simplification (e.g. primary coolant pumps and emergency coolant injection system). The cost savings associated with the use of advanced construction and fabrication techniques for modem large reactras would also ai ly to small reactors. 

POWER GRID FREQUENCY DEGRADATION AND EFFECT ON PRIMARY COOLANT PUMPS... 

Items of equipment, l e , a primary coolant pump, would sharply reduce the capacity of the heat diaaipation system The loss of some items, e.g, the plant turbine generator condenser, would require a reactor shutdown Power reductions, or reactor shutdown can he accomplished without fuel element damage ... 

Extreme recovery measures will usually be implemented only with increasing severity of the challenge. For example, if a safety function restoration measure could result in severe damage to important plant equipment (e.g. a primary coolant pump, a secondary system, etc.) this measure will only be taken when all other possible restoration measures have been tried and have failed. The actions that must be taken are strictly a matter of priority. The optimal recovery procedures would normally be written in such a way as to protect the integrity of plant systems and equipment. However, since plant systems and equipment have a lower priority than the reactor core and preventing the release of radioactivity they will be sacrificed before the latter are allowed to occur. 

Thermal-hydraulic characteristics Core inlet temperature Core outlet temperature Primary coolant flow rate Primary coolant cover gas pressure Temperature limit for cladding Maximum fuel temperature Maximum cladding inner surface temperature during normal operation Average fuel temperature Average cladding inner surface temperature Natural circulation of lead primary coolant. No primary coolant pumps. 420°C 566°C 2125 Kg/s Slightly below 1 atmosphere 650°C 953°C 650°C 628°C 567°C ... 

Natural circulation of lead primary coolant. No primary coolant pumps. 

At the beginning of the eighties, it was noticed that a thermal ageing with an increasing embrittlement and a loss of resilience and toughness affected austemo-ferritic molden steel, in particular RCCS elbows and volutes of primary coolant pumps. 

In the frame of beyond DBA analysis some specific devices have been added to improve safety as specific backup in case of blackout. A specific GUS (ultimate backup device) turbine generator (gas turbine) for 1300 and 1400 MW subseries or diesel for 900 MW subseries, (allows maintaining seal water injection to the primary coolant pump via the test pump, and necessary control for operators). 

Ul Ultimate procedure depending on the changes occurred in the core outlet temperature and the availability of SG, that procedure determine the most effective measures to be taken in connection with SG utilization, safety injection, pressurizer relief valves and primary coolant pumps. 

Which ONE of the following methods is used to measure the flow rate through the primary coolant pump ... 

Intermediate heat exchangers. Horizontal tube-and-shell IHXs with three modules connected in series, made of U-shaped tubes are used in the BN-350. The IHX of each loop consists of two sections connected in parallel both for primary and secondary coolant flows. The IHX is located in a suction loop upstream of the primary coolant pump, while in the secondary circuit it is in a pressure loop downstream of the circulating pump. The IHX tube bundles can be removed if necessary and replaced with new ones. The most stressed units in the IHX are the fixing joints for the tube module covers and for the fi-ame which stiffens the flat walls of the IHX body. Measurements of temperatures and stresses in various items of the IHX were carried out during reactor plant operation. On this basis requirements were formulated to limit the rate of the IHX heating-up in steps of 10% specified power with delays of 5-10 h in each step. By 1995 the IHXs have operated more than 160000 h at various power levels without any disturbances and failures. 

On the basis of the test rig operation the BN-350 and BN-600 impeller vane profile was optimised. Spare impellers with new vane profiles were fabricated for the BN-600 pumps. Replacement of the BN-350 primary coolant pump impellers is plaimed. 

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