Pumps – Combined
Patent
1994-11-16
1997-04-08
Thorpe, Timothy
Pumps
Combined
417405, F04B 1700
Patent
active
056181663
DESCRIPTION:
BRIEF SUMMARY
This invention relates to a submersible pump for pumping liquids, particularly radioactive liquids, from a tank or similar vessel.
FIELD OF THE INVENTION
In the nuclear industry, particularly in nuclear fuel reprocessing operations, there are a number of processes in which radioactive liquids require to be transferred by means of a pump. One such process is the decanning of spent nuclear fuel elements. This process involves transporting the spent fuel elements in water-filled skips from a storage pond into a shielded decanning cave where the cladding is mechanically stripped from the fuel elements. Water, which is radioactively contaminated by the spent fuel elements, is then removed from the skips by pumps.
Operations within the decanning cave are controlled from outside the cave so as to protect the operators from exposure to radiation. It is important therefore that the pumps can be serviced or maintained in the cave by the use of remotely controlled manipulators installed in the cave. When a pump becomes inoperative or malfunctions it is desirable that repairs are carried out quickly and, in particular, that replacement of defective components can be achieved by use of a manipulator.
Another desirable feature is that the pump should be as compact as possible so that when it is scrapped the volume of radioactive waste for disposal is kept to a minimum.
SUMMARY OF THE INVENTION
According to the invention there is provided a submersible apparatus for pumping radioactive liquids in which the apparatus is submersed, said apparatus comprising a pump cartridge, said pump cartridge having a casing provided with a liquid inlet and a liquid outlet and adapted for housing an impeller and a pneumatically operated motor to which the impeller is drivingly connected, the apparatus further comprising a pump body having a cavity formed therein in which said pump cartridge is removably mounted, and a liquid outlet duct communicating with the liquid outlet in the cartridge casing and extending from the pump body for conveying pumped liquid to a remote location, wherein compressed air is supplied to the motor through an air inlet tube extending through the liquid outlet duct and air is exhausted through an air outlet tube extending through the interior of the liquid outlet duct.
Preferably the liquid outlet duct includes a flexible hose through which the air inlet tube and air outlet tube pass to said remote location. The liquid outlet duct may further include a pipe formed on and extending from the pump body, the flexible hose being connected to the pipe to form a continuous liquid outlet duct.
In a preferred embodiment the cartridge casing includes an interior pump chamber housing the impeller, the liquid inlet being arranged coaxially with the pump chamber, and a filter located at said liquid inlet for removing solid matter entrained in the liquid passing into the pump chamber, the cartridge casing further including an interior motor chamber arranged coaxially with the pump chamber and housing the motor, the motor chamber having a further filter for removing solid matter from the compressed air passing to the motor.
The compressed air preferably is supplied to the motor through an air inlet passage formed in and extending through the pump body and communicating with the air inlet tube and the pump body cavity, and air is exhausted from the motor through an air outlet passage formed in and extending through the pump body and communicating with the air outlet tube and the pump body cavity.
Preferably, seals are interposed between the cartridge casing and the pump body cavity, a first seal being arranged between the positions at which the air inlet passage and the air outlet passage communicate with the pump body cavity, and a second seal being arranged between the positions at which the air outlet passage and the liquid outlet communicate with the pump body cavity.
Advantageously, an external screw thread is provided on the cartridge casing and a corresponding internal screw thread is formed on the pump body cavity
REFERENCES:
patent: 3759290 (1973-09-01), D'Alba
patent: 4138202 (1979-02-01), Eller
Legett Clive
Taylor Leonard S. D.
Walton Colin
White Simon J.
British Nuclear Fuels PLC
Korytnyk Peter G.
Thorpe Timothy
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