Electromagnetic pumping

Techniques for handling sodium in commercial-scale appHcations have improved (5,23,98,101,102). Contamination by sodium oxide is kept at a minimum by completely welded constmction and inert gas-pressured transfers. Residual oxide is removed by cold traps or micrometallic filters. Special mechanical pumps or leak-free electromagnetic pumps and meters work well with clean Hquid sodium. Corrosion of stainless or carbon steel equipment is minimi2ed by keeping the oxide content low. The 8-h TWA PEL and ceiling TLV for sodium or sodium oxide or hydroxide smoke exposure is 2 mg/m. There is no defined AID for pure sodium, as even the smallest quantity ingested could potentially cause fatal injury. 

There are four (4) major types of pumps (I) positive displacement, (2) dynamic (kinetic), (3) lift, and (4) electromagnetic. Piston pumps are positive displacement pumps. The most common centrifugal pumps are of dynamic type ancient bucket-type pumps are lift pumps and electromagnetic pumps use electromagnetic force and are common in modern reactors. Canned pumps are also becoming popular in the petrochemical industiy because of the drive to minimize fugitive emissions. Figure 10-24 shows pump classification ... 

FIG. 10-60 Simpl ified diagram of a direct-current-operated electromagnetic pump. 

In fig. 1 a diagram is given of the general experimental arrangement. A hydrodynamic circuit is used in which the flow is maintained by an electromagnetic pump P. R is... 

Electrostatic fields (dc or ac) are applied in many different ways to dielectric fluids. Generally speaking, electrostatic fields can be directed to cause greater bulk mixing of fluid in the vicinity of the heat transfer surface, which enhances heat transfer. An electrical field and a magnetic field may be combined to provide a forced convection or electromagnetic pumping. 

Figure 5. Direct current electromagnetic pump for cold trap operations...

Figure 7. Direct current electromagnetic pump in operation at 800°C. (1472°F.)...

A highly desirable characteristic of electromagnetic pumps is their ease of control. Reducing the voltage applied to the alternating current type, or the current supplied to the direct current type, produces a reduction in the pressure developed in each. The corresponding change in flow is determined by the... 

Figure 1. Direct current conduction electromagnetic pump...

The initial failure in this unit was first indicated by a drop in the sodium fiow to zero during a natural circulation heat transfer run. The unit at this time was operating with a sodium-inlet temperature of about 700 °F., a sodium pressure of about 5 pounds per square inch gage, and a boiling water pressure of 485 pounds. Flow was restored in about 0.5 hour by applying additional heat to the sodium and by activating the loop electromagnetic pump. Operation of the loop was then continued for about 9 hours in order to prove conclusively the existence of a sodium-water leak. 

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