Recipe Cards - 57 Protactinium generator

57
Protactinium generator
Comment: Protactinium-234 has a half life of about 70 s which is convenient for measurement. It is a radioactive granddaughter product of uranium-238. The generator is a sealed, thin-walled plastic bottle containing an aqueous
solution of acidified uranyl(VI) nitrate(V) beneath an equal volume of organic solvent. When the bottle is
shaken for 10 to 15 s, only protactinium passes into the top organic liquid layer. The decay of the protactinium
by beta-emission can then be followed with a Geiger-Müller (GM) tube placed outside the bottle opposite the
top layer. The two liquid layers in the bottle should have approximately equal depths, each about the diameter
of the GM tube window. A new generator should be prepared annually, certainly after 5 years.
Hazards
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Control measures
Concentrated hydrochloric acid is CORROSIVE (see Hazcard 47A). Uranyl(VI) nitrate(V)-6-water is VERY
TOXIC if swallowed and by inhalation of the solid (see Hazcard 105). It is also radioactive. Pentyl
ethanoate (amyl acetate) (see Hazcard 43B), a more suitable solvent than butanone mentioned in the
CLEAPSS Laboratory Handbook, is HARMFUL & FLAMMABLE. The vapour is not radioactive and is not
harmful if not directly inhaled.
Wear eye protection, disposable gloves and a protective overall. Refer to local rules for handling
open radioactive sources. See CLEAPSS Guide L93 and Hazcard 105 for an outline of the disposal
procedure. Where there is a possibility of contaminating apparatus which cannot be washed up, use
disposable tissues to hold bottles or operate balance controls. Whoever is preparing the generator
should personally wash up all items using detergent in a sink close to the laboratory drain outlet. The
sink should finally be thoroughly washed and flushed with water. All disposable material (eg, tissues,
filter paper) should be put in a polythene bag which is knotted or tied and added to the school refuse.
Procedure to prepare a 30 ml protactinium generator
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1
Place a 30 ml polypropylene narrow-neck leak-proof bottle (eg, Azlon BNP0030PN1) on a sheet of filter paper
on a top-pan balance. Tare the balance.
Use a spatula to add 1.5 g uranyl(VI) nitrate(V) crystals to the bottle.
Place the bottle in an enamel tray, to catch spills, and add 4.5 ml of pure water to dissolve the crystals.
Add 10.5 ml of concentrated hydrochloric acid followed by 15 ml of pentyl ethanoate.
Screw the bottle cap on firmly and label the bottom half of the bottle “Radioactive protactinium generator”
with the date. Label the cap “Do not open”.
Available from Just Plastics Ltd, The Maltings, Wayford Bridge, Norwich NR12 9LL. Tel: 01692 581000, Fax: 01692 581848.
© CLEAPSS 2007