Page 120 - Radiochemistry and nuclear chemistry

106 Radiochemistry and Nuclear Chemistry

Cladfled pregnant,
1 ~ U308 SCAVENGING
75
Waste
2O
=,. - =911. -
!
I
, 1
I I FOUR STAGES INTERNAL MIXER - SETTLERS, EXTRACTION I
, 12o
I = Amine 3% I I
Alcohol 3% = ~..,._..,

-I l
FOUR STAGES EXTERNAL MIXER SETTLERS, STRIPPING i ~ = '
"
!
i "
,,..~uale Steam ,:. |NH3
i lira :

~ To Mo recovery

NaCl gO g/I
Drier ",
Filter press
AqtmotB
Yellow cake product ...... Organic
75 Flow rate, I/$
FIG. 5.2. Amine extraction circuit, Kerr-McGee Corp., Grants Mill, New Mexico. Each
S-X battery consists of 4 mixer-settlers. Solid lines aqueous, dashed lines organic flow.
Numbers are flow rates O/s).

ammonium diuranate, which is referred to as yellow cake; it contains 65-70% U. It is so
free of radioactive uranium daughters that it can be handled safely in drums without any
radiation protection. Yellow cake is further purified in order to obtain a final pure product
of U308, usually better than 99.98 % pure; its content of neutron poisons (nuclides which
have high capture cross-sections for neutrons such as B, Cd, Dy; see Ch. 19) is less than
0.00002%.
Heating yellow cake in hydrogen gas produces UO 2 which in sintered form is used as
nuclear reactor fuel. If the UO 2 is exposed to F 2, UF 4 is obtained ("green salt'), which in
a thermite process with calcium metal yields metallic uranium. The metal is slowly oxidized
in air at room temperature; the metal powder is very reactive at elevated temperatures and
can then be used to remove practically all impurities from rare gases.