THE RADIOCHEMISTRY OF PLUTONIUM - Sciencemadness.org

(e)
(f)
(g)
(h)
Where C
v
E
The precipitate is easily washed from the narrow portion of the
tube, but it is difficult to remove it if it is allowed to dry on the
wider part of the tube.
The stab flity of the counter may be checked statistically using a
standard plutonium source (see Appendix H).
The background should not normally exceed 2 cpm.
The ratio El/ E2 may be replaced by the ratio of the counting rates
of the plutonium control source at the time of standardizing and at
the time of sample count provided that the same control source is
used.
.
‘1 ‘
E2 =
Counting rate of sample source corrected for background as cpm.
Volume of sample in ml.
Percentage efficiency of the coumting equipment for the standard
plutonium source (Appendix I).
Percentage efficiency of the counting equipment for the Pu control
source at the time of calibration (Appendix I).
Percentage for the Pu control source at the time of sample count
(para. 11).
APPENDIX I. Calibration of the a-counting equipment.
Using 500 IJl of the standard Pu solution (O. 5 Hg Pu/ml) (see Section B,
para. 7) obtain a series of standard sources by the procedures described in Section
D, paras. 2 to 10.
Measure the counting rate of each source and correct for background.
Determine the disintegration rate of each source using an a -proportional
counter of known efficiency. (This efficiency is measured with a source calibrated in
a low geometry counter. )
Calculate in each case the ratio
Corrected counting rate as cpm
Disintegration rate as dpm
and calculate the counter efficiency E = 100 mean ratio.
APPENDIX II. Preparation of the Pu control source.
Prepare a standard Pu solution containing about 10 pg/rnl of Pu. Transfer
approximate@ 20 mg of this solution from a weight pipette to a clean prepared counting
tray, ensuring that the liquid forms a small spot in the center of the tray. Evaporate
the liquid on the tray to dryness by warming gently beneath a radiant heater. Allow
the tray to cool and add just sufficient of a solution containing 10 ~g/ml of collodion
in acetone to cover the spot of activity. Allow to dry at room temperature. Determine
the counting rate of the control source and determine the disintegration rate using an
a-proportional counter of known efficiency. Calculate the efficiency of the counting
equipment.
110