to this peak
and we
can get
an
accurate number
in disintegrations per
minute of plutonium-239, which effectively gives you picocuries per gram.
A couple of things you should look at in this figure is the resolution
of_the spectra.
If you have plating prob lems or detector problems, these
peaks will get much wider and you will get overlaps and it's difficult to
‘extract the information from them.
50-60 keV, if I remember correctly.
obviously coming from thorium.
interfere ‘signtficant ly with
The resolution here is on the order of
There are other peaks in the spectra,
I wanted you to see that they don't really
the plutonium-239
and
-236.
There
is one
10
smal] interference.
11
Radium-224 has a three-day half-life and it ingrows because it's eliminated
12
in the chemistry, but as soon as you plate it, it starts ingrowing from the
13
thorium.
14
plutonium-236, so we have taaccount for the length of time between the
15
plating and the counting and~the ingrowth of the radium-224 and subtract
16
that from the plutonium-236.
17
tially zero.
18
the thorium-228 peak which gives you an estimate of what kind of error
This thorium-228 has a daughter which is radium-224.
Its peak ties_right here and can create a shoulder
in the
If you do it within a few hours, it's essen-
If you wait several weeks, it can go into the same height as
19
20
One last point.
The reason that youcan't do plutonium-240 this way,
21
and you have to go with the mass spectroscopy is that the energy of the
22
plutonium-240 jis the same as the plutonium-239.
23 - 239 and 240.
I should have written this
The 236 has a different energy but--we are just unlucky in
24
that 239 and 240 have the same alpha energy and you—just_can't discriminate
25
between them.
;
26
That concludes my presentation.
27
CHAIRMAN MOSELEY:
28
DR. WRENN:
Are there any questtons?
Or. Wrenn.
If you do radiochemical
165
separation, why do you have so