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