16. After 2.5 hours and with current still on, add two drops of phenolphthalein indicator and make basic with 1% NH4OH. 17. Remove the plating cells and wash them with two 10 ml washes of deionized water. 18. Removethe dise from the cell and allow the dise to air dry. 19. Cool and count 400 minutes on the alpha spectrometer. 20. Caiculate dpm of 239pu per sample as follows: a. Add the net counts within the 239pu channels to obtain total 239pu counts. b. Add the net counts within the 236pyu channels to obtain total 236pu counts. ec. Divide total 239pu counts by total 236pu counts and multiply this ratio by the total dpm 236 pu added in step 1: 239 Pu counts , dpm 236 py added = dpm 239py 236 pu counts A-10-2