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Vol. 43, No. 7 extremely high. A decontamination factor of 104 would be equivalent to B removal efficiency of 99.99%, 106 to 99.999%, etc. The amounts of radioactivity involved in these tests varied widely, but the minute amounts escaping the system remained practically constant in each test. ConclusionsThe efficiency of the nozzle system in removing radioactive particles from the flue gas stream has steadily increased. The increase from 78.6 to 97.0% can be attributed to the higher steam pressures. The increase from 97.0 to 99.Syo was accomplished by operating the nozzle without its water jets and by improving the action of the second Pease-Anthony scrubber. The efficiencies of the Chemical Warfare Service filter and of the Nash compressor (for particle removal) have been much better than expected. On the basis of these pilot plant results, a full scale incineration process is n o v being designed. The over-all efficiency of the rough washer, Pease-Anthony scrubber, and Nash compressor (combined) is of the same order of magnitude as that obtained from the standard commercial-type steam exhauster used in the first pilot plant. This would tend to support the theory that a steam exhauster of that type acts on an impactiondiffusion principle, as do these scrubbers.

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Perhaps a note which states how you calibrated your instruments to obtain the overall counting efficiency and calls explicit attention to the difference between counts per minute and disintegrations per minute would be appropriate. AnswerAll of our counting was done with a standard end-window type Geiger counter. With a counter of this type, the counting efficiency is dependent on the energy of the sample radiation and will vary from 0 to approximately 10 per cent for energies between approximately 0.1 Mev and 3.5 Mev. Emmons and I have done some work on this subject, and although the data are not ready for publication, we have established that the relation between counting efficiency and particle energy may be represented by a curve, the shape and position of which will vary depending on the characteristics of the counter and on the method of sample preparation. The average energy of the sample radiation can be closely approximated by absorption measurements. By using this method we were able to determine that the counting efficiency for the influent water should be 8.5 per cent, whereas that for the effluent, which was of different composition, F O LLOW I NG the appearance of an article on decontamination experiments in the May 1951 issue of the JOURNAL (1), Mr. Diskant asked Mr. Lauderdale .several questions related to the original articles. Those questions, together with Mr. Lauderdale's answers are presented below.