The 70-day, 45-day, 5.5-hour, and 19-second activities of Hf have been investigated by spectrometric, spectrographic, absorption, and coincidence methods. From activation experiments on the separated Hf isotopes, the following assignments have been made: 70-day-7 2 Hf m ; 19-second-r 2 Hf 179 *; 5.5-hour-7 2 Hf 180 *; 45-day-7 2 Hf m .70-day period,-The photographic spectrograms of the internal conversion electrons associated with the 70-day period in 72H1 175 indicated the presence of four gamma-rays. The association of Lu work functions with the various lines confirmed the hypothesis of K electron capture in 72H1 176 leading to an excited state of 7iLu 176 .45-day period.-An investigation of the internal conversion electron spectrum in the Argonne 180° beta-ray spectrometer indicated the presence of one beta-ray of 0.42=b0.01 Mev and five gamma-rays. An upper limit of 1 percent may be placed on any more energetic beta-ray. Single and coincidence absorptions in lead and aluminum showed the three strongest gamma-rays and the single beta-ray. Delayed coincidence absorption indicated that the 0.42-Mev beta-ray leads directly to the 22-microsecond metastable state of 73Ta 181 . No delayed gamma-coincidences were 1 H. Neuert
Portions of this document may be illegible in electronic image products. Images are produced from the best available original document. DISCLAJMERThis report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof.
Spray systems in nuclear reactor containments are described. The scrubbing of aerosols from containment atmospheres by spray droplets is discussed. Uncertainties are identified in the prediction of spray performance when the sprays are used as a means for decontaminating containment atmospheres. A mechanistic model based on current knowledge of the physical phenomena involved in spray performance is developed. With this model, a quantitative uncertainty analysis of spray performance is conducted using a Monte Carlo method to sample 20 uncertain quantities related to phenomena of spray droplet behavior as well as the initial and boundary conditions expected to be associated with severe reactor accidents. Results of the uncertainty analysis are used to construct simplified expressions for spray decontamination coefficients. Two variables that affect aerosol capture by water droplets are not treated as uncertain; they are (1) ^Q', spray water flux into the containment, and (2) "H', the total fall distance of spray droplets. The choice of values of these variables is left to the user since they are plant and accident specific. Also, they can usually be ascertained with some degree of certainty. The spray decontamination coefficients are found to be sufficiently dependent on the extent of decontamination that the fraction of the initial aerosol remaining in the atmosphere, m^^, is explicitly treated in the simplified expressions. The simplified expressions for the spray decontamination coefficient are: X(hr ~h = X(mf = 0.9) [X(mf)/X(mf = 0.9
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