The cavity pressure following a nuclear detonation in alluvium at the Atomic Energy Commission’s Nevada Test Site has been measured from about 45 sec until subsidence at 10.2 min. The pressure was found to follow the expression P (bars) = 36.7 e−0.36t + 7.8 for about 7 min. Such a pressure history corresponds to simple cooling of a steam‐filled cavity with a surface heat‐transfer coefficient of 0.012 cal/cm² sec °K. Original pressure, after the completion of cavity growth, was apparently just overburden pressure. The difference between measured and calculated pressure after about 7 min can be explained as the result of condensation of the steam. After condensation begins, the pressure is simply the vapor pressure of water. The observed pressure is used to calculate the apparent rate of condensation and the necessary heat‐transfer rate. The surface heat‐transfer coefficient after the onset of condensation is found to be about 1 cal/cm² sec °K, a value that implies spalling of the cavity surface.

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NOTICE TW report was prepared as an account of work I s w~e d by the united state8 Oovsmment. Neither the United States nor the United Stat-Atomic Enem 1 c~m m i d & , nor my of their enrployn, nor MY of the& contractors, subcontrocton, or thsir employees. &, my mnmty, express or ImpUed, or mum-any 1eg.l u.buity or responsibility for tbe accurwy, Cornplelenen or usefulnw of my Momation, O P P~~W 1 pro&& or proetr~ dh~bead, or rsprewnta that its would not infrfngo privately owned W M .

Strain error in pressure measurements is recognized as a trouble source, but seldom Is it the major source of error in measurement. In experiments at the USERDA*s Nevada Test Site, it has been necessary to obtain dynamic pressure data from inside pipes which are subject to an initial tensile stress of about one-half yield which changes rapidly to failure in a compressive mode.Static and dynamic data show that representative pressure trans ducers are subject to strain error and that the error is not only a function of stress in the mounting, but is also dependent on the rotational position of the transducer (about its own axis) as it is ported into the pipe.Schemes for decoupling the transducer from the pipe without seriously decreasing the burst capability of the installation have been investigated.A mounting using an annular cut-out around the transducer barrel has been devised which significantly decreases strain error and has little effect on the installation integrity or the response to dynamic gas pressure.