ject has potentialities and should be reinstituted on a larger scale for future tests. D. Results from Previous Operationz. Due to the small number of surface shots detonated prior to CASTLE, only a limited amount of data was available on the longrange fallout aspects of this type burst, and in particular, oniy the close-in phenomena were available for the high yield type. As a consequence, although certain factors couid be reited on, in general only assumptions could be made in reference to these devices prior to the operational pericd. The CASTLE experience, however, will be of inestimable value to radsafe planners in future opera= tions. . For example, the CASTLE experience developed two important areas of radiologizal study about the Operaticn. which little was known prior to It had been predicted that significant fallout would occur during the first twelve nours following the flring of the device. Past experience in this matter seemed to favor a six- hour pericd for significant fallcut3 however, since the off-site fallout aspects of MIKE 2hot cf Operatice IVY were mct known, tne value of twelve hcurs was used as a margin of safety. the! sHor/ and [sor2 experience revised this thinking somewrat for from the action of these shots it became apparent that something on the ore der of at least eighteen and possitly twenty-four hours would be more realistic, especiaily for surface iand bursts, As a conss- quence, a new technique was developed to approximate the signifi-