Caratteristiche e condizioni:
cm. 19,5 x 13, pp. 80, legatura a punti metallici, in ottime condizioni.
Contenuto:
On January 8, 1957, the National Committee on Radiation Protection and Measurements issued a Preliminary Statement setting forth its revised philosophy on Maximum Permissible Radiation Exposures to Man. Since that time several of the NCRP subcommittees have been actively studying the necessary revisions of their respective handbooks. These studies have shown the need for clarification of the earlier statement and modification or extension of some of the concepts in that statement. Furthermore, the International Commission on Radiological Protection has made minor changes in their recommendations. Accordingly, the NCRP has prepared a set of guides, given below, that will assure uniformity in the basic philosophy to be embodied in the various handbooks. Since many of the handbooks are followed closely in planning radiation operations in the United States, and since the modification of a handbook may require many months of effort, it seems wise to make the overall guiding principles available in advance of the reissuance of the revised handbooks. These guides are not designed to take the place of any of the handbooks; the principles given below will be extensively treated later in appropriate places. In the meantime, handbook revisions or supplementary statements will be issued as rapidly as possible.
Since the statement of an average per capita dose for the whole population does not directly influence the substance of the NCRP Handbooks, no further statements regarding such a number will be made at this time. In any discussion of the MPD it is impractical to take into consideration the dose from natural background and medical or dental procedures.
The changes in the accumulated MPD are not the result of positive evidence of damage due to use of the earlier permissible dose levels, but rather are based on the desire to bring the MPD into accord with the trends of scientific opinion; it is recognized that there are still many uncertainties in the available data and information. Consideration has also been given to the probability of a large future increase in radiation uses. In spite of the trends, it is believed that the risk involved in delaying the activation of these recommendations is very small if not negligible. Conditions in existing installations should be modified to meet the new recommendations as soon as practicable, and the new MPD limits should be used in the design and planning of future apparatus and installations. Because of the impact of these changes and the time required to modify existing equipment and installations, it is recommended on the basis of present knowledge that a conversion period of not more than 5 years from January 1957 be adopted within which time all necessary modifications should be completed.