Changes in international radiation protection standards.

The International Commission on Radiological Protection, ICRP, is the only organization that has ever effectively set standards at the international level for protection from exposure to ionizing radiation. Thus, this paper deals primarily with the ICRP, its shortcomings, and changes that should be made in ICRP and its operation.

Health physics: its development, successes, failures, and eccentricities.

Health Physics began at the University of Chicago as a science and profession during the early World War II years. It was initiated by Drs. A.H. Compton and R.S. Stone, director and associate director, respectively, of the early Plutonium Project cryptically called the Metallurgical Laboratory. It was to be a science and a profession to protect radiation workers and members of the public from exposure to ionizing radiation. It succeeded to some extent in this objective but during the past decade in the United States, it has reverted into an organization primarily to protect the nuclear industry from liability resulting from radiation exposure.

Neutron dosimetry in high energy X-ray beams of medical accelerators.

High energy X-ray beams from medical accelerators are used in cancer therapy. In such beams, neutrons are also produced due to photon-neutron interactions in the target material, collimator and beam flattening filter. The feasibility of employing fast-neutron-induced recoil particle tracks in polycarbonate foils developed by the electrochemical etching (ECE) method for the dosimetry of such neutrons was investigated. The experiments were carried out in, and out of, the beam of a Varian Clinac-18, an Allis-Chalmers 25 MeV betatron and a Brown Boveri 45 MeV betatron. Neutron dose equivalents were found both as a function of the photon dose and of the distance away from the centre of the beam. The neutron dose equivalent was found to be 0.6 and 1.3% of the X-ray dose at the centre position of the beam for a TSD = 100 cm and a 10 x 10 cm2 field for the 25 and 45 MeV betatrons respectively. Although the dosemeter showed adequate sensitivity to neutrons in the beam of the betatrons, it showed insensitivity to neutrons in the beam of the Clinac-18 which has a softer spectrum than the neutron energy threshold of the dosemeter. It can be concluded that this dosimetry method provides a new approach with a number of advantages compared to some other existing techniques for such measurements above the energy threshold of the dosemeter.

A new polycarbonate fast neutron personnel dosimeter.

Registration of fast-neutron-induced recoil and (n,alpha) tracks directly in sensitive polymers especially polycarbonate foils when etched by the electrochemical etching (ECE) method provides a simple, sensitive, and inexpensive means of fast neutron dosimetry. The wide dose range and a dose equivalent response, negligible fading rate, and insensitivity to X, beta, and gamma radiations make such a method feasible for many neutron dosimetry applications, especially personnel dosimetry. Due to very large size of the tracks, even the unaided eye can be used as a reading device.

Suggested reduction of permissible exposure to plutonium and other transuranium elements.

The historical development of the value of maximum permissible body burden ot 239Pu is presented and present considerations for the revision of this standard are given. Some evidence is presented that the linear hypothesis may not be sufficiently conservative at low dose rates and especially for the actinide elements. Until certain questions are answered about the particle problem, it will not be possible to set a satisfactory maximum permissible body burden for 239Pu based on lung as the critical organ, but in the meantime some studies suggest that the present maximum premissible body burden based on bone should be reduced at least by a factor of 200.