The errors in question are caused by many factors, such as the counting rate of radiation, pulse height spectrum induced in a radiation detector, transfer function of a measuring system and absorption characteristics of samples. The relationship between these factors has been given by a formula. The statistical properties of the output wave have been proved to be similar to the Gaussian noise. Using these properties, a formula has been induced for calculating the optimum intensity of radiation to detect a given small change of thickness.
The separation of231Th from (natural) uranium sample and from the products of the nuclear reactions such as232Th (n, 2n) and232Th (γ, n) is examined to obtain the sample of 231Th having as high specific activity as possible. Some discussions are made as to the fact that231Th formed by nuclear reactions is affected by the existence of the Th series daughter nuclides. As231Th may recoil from the target materials in nuclear reaction, the enrichment of231Th hot atom formed by (n, 2n) reaction is examined by physical or chemical method. The231Th recoiling from Th target foil is caught by Al-tetron or mylar foils, and then purified from fission fragments by several chemical separation processes. The identification is made by231Th β decay curve and the range of recoiled231Th is estimated to be slightly larger than the thickness (10, μg/cm2) of aluminum on Al-tetron foil.
Intravenously injected radiographic contrast media are known to be excreted by both the urinary and biliary tracts. The urographic and angiographic contrast media are primarily excreted by the kidney. The authors encountered two cases in which vicarious excretion of angiographic contrast medium and mercurial diuretics203Hg-neohydrin was made by the liver and subsequent by those materials accumulated in the gastrointestinal tract. The detection of contrast materials within the gut suggests a vicarious excretion in the person with severe renal disease. The authors accordingly thought it significant to investigate the extra-renal pathways-the liver and the digestive tract for the excretion of angiographic contrast medium. Isotopic experiments on the distribution and transmucosal excretion o f intravenously injected angiographic contrast medium were performed using radioactive131I- sodium iothalamate (131I-iothalamate) .1) Intravenously injected131 I-iothalamate particularly concentrated in the %idn1v and rapidly disappeared from the organs or body of the rat within two hours. 2) Low thyroid concentration was probably due to the lack of free iodine, namely the nonoccurrence of deg gradation of iothalamate in the body. 3) The additional transmucosal excretion of contrast medium into gastrointestinal tract, especially into gastric lumen, has been confirmed by this study. The hepatic and enteric route is definitely a course of excretion of contrast medium that is detectable in angiography in the bowel of normal subjects when high doses of contrast lneeliutu are used and in urography of patients with renal insufficiency. The liver may be the major vicarious pathway. Gastrointestinal excretion, which would be a poor but ordinary mechanism for clearing the blood flow of contrast medium, may be an additional route of vicarious excretion.
It is desirable that the paints which are used for surface coating to protect facilities for nuclear power and radioisotopes from radioactive contamination have low contaminability, high decontaminability and radiation resistibility. In order to investigate the influence of r radiation on paint film appearance and also on the contaminability and decontaminability of the paint, many kinds of paints were exposed to r radiations by60Co. When γ radiation dose was less than 107R, JIS product vinyl chloride resin paint, chlorinated rubber paint and nitrocellulose-acryl resin paint showed low contaminabilities and high decontaminabilities. With respect to γ radiation resistibilities, all of the two liquids hardening type epoxy resin paints were fairly good. To enable the paint to function as surface materials for radioactive contamination protection, the upper limit of γ radiation dose may be 109R.