1/9/2023 0 Comments Radium glass vs uranium glass![]() The members of the Thorium decay series and their half-lives are as follows: Th-232 Almost all thorium is obtained from the mineral monazite. Thorium is a dense, insoluble metal that was discovered in 1828 by the Swedish chemist, Jons Berzelius. Paul Frame, Oak Ridge Associated Universities (2) Source material contained in the following products: (i) Glazed ceramic tableware, provided that the glaze contains not more than 20 percent by weight source material (ii) Piezoelectric ceramic containing not more than 2 percent by weight source material (iii) Glassware containing not more than 10 percent by weight source material but not including commercially manufactured glass brick, pane glass, ceramic tile, or other glass or ceramic used in construction (c) Any person is exempt from the regulation in this part and from the requirements for a license set forth in section 62 of the Act to the extent that such person receives, possesses, uses, or transfers: Pertinent Regulationsġ0 CFR 40.13 Unimportant quantities of source material. ![]() It is true that the clay used to produce the body of the ceramic (rather than the glaze) can be a source of radon, but this is true for all ceramics, with or without a uranium glaze. Since Ra-226 is not present, there is no radon (Rn-222) production. Chemically purified uranium contains: U-238 plus its two short-lived decay products, Th-234 and Pa-234m U-234 and U-235 plus its decay product Th-231. This is incorrect because the glaze contains chemically purified uranium, not the complete uranium series. One common misconception is that a uranium-containing glaze can be a source of radon-222. One FDA study measured 1.66 x 10-5 uCi/ml in a 4 % acetic acid solution in contact with the ceramic dinnerware for 50 hours-this exceeded the ICRP’s maximum permissible concentration (MPC). It is likely that the major health issue associated with this dinnerware is not the radiation exposures, but the ingestion of uranium or other metals that have leached into food or drink in contact with the dinnerware. It also reported the results of an Oak Ridge National Laboratory analysis that predicted 34.4 mrem/year to a dishwasher at a restaurant using ceramic plates containing 20% uranium in the glaze, 7.9 mrem/year to the waiters, and 0.2 mrem to a patron for a four hour exposure. NUREG/CRCP-0001 reported a measurement of approximately 0.7 mR/hr at 25 cm from a Fiesta red dinner plate. If a measurement is reported in mR/hr, the detector should not be responding to beta particles. The exposure rate, in mR/hr, is defined for x-rays or gamma rays. Measurements of the radioactivity of ceramics that are reported in mR/hr are difficult to interpret unless it is known whether or not the detector was responding to beta particles. NCRP Report 95 reported the following measurements for dinnerware employing uranium glazes: 0.2 to 20 mrad per hour on contact as measured using film badges. The beta particles are the easiest to detect, and they are also responsible for the bulk of the radiation exposure to those handling ceramics that employ a uranium glaze. Potential DosesĪlthough the uranium in the glaze emits gamma rays, alpha particles, and beta particles, the gamma and alpha emissions are weak. In 1987, NCRP Report 95 indicated that no manufacturers were using uranium-glaze in dinnerware. The use of uranium in ceramic glazes ceased during World War II and didn’t resume until 1959. The glaze can serve two functions: it provides color, and it seals the ceramic. It is widely known that uranium was used in the glaze of orange-red Fiesta dinnerware, but uranium glazes have also been used other types of ceramics: wall and floor tiles, pottery, laboratory ceramics, etc. Perhaps they should have been spelt “uranyls?”Ĭeramics can be particularly radioactive if some compound of uranium (e.g., uranium oxide, sodium urinate) has been used to impart color (e.g., orange-red, green, yellow, black) to the glaze. As another example, health physicists at Oak Ridge National Laboratory reported excessively high readings while surveying newly purchased urinals for the men’s restrooms. For example, I was once at a truck weigh station when a vehicle carrying toilets set off a radiation monitor. Sometimes the higher readings are due to uranium in the glaze, sometimes they are due to the radionuclides in the clay that was used to produce the ceramic. Because of this, health physicists who are conducting radiation surveys expect to see higher readings when they are making measurements over ceramic tiles and similar materials. Ordinary ceramics often contain elevated levels of naturally occurring radionuclides, e.g., K-40 and the various members of the uranium and thorium decay series. Paul Frame, Oak Ridge Associated Universities General ![]() General Information about Uranium in Ceramics
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |