Patent GB-968749-A (GB)
Title: Improvements in or relating to radiometric detection of non-radioactive materials
IPC: G21H5/02
Filed: 1962-06-28
Abstract: Non-radio-active material is detected by impregnating a portion of a porous medium with a solution suspected to contain said material, treating said impregnated portion with a solution forming a radio-active precipitate with said material, washing said portion to remove unreacted radio-active solution and detecting any radiation present in said portion.  The test may be made quantitative by impregnating another portion of the porous medium with a solution of the material of known strength, treating both portions as indicated above and comparing the radio-activity of the two portions.  In Example (1) a beryllium sulphate solution is continuously monitored by applying a streak of the solution through a capillary to a moving film of filter paper whilst a series of parallel streaks of solutions of known concentrations are applied through other capillaries.  The film is dried and passed through a tank of 0,1M diammonium phosphate containing 2-3 millicuries/l. of phosphorus-32, buffered with sodium acetate and containing EDTA to prevent interference by magnesium. The film now containing precipitates is passed through a wash tank of water or saturated (inactive) beryllium ammonium phosphate in 0,1M diammonium phosphate.  The film is finally dried and passed beneath a series of Geiger counters connected to ratemeters the outputs of which are displayed on a multipoint recorder.  (2) A chloride solution is estimated by feeding each of a 0,05 ml. sample and solutions of known concentrations respectively to a point on a filter paper supported on an intermittently rotating disc.  The disc has a hole beneath each of the points to which the liquids are fed and the liquids may thus be successively subjected at a series of locations as the disc rotates to (a) drying by passage of warm air, (b) addition of acidified silver nitrate containing silver-110m, (c) suction to remove excess reagent, (d) a wash solution of nitric acid, (e) drying by passage through the paper of warm air, and (f) measurement of radio-activity by means of a gamma ray scintillation counter.  (3) A beryllium solution is determined by the method of (1) but employing an apparatus comprising conveyers whereby aluminium planchets, to each of which a filter paper disc is attached, pass with manual assistance to a similar series of locations to those described in (2) above.  Each disc carries a single portion of sample or standard solution.  A beta radiation counter is additionally present at a location prior to the final Geiger counter.  (4) A fluoride solution is determined by means of an apparatus in which asbestos string is drawn in sequence through acetone as a wash liquid, an air-drying location, the fluoride-containing solution, an air-drying location, a solution of cerous salt containing cerium-144, an acetic acid wash solution, a further air-drying location and a radiation detector. The apparatus is calibrated with known fluoride solutions.  The invention may be applied to the estimation of substances such as Be in atmospheric dust by applying vacuum to a porous pad and treating the absorbed solids with a solvent for the substance to be detected: other applications mentioned are phosphate in urine and chloride in tap water.