Search Results

You are looking at 1 - 10 of 28 items for :

  • Author or Editor: J. Smith x
  • Chemistry and Chemical Engineering x
  • Refine by Access: All Content x
Clear All Modify Search

Abstract  

The determination of bromine in biological material by thermal neutron activation analysis using instrumental [Ge(Li)] and radiochemical separation techniques is described. The radiochemical method is ten times more sensitive (0.4 ng) than the instrumental technique but both may be used for analysis of the majority of human tissue samples. Both techniques are rapid, simple, accurate and may be used for batch analysis.

Restricted access

Abstract  

Robust sample handling and liquid scintillation counting (LSC) procedures have been developed to routinely monitor tritium in the field relative to the 20,000 pCi/L drinking water standard. This procedure allows tritium to be monitored hourly during 24 hour drilling operations at depths in the saturated zone potentially contaminated by sub-surface nuclear weapons testing at the Nevada Test Site. Using retrofitted, shock hardened, vibration damped counters and strict analytical protocols, tritium may be measured rapidly in the field under hostile conditions. Concentration standards and dead tritium backgrounds are prepared weekly in a central laboratory and delivered to remote drilling locations where they are recounted daily as a check on counter efficiency and calibration. Portable LSC counters are located in trailers and powered off a battery pack and line filter fed by mobile generator. The samples are typically groundwaters mixed with drilling fluids returned after circulation through a drill string. Fluids are aerated and de-foamed, filtered, mixed with scintillation cocktail and dark adapted before counting. Real-time monitoring affords drilling and field personnel early warning against intercepting down-gradient plumes of radioactivity. For routine operations, the tritium activity may not exceed a 10,000 pCi/L threshold.

Restricted access

Abstract  

A survey of the mercury content of the diet in the Glasgow area is described. A higher intake of mercury (60 μg/day/person) than that expected is found. However, there does not appear to be any concentration of mercury by man. None of the foodstuffs show any exceptional mercury content. Fish levels are similar to other foods and a preliminary sample of shellfish from the Clyde estuary, a contaminated area, shown no sign of their having concentrated mercury to any significant degree.

Restricted access

Abstract  

Inductively coupled plasma-mass spectrometry (ICP-MS) was used to concurrently determine multiple long-lived (t1/2>104 y) actinide isotopes in soil leachates. Ultrasonic nebulization was found to maximize instrument sensitivity. Instrument detection limits for actinides in solution ranged from 50 mBq L–1 (239Pu) to 2Bq L–1 (235U). Hydride adducts of232Th and238U interfered with the determinations of233U and239Pu; thus, extraction chromatography was used to concentrate the analytes and separate uranium from the other actinides in advance of mass spectrometric determination. Alpha spectrometric determinations of230Th,239Pu, and the234U/238U activity ratio in soil leachates compared well with ICP-MS determinations; however, there were some small systematic differences (ca. 10%) between ICP-MS and -spectrometric determinations of234U and238U activities. These differences were attributed to the use of different isotope dilution spikes for ICP-MS and -spectrometry.

Restricted access

Abstract  

This paper describes the measurement of210Bi by Cerenkov counting in a commercial liquid scintillation counter. The counting efficiency in water is 0.17 counts per second per Becquerel (17%). When the enhancers Triton X-100 (15% v/v) and sodium salicylate (1% m/v) are added to the solution the counting efficiency for210Bi increases from 17% to 75%. The210Po daughter of210Bi causes interference of 0.85 counts per second per Becquerel in the presence of the enhancers but not in water. When210Bi and210Po are present in secular equilibrium the total counting efficiency is 160%. When210Bi and210Po are not in secular equilibrium the210Po can be removed immediately before counting by plating onto silver foil. The use of the enhancers gives a substantial increase in counting efficiency compared to counting in water. Compared with solutions used in liquid scintillation counting the enhancer solution is inexpensive and can be disposed of without environmental hazard.

Restricted access

Abstract  

A method for measuring radium activity using electrodeposition onto stainless steel from solutions to which platinum ions have been added was developed. This gave high recovery with reduced electroplating times, and yielded deposits giving alpha-spectra of high resolution. Retention of the decay products in the deposit allows inference of some Ra isotopes from measurement of the activities of the high energy Po daughters. Application of the method to determination of226Ra in a marine manganese deposit is described.

Restricted access

Abstract  

This paper examines the process of making a decision on the optimum technique for the measurement of low concentrations of226Ra in environmental materials. The available counting techniques are alpha spectrometry, high resolution gamma spectrometry and liquid scintillation counting. The properties of the analytical technique; sensitivity, lower limit of detection (LLD) and precision are considered. Method selection is also restricted by the available sample size and activity. The influence of procedure backgrounds, geometric efficiency, chemical recovery, counting time, sample size and activity on the precision and LLD are investigated. The process of method selection, applicable to a wide range of samples, is illustrated by reference to sediments, waters and tissues.

Restricted access

Abstract  

Rare-Earth Element (REE) concentrations in briny groundwaters are very low, and range from ppb to ppt levels. REE can be measured at these low levels using prechemistry to concentrate the REE, postchemistry as an REE group separation following neutron activation, and reactivation for chemical yields. The brine solutions appear to be stable with respect to trace elements (such as the REE) over the four years of sample storage. The brine REE patterns are highly fractionated from light REE to heavy REE, including a negative Eu anomaly. The REE patterns appear to be characteristic of each formation and its source region.

Restricted access