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Abstract  

The National Physical Laboratory is the national standards laboratory of the UK and is charged with maintaining primary measurement standards in the UK. These include standards in the field of ionising radiation and, in common with other National Standards Laboratories, NPL develops and maintains absolute standards of radioactivity. These are used to calibrate secondary standard instruments and also to prepare traceable standards of radioactivity at levels appropriate to the user community. Over the past eight years NPL has run a series of six environmental radioactivity measurement intercomparisons, aimed at evaluating the capabilities of laboratories measuring environmental radioactivity in the UK. This paper reviews the general progress made over the years by the participating laboratories with reference to those laboratories who are accredited by the United Kingdom Accreditation Service (UKAS). The first exercises made clear that (1) there was no account taken of cascade summing effects in γ-ray spectrometry measurements by many laboratories, (2) the calibration standards used, in some cases, were completely inappropriate for the work being undertaken, and (3) the nuclear decay data utilised by many laboratories (and in some cases, supplied by reputable manufactures) were either of an old vintage or incorrect. Over the years, the situation has changed somewhat in that participants are more aware of the pitfalls of measuring radioactivity. Finally, the effect that this has had on NPL's activities in the area of radionuclide metrology will also be described.

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Abstract  

The concentrations of iodine in fresh waters are known to be within the range of 0.5 to 35 ng·ml−1, much lower than in oceanic waters. The iodine concentrations, particularly that of129I which is significant from the radiation safety aspect, in public drinking waters have to be specified in order to verify the required level before distribution for domestic use. A modified version of an established method was used in the adsorption of iodine, iodate, total inorganic iodine and charcoal-adsorbable iodine using activated carbon prepared from oil palm kernel wastes. A thorough investigation of the physical properties of the activated carbon was carried out to determine its viability as an adsorbent for volatile species such as iodine. The iodine species were preconcentrated from water samples collected from wells in villages and from water intake points along rivers. The quantitative analysis of the species adsorbed was done by irradiating the activated charcoal loaded with the respective species in a neutron flux of 5.1·1012 n·cm−2·s−1 from a TRIGA MkII, nuclear reactor. Recovery experiments using spiked samples was done to provide quality assurance controls.

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Abstract  

The contents of mercury and organic mercury in various types of seafood from various location in Malaysia were determined by neutron activation analysis. Total mercury was determined by instrumental neutron activation analysis (INAA) whilst organic mercury was determined by INAA after chemical separation. Samples were digested in acid media and into the solution was added copper ion and KBr to release organic mercury compound from sulphur component of the tissue. The organic mercury was then extracted into toluene and then treated with cysteine paper to convert the compound into sub-organo-mercury from. The paper was then transferred into polyethylene vials and irradiated in the MINT TRIGA Reactor. Analytical results of organic mercury in Indian mackerel (Rastrelliger kanagurta), Spanish mackerel (Scomberomurus commersoni), shrimp (Peneaus sp.), squid (Loligo sp.) and cockle (Anadara granosa) is in the range of 45%–94% of the total mercury.

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Abstract  

A melting point measurement facility for the UK has been developed and accredited to ISO/IEC 17025 Calibration status for the determination of the liquefaction temperature of pure substances from 35 to 250°C. The facility is based upon a commercial instrument, i.e. an oil bath fitted with an aluminium block (Isotech, model 798 EHT), a precision multimeter (Isotech TTI-7), a thermocouple directly inserted in the sample under investigation and a platinum resistance thermometer (PRT) tracking the block temperature. The homogeneity of temperature bath/block was investigated and the PRT used for the traceability of the measurements was calibrated by NPL and traceable to ITS-90. The process was validated using four current LGC Certified Reference Materials (CRMs): •  Phenyl salicylate; material number: LGC2411, batch number: 001; liquefaction point: 41.85±0.05°C •  4-Nitrotoluene; material number: LGC2401, batch number: 007; liquefaction point: 51.71±0.21°C •  Benzoic acid; material number: LGC2405, batch number: 005; liquefaction point: 122.37±0.21°C •  Carbazole; material number: LGC2409, batch number: 007; liquefaction point: 245.58±0.07°C •  Different approaches were used to identify reproducible features of the melting point (time-temperature) curves of these four CRMs. Excellent correlation was observed between the certified values for the liquefaction point of the four CRMs and the temperature at the end of their respective melting point curve plateau, determined using a temperature differential approach. An uncertainty budget was derived and the expanded uncertainty at the 95% confidence interval (k=2) was found to be •  Phenyl salicylate: ±0.20°C; 4-Nitrotoluene: ±0.17°C; Benzoic acid: ±0.24°C; Carbazole: ±0.27°C

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Abstract  

The aim of this study is to investigate the contents of toxic and essential trace element such as As, Hg, Se and Zn by neutron activation analysis in coastal fishes consumed by the general population of Malaysia. The mean values of the elements analysed expressed in mg/kg fresh weight ranged 1.42–5.61, 0.06–0.42, 4.2–20.6, 0.41–1.28 for As, Hg, Zn and Se, respectively. The maximum permissible limit for As in food was set at 1.0 mg/kg under the Malaysian Food Regulations. Our results showed that consumption of coastal fishes is not permitted under the regulations, while the levels of Hg, Se and Zn were within the permissible limits. The daily dietary intake of As and Hg at 400 g and 30g respectively are still within the tolerance levels.

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Abstract  

The multi-elemental content of sixteen glass beads and eight glass samples from archeological site Sg Mas in Bujang Valley (finding from 5 th to 14 th century) were assayed by neutron activation analysis (NAA). Ten beads differed in colour and eight of them were opaque. Contents of twentyfour elements, which might be present in the samples as a flux, stabilizer, colorants or opacifier were examined. The elements Al, Br, Cl, Co, Cr, Fe, Hf, K, Mn, Na, Sc,Th, Zn and Zr were detectable in all samples. On the other hand, concentration of the elements As, Ba, Ca, Cs, Rb, Sb, Ta, Ti, U, and V were below the detection limit in some samples. The concentration of elements found are discussed in terms of color and/or opacity of the glass bead and glass samples. Although the elemental composition does not fully explain the color and opacity of the studied materials, it can still be used as fingerprint of the glass used for the bead making.

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Journal of Radioanalytical and Nuclear Chemistry
Authors:
M. Ebihara
,
Y. S. Chung
,
W. Chueinta
,
B.-F. Ni
,
T. Otoshi
,
Y. Oura
,
F. L. Santos
,
F. Sasajima
,
Sutisna
, and
A. K. B. H. Wood

Summary  

Seven Asian countries have been collaborating in collecting airborne particulate matter (APM) in their individual countries and analyzing them by neutron activation analysis as a common analytical tool. APM samples were collected into two fractions of fine and coarse grains (PM2 and PM2-10, respectively). Analytical data were compared from several viewpoints such as particulate sizes, locality of sampling sites (either urban or rural) and geographical location of participating countries. Chemical composition and their monthly variations as well as mass concentrations appear to be highly characteristic for individual sampling sites, suggesting that NAA data are suitable for evaluating the air quality in each site.

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Journal of Radioanalytical and Nuclear Chemistry
Authors:
K. Inn
,
Zhichao Lin
,
Zhongyu Wu
,
C. McMahon
,
J. Filliben
,
P. Krey
,
M. Feiner
,
Chung-King Liu
,
R. Holloway
,
J. Harvey
,
I. Larsen
,
T. Beasley
,
C. Huh
,
S. Morton
,
D. McCurdy
,
P. Germain
,
J. Handl
,
M. Yamamoto
,
B. Warren
,
T. Bates
,
A. Holms
,
B. Harvey
,
D. Popplewell
,
M. Woods
,
S. Jerome
,
K. Odell
,
P. Young
, and
I. Croudace

Abstract  

In 1977, the Low-level Working Group of the International Committee on Radionuclide Metrology met in Boston, MA (USA) to define the characteristics of a new set of environmental radioactivity reference materials. These reference materials were to provide the radiochemist with the same analytical challenges faced when assaying environmental samples. It was decided that radionuclide bearing natural materials should be collected from sites where there had been sufficient time for natural processes to redistribute the various chemically different species of the radionuclides. Over the succeeding years, the National Institute of Standards and Technology (NIST), in cooperation with other highly experienced laboratories, certified and issued a number of these as low-level radioactivity Standard Reference Materials (SRMs) for fission and activation product and actinide concentrations. The experience of certifying these SRMs has given NIST the opportunity to compare radioanalytical methods and learn of their limitations. NIST convened an international workshop in 1994 to define the natural-matrix radionuclide SRM needs for ocean studies. The highest priorities proposed at the workshop were for sediment, shellfish, seaweed, fish flesh and water matrix SRMs certified for mBq per sample concentrations of 90 Sr, 137 Cs and 239 Pu + 240 Pu. The most recent low-level environmental radionuclide SRM issued by NIST, Ocean Sediment (SRM 4357) has certified and uncertified values for the following 22 radionuclides: 40 K, 90 Sr, 129 I, 137 Cs, 155 Eu, 210 Pb, 210 Po, 212 Pb, 214 Bi, 226 Ra, 228 Ra, 228 Th, 230 Th, 232 Th, 234 U, 235 U, 237 Np, 238 U, 238 Pu, 239 Pu + 240 Pu, and 241 Am. The uncertainties for a number of the certified radionuclides are non-symmetrical and relatively large because of the non-normal distribution of reported values. NIST is continuing its efforts to provide the ocean studies community with additional natural matrix radionuclide SRMs. The freeze-dried shellfish flesh matrix has been prepared and recently sent to participating laboratories for analysis and we anticipate receiving radioanalytical results in 2000. The research and development work at NIST produce well characterized SRMs that provide the world's environment-studies community with an important foundation component for radionuclide metrology.

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