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Abstract  

An intercomparison exercise has been carried out on the measurement of237Np in a sample of sea-born sediment taken from the estuary of the River Esk in Cumbria, United Kingdom. The sediment had been contaminated by radioactive liquid discharges from the nuclear fuels reprocessing plant at Sellafield. The measure of agreement between the submitted values was such that one would accept with confidence237Np analyses reported by the participating laboratories. The exercise was arranged by the Analysts' Informal Working Group (AIWG). The AIWG is a small group of chemists from several Government laboratories in the United Kingdom having an interest in radionuclides in the environment. From time-to-time the Group arranges intercomparison exercises; these exercises are in addition to the members' normal quality assurance schemes, and in addition to intercomparison exercises arranged by other organizations. So far as the authors are aware, there has been no report of such an exercise involving237Np, and there appear to be no natural matrix reference materials available for environmental237Np.

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Abstract  

The Standard Reference Material 4351 from the National Institute of Standards and Technology is acknowledged to be inhomogeneous. The value of a single analysis for239Pu+240Pu could lie within a wide range, but the accuracy of the analysis can be corroborated by comparing the corresponding238Pu/239Pu+240Pu or240Pu/239Pu values with the relationships between these ratios and the total plutonium concentration.

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Journal of Radioanalytical and Nuclear Chemistry
Authors:
K. Inn
,
W. Liggett
,
H. Volchok
,
M. Feiner
,
J. Mcinroy
,
D. Popplewell
,
D. Percival
,
R. Wessman
,
V. Bowen
,
H. Livingston
,
R. Kathren
, and
H. Kawamura

Abstract  

An international laboratory intercomparison of actinides in human tissues was organized by the United States Transuranium Registry and the National Institute of Standards and Technology. Five laboratories from the United States, United Kingdom, and Japan participated in the intercomparison. The laboratories were requested to analyze Standard Reference Materials 4351 (Human Lung) and 4352 (Human Liver) for239Pu and240Pu concentration. Approximately equivalent measurement capabilities were generally found among the participants. The results of this intercomparison were statistically comparable to those used for the original certification of the SRM's and were combined for a re-evaluation of the certified values. The combined data sets provide a better characterization of the inhomogeneity of these reference materials and result in a better basis for certification.

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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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