NIST DEVELOPS LOW-LEVEL RADIONUCLIDE SEAWEED: SRM 4356.

In collaboration with the International Committee on Radionuclide Metrology (ICRM), NIST is leading an international group of experienced laboratories in the development of a unique seaweed standard reference material for low-level radionuclides in seaweed specimens. Seaweed is one of the most important oceanic biological sinks for a number of long-lived radionuclides, and accurate determination of the radionuclides in seaweed specimens is essential for improving geokinetics modeling and assessing the spread of radionuclide waste repository contamination. However, lack of a seaweed standard for method validation and quality control in analytical measurements limits the reliability of the current analytical results and the data comparability among national and international laboratories. An interlaboratory comparison among experienced radioecology metrology laboratories will determine the massic activities of [Sr.sup.90], [Ra.sup.226], [Th.sup.230], [Th.sup.232], [U.sup.234], [U.sup.238], [Pu.sup.238], [Pu.sup .(239+240)], and [Cm.sup.(243+244)] using a variety of radiochemical procedures and detection methods. Statistical techniques, including analysis of variance, data distribution fitting, and bootstrap analysis, will be used for the evaluation of the analytical results.