Standard Guide for Rapid Screening of Vegetation for Radioactive Strontium Aerial Deposition
Strontium-90 is a major component of nuclear waste and is also a potential radioisotope for use as a weapon of mass destruction in a radiological dispersal device. It is a beta-emitting radioisotope with moderate half-life (~30 years). Strontium-89 is also a beta emitting radionuclide, but with a half-life of only ~50 days it is not usually present in significant quantities. If ingested the radiostrontium may deposit in the bone of an individual and thus can contribute a significant radiological dose to an affected person.
Following an explosion in which radioactive material was present, the potential exists for the material to become airborne. It will quickly attach to atmospheric particles and be deposited on surfaces as the plume passes. This guide provides a rapid procedure by which vegetation can be screened to determine if radiostrontium is present and to provide a conservative estimate of its deposition on vegetation.
This guide is intended to be used in a field portable lab, or if needed, can be performed completely in the field; therefore no hazardous chemicals are required to complete the analysis. However, an option for the use of acid in certain steps is documented in this guide.
This guide is not intended to be used for screening food products or animal feed following an accident or incident.
1.1 This guide provides a rapid procedure by which vegetation samples may be screened for surface contamination of radioactive strontium (89Sr and 90Sr, collectively referred to as radiostrontium) following an airborne radioactive dispersal event. It provides a conservative estimate of radiostrontium deposition that can be used by decision makers for immediate actions prior to obtaining definitive results from a fixed laboratory asset.
1.2 Insoluble forms of radiostrontium, such as the strontium (90Sr) titanate (SrTiO3) used in radio-isotope thermal-electric generators (RTGs), will not be measured by this method.
1.3 Non-SI units are used in the calculations of this guide for ease of use during the emergency phase of an event. The instrumentation used typically provides count rates in counts per minute (cpm) rather than per second (s-1, the SI unit), thus activity is expressed in dpm (decays per minute) rather than Bq. Additionally, US EPA protective guidelines for surface contamination are expressed in dpm/100 cm2.
1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
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