The Fukushima accident revealed that permanently installed radiation monitoring instruments at and around nuclear power plants should be able to operate on batteries for long periods of time, at least a week, with plans in place to replace or recharge them thereafter. Also, because multiple parallel pathways for releases of radiation exist, instrumentation that gives continuous readout of the quantities of radionuclides being discharged from these pathways under accident conditions would improve accuracy of the information used to support decision making. A problem anticipating which pathways will be effective is that plant damage can create new pathways that would not be obvious from the “as built” status of the plant.
Additionally, there is a need for instruments to be quickly available at and near nuclear power plant sites that can measure (i) the quantities of radioactive iodine and cesium in the plume, whether or not the plume is elevated off the ground as a result of an initial rise due to its temperature; and (ii) what the initial cross-wind dimensions of the plume are whatever the direction in which it is being blown.1 This information would be essential
1 Concepts for evaluation include (1) imaging Compton gamma-ray spectrometers (Kataoka et al., 2013), (2) drones equipped with radiation detectors capable of distinguishing gamma and beta energies (Pöllänen et al., 2009), and (3) resonance-enhanced multiphoton ionization detected by microwave scattering (Shneider and Miles, 2005; Dogariu and Miles, 2011).
initialization for atmospheric models that project dose rates and cumulative doses to the population in different directions and at different distances.2
Thus there appears to be potential for reducing uncertainty in activity estimates and forecasts of plume behavior, although dose predictions will always carry significant uncertainties. Examples of quantities whose measurement might be used to assay the quantities of radioisotopes in the plumes are the intensities, directions, and energy spectra of gamma rays from the plume and measurements of the concentration profiles of cesium and iodine in the plume, which could be far above natural background levels for these isotopes.3 The Defense Advanced Research Projects Agency (DARPA), an agency of the Department of Defense responsible for developing new technologies for use by the military, is already seeking novel approaches to low-cost, high-efficiency, packaged radiation detectors for identifying hidden threats, ranging from special nuclear material (SNM) to radiological sources (Federal Business Opportunities, 2013).
In improving capabilities of forecasting plume behavior, plants may consider extending the distance requirement for meteorological monitoring programs for providing atmospheric transport and diffusion estimates, which is currently within the 10-mile emergency planning zone (USNRC, 2007).
2 The capabilities described here would go beyond existing capabilities. Currently, state and local agencies rely on field monitoring teams and appropriate instrumentation, the specifics of which vary from site to site. These capabilities are supplemented by the Federal Radiological Monitoring and Assessment Center and other federal resources, including the U.S. Department of Energy’s capabilities to provide aerial mapping of the depositions from the plume. In addition, the U.S. Environmental Protection Agency’s Radnet monitors and monitors established by the nuclear power plants for routine environmental monitoring can provide real-time air monitoring. These instruments could be multipurpose so that they can be used for a wide variety of emergency response activities including monitoring plumes from chemical releases.
3 For example, if a release of the same magnitude as occurred at Fukushima Daiichi took place over a period of 1 to 10 hours, concentrations of 0.01 to 100 ppb of radioactive cesium and iodine would be expected near the plant depending upon the plume cross-section. Consider that a hypothetical release of cesium-137 and iodine-131 then would be 0.25 mega-curie (MCi) (2.8 kg) and 1.9 MCi (15 g), respectively. Although it would be an insignificant contributor to the dose because of its long half-life (17 million years), there also would be 17 times as much iodine-129 as iodine-131 by mass (0.26 kg). Thus, in total, there would be about 1,025 atoms of cesium and 1,024 atoms of iodine in the plume.