In this second part of a multi-paper series, we present results from outdoor aerial measurements of surrogate distributed gamma-ray sources. We detail the design, manufacture, and testing of 300 individual ~7 mCi Cu-64 sealed sources at the Washington State University research reactor, and their deployment in various source patterns (each comprising up to 100 point sources) during the aerial measurement campaign. We show the results of two such measurements, in which approximate source shapes and qualitative source intensities can be seen from the count rate vs. position plots, even without performing reconstructions. We also detail our efforts in ground-truthing the deployed sources and comparing measured gamma ray data to model predictions. In particular we compare measured vs. expected count data using the Poisson deviance formalism of Part I to evaluate whether the fielded surrogate point-source arrays “look like” their truly continuous distributed source analogues. More generally, we find that the point-source array technique provides high source placement accuracy, relative ease of quantifying the true source configuration, scalability to source dimensions of ≲100 m, ease of reconfiguration and removal, and relatively low dose to personnel. Finally, we consider potential improvements and generalizations of the point-source array technique for future measurement campaigns.

Bromine-82, Potassium-42 and Copper-64 have been successfully adopted as radioactive surrogates for outdoor large area contamination training. The goal of this project was to discover new materials that could supplement potassium bromide (KBr) and copper pellets in radiological dispersal device (RDD) training events to reduce the down time of the training fields and to broaden the toolbox of the RDD surrogates at Idaho National Laboratory. Of the ten different materials investigated, sodium nitrite, gallium metal, and gallium oxide presented the greatest promise due to their ability to meet or exceed selection criteria: half-lives (between 10 and 36 h), limited impurities (99.9%), and favorable National Fire Protection Agency (NFPA) rating.

We demonstrate a method for using arrays of point sources that emulate -- when measured from a standoff of at least several meters -- distributed gamma-ray sources, and present results using this method from outdoor aerial measurements of several planar arrays each comprising up to $100$ ${\sim}7$ mCi Cu-64 sealed sources. The method relies on the Poisson deviance to statistically test whether the array source ''looks like'' its continuous analogue to a particular gamma-ray detector given the counts recorded as the detector moves about 3D space. We use this deviance metric to design eight different mock distributed sources, ranging in complexity from a $36\times36$ m uniform square grid of sources to a configuration where regions of higher and zero activity are superimposed on a uniform baseline. We then detail the design, manufacture, and testing of the ${\sim} 7$ mCi Cu-64 sealed sources at the Washington State University research reactor, and their deployment during the aerial measurement campaign. We show the results of two such measurements, in which approximate source shapes and qualitative source intensities can be seen. Operationally, we find that the point-source array technique provides high source placement accuracy and ease of quantifying the true source configuration, scalability to source dimensions of ${\lesssim}100$ m, ease of reconfiguration and removal, and relatively low dose to personnel. Finally, we consider potential improvements and generalizations of the point-source array technique for future measurement campaigns.

Quantification of low-activity noble gases in air is typically accomplished through separation of the noble gas from air followed by radiometric assay. This work is aimed at quantification of radioactive noble gas in air without extraction. A high pressure aluminum Marinelli counting vessel was designed and fabricated that can be placed on a coaxial high purity germanium detector for gamma counting. Characterization of the performance of this Marinelli using MCNP modeling, large excesses of activity, and low-activity noble gas in air is discussed. Minimum detectable concentrations achieved during a 24 h count are: 5, 10, 50, and 1 Bq/m3 for 133Xe, 133mXe, 131mXe, and 135Xe, respectively.

Research is underway to develop instruments and methods to determine the activity of radionuclides present in the fallout debris from the detonation of a radiological dispersal device (RDD). Handheld instruments, including commonly used health physics survey instruments, have been incorporated into a portable telemetry kit containing a global positioning system receiver, WiFi and radio communications, and a small microcomputer to facilitate data processing, logging, and transmission. An operator carries the system and walks through the RDD post-blast environment, real-time radiological data is logged, stored locally, and transmitted to a base station outside of the RDD hot zone. A map of the distributed radiological dispersal is generated, subdividing the world into 1-m(2) squares. Separate measurements of ground activity taken at a finite number of discrete locations is used to cross-correlate the survey data, transforming the health physics data (e.g., mrem hr(-1)) to surface activity (Bq m(-2)). The map data, smoothed using standard Kriging approaches, is then analyzed by summing each discrete square area, producing an estimate for the total dispersed ground activity. The instrumentation and method have been field tested multiple times at Idaho National Laboratory during field exercises using short-lived radionuclides detonated in small-scale experiments.

Cs-135/Cs-137 isotope ratios can provide the age, origin and history of environmental Cs contamination. Relatively high precision Cs-135/Cs-137 isotope ratio measurements from samples containing femtogram quantities of (CS)-C-137 are needed to accurately track contamination resuspension and redistribution following environmental Cs-137 releases; however, mass spectrometric analyses of environmental samples are limited by the large quantities of ionization inhibitors and isobaric interferences which are present at relatively high concentrations in the environment. We report a new approach for Cs purification from environmental samples. An initial ammonium molybdophosphate-polyacrylonitrile (AMP-PAN) column provides a robust, selective method for extracting Cs under a wide variety of sample matrices and mass loads. Application of a novel cation exchange separation approach using AMP-PAN results in more than two orders of magnitude greater Cs/Rb separation factors than commercially available strong cation exchangers. Final sample purification using a microcation column (AG50W resin) enables consistent 2-4% (2 sigma) measurement errors for samples containing 3-6000 fg Cs-137, representing the highest precision (CS)-C-135/Cs-137 ratio measurements currently reported for soil samples at the femtogram level. Published by Elsevier B.V.

Four of the radioactive xenon isotopes ((131m)Xe, (133m)Xe, (133)Xe and (135)Xe) with half-lives ranging from 9 h to 12 days are produced from nuclear fission and can be detected from days to weeks following their production and release. Being inert gases, they are readily transported through the atmosphere. Sources for release of radioactive xenon isotopes include operating nuclear reactors via leaks in fuel rods, medical isotope production facilities, and nuclear weapons' detonations. They are not normally released from fuel reprocessing due to the short half-lives. The Comprehensive Nuclear-Test-Ban Treaty has led to creation of the International Monitoring System. The International Monitoring System, when fully implemented, will consist of one component with 40 stations monitoring radioactive xenon around the globe. Monitoring these radioactive xenon isotopes is important to the Comprehensive Nuclear-Test-Ban Treaty in determining whether a seismically detected event is or is not a nuclear detonation. A variety of radioactive xenon quality control check standards, quantitatively spiked into various gas matrices, could be used to demonstrate that these stations are operating on the same basis in order to bolster defensibility of data across the International Monitoring System. This paper focuses on Idaho National Laboratory's capability to produce three of the xenon isotopes in pure form and the use of the four xenon isotopes in various combinations to produce radioactive xenon spiked air samples that could be subsequently distributed to participating facilities.

Fractionation of the two longer-lived radioactive cesium isotopes ((135)Cs and (137)Cs) produced by above ground nuclear tests have been measured and used to clarify the dispersal mechanisms of cesium deposited in the area between the Nevada Nuclear Security Site and Lake Mead in the southwestern United States. Fractionation of these isotopes is due to the 135-decay chain requiring several days to completely decay to (135)Cs, and the 137-decay chain less than one hour decay to (137)Cs. Since the Cs precursors are gases, iodine and xenon, the (135)Cs plume was deposited farther downwind than the (137)Cs plume. Sediment core samples were obtained from the Las Vegas arm of Lake Mead, sub-sampled and analyzed for (135)Cs/(137)Cs ratios by thermal ionization mass spectrometry. The layers proved to have nearly identical highly fractionated isotope ratios. This information is consistent with a model where the cesium was initially deposited onto the land area draining into Lake Mead and the composite from all of the above ground shots subsequently washed onto Lake Mead by high intensity rain and wind storms producing a layering of Cs activity, where each layer is a portion of the composite.

There are multiple paths by which radioactive cesium can reach the effluent from reactor operations. The radioactive (135)Cs/(137)Cs ratios are controlled by these paths. In an effort to better understand the origin of this radiation, these (135)Cs/(137)Cs ratios in effluents from three power reactor sites have been measured in offsite samples. These ratios are different from global fallout by up to six fold and as such cannot have a significant component from this source. A cesium ratio for a sample collected outside of the plant boundary provides integration over the operating life of the reactor. A sample collected inside the plant at any given time can be much different from this lifetime ratio. The measured cesium ratios vary significantly for the three reactors and indicate that the multiple paths have widely varying levels of contributions. There are too many ways these isotopes can fractionate to be useful for quantitative evaluations of operating parameters in an offsite sample, although it may be possible to obtain limited qualitative information for an onsite sample.

The primary objective of this study was to test the effectiveness of a two-step solvent extraction-precipitation process for separating transmutation and fission products from irradiated beryllium. Beryllium metal was dissolved in nitric and fluoroboric acids. Isotopes of (241)Am, (239)pu, 85 sr, (60)Co, and (137)Cs were then added to make a surrogate beryllium waste solution. A series of batch contacts was performed with the spiked simulant using chlorinated cobalt dicarbollide and polyethylene glycol diluted with sulfone to extract the isotopes of Cs and Sr. Another series of batch contacts was performed using a combination of octyl (phenyl)-N,N-diisobutylcarbamoylmethylphosphine oxide in tributyl phosphate diluted with dodecane for extracting the isotopes of Pu and Am. The (60)Co was separated by first forming a cobalt complex and then selectively precipitating the beryllium as a hydroxide. The results indicate that >99.9% removal can be achieved for each radionuclide. Transuranic isotope contamination levels are reduced to <100 nCi/g, and sources of high beta-gamma radiation ((60)co, (137)Cs, and (90)Sr) are reduced to levels that will allow the beryllium to be contact handled. The separation process may be applicable to a recycle or waste disposition scenario.