Design considerations for future radionuclide aerosol monitoring systems.

Pacific Northwest National Laboratory (PNNL) staff developed the Radionuclide Aerosol Sampler Analyzer (RASA) for worldwide aerosol monitoring in the 1990s. Recently, researchers at PNNL and Creare, LLC, have investigated possibilities for how RASA could be improved, based on lessons learned from more than 15 years of continuous operation, including during the Fukushima Daiichi Nuclear Power Plant disaster. Key themes addressed in upgrade possibilities include having a modular approach to additional radionuclide measurements, optimizing the sampling/analyzing times to improve detection location capabilities, and reducing power consumption by using electrostatic collection versus classic filtration collection. These individual efforts have been made in a modular context that might constitute retrofits to the existing RASA, modular components that could improve a manual monitoring approach, or a completely new RASA. Substantial optimization of the detection and location capabilities of an aerosol network is possible and new missions could be addressed by including additional measurements.

Using Atmospheric Dispersion Theory to Inform the Design of a Short-lived Radioactive Particle Release Experiment.

Atmospheric dispersion theory can be used to predict ground deposition of particulates downwind of a radionuclide release. This paper uses standard formulations found in Gaussian plume models to inform the design of an experimental release of short-lived radioactive particles into the atmosphere. Specifically, a source depletion algorithm is used to determine the optimum particle size and release height that maximizes the near-field deposition while minimizing both the required source activity and the fraction of activity lost to long-distance transport. The purpose of the release is to provide a realistic deposition pattern that might be observed downwind of a small-scale vent from an underground nuclear explosion. The deposition field will be used, in part, to study several techniques of gamma radiation survey and spectrometry that could be used by an On-Site Inspection team investigating such an event.

PRex: An Experiment to Investigate Detection of Near-field Particulate Deposition from a Simulated Underground Nuclear Weapons Test Vent.

A radioactive particulate release experiment to produce a near-field ground deposition representative of small-scale venting from an underground nuclear test was conducted to gather data in support of treaty capability development activities. For this experiment, a CO2-driven "air cannon" was used to inject (140)La, a radioisotope of lanthanum with 1.7-d half-life and strong gamma-ray emissions, into the lowest levels of the atmosphere at ambient temperatures. Witness plates and air samplers were laid out in an irregular grid covering the area where the plume was anticipated to deposit based on climatological wind records. This experiment was performed at the Nevada National Security Site, where existing infrastructure, radiological procedures, and support personnel facilitated planning and execution of the work. A vehicle-mounted NaI(Tl) spectrometer and a polyvinyl toluene-based backpack instrument were used to survey the deposited plume. Hand-held instruments, including NaI(Tl) and lanthanum bromide scintillators and high purity germanium spectrometers, were used to take in situ measurements. Additionally, three soil sampling techniques were investigated and compared. The relative sensitivity and utility of sampling and survey methods are discussed in the context of on-site inspection.

Physical properties of compounds promoting oral delivery of macromolecular drugs.

The spectroscopic and solution properties of a series of amidated acids (delivery agents), which promote the gastrointestinal absorption of USP heparin and other drugs that show poor oral bioavailability, are investigated using Raman and NMR spectroscopy. The results show evidence for self-association at low concentrations of delivery agents that increases as the concentration of the delivery agent is increased. The self-associate is characterized by ring-ring stacking interactions, and the best geometrical arrangement for the stacking is the parallel-shifted arrangement of the rings. In addition, the amide group participates in the formation of intermolecular hydrogen bonds in the self-associate. Unlike the rigid ring, the tails of these delivery agents remain relatively flexible in the self-associate. It is suggested that the limited solubility of the delivery agents at physiological pH arises from a percentage of protonated carboxyls. Their presence promotes the formation of intermolecular hydrophobic and ring stacking interactions, which are otherwise weakened by an ionized carboxyl group.

Interactions of amidated acids with heparin.

Raman and NMR studies are performed to characterize the solution structures of complexes between heparin and a group of amidated acids, which act as delivery agents that facilitate the gastrointestinal absorption of orally administered heparin. At concentrations typically employed for the oral drug delivery of heparin, the contact points between heparin complexed with the delivery agents include points near the OH groups of heparin. The results suggest that heparin interacts rather nonspecifically with the amidated acids as monomers and with self-associated complexes of the delivery agents. It is also found that the carboxyl groups of at least one of the bioactive delivery agents easily protonates when it forms complexes with itself or heparin. This attribute may be one reason why this class of compounds is effective in the oral delivery of heparin.