P. M. Grant

Nuclear forensics in law enforcement applications

Over the past several years, the Livermore Forensic Science Center has conducted analyses of nuclear-related samples in conjunction with domestic and international criminal investigations. Law enforcement officials have sought conventional and nuclear-forensic analyses of questioned specimens that have typically consisted of miscellaneous metal species or actinide salts. The investigated activities have included nuclear smuggling and the proliferation of alleged fissionable materials, nonradioactive hoaxes such as “Red Mercury,” and the interdiction of illegal laboratories engaged in methamphetamine synthesis.

Analysis of tetrodotoxin

Abstract Law enforcement personnel interdicted an illegal shipment of a chemical suspected to be an illicit drug. However, literature within the package indicated that the substance was actually tetrodotoxin, a potent marine neurotoxin. Analyses of the questioned samples by gas chromatography–mass spectrometry revealed no evidence for the presence of illicit drugs, but this technique was ineffectual for the identification of tetrodotoxin. Direct-inlet-probe mass spectrometry was likewise unable to characterize the chemical identity of the subject material. Electrospray-ionization mass spectrometry was implemented to successfully identify the interdicted substance as tetrodotoxin.

Solid debris collection for radiochemical diagnostics at the National Ignition Facility.

Radiochemical analysis of post-ignition debris inside the National Ignition Facility (NIF) target chamber can help determine various diagnostic parameters associated with the implosion efficiency of the fusion capsule. This technique is limited by the ability to distinguish ablator material from other debris and by the collection efficiency of the capsule debris after implosion. Prior to designing an on-line collection system, the chemical nature and distribution of the debris inside the chamber must be determined. The focus of our current work has been on evaluating capture of activated Au hohlraum debris on passive foils (5 cm diameter, 50 cm from target center) post-shot. Preliminary data suggest that debris distribution is locally heterogeneous along the equatorial and polar line-of-sights.

Nuclear forensic analysis of thorium

A comprehensive radiochemical isolation procedure and data analysis/interpretation method for the nuclear forensic investigation of Th has been developed. The protocol includes sample dissolution, chemical separation, nuclear counting techniques, consideration of isotopic parent-daughter equilibria, and data interpretation tactics. Practical application of the technology was demonstrated by analyses of a questioned specimen confiscated at an illegal drug synthesis laboratory by law enforcement authorities.

Calorimetric determination of the enthalpies of complexation of thorium(IV) with amine-N-polycarboxylic acids

Abstract The enthalpies of complexation of a number of thorium complexes with amine-N-polycarboxylic acids have been measured using titration calorimetry. Values of Δ H 101 and Δ S 101 were thus determined for nitrilotriacetic acid (NTA), N-(2-hydroxyethyl)ethylenedinitrilo-N,N′,N′-triacetic acid (HEDTA), ethylenedinitrilotetraacetic acid (EDTA) and diethylenetrinitrilopentaacetic acid (DTPA). A protonated species, ThHL, was necessary to interpret heats measured for EDTA and DTPA in low-pH solution, and thermodynamic parameters are reported for these complexes as well. Although the stability of these complexes is the result of strong entropy effects, the enthalpy values show important trends in the coordinate bonding of these species.

Development of a high‐sensitivity, computer‐controlled titration calorimeter

A highly sensitive, adiabatic titration calorimeter controlled by a personal computer is described. Operation of the entire calorimetric titration is automated, including the thermoelectric offset of the heat of stirring, the electrical calibration of the heat capacity, the addition of titrant, and the measurement of the heat of reaction. The average uncertainty in heat measurements was ≊±0.003 J for titrant additions generating 0.025 to 1.0 J of heat change in a 50‐ml sample. Calibration of the calorimeter using tris‐(hydroxymethyl) aminomethane [TRIS] gave excellent agreement with previously published values.

Solution thermodynamics of Europium−fluoride complexation

Abstract The enthalpy of formation of EuF 2+ in solution has been redetermined by titration calorimetry. Experiments at a constant ionic strength of μ = 1.0 M (NaClO 4 ), but at a variety of fluoride titrant concentrations, gave ΔH 101 =(9.61 ± 0.03) kJ/mol at 25 °C. This value is considerably lower than that previously reported in the literature. The corresponding entropy, however, is now consistent with an electrostatic model which has bcen shown to describe the behavior of a wide variety of metal-fluoride complexes.

Nuclear fission product analysis using capillary separation techniques

Capillary electrophoresis has been used to separate metal ions characteristically associated with nuclear fission. Electrokinetic injections and transient isotachophoretic techniques were employed to increase sample loading and provide on-column concentration of the analyte. On-line concentration factors of approximately 700-fold have been achieved. Indirect-UV absorbance, on-line radioactivity, and indirect laser-induced fluorescence detection were used to monitor analytes of interest. The radioactivity detector consists of a plastic scintillator and photomultiplier tube with a 4π detection geometry. The efficiency was determined to be approximately 80%, enabling samples resident in the detector window for 0.1 minutes to be reliably assayed. Detection of152Eu and137Cs was achieved at the low nCi level. Indirect fluorescence was performed with quinine sulfate as the background fluorophor with α-hydroxysobutyric acid added as a complexing agent. An argon ion laser was used as the excitation source with a diode array detector. Limits of detection for La3+, Ce3+, Pr3+, Nd3+, Sm3+, and Eu3+ were determined to be in the sub — 10 ppb range (6–11 nM) with indirect laser-induced fluorescence detection.

Note: Radiochemical measurement of fuel and ablator areal densities in cryogenic implosions at the National Ignition Facility

A new radiochemical method for determining deuterium-tritium (DT) fuel and plastic ablator (CH) areal densities (ρR) in high-convergence, cryogenic inertial confinement fusion implosions at the National Ignition Facility is described. It is based on measuring the (198)Au/(196)Au activation ratio using the collected post-shot debris of the Au hohlraum. The Au ratio combined with the independently measured neutron down scatter ratio uniquely determines the areal densities ρR(DT) and ρR(CH) during burn in the context of a simple 1-dimensional capsule model. The results show larger than expected ρR(CH) values, hinting at the presence of cold fuel-ablator mix.

Search for evidence of nuclear involvement in the fatal explosion of a “cold fusion” experiment

Forensic analyses of debris from the fatal explosion of an electrochemical “cold fusion” cell at SRI International were conducted at LLNL at the request of Cal-OSHA. One investigation focused on the possibility of conventional nuclear reaction mechanisms contributing to the total energy inventory of the incident. Selected metal components of the electrolysis apparatus were subjected to nondestructive γ-ray spectrometry with high-sensitivity, low-background Ge detector systems. The anticipated analytes in these studies were radioactivation products potentially induced in the explosion residue by either fast or thermal neutrons. The results of this investigation were negative within the temporal constraints of the incident and the analytical sensitivities of the instrumentation.