Nuclear Technique in Forensic Science Ta-Chung Ong NCSS

What is Nuclear Forensic? Extract information from evidence –Radioactive material –What? Where? When? Isotopic composition Place of origin Age Track the material, solve the crime

Applications Homeland Security –Nuclear Weapon –Dirty Bomb Drug Law Enforcement –Thorium and methamphetamine Elemental Analysis –“Red Mercury” hoax

Homeland Security Danger of nuclear proliferation after Cold War –Soviet nuclear material (U and Pu) Lack proper security Close proximity to unfriendly nations (i.e. Iran) and terrorist organizations (i.e. Al-Qaeda) Some material seized in Germany and Czech Republic

Homeland Security Seized material as evidence –Origin determination Isotopic composition (fingerprint) Pinpoint place of production –Age determination Parent/daughter ratio Determine time of last purification

Homeland Security Isotopic Composition –Measure ratio of 234 U, 235 U, 236 U, 238 U, 239 Pu, 240 Pu, and 242 Pu –Mass Spectrometry –Match result to database of known material –Pinpoint place of production

Homeland Security Age Determination –Parent/Daughter Ratio: 234 U/ 230 Th and 235 U/ 231 Pa –Th and Pa are in small concentration Need accurate and precise separation Solvent Extraction Chromatography –Alpha and Gamma Spectroscopy

Drug Law Enforcement ThO 2 –Catalyst in the synthesis of phenylacetone (P2P) from acetic and phenylacetic acid –P2P is an intermediate in the synthesis of methamphetamine Determine source and age of ThO 2 seized in clandestine lab

Drug Law Enforcement Determine source of purified ThO 2 –No detectable U – 232 Th/ 230 Th pair (not parent/daughter!) –Calculate 238 U –Reveal composition of 232 Th and 238 U –Match result to ore database, determine ore body

Drug Law Enforcement Determine age of ThO 2 – 232 Th/ 228 Th pair (parent/daughter) – 232 Th, 228 Ra, 228 Th equilibrium (ore) –No 228 Ra in purified ThO 2 –Smaller amount of 228 Th in purified sample than ore

Elemental Analysis Elemental Composition of metal –X-ray fluorescence –Gamma and alpha spectroscopy

Elemental Analysis Example: Red Mercury hoax –Mythical ballotechnic substance (emit energetic gamma ray) –Can trigger fusion –Make portable H-bomb possible –Never have been found

Elemental Analysis Perpetration of the hoax –Existence strongly advocated by Sam Cohen, inventor of neutron bomb –Black Market and would-be terrorists Price of Red Mercury: $500,000/Kg Advertised as ballotechnic, or highly enriched uranium, or component to missile guidance system

Elemental Analysis Analysis of seized “Red Mercury” in Livermore National Lab –Brownish red liquid –X-ray fluorescence: Mostly Hg, some Cd, Ag, and Zn –Gamma Spectroscopy: Indistinguishable from background –Conclusion: Ordinary mercury!

Elemental Analysis Possible candidate for Red Mercury –Cinnabar (HgS) –HgI 2 (Red Color) –Any other mercury or mercury oxide with red pigment –Codename for something else, not mercury at all Search continues…

Conclusion Nuclear Forensic –Extract Information from seized evidence Isotopic Composition Place of origin/production Age –Provide valuable aid in criminal investigation