Serpentinite forms from mafic rocks through serpentinization by sea water. Main minerals include antigorite, lizardite, chrysotile, and magnetite. Forms at mid-ocean ridges and subduction zone forearc mantles
Control rods regulate nuclear fission rate in reactors using neutron-absorbing elements. Rods are inserted into reactor core to control power output and temperature. Reactivity above 1 increases reaction rate exponentially, below 1 decreases it. Modern reactors typically shutdown in two seconds for 90% reduction
Radioactive contamination is the presence of unwanted radioactive substances in environment. Sources can be natural (uranium, thorium) or man-made (nuclear accidents). Contamination produces ionizing radiation that can harm humans
Most common uranium isotope with 99.284% natural abundance. Has half-life of 1.41×1017 seconds (4.468 billion years). Produces ~40% of Earth's radioactive heat. Can be fissioned by fast neutrons but not in thermal reactors
Nuclear accident is an event causing significant consequences to people, environment or facility. Over 100 serious nuclear accidents occurred worldwide as of 2014. 57 accidents occurred since Chernobyl, 60% in USA
Scintillation counter detects radiation using light flashes produced by particles. Consists of scintillator generating photons and photodetector converting light to signal. Radiation interacts with scintillator, producing flashes proportional to energy