Wikipedia:Reference desk/Archives/Science/2014 February 15

= February 15 =

Can't neutrinos kill you?
If they can be detected, they must interact with matter. Could not a sufficient number kill you by interacting with your body? Thanks. μηδείς (talk) 02:34, 15 February 2014 (UTC)
 * Randall has addressed this question in some detail. --Trovatore (talk) 02:37, 15 February 2014 (UTC)
 * Thanks. To save everyone a lot of reading (unless you want to check his math, or argue for the sake of it) he gives the lethal distance as 2.3 AU, which gives a 4 Sievert dose.  I assume that's an LD50 figure. μηδείς (talk) 03:38, 15 February 2014 (UTC)
 * I would guess that it's more of a guess. It's basically impossible for us to produce a neutrino flux that deposits any measurable amount of energy in human tissue, so there is no way to evaluate the relative biological effectiveness experimentally.  --Trovatore (talk) 03:46, 15 February 2014 (UTC)


 * The paper he uses as a reference is available online. The energy of neutrinos released in supernovae is (apparently) known as is the number of neutrinos released. From this, assuming they move out in all directions in a spherical shape, you can calculate the number of neutrinos per unit of surface area at a given distance from the center of the supernova. Then he uses another paper to determine the dose equivalence. Obviously subjecting test subjects to supernova-levels of neutrino flux would be impossible as well as unethical, but we know what interactions can occur, the cross sections for those processes (the probability that they will occur), and the linear energy transfer resulting from the interaction. The only real guess in the process is for the quality factor, used to determine the dose in sieverts. The sievert is used to decouple the type of radiation from the effect: 1 Sv of x-rays should have the same effect as 1 Sv of neutrons. The LD50 is actually around 4.8 Sv according to Orders of magnitude (radiation). 2.3 AU is the distance from a supernova at which the neutron flux would be theoretically lethal. To get the actual lethal fluence, you can use the equations and values from the papers. For 15 MeV neutrinos, you get a dose equivalent per fluence of around 3.8*10-22 microsieverts cm2, so to get 4.8 Sv, you would need a fluence of ~1.26*1028 neutrinos/cm2, equivalent to around 6 billion years of the solar neutrino flux Earth experiences. Mr.Z-man 06:50, 15 February 2014 (UTC)
 * So, what sort of timescale are we talking about here? That is, how long would it take this flood of neutrinos to kill you? -- Auric    talk  17:16, 15 February 2014 (UTC)
 * If 4.8 sieverts is an LD50 (median lethal dose) i.e., low enough that half the people exposed survive it, then it would take from a day or so to a month, as has happened with people exposed to blue flashes in industrial accidents. See radiation poisoning.  Death could be pretty much instantaneous at higher doses due to widespread disruption of cell membranes causing nervous and muscular failure.  And if the heat generated is high enough you will simply cook from the inside. μηδείς (talk) 17:54, 15 February 2014 (UTC)
 * Do not skip the top ref... it's a great read. I mean, this is priceless: which is brighter,
 * "A supernova, seen from as far away as the Sun is from the Earth, or
 * The detonation of a hydrogen bomb pressed against your eyeball?"
 * Wnt (talk) 22:22, 15 February 2014 (UTC)


 * Some interesting facts from our blue flash article (Daghlian received 5.1 sieverts, Kelley received about 7-10 times the median lethal dose):


 * On 21 August 1945, Los Alamos scientist Harry K. Daghlian, Jr. suffered fatal radiation poisoning and died 25 days later[6] after accidentally dropping a tungsten carbide brick onto a sphere of plutonium, which was later nicknamed the demon core. The brick acted as a neutron reflector, bringing the mass to criticality. This was the first known criticality accident causing a fatality.[7]


 * On 21 May 1946, another Los Alamos scientist, Louis Slotin, accidentally irradiated himself during a similar incident (called the "Pajarito accident" at the time) using the same sphere of plutonium responsible for the Daghlian accident. Slotin surrounded the plutonium sphere with two 9-inch diameter hemispherical cups of neutron-reflecting material (beryllium); one above and one below.[8] He was using a screwdriver to keep the cups slightly apart, which kept the assembly subcritical. When the screwdriver accidentally slipped, the cups closed completely around the plutonium, sending the assembly supercritical. Immediately realizing what had happened, he quickly disassembled the device, likely saving the lives of seven fellow scientists nearby. Slotin succumbed to radiation poisoning nine days later.[9]


 * On 16 June 1958, the first recorded uranium-processing–related criticality occurred at the Y-12 Plant in Oak Ridge, Tennessee. During a routine leak test a fissile solution was unknowingly allowed to collect in a 55-gallon drum. The excursion lasted for approximately 20 minutes and resulted in eight workers receiving significant exposure. There were no fatalities, though five were hospitalized for forty-four days. All eight workers eventually returned to work.[12][13]


 * On 30 December 1958, the Cecil Kelley criticality accident took place at the Los Alamos National Laboratory. Cecil Kelley, a chemical operator working on plutonium purification, switched on a stirrer on a large mixing tank, which created a vortex in the tank. The plutonium, dissolved in an organic solvent, flowed into the center of the vortex. Due to a procedural error, the mixture contained 3.27 kg of plutonium, which reached criticality for about 200 microseconds. Kelley received 3,900 to 4,900 rads according to later estimates. The other operators reported seeing a flash of light and found Kelley outside, saying "I'm burning up! I'm burning up!" He died 35 hours later.[18]


 * μηδείς (talk) 00:31, 16 February 2014 (UTC)


 * Neutrinos, they are very small.
 * They have no charge and have no mass
 * And do not interact at all.
 * The earth is just a silly ball
 * To them, through which they simply pass,
 * Like dustmaids down a drafty hall,
 * Or photons through a sheet of glass.
 * (John Updike) — Preceding unsigned comment added by 79.237.65.126 (talk) 03:00, 16 February 2014 (UTC)

Neutrinos can kill in theory despite having a very weak interaction strength, simply because whether or not a neutrino will interact is not determined, there is always a small chance that it will. If an ultra high energy neutrino of energy 10^20 eV collides with an iron nucleus in your body (an ulikely event, but it has nonzero probability), more than a joule of energy will be deposited in your body (you'll get the equivalent of an air shower triggered by an ultra high energy cosmic ray, but then inside your body instead of in the upper atmosphere). We're then talking about something of the order of a Sievert of radiation dose, which is potentially fatal. Count Iblis (talk) 12:15, 18 February 2014 (UTC)