Ionizing radiation. Quantities matter! 5000 msv kills half of those exposed (LD 50). Natural background: 3 msv/year. Ionizing radiation

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1 Ionizing radiation This is different than electromagnetic fields from power lines or cell phones, where the energy per photon is too low to affect chemical bonds. Ionizing radiation refers to photons and particles with energies above 3 10 ev! What s easy to calculate? Energy absorbed per mass. The SI unit is the Gray (named after a British radiation biologist): 1 Gray=1 Joule/kg. Older unit: 1 rad=1 erg/g, with 1 Gray=100 rad. Different radiations α (helium nuclei), β (electrons), γ (photons) and neutrons have slightly different Relative Biological Effectiveness or RBE. RBE factors range from around 1 to around 10 for the most part. 1 Sievert=(1 Gray) RBE, and 1 REM=(1 Rad) RBE (REM=Röntgen Equivalent Man). To get some numbers out there: 5000 msv kills half of those exposed (LD 50). Natural background: 3 msv/year. Quantities matter!

2 Radiation in the Garden of Eden Radiation has been part of the planet since before life began. Life has evolved in the presence of ionizing radiation. We (and bacteria and earthworms and...) have repair mechanisms (DNA single-strand breakage repair) to deal with low-level radiation. Radiation from the sun: shielded in part by earth s magnetic field, and by atmosphere. Radiation from radioactive rocks, soils. Great variation! Estimated background doses in US: Florida: 2 msv/year. Northeastern Washington state: 17 msv/year. (NY Times, July 19, 2005). Cosmic ray dose with altitude: Denver (5000 ): add 0.2 msv/year to sea-level dose. Santa Fe (7000 ): add 0.45 msv/year to sea-level dose.

3 Cosmic ray flux You re getting drilled right now, right here! This figure: from Wikipedia.

4

5 Magnets do protect us! Well, the Earth s magnetic field does... The Northern Lights are telling us something! http: //srag-nt.jsc.nasa.gov/docs/tm104782/techmemo.htm

6 Radiation today Still dominated by the Garden of Eden! Natural sources 82.0% Medical X rays: 10.4% Radiation therapy: 3.8% Consumer products: 2.9% 0.9% Occupational exposure: 0.4% Fallout: 0.4% Nuclear power: 0.2% Source: 2005 BIER report (NAS).

7 Radiation deaths? Total deaths in US in 1999: 2,400,000 Heart disease: 725,000 All cancers: 550,000 (23%) Respiratory diseases: 188,000 Stroke etc.: 170,000 Accidents: 98,000 Diabetes: 69,000 How much of a role does radiation play in cancer deaths? What event can we learn from to measure this?

8 Hiroshima today I

9 Hiroshima today II

10 Hiroshima today II

11 Hiroshima and Nagasaki survivors Best data source: about 80,000 survivors of Hiroshima and Nagasaki. 41,719 received doses greater than 5 msv. Radiation dose estimated for each survivor based on location. Half of the 80,000 were still alive in 2001! Statistically, would have expected 12,000 to have died of cancer without any extra radiation exposure. About 700 extra deaths. Our best data on human risks from radiation exposure. A good summary is in The New York Times, Nov. 27, 2001.

12 Hiroshima and Nagasaki data Assume linear extrapolation from high dose data to low doses. Approximate risk due to radiation is 500 excess deaths per 100,000 people for an acute exposure of 100 msv, or 500 deaths (10 5 people) (0.1Sv) The risk is continuously being re-evaluated. Linear extrapoliation to low dose is very controversial. Frequent s by a panel at the National Academy of Sciences ( Latest is Health risks from exposure to low levels of ionizing radiation: BEIR VII - Phase 2.

13 BIER VII risk Hiroshima and Nagasaki data summarized in the BIER VII report: Cancer Solid Range Low Dose Leukemia (for comparison) of Excess Relative Risk Linear fit, Sv Linear-quadratic fit, Sv Radiation Dose (Sv) FIGURE ES-1 Excess relative risks of solid cancer for Japanese atomic bomb survivors.

14 Low level risks: numbers Dose: 1 Gray=1Joule/kg of absorbed ionizing radiation. Exposure: 1 Sievert=(1 Gray) RBE, where the Relative Biological Effectiveness (RBE) for X rays is 1. Radioactive isotopes: Curies or Becquerels measure decays per second, and when coupled with half-life they tell you the number of radioactive nuclei. These units get mixed up all the time In news reporting of the Fukushima reactors following the Tsunami in Japan, you d see statements like the reactor released 100 msv of radiation. What they should have said was the reactor released X Curies of 137 Cs, and the exposure to people 1 km downwind is estimated at 100 msv/hour or something to that effect. Lethal acute dose in people: around 5,000 msv. Between cosmic rays, radioactivity in rock and soils, and medical diagnostics, we receive a dose of about 3 4 msv per year. APS experimental floor: less than msv/hour, or 0.3 msv/year.

15 Airline flights New York Times, June 12, Dose can be msv/hour at altitude. See also

16 Airport scanners Use Compton scattering from 60 kev X rays, scanned across the body. 1 absorption length is about 5 cm. UK Departument of Transport ( assessment-of-comparative-ionising-radiation-rapiscan-security-scanner): The effective dose from one scan from an x-ray backscatter unit (single or double scan) is 0.02 micro Sv [ msv] or less (worst case scenario). Effective dose is a quantity that integrates radiation dose across the whole body. See also ( which goes over the physics and estimates a skin dose of to msv using 120 kev. Again, dose in flight is more like msv per hour.

17 Spaceflight Shuttle: 0.05 msv/day in low orbit (160 nautical miles), 1.2 msv/day in highest orbit (330 nautical miles, like in STS-31 to deploy Hubble Space Telescope). Apollo: about 12 msv during the nine day mission. Skylab: about 180 msv during 87 days. Solar flares: was one in August 1972, between Apollo 16 and 17. Dose if during a spacewalk or on lunar surface would have been 40,000 msv (fatal!). Dose in command module would have been 4,000 msv (about LD 50 ). Mars trip: maybe 1,300 msv over 2.5 years, but greater fraction of heavy ions. If every neuron in your brain gets hit, do you come back being a blithering idiot, or not? asked Dr. Derek I. Lowenstein, the chairman of Brookhaven s collider accelerator department. (NY Times, Dec. 9, 2003). Another set of estimates:

18 Further examples Accidental FedEx shipment: 100 msv/hour at package exterior. FedEx shipped a high radiation package, New York Times, Jan. 10, 2002, p. A22. Dirty bombs: Use conventional explosives to disperse radioactive material (such as from medical sources). Will likely produce a small-area hotspot (some cleanup possible) plus a large area with very sparse, dispersed particles. Inhalation of dispersed particles can be particularly problematic: very low whole-body dose, but very high local dose to a small region in the lung, possibly inducing lung cancer. Do you really want to shut down the port of Seattle because you don t want to get 5 or 10 millirem of dose? [=0.05 or 0.10 msv]. U.S. plans to offer guidance for a dirty-bomb aftermath, New York Times, Sep. 17, 2004, p. A20.

19 Tokaimura accident Nuclear fuel reprocessing: take used fuel rods and extract 239 Pu produced by neutron irradiation of 238 U to obtain more fissionable material. Reprocessing plant in Tokaimura, Japan, September 30, 1999: accidental accumulation of a critical mass in one vessel (liquid solution). A Slow Death: 83 Days of Radiation Sickness (H. Iwamoto, Vertical Press, New York, 2008): They were on their seventh bucket. When [Hisashi] Ouchi s colleague started pouring the last of the uranium solution, Ouchi heard a loud smack accompanied by a blue light... See

20 Tokaimura II

21 Tokaimura III All ran from room. Ouichi then vomited and lost consciousness. 24 Na detected in vomit, due to neutron activation. Chromosomal analysis indicates about 18,000 msv dose. Day 11: tracheotomy performed. Day 59: cardiac arrest. Day 83: dies. Masato Shinohara: dose of 6,000-10,000 msv. Conscious and stable 3 months later, but died on day 211. Yutaka Yokokawa: dose of 2,500 msv. Released from hospital December 1999, 2.5 months after accident.

22 Goiânia, Brazil, September 1987 Cancer therapy clinic abandoned but therapy source left in place: 137 Cs, 2000 Ci in 1971, 1375 Ci in Dose rate at 1 meter: 4,600 msv/hour. Squatters and scavengers occupy the abandoned buildilng. Irradiation source partly dismantled. Cool! What s that blue glow? Source sold to a junkyard owner who thought he might make a ring for his wife. Source gets broken up. People started to get sick; junkyard owner s wife brought remains of source to a doctor at a hospital; accident response kicks in two weeks after initial incident. Squatters who sold source to junkyard: one has arm amputated due to radiation burns. Two junkyard workers die. Junkyard owner s wife dies. Six-year-old child dies; sat on floor with radioactive dust; buried in a lead-lined coffin. For more detail, see and links therein.

23 Radiation exposure examples Accidental FedEx shipment: 100 msv/hour at package exterior. FedEx shipped a high radiation package, New York Times, Jan. 10, 2002, p. A22. Dirty bombs: Use conventional explosives to disperse radioactive material (such as from medical sources). Will likely produce a small-area hotspot (some cleanup possible) plus a large area with very sparse, dispersed particles. Do you really want to shut down the port of Seattle because you don t want to get 5 or 10 millirem of dose? [=0.05 or 0.10 msv]. U.S. plans to offer guidance for a dirty-bomb aftermath, New York Times, Sep. 17, 2004, p. A20.

24 This figure from Georgia State s Hyperphysics web site Ionizing radiation Curve of binding energy Here s the curve of binding energy shown inverted, so that nuclei like to roll up the hill. Notice the bumps near magic numbers 2 [2, 8, 20, 28, 50, 82, 126]; these are analogous to closed electron shells with atoms (i.e., noble gases).

25 (Wikipedia)

26 Nuclear waste disposal Nuclear waste is hot and nasty stuff (the scale at left tops off at 10 4 TBq, or = decays/sec). However, it s compact and contained. Note how 137 Cs with a half life of 30 years dominates the activity at first. U.S. does not yet have an agreed-upon, operating permanent repository for high level waste. There are both technical questions (how do you guarantee containment for millions of years?) and political ones.

27 Three Mile Island Two nuclear power reactors near Harrisburg, Pennsylvania. TMI-2 began operating on March 28, March 16, 1979: release of the movie The China Syndrome, about a near-meltdown of a nuclear power plant. On Wednesday, March 28, 1979, 4:00 am (one year after plant operations began): hiccup in water flow to core. Cooling system automatically shut down. Pressure release valve opened, but then stayed open. Emergency water feed pumps kicked in, but valves from them to the core had been closed for a test 42 hours before! By 7 am, the water level drops below the tops of fuel rods and an emergency is declared. Enormous national press attention. Release of about 13 MCi of radioactive noble gases. However, only about 15 Curies of chemically reactive gas released: 137 Cs.

28 TMI site

29 TMI schematic

30 TMI consequences Cleanup of TMI-2: 1979 to 1993, costing about $1 Billion. TMI-1 began operating again in Maximum cumulative dose someone would have received at plant boundary was 1 msv. Average dose to 2 million people in vicinity of the plant: 0.02 msv (compare with average background dose of 3 msv/year). See No excess cancer risk has been found in population near Three Mile Island. See Normal cancer rate found near Three Mile Island, New York Times, Nov. 1, 2002, p. A25.

31 Chernobyl accident Chernobyl reactor: graphite moderator with water cooling. With water reactors, loss of coolant means the loss of the moderator and the reaction shuts off. Not so with graphite... Recall that with graphite moderators, one can have poisoning of the reaction by buildup of 135 Xe in the graphite as long as the power is low. April 26, 1986, in Kiev during the last few years of the Soviet Union. Test of turbines used to power coolant system done at 1 am. Water pumps turned up to high (extra neutron moderation) which necessitated removal of control rods to an unallowed degree. Low power operation led to 135 Xe poisoning, or excess neutron absorption. Water pumps turned off; 135 Xe burns off; reactor heats up; control rod tubes get warped from heat so they can t be inserted. Reactor power increases from 0.2 to 30 gigawatts. Fuel rods melt, and steam blows off roof. All of this takes place over about 43 seconds.

32 Chernobyl II Graphite catches fire, and fire department called in. Radiation release: 100 MCi, including 2.5 MCi of 137 Cs which is in same column of periodic table as sodium so it is readily taken up by the body. 2 pm the following day (April 26): evacuation of nearby town of Pripyat ordered. April 27 (two days after accident): monitors in Sweden pick up radioactivity, and investigations point to the USSR. That night the USSR finally admits that an accident took place, but no details given til May tons of sand, lead, and boric acid in bags tossed from helicopters onto the destroyed reactor in the coming weeks. By December a crude concrete sarcophagus covers the core, but it is crumbling and unstable today...

33 From Wikipedia: Chernobyl photo

34 Chernobyl accident: continued The control room operators received fatal radiation doses. Of the firefighters, 21 received between 6,000 and 16,000 msv (20 died), 21 received between 4,000 and 6,000 msv (7 died), 55 received between 2,000 and 4,000 msv (1 died), and 140 received between 1,000 and 2,000 msv (none died). Estimates are that 24,000 people in the surrounding area received doses of around 500 msv. Some children had doses in the thyroid as high as 2,500 msv due to 137 Cs uptake. Particulates spread around a 30 km radius. Gaseous products spread throughout USSR and Europe. A French estimate is that about 670 excess cancer deaths can be expected, peaking in about 2020 (especially thyroid cancer in exposed children). For more info, see December 1986 Physics Today, or http: //en.wikipedia.org/wiki/chernobyl_disaster.

35 Fukushima International Atomic Energy Agency report: meetings/pdfplus/2011/cn200/documentation/cn200_final-fukushima-mission_report.pdf

36 Earthquake and tsunami March 11, 2011: magnitude 9 earthquake at 11:45 am local. Reactors 1 3 successfully shut down after earthquake; reactors 4 6 were down for refueling and maintenance. Tsunami arrived 46 minutes later:

37 Tsunami effects Fukushima Dai-ichi: designed to withstand tsunami waves 5.7 m high, but the tsunami that hit had a peak water height of 14 m. Three workers died from non-radiation-related injuries caused by the earthquake and tsunami. Caused loss of all instrumentation and control systems at reactors 1 4, with 1 of 12 emergency diesel generators surviving (powering units 5 6); a 13 th was down for maintenance. The seawater pumps and motors located at the intake were totally destroyed so the ultimate heat sink was lost. Units 1 and 2 lost their batteries for backup control (flooding), while Unit 3 s batteries lasted 30 hours. After about 18 hours, seawater was pumped directly into the containment vessels, effectively ruining a $5 10B investiment (corrosion).

38 Disaster strikes With no means to confirm the parameters of the plant or cool the reactor units, the three reactor units at Fukushima Dai-ichi that were operational up to the time of the earthquake quickly heated up due to the usual reactor decay heating. Despite the brave and sometimes novel attempts of the operational staff to restore control and cool the reactors and spent fuel, there was severe damage to the fuel and a series of explosions occurred. The operators were faced with a catastrophic, unprecedented emergency scenario with no power, reactor control or instrumentation, and in addition, severely affected communications systems both within and external to the site. They had to work in darkness with almost no instrumentation and control systems to secure the safety of six reactors, six nuclear fuel pools, a common fuel pool and dry cask storage facilities. International Atomic Energy Agency report: meetings/pdfplus/2011/cn200/documentation/cn200_final-fukushima-mission_report.pdf

39 Unit 1 kpa State of Reactor 1 Venting Water level measurement errors! Reactor core water level A Reactor core water level B RPV pressure A RPV pressure B Dry well pressure Suppression chamber pressure mm Earthquake Fresh water / Explosion Sea water injection am 12 pm 12 am 12 pm 12 am 12 pm 12 am 12 pm 12 am 3/11 3/12 3/13 3/14 3/15

40 Explosions Falling water levels led to parts of the core being exposed; high heat led to generation of hydrogen gas which then exploded. This happened in Units 1 3.

41 Dose rate at fence Around 30 workers received doses of between 100 and 250 msv. Three workers received radiation burns from standing in contaminated water in a turbine basement. Dose rate (msv/h) Measuring point 4 (north-west) Venting Unit 3 8:41 pm Explosion Unit 1 3:36 pm Venting Unit 3 ~1 pm 6:00 Explosion in Unit 4 6:10 Explosion in Unit 2 6:00-11:00 Fires in Unit 4 Measurements at Main Gate (south-west) Venting Unit 3 5:20? Venting Unit 2 8:35 pm 10-12:00 Smoke at Unit 1 10:45-11:30 Evacuation Unit 3? 2 Venting Unit 1 10:17,1:42pm 0 12 am 12 pm 12 am 12 pm 12 am 12 pm 12 am 12 pm 12 am 12 pm 12 am 12 pm 12 am 12 pm 12am March 12th 13th Venting Unit 3 9:20 14th Explosion Unit 3 11:01 15th 16th Time of measurement (local time) 17th Measurements at West Gate 18th Measurements by TEPCO 19th

42 Dose rate at 3 weeks From the US National Nuclear Security Agency

43 From mext.go.jp Dose rate over time

44 Dose map From mext.go.jp. Recall background dose is about 3 msv/year (or 3000 µsv/year), and LD 50 is about 5000 msv.