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Ionizing radiation• This is different than electromagnetic fields from power lines or

cell phones, where the energy per photon is too low to affectchemical bonds.

• Ionizing radiation refers to photons and particles with energiesabove 3–10 eV!

• What’s easy to calculate? Energy absorbed per mass. The SI unit isthe Gray (named after a British radiation biologist): 1 Gray=1Joule/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 BiologicalEffectiveness or RBE. RBE factors range from around 1 to around10 for the most part. 1 Sievert=(1 Gray)·RBE, and 1 REM=(1Rad)·RBE (REM=Röntgen Equivalent Man).

• To get some numbers out there:• 5000 mSv kills half of those exposed (LD50).• Natural background: ∼ 3 mSv/year.

Quantities matter!

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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 (DNAsingle-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/yearto sea-level dose. Santa Fe (7000’): add 0.45 mSv/year to sea-leveldose.

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Cosmic ray flux

You’re getting drilledright now, right here!This figure: fromWikipedia.

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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

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Radiation today

Still dominated by the Garden of Eden!Medical X rays: 10.4%

Occupational

exposure:

0.4%

Consumer products: 2.9%

Fallout: 0.4%

Nuclear

power:

0.2%

0.9%

Natural

sources

Radiation therapy: 3.8%

82.0%

Source: 2005 BIER report (NAS).

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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 eventcan we learn from to measure this?

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Hiroshima today I

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Hiroshima today II

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Hiroshima today II

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Hiroshima and Nagasaki survivors

• Best data source: about 80,000 survivors of Hiroshima andNagasaki. 41,719 received doses greater than 5 mSv. Radiationdose 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.

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Hiroshima and Nagasaki data

• Assume linear extrapolation from high dose data to low doses.Approximate risk due to radiation is 500 excess deaths per 100,000people for an acute exposure of 100 mSv, or

500 deaths(105 people) · (0.1Sv)

• The risk is continuously being re-evaluated. Linear extrapoliationto low dose is very controversial. Frequent reviews by a panel at theNational Academy of Sciences (http://www.nas.edu). Latest is“Health risks from exposure to low levels of ionizing radiation:BEIR VII - Phase 2.” http://www.nap.edu/openbook.php?isbn=030909156X

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BIER VII risk

Hiroshima and Nagasaki data summarized in the BIER VII report:

Radiation Dose (Sv)

0.0 0.5 1.0 1.5 2.0

0.0

0.5

1.0

1.5

egnaR eso

D woL

Linear fit, 0 - 1.5 SvLinear-quadratic fit, 0 - 1.5 Sv

0.0 0.5 1.0 1.5 2.0

01

23

45

6

Leukemia(for comparison)

recnaC diloS fo ksi

R evitaleR ssecxE

FIGURE ES-1 Excess relative risks of solid cancer for Japanese atomic bomb survivors.

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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 ofradioactive 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 ofradiation.” What they should have said was “the reactor released XCuries of 137Cs, and the exposure to people 1 km downwind isestimated 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 0.000 15 mSv/hour, or 0.3

msV/year.

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Airline flights

New York Times, June 12, 2001. Dose can be 0.005 mSv/hour at altitude.

See also http://www.acd.ucar.edu/Events/Meetings/HEPPA/pdf_files/Aviation_Hazards/Shea.pdf

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Airport scanners

• Use Compton scattering from ∼ 60 keV X rays, scanned across thebody. 1 absorption length is about 5 cm.

• UK Departument of Transport (http://www.dft.gov.uk/publications/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 [0.000 02 mSv] or less(worst case scenario). Effective dose is a quantity that integratesradiation dose across the whole body.”

• See also (http://www.public.asu.edu/~atppr/images/RPD-Manuscript.pdf), which goesover the physics and estimates a skin dose of 0.000 4 to 0.009 mSvusing 120 keV.

• Again, dose in flight is more like 0.005 mSv per hour.

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Spaceflight

• Shuttle: 0.05 mSv/day in low orbit (160 nautical miles), 1.2mSv/day in highest orbit (330 nautical miles, like in STS-31 todeploy 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 been40,000 mSv (fatal!). Dose in command module would have been4,000 mSv (about LD50).

• Mars trip: maybe 1,300 mSv over 2.5 years, but greater fraction ofheavy ions. “If every neuron in your brain gets hit, do you comeback being a blithering idiot, or not?” asked Dr. Derek I.Lowenstein, the chairman of Brookhaven’s collider acceleratordepartment. (NY Times, Dec. 9, 2003).

• Another set of estimates:http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20070010704_2007005310.pdf

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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 inthe lung, possibly inducing lung cancer.

• “Do you really want to shut down the port of Seattle because youdon’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 YorkTimes, Sep. 17, 2004, p. A20.

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Tokaimura accident

• Nuclear fuel reprocessing: take used fuel rods and extract 239Puproduced by neutron irradiation of 238U to obtain more fissionablematerial.

• Reprocessing plant in Tokaimura, Japan, September 30, 1999:accidental accumulation of a critical mass in one vessel (liquidsolution).

• A Slow Death: 83 Days of Radiation Sickness (H. Iwamoto,Vertical Press, New York, 2008): “They were on their seventhbucket. When [Hisashi] Ouchi’s colleague started pouring the lastof the uranium solution, Ouchi heard a loud smack accompanied bya blue light. . .”

• Seehttp://www.iaea.org/worldatom/Press/P_release/1999/jap_report.shtml

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Tokaimura II

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Tokaimura III• All ran from room. Ouichi then vomited and lost consciousness.• 24Na 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.

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Goiânia, Brazil, September 1987

• Cancer therapy clinic abandoned but therapy source left in place:137Cs, 2000 Ci in 1971, 1375 Ci in 1987. Dose rate at 1 meter:4,600 mSv/hour.

• Squatters and scavengers occupy the abandoned buildilng.Irradiation source partly dismantled. “Cool! What’s that blueglow?” Source sold to a junkyard owner who thought he mightmake a ring for his wife. Source gets broken up. People started toget sick; junkyard owner’s wife brought remains of source to adoctor at a hospital; accident response kicks in two weeks afterinitial incident.

• Squatters who sold source to junkyard: one has arm amputated dueto radiation burns. Two junkyard workers die. Junkyard owner’swife dies. Six-year-old child dies; sat on floor with radioactivedust; buried in a lead-lined coffin.

• For more detail, seehttp://en.wikipedia.org/wiki/Goiania_accident andlinks therein.

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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 YorkTimes, Sep. 17, 2004, p. A20.

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Curve of binding energyHere’s the curve of binding energy shown inverted, so that nuclei like toroll up the hill. Notice the “bumps” near magic numbers2 · [2, 8, 20, 28, 50, 82, 126]; these are analogous to closed electron shellswith atoms (i.e., noble gases).

This figure from Georgia State’s Hyperphysics web site

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(Wikipedia)

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Nuclear waste disposal• Nuclear waste is hot and

nasty stuff (the scale atleft tops off at 104 TBq,or 104 · 1012 = 1016

decays/sec). However, it’scompact and contained.Note how 137Cs with ahalf life of 30 yearsdominates the activity atfirst.

• U.S. does not yet have anagreed-upon, operatingpermanent repository forhigh level waste. Thereare both technicalquestions (how do youguarantee containment formillions of years?) andpolitical ones.

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Three Mile Island• Two nuclear power reactors near Harrisburg,

Pennsylvania. TMI-2 began operating on March28, 1978.

• March 16, 1979: release of the movie “TheChina Syndrome,” about a near-meltdown of anuclear power plant.

• On Wednesday, March 28, 1979, 4:00 am (oneyear after plant operations began): hiccup inwater flow to core. Cooling system automaticallyshut down. Pressure release valve opened, butthen stayed open. Emergency water feed pumpskicked in, but valves from them to the core hadbeen closed for a test 42 hours before!

• By 7 am, the water level drops below the tops of fuel rods and anemergency is declared. Enormous national press attention.

• Release of about 13 MCi of radioactive noble gases. However, onlyabout 15 Curies of chemically reactive gas released: 137Cs.

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TMI site

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TMI schematic

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TMI consequences

• Cleanup of TMI-2: 1979 to 1993, costing about $1 Billion. TMI-1began operating again in 1985.

• Maximum cumulative dose someone would have received at plantboundary was 1 mSv. Average dose to 2 million people in vicinityof the plant: 0.02 mSv (compare with average background dose of∼ 3 mSv/year). Seehttp://www.nrc.gov/OPA/gmo/tip/tmi.htm

• No excess cancer risk has been found in population near ThreeMile Island. See “Normal cancer rate found near Three MileIsland,” New York Times, Nov. 1, 2002, p. A25.

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Chernobyl accident

• Chernobyl reactor: graphite moderator with water cooling. Withwater reactors, loss of coolant means the loss of the moderator andthe reaction shuts off. Not so with graphite. . .

• Recall that with graphite moderators, one can have “poisoning” ofthe reaction by buildup of 135Xe in the graphite as long as thepower is low.

• April 26, 1986, in Kiev during the last few years of the SovietUnion. Test of turbines used to power coolant system done at 1 am.Water pumps turned up to high (extra neutron moderation) whichnecessitated removal of control rods to an unallowed degree. Lowpower operation led to 135Xe “poisoning,” or excess neutronabsorption.

• Water pumps turned off; 135Xe burns off; reactor heats up; controlrod tubes get warped from heat so they can’t be inserted. Reactorpower increases from 0.2 to 30 gigawatts. Fuel rods melt, andsteam blows off roof. All of this takes place over about 43 seconds.

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Chernobyl II

• Graphite catches fire, and fire department called in.• Radiation release: ∼100 MCi, including 2.5 MCi of 137Cs which is

in same column of periodic table as sodium so it is readily taken upby the body.

• 2 pm the following day (April 26): evacuation of nearby town ofPripyat ordered.

• April 27 (two days after accident): monitors in Sweden pick upradioactivity, and investigations point to the USSR. That night theUSSR finally admits that an accident took place, but no detailsgiven til May 1.

• 5000 tons of sand, lead, and boric acid in bags tossed fromhelicopters onto the destroyed reactor in the coming weeks. ByDecember a crude concrete sarcophagus covers the core, but it iscrumbling and unstable today. . .

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Chernobyl photoFrom Wikipedia:

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Chernobyl accident: continued

• The control room operators received fatal radiation doses. Of thefirefighters, 21 received between 6,000 and 16,000 mSv (20 died),21 received between 4,000 and 6,000 mSv (7 died), 55 receivedbetween 2,000 and 4,000 mSv (1 died), and 140 received between1,000 and 2,000 mSv (none died). Estimates are that 24,000 peoplein the surrounding area received doses of around 500 mSv. Somechildren had doses in the thyroid as high as 2,500 mSv due to 137Csuptake.

• Particulates spread around a 30 km radius. Gaseous productsspread throughout USSR and Europe. A French estimate is thatabout 670 excess cancer deaths can be expected, peaking in about2020 (especially thyroid cancer in exposed children).

• For more info, see December 1986 Physics Today, or http://en.wikipedia.org/wiki/Chernobyl_disaster.

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Fukushima

International Atomic Energy Agency report: http://www-pub.iaea.org/mtcd/

meetings/pdfplus/2011/cn200/documentation/cn200_final-fukushima-mission_report.pdf

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Earthquake and tsunami

March 11, 2011: magnitude 9 earthquake at 11:45 am local. Reactors1–3 successfully shut down after earthquake; reactors 4–6 were downfor refueling and maintenance. Tsunami arrived 46 minutes later:

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Tsunami effects

• Fukushima Dai-ichi: designed to withstand tsunami waves 5.7 mhigh, but the tsunami that hit had a peak water height of 14 m.

• Three workers died from non-radiation-related injuries caused bythe earthquake and tsunami.

• Caused loss of all instrumentation and control systems at reactors1–4, with 1 of 12 emergency diesel generators surviving (poweringunits 5–6); a 13th was down for maintenance.

• “The seawater pumps and motors located at the intake were totallydestroyed 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 thecontainment vessels, effectively ruining a $5–10B investiment(corrosion).

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Disaster strikes

• “With no means to confirm the parameters of the plant or cool thereactor units, the three reactor units at Fukushima Dai-ichi thatwere operational up to the time of the earthquake quickly heated updue to the usual reactor decay heating. Despite the brave andsometimes novel attempts of the operational staff to restore controland cool the reactors and spent fuel, there was severe damage to thefuel and a series of explosions occurred.”

• “The operators were faced with a catastrophic, unprecedentedemergency scenario with no power, reactor control orinstrumentation, and in addition, severely affected communicationssystems both within and external to the site. They had to work indarkness with almost no instrumentation and control systems tosecure the safety of six reactors, six nuclear fuel pools, a commonfuel pool and dry cask storage facilities.”

• International Atomic Energy Agency report: http://www-pub.iaea.org/mtcd/

meetings/pdfplus/2011/cn200/documentation/cn200_final-fukushima-mission_report.pdf

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Unit 1

State of Reactor 1kPa mm

0

100

200

300

400

500

600

700

800

900

-3000

-2500

-2000

-1500

-1000

-500

0

500

1000

1500

12 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

Venting

ExplosionEarthquake

Water level measurement errors!

Sea water injectionFresh water /

RPV pressure A

RPV pressure B

Dry well pressure

Suppression chamber pressure

Reactor core water level A

Reactor core water level B

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Explosions

Falling water levels led to parts of the core being exposed; high heat ledto generation of hydrogen gas which then exploded. This happened inUnits 1–3.

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Dose rate at fenceAround 30 workers received doses of between 100 and 250 mSv. Threeworkers received radiation burns from standing in contaminated water ina turbine basement.

0

2

4

6

8

10

12

14

12 pm 12 am

13th

12 pm 12 am

14th

12 pm 12 am

15th

12 pm 12 am

16th

12 pm 12 am

17th

12 pm 12 am

18th

12 pm 12am

19th

Do

se

ra

te (

mS

v/h

)

Time of measurement (local time)

Venting

Unit 1

10:17,1:42pm

Explosion

Unit 3

11:01

Venting

Unit 2

8:35 pm

6:00 Explosion in Unit 4

6:10 Explosion in Unit 2

6:00-11:00 Fires in Unit 4

Measurements

at West Gate

Measurements by TEPCO

Venting

Unit 3

9:20

Explosion

Unit 1

3:36 pm

?

Venting

Unit 3

8:41 pm

10-12:00 Smoke at Unit 1

10:45-11:30 Evacuation Unit 3

Venting

Unit 3

5:20 ?

Venting

Unit 3

~1 pm

Measuring point 4

(north-west)Measurementsat Main Gate(south-west)

12 am

12thMarch

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Dose rate at 3 weeksFrom the US National Nuclear Security Agency

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Dose rate over time

From mext.go.jp

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Dose map

From mext.go.jp. Recall background dose is about 3 mSv/year (or3000 µSv/year), and LD50 is about 5000 mSv.