Monitoring radiation levels in the Pacific Northwest The Fukushima Nuclear Crisis:Separating Fact from Fiction Simon Fraser University April 11, 2011 Krzysztof Starosta (SFU) The Fukushima Nuclear Crisis April 11, 2011 1 / 23
The nuclei The nuclear chart Number of protons Z Number of neutrons N Krzysztof Starosta (SFU) The Fukushima Nuclear Crisis April 11, 2011 2 / 23
Nuclear decay Nuclear decay half-life 0 1 2 3 4 T 1/2 T 1/2 T 1/2 T 1/2 131 I 137 239 Cs Pu 8 days 30 years 24100 years Krzysztof Starosta (SFU) The Fukushima Nuclear Crisis April 11, 2011 3 / 23
Nuclear fission Nuclear fission Krzysztof Starosta (SFU) The Fukushima Nuclear Crisis April 11, 2011 4 / 23
Nuclear fission Fission fragments Number of protons Z 235 U 239 Pu 232 Th 238 U Number of neutrons N Krzysztof Starosta (SFU) The Fukushima Nuclear Crisis April 11, 2011 5 / 23
Nuclear fission The nuclear chart Number of protons Z Number of neutrons N Krzysztof Starosta (SFU) The Fukushima Nuclear Crisis April 11, 2011 6 / 23
Fuel release Fresh and spent nuclear fuel Krzysztof Starosta (SFU) The Fukushima Nuclear Crisis April 11, 2011 7 / 23
Fuel release Nuclear chain reaction Krzysztof Starosta (SFU) The Fukushima Nuclear Crisis April 11, 2011 8 / 23
Fuel release Plutonium Plutonium (Pu) is a man made, radioactive, heavy element containing 94 protons. 239 Pu is produced in fuel containing 238 U. 239 Pu is the material of choice for nuclear weapons. Mixed Oxide nuclear fuel used in one of the Fukushima reactors contains Pu/U mixture. The element of Pu is highly toxic when inhaled, (less toxic when ingested). Animal studies found that an accumulated dose of a few milligram of plutonium per kilogram of tissue is lethal. Traces of Pu were reported to be found at the Fukushima site (but not talked about recently). Krzysztof Starosta (SFU) The Fukushima Nuclear Crisis April 11, 2011 9 / 23
Fission fragments release Radio-iodine 131 I 131 I is a man made radioactive isotope of Iodine. 131 I has a half life of 8 days. 131 I is an abundant fission fragment. 131 I is used in radiotherapy of cancer. 131 I is not found in the atmosphere in normal conditions. 131 I is a good indicator of radioactivity release in reactor accidents, the signal is not obstructed by background. Iodine accumulates in the thyroid, thus large scale exposure to 131 I is a potential health hazard. Krzysztof Starosta (SFU) The Fukushima Nuclear Crisis April 11, 2011 10 / 23
Fission fragments release Radioactive 137 Cs 137 Cs is a man made radioactive isotope of Cesium. 137 Cs has a half life of 30 years. 137 Cs is an abundant fission fragment. 137 Cs is used in radiotherapy of cancer and in food irradiation. 137 Cs was not present in the environment before 1940 s when fission started to be used for nuclear power releases. 137 Cs background from nuclear weapon tests and previous nuclear accidents obscures the signal from Fukushima. Contamination with 137 Cs is long lasting. Krzysztof Starosta (SFU) The Fukushima Nuclear Crisis April 11, 2011 11 / 23
Fission fragments release Nuclear weapon tests 2000 reported tests 550 atmospheric explosions Krzysztof Starosta (SFU) The Fukushima Nuclear Crisis April 11, 2011 12 / 23
Fission fragments release Fission fragments release Release depends critically on the accident scenario. Fission fragments which exists as gases, vapours, or aerosols are released first. The Three Mile Island accident released gases only, including 131 I. The explosions and fires following the Chernobyl accident resulted in a release of 6 tons of fragmented fuel along with radioactive gases. The release of 131 I from the Chernobyl was 2.4 million times larger than from the Three Mile Island accident. The crisis management at Fukushima successfully prevented large-scale radioactivity release in the past month, however, the cooling operates under emergency conditions. Krzysztof Starosta (SFU) The Fukushima Nuclear Crisis April 11, 2011 13 / 23
Radiation detection Characteristic decay spectra Blue: 137 Cs Red: 60 Co 2000 1000 500 Counts per Channel 200 100 50 20 10 5 2 200 600 1000 1400 1800 Energy [arb.] Krzysztof Starosta (SFU) The Fukushima Nuclear Crisis April 11, 2011 14 / 23
Radiation detection GEARS: Germanium detector for Elemental Analysis and Radioactivity Studies Krzysztof Starosta (SFU) The Fukushima Nuclear Crisis April 11, 2011 15 / 23
Radiation detection Background suppression Blue: shielded Red: unshielded 1460 10 4 511 1764 2611 352 293 Counts per Channel 609 728 911 970 1121 1237 10 3 10 2 91 182 236 1376 1508 1726 1847 2103 2202 2444 10 1 200 600 1000 1400 1800 2200 2600 Energy (kev) Krzysztof Starosta (SFU) The Fukushima Nuclear Crisis April 11, 2011 16 / 23
Monitoring of Fukushima releases Credits for sample collection and handling SFU Burnaby rainwater : SFU Nuclear Science graduate students Aaron Chester Rachel Ashley North Vancouver seaweed : SFU Physics Ken Myrtle Bamfield seaweed : Bamfield Marine Sciences Centre David Riddell Hana Kucera Krzysztof Starosta (SFU) The Fukushima Nuclear Crisis April 11, 2011 17 / 23
Monitoring of Fukushima releases 131 I signature in the SFU rainwater 250 352 511 March 18 Counts 150 365 50 250 352 511 March 20 Counts 150 365 50 250 352 511 March 29 Counts 150 365 50 340 380 420 460 500 540 Energy [kev] Krzysztof Starosta (SFU) The Fukushima Nuclear Crisis April 11, 2011 18 / 23
Monitoring of Fukushima releases Time profile of the 131 I signature in Burnaby rainwater 131 Specific activity of I in Burnaby rainwater Specific activity [Bq/l] 16 14 12 10 8 6 4 2 0 03/11 03/18 03/25 04/01 04/08 Date Krzysztof Starosta (SFU) The Fukushima Nuclear Crisis April 11, 2011 19 / 23
Monitoring of Fukushima releases 131 I sampling in seaweed Krzysztof Starosta (SFU) The Fukushima Nuclear Crisis April 11, 2011 20 / 23
Monitoring of Fukushima releases 131 I signature in the North Vancouver seaweed Blue: March 15 Red: March 22 250 511 Counts 150 50 250 352 365 352 511 Counts 150 50 340 380 420 460 500 540 Energy [kev] Krzysztof Starosta (SFU) The Fukushima Nuclear Crisis April 11, 2011 21 / 23
Monitoring of Fukushima releases Time profile of the 131 I signature in seaweed Specific activity [Bq/kg] 131 Specific activity of I in seaweed 500 400 300 SFU North Vancouver Bamfield Marine Science Center 200 100 0 03/11 03/18 03/25 04/01 04/08 Date Krzysztof Starosta (SFU) The Fukushima Nuclear Crisis April 11, 2011 22 / 23
Monitoring of Fukushima releases Time profile of the 131 I signature 131 Specific activity of I Specific activity [arbitrary] 25 20 15 10 rainwater seaweed NV seaweed BMSC 5 0 03/11 03/18 03/25 04/01 04/08 Date Krzysztof Starosta (SFU) The Fukushima Nuclear Crisis April 11, 2011 23 / 23