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 / 22
The nuclei
The nuclear chartN
um
ber
of
pro
ton
s Z
Number of neutrons N
Krzysztof Starosta (SFU) The Fukushima Nuclear Crisis April 11, 2011 2 / 22
Nuclear decay
Nuclear decay half-life
T1/2 T1/2T1/2 T1/2
8 days
30 years
24100 years
0 1 2 3 4
Pu
Cs
I131
137
239
Krzysztof Starosta (SFU) The Fukushima Nuclear Crisis April 11, 2011 3 / 22
Nuclear fission
Nuclear fission
Krzysztof Starosta (SFU) The Fukushima Nuclear Crisis April 11, 2011 4 / 22
Nuclear fission
Fission fragmentsN
um
ber
of
pro
ton
s Z
Number of neutrons N
U235
Pu239
238U
232Th
Krzysztof Starosta (SFU) The Fukushima Nuclear Crisis April 11, 2011 5 / 22
Nuclear fission
The nuclear chartN
um
ber
of
pro
ton
s Z
Number of neutrons N
Krzysztof Starosta (SFU) The Fukushima Nuclear Crisis April 11, 2011 6 / 22
Fuel release
Fresh and spent nuclear fuel
Krzysztof Starosta (SFU) The Fukushima Nuclear Crisis April 11, 2011 7 / 22
Fuel release
Nuclear chain reaction
Krzysztof Starosta (SFU) The Fukushima Nuclear Crisis April 11, 2011 8 / 22
Fuel release
Plutonium
Plutonium (Pu) is a man made, radioactive, heavy element containing94 protons.
239Pu is produced in fuel containing 238U.
239Pu is the material of choice for nuclear weapons.
Mixed Oxide nuclear fuel used in one of the Fukushima reactorscontains Pu/U mixture.
The element of Pu is highly toxic when inhaled, (less toxic wheningested).
Animal studies found that an accumulated dose of a few milligram ofplutonium per kilogram of tissue is lethal.
Traces of Pu were reported to be found at the Fukushima site (but nottalked about recently).
Krzysztof Starosta (SFU) The Fukushima Nuclear Crisis April 11, 2011 9 / 22
Fission fragments release
Radio-iodine 131I
131I is a man made radioactive isotope of Iodine.
131I has a half life of 8 days.
131I is an abundant fission fragment.
131I is used in radiotherapy of cancer.
131I is not found in the atmosphere in normal conditions .
131I 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 131I isa potential health hazard.
Krzysztof Starosta (SFU) The Fukushima Nuclear Crisis April 11, 2011 10 / 22
Fission fragments release
Radioactive 137Cs
137Cs is a man made radioactive isotope of Cesium.
137Cs has a half life of 30 years.
137Cs is an abundant fission fragment.
137Cs is used in radiotherapy of cancer and in food irradiation.
137Cs was not present in the environment before 1940’s when fissionstarted to be used for nuclear power releases.
137Cs background from nuclear weapon tests and previous nuclearaccidents obscures the signal from Fukushima.
Contamination with 137Cs is long lasting.
Krzysztof Starosta (SFU) The Fukushima Nuclear Crisis April 11, 2011 11 / 22
Fission fragments release
Nuclear weapon tests
∼2000 reported tests ∼550 atmospheric explosions
Krzysztof Starosta (SFU) The Fukushima Nuclear Crisis April 11, 2011 12 / 22
Fission fragments release
Fission fragments release
Release depends critically on the accident scenario.
Fission fragments which exists as gases, vapours, or aerosols arereleased first.
The Three Mile Island accident released gases only, including 131I.
The explosions and fires following the Chernobyl accident resulted ina release of 6 tons of fragmented fuel along with radioactive gases.
The release of 131I from the Chernobyl was 2.4 million times largerthan from the Three Mile Island accident.
The crisis management at Fukushima successfully preventedlarge-scale radioactivity release in the past month, however, thecooling operates under emergency conditions.
Krzysztof Starosta (SFU) The Fukushima Nuclear Crisis April 11, 2011 13 / 22
Radiation detection
Characteristic decay spectra
Blue: 137Cs Red:60Co
200 600 1000 1400 1800Energy [arb.]
2
5
10
20
50
100
200
500
1000
2000
Cou
nts
per
Cha
nnel
Krzysztof Starosta (SFU) The Fukushima Nuclear Crisis April 11, 2011 14 / 22
Radiation detection
GEARS: Germanium detectorfor Elemental Analysis and Radioactivity Studies
Krzysztof Starosta (SFU) The Fukushima Nuclear Crisis April 11, 2011 15 / 22
Radiation detection
Background suppression
Blue: shielded Red: unshielded
200 600 1000 1400 1800 2200 2600Energy (keV)
10 1
10 2
10 3
10 4
Cou
nts
per
Cha
nnel
1460
1764 26
11
2444
2202
2103
1847
511
60935
229
323
618
2
1121
1237
1376
970
911
728
1726
1508
91
Krzysztof Starosta (SFU) The Fukushima Nuclear Crisis April 11, 2011 16 / 22
Monitoring of Fukushima releases
131I signature in the SFU rainwater
50
150
250
Cou
nts
50
150
250
Cou
nts
340 380 420 460 500 540Energy [keV]
50
150
250
Cou
nts
365
352 51
1
365
352 51
1
365
352 51
1
March 18
March 20
March 29
Krzysztof Starosta (SFU) The Fukushima Nuclear Crisis April 11, 2011 17 / 22
Monitoring of Fukushima releases
Time profile of the 131I signature in Burnaby rainwater
Date03/11 03/18 03/25 04/01 04/08
Sp
ecif
ic a
ctiv
ity
[Bq
/l]
0
2
4
6
8
10
12
14
16
I in Burnaby rainwater131Specific activity of
Krzysztof Starosta (SFU) The Fukushima Nuclear Crisis April 11, 2011 18 / 22
Monitoring of Fukushima releases
131I sampling in seaweed
Krzysztof Starosta (SFU) The Fukushima Nuclear Crisis April 11, 2011 19 / 22
Monitoring of Fukushima releases
131I signature in the North Vancouver seaweed
Blue: March 15 Red: March 22
340 380 420 460 500 540Energy [keV]
50
150
250
Cou
nts
50
150
250
Cou
nts
365
352
511
352
511
Krzysztof Starosta (SFU) The Fukushima Nuclear Crisis April 11, 2011 20 / 22
Monitoring of Fukushima releases
Time profile of the 131I signature in seaweed
Date03/11 03/18 03/25 04/01 04/08
Sp
ecif
ic a
ctiv
ity
[Bq
/kg
]
0
100
200
300
400
500SFU North Vancouver
Bamfield Marine Science Center
I in seaweed131Specific activity of
Krzysztof Starosta (SFU) The Fukushima Nuclear Crisis April 11, 2011 21 / 22
Monitoring of Fukushima releases
Time profile of the 131I signature
Date03/11 03/18 03/25 04/01 04/08
Sp
ecif
ic a
ctiv
ity
[arb
itra
ry]
0
5
10
15
20
25rainwater
seaweed NV
seaweed BMSC
I131Specific activity of
Krzysztof Starosta (SFU) The Fukushima Nuclear Crisis April 11, 2011 22 / 22
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