Fukushima Accident. Radioactivity Impact on the Environment

388 Pages·2013·11.42 MB·English

by  Pavel P. Povinec

1
INTRODUCTION
CHAPTER OUTLINE
1.1 FukushimaAccident 1
1.2 Sources of Radionuclides inthe Environment 5
1.3 Pacific Ocean: Hydrography Background 12
1.4 Pre-FukushimaRadionuclide Datafor thePacific
Ocean 14
References
1.1 Fukushima Accident
The Fukushima accident happened due to the
failure of the cooling system of the Fukushima
Dai-ichinuclearpowerplant(NPP)aftertheTohoku
earthquake and the subsequent unexpectedly high
tsunamiwaveson11March2011(IAEA,2011;NSCJ,
2011;NISA,2012;NERH,2012;TEPCO,2012).Dueto
the damage of the electrical network, as well as the
emergency diesel generators, it was not possible to
provide electricity to cool nuclear reactors and the
fuel storage pools, which resulted in numerous
explosions and total damage of the Fukushima
Dai-ichiNPP (Fig.1.1).
Theatmosphericradionuclidereleasesduringthe
Fukushimaaccidentwereestimatedtobethehighest
for131I(153e160PBq)and137Cs(13e15PBq)(Chino
etal.,2012).Stohletal.(2012)estimatedevenhigher
atmospheric releases for 137Cs (23e50PBq). The
discharged radioactive material, in addition to 131I
and 137Cs, also included 134Cs, 132Te, 132I, 136Cs, and
other radionuclides, as well as radioactive noble
gases (133Xe, 135Xe) (Bowyer et al., 2011). The
contribution of 134Cs was similar to that of 137Cs, as
the 134Cs/137Cs activity ratio was close to 1 (Masson
et al., 2011).
FukushimaAccident.http://dx.doi.org/10.1016/B978-0-12-408132-1.00001-2 1
Copyright(cid:1)2013ElsevierInc.Allrightsreserved.
2 Chapter 1 INTRODUCTION
The Fukushima accident was classified by the
Government of Japan on the international nuclear
and radiological event scale at the maximum level
of 7, similar to the Chernobyl accident, which
(a) (c)
(d)
(e)
(b)
Figure1.1 (aej)ViewsofthedamagedFukushimaDai-ichinuclearpowerplant.(Source:(a,b)-
Wikipedia;(cej)-ReprintedwithpermissionfromTEPCO).
Chapter1 INTRODUCTION 3
(f) (g)
(h)
(i) (j)
Figure 1.1 Continued
happened in 1986 in the former Soviet Union (pres-
ently Ukraine)(IAEA,2003; WHO, 2005).
Apart from the contamination of the Japanese
territory (Hirose, 2012; Kanai, 2012; Tanaka et al.,
2012), the Japan Sea (Inoue et al., 2012a), and the
Korean Peninsula (Herna´ndez-Ceballos et al., 2012;
Leeetal.,2012),duetoprevailingwesternwinds,the
radionuclides emitted to the atmosphere were
mainlytransportedfromFukushimaoverthePacific
Ocean(Kamen´ıketal.,2013),thentoNorthAmerica
(Bowyeretal.,2011;Biegalskietal.,2012;Diaz-Leon
et al., 2011; Sinclair et al., 2011), the Atlantic Ocean,
4 Chapter 1 INTRODUCTION
Europe (Baeza et al., 2012; Barsanti et al., 2012;
Beresfordetal.,2012;Bikitetal.,2012;Bossewetal.,
2012; Carvalho et al., 2012; Clemenza et al., 2012;
Cosma et al., 2012; Evrard et al., 2012; Ioannidou
et al., 2012; Kritidis et al., 2012; Kirchner et al., 2012;
Loaiza et al., 2012; Lujaniene´ et al., 2012a,b, 2013;
Manolopoulou et al., 2011; Perrot et al., 2012; Pham
et al., 2012; Pin(cid:1)ero Garc´ıa and Ferro Garc´ıa, 2012;
Pittauerova et al., 2011; Povinec et al., 2012a,c,
Povinec et al., 2013a,b; Tositti and Brattich, 2012),
Arctic(Paateroetal.,2012),andbackintoAsia.Inthe
beginning of April, the global atmosphere had been
labeled with Fukushima-derived radionuclides
(Herna´ndez-Ceballosetal.,2012;Massonetal.,2011;
Povinec et al., 2013a). The released radionuclides
were mostly deposited over the North Pacific Ocean
(about 80%), about 20% was deposited over Japan,
and less than about 1% was deposited over the
AtlanticandEurope(Morinoetal.,2011;Stohletal.,
2012;Yoshida and Kanda, 2012).
Except atmospheric radionuclide releases which
occurred mostly due to hydrogen explosions at the
FukushimaNPP,large amounts ofliquid radioactive
wastesweredirectlydischargedfromtheFukushima
Dai-ichi NPP into the ocean. Large volume of
contaminated water was produced during emer-
gencycoolingofreactorsusingfreshwater,andlater
also by seawater. Some of this water was uninten-
tionally discharged directly to the sea, which widely
contaminatedcoastalwatersofftheFukushimaNPP,
as reported by the Tokyo Electric Power Company
and the Ministry of Education, Culture, Sports,
Science and Technology, and other investigators
(Aoyama et al., 2012, 2013; Buesseler et al., 2011,
2012;Hondaet al.,2012;MEXT, 2012;Povinecet al.,
2012a,c, 2013b; TEPCO, 2012; Tsumune et al., 2012).
The total amounts of 137Cs directly released into the
sea have been estimated to range from 1 to 4PBq
(Dietze and Kriest, 2012; JG, 2011; Kawamura et al.,
2011;Tsumuneetal.,2012)to16.2(cid:1)1.6PBq(Rypina
etal.,2013),andto27(cid:1)15PBq(BaillyduBoisetal.,
2012). As the cooling water directly interacted with
rupturednuclearfuelrods,ithasbeenestimatedthat
0.1w1PBqof90Srhasalsobeenreleasedtotheocean
(Povinecet al.,2012b).
Chapter1 INTRODUCTION 5
Thedirectdischargeofcontaminatedwatertothe
sea has significantly elevated radionuclide concen-
trations in coastal seawater, as well as in the north-
western (NW) Pacific Ocean. The peak 137Cs values
were observed at the discharge point of the
Fukushima NPP to the sea on 30 March (47kBq/l)
and on 6 April (68kBq/l) (TEPCO, 2012). Several
papers have already discussed 134Cs and 137Cs
concentrations in surface waters of the NW Pacific
Ocean. In the open ocean, the 137Cs activity
concentrations ranged from a few millibecquerels
per liter to a few becquerels per liter (Aoyama et al.,
2012;Buesseleretal.,2011, 2012;Hondaetal.,2012;
Inoue et al.,2012b;Povinec et al., 2013b).
1.2 Sources of Radionuclides in the
Environment
There are five main sources of radionuclides that
could be found in the environment prior to the
Fukushima accident:
1. Natural: cosmogenic radionuclidesdresults of
interactions of cosmic rays with atoms in the
atmosphere and their subsequent deposition on
the Earth and the ocean surface (e.g. 3H, 7Be,
10Be, 14C,26Al, 53Mn, etc.).
2. Natural: primordial radionuclides (e.g. 40K, 238U,
232Th) and their decay products (e.g. 226Ra, 230Th,
etc.)foundintheEarth’scrust;duetoradonemana-
tion,itsdecayproductsarealsofoundintheatmo-
sphere,andthenafterdeposition,intheterrestrial
andmarineenvironments(e.g.210Po,210Pb,etc.).
3. Anthropogenic: global fallout radionuclidesd
produced during atmospheric tests of nuclear
weapons (e.g. 3H, 14C, 90Sr, 137Cs, Pu isotopes,
241Am,etc.).
4. Anthropogenic:radionuclidesreleasedfromnuclear
installationsdmostly from reprocessing nuclear
facilities(e.g.3H,14C,90Sr,99Tc,129I,137Cs,etc.).
5. Anthropogenic:radionuclidesreleasedduringthe
Chernobyl accident which occurred in 1986 (e.g.
137Cs,Pu isotopes, etc.)
Thelargestamountofradionuclides(w950PBqof
137Cs) released to the atmosphere up to now,
6 Chapter 1 INTRODUCTION
representing the main source of anthropogenic
radionuclidesintheworldocean,hasbeen,however,
global fallout resulting from atmospheric tests of
nuclearweaponscarriedoutmainlyinthe1950sand
the early the 1960s (Livingston and Povinec, 2002;
UNSCEAR,1993,2008).Althoughglobalfalloutisthe
dominant source of anthropogenic radionuclides in
the environment, large quantities of radioactive
materials released to the atmosphere and coastal
watersfollowinganuclearaccidentattheFukushima
Dai-ichi NPP increased considerably the 137Cs
concentrationsincoastalseawateroffFukushimaup
toeightordersofmagnitudeabovetheglobalfallout
background(TEPCO,2012;MEXT,2012).
We shall focus in this book only on a few anthro-
pogenicradionuclides,specificallyonthose,thathave
beenfrequentlystudiedaftertheFukushimaaccident
both in the atmosphere and in the marine environ-
ment(Table1.1).Although131Iwasreleasedafterthe
Fukushima accident in largest amounts, it does not
represent a radionuclide frequently studied in the
terrestrial and marine environment due to its short
half-life (T ¼8.02days). The most important
1/2
radionuclideintheFukushimacaseis137Cs,asitwas
releasedinlargequantities,andithasarelativelylong
half-life(T ¼30.17years).
1/2
Therelativelyshort-livedisotopeofcesium(134Cs,
T ¼2.06years) because of its shorter half-life has
1/2
alsonotbeenfrequentlystudiedintheenvironment;
however,oneadvantageofitsshorterhalf-lifeisthat
itcanclearlyidentifycesiumofFukushimaorigin,as
there is no remaining contribution from global
fallout and the1986 Chernobyl accident.
Anthropogenic tritium and 129I have been recog-
nized as ideal short-term (3H half-life T ¼
1/2
12.32years) and long-term (129I half-life T ¼15.7
1/2
Million years) atmospheric and oceanographic
tracers, important for investigation of circulation
processes in the atmosphere and the ocean, as well
as for the study of atmosphereeocean exchange
processes(Houetal.,2000;Povinecetal.,2010,2011;
Raisbeck and Yiou,1999; Schlosser et al.,1999).
137Cshasbeenrecognizedradiologicallyasoneof
the most important long-lived radionuclides of
anthropogenicorigin, whichhasaccumulatedinthe
Table 1.1. Anthropogenic Radionuclides of Interest in the
Environment After the Fukushima accident
Radiation Used
Radionuclide Half-Life for the Detection Energy (keV) Detection Method
3H 12.32years Beta 18.6 Beta-spectrometry,3Heingrowth
massspectrometry
89Sr 50.6days Beta 1492 Beta-spectrometry
90Sr 28.15years Beta 546(oringrowth90Y:2284) Beta-spectrometry
99Tc 2.14•105years Beta 294 ICPMS
129I 1.57•107years Beta 151.2 AMS
131I 8.02days Gamma 364;606.3 Gamma-spectrometry
133Xe 8.24days Beta 346.3 Beta-gamma-spectrometry
Gamma 80.99
134Cs 2.06years Gamma 604.69;795.84 Gamma-spectrometry
137Cs 30.17years Gamma 661.66(137mBa) Gamma-spectrometry
238Pu 87.74years Alpha 5499 Alpha-spectrometry
239Pu 2.411•104years Alpha 5156 Alpha-spectrometry1,AMS
240Pu 6563years Alpha 5168 Alpha-spectrometry1,AMS
241Pu 14.4years Beta 20.8 Beta-spectrometry
AMS,acceleratormassspectrometry;IPCMS,inductivelycoupledplasmamassspectrometry.
1Simultaneous239,240Puanalysis.
8 Chapter 1 INTRODUCTION
Figure 1.2 Recordof137Csinatmosphericaerosolsand14Cinatmosphericcarbondioxidein
centralEurope(Bratislava,Slovakia)duringthepre-Fukushimatime.(AdaptedfromPovinecetal.,
2012a,c).
terrestrial and marine environment, and it is still
measurable in the atmosphere as well (Livingston
andPovinec,2000,2002).137Cstogetherwith14Chas
beenthemostfrequentlystudiedradionuclideinthe
atmosphere. Figure 1.2 shows as an example the
typical137Cslevelsobservedinatmosphericaerosols
(and 14C levels in atmospheric carbon dioxide) in
Central Europe(Bratislava, Slovakia)during thepre-
Fukushimatime (Povinec et al.,2012b).
137Cs has been considered to be the most impor-
tantforthelong-termradiologicalimpactbecauseof
largereleases,relativelylonghalf-life,anditsrelative
high bioavailability. Because of its accumulation in
tissues,ithasbeenimportantfordeliveringradiation
dosestothepublicfromtheconsumptionofseafood
(Aarkroget al.,1997).
The most dominant source of 137Cs in the atmo-
sphere,thebiosphereandtheoceanhasbeenglobal
fallout originating from the atmospheric nuclear
weapons testing (Table 1.2). Its main input into the
oceanoccurredin1963andafterwardduetothewet
and dry deposition of 137Cs, after large-scale atmo-
spheric nuclear weapons tests, which were carried
outduring1961e1962bytheformerSovietUnionat
Table 1.2. Pre-Fukushima Anthropogenic Radionuclide Inventories
and Releases in the Atmosphere and Ocean (in PBq)
Discharges from
Global Fallout Inventory Reprocessing
inthe Ocean2 Facilities2 Chernobyl
Total
Global inventory Inventory
Natural Fallout in the in2010 in Total Inventory
Nuclide Inventory1 Atmosphere1 ocean theocean inventory in2010 Atmosphere3 Ocean2
3H 2200 113,000 8000 410 45
90Sr 600 380 105 7 4 1
129I 0.6(cid:3)10(cid:4)3 0.3(cid:3)10(cid:4)3 0.3(cid:3)10(cid:4)3 0.04 0.04 0.013(cid:3)10(cid:4)3
131I e e e 39 e 1760
137Cs e 950 600 170 40 26 85 16
1UNSCEAR,2008.
2IAEA,2005(onlydischargesintotheseafromtheSellafield(UK)andLaHague(France)nuclearreprocessingfacilities).
3IAEA,2003.
10 Chapter 1 INTRODUCTION
Figure 1.3 Integrateddepositiondensityof90Srfromglobalfallout.(AdaptedfromIAEA,2005).
Novaya Zemlya in the Kara Sea (Livingston and
Povinec, 2002).
The major deposition of 137Cs occurred in the
midlatitudes of the northern hemisphere, similar to
thecase of 90Sr (Fig. 1.3,IAEA,2005).
The largest depositions due to specific meteoro-
logicalconditionswereobserved,however,intheNW
Pacific Ocean (Aoyama et al., 2006). The NW Pacific
Oceanhasthereforebeenwellknownastheareawith
thehighestdepositionofglobalfalloutradionuclides
into the ocean (Povinec et al., 2005; Inomata et al.,
2009). Because of its huge size, the Pacific Ocean
capturedabout52%of137Cs.TheAtlanticOceangot
33%,theIndianOceangot14%,andtheArcticOcean
gotonly 1% (and similarly, e.g. for 90Sr).
Large amounts of 137Cs were also released from
nuclear reprocessing facilities in Sellafield (situated
on the western coast of England) and in La Hague
(situated in the English Channel) (Table 1.2), which
have mainly impacted the European seas, as shown
inFig. 1.4 (Povinec et al.,2003b).
137Cshasbeenthemostabundantanthropogenic
radionuclide in the marine environment, as docu-
mentedinFig.1.5.WhiletheIrishSeaandtheNorth
Sea have been mostly influenced by the discharges
from the Sellafield and the La Hague reprocessing
facilities,137CsintheBalticSeaandtheBlackSeahas