EnvironmentalRadioactivity inNew Zealandand Rarotonga
AnnualReport2011

Citation: Ministry of Health. 2013. Environmental Radioactivity in New Zealand and Rarotonga: Annual Report2011. Wellington: Ministry of Health.

Published in May 2013 by the
Ministry of Health
PO Box 5013, Wellington 6145, New Zealand

ISBN 978-0-478-40212-4 (online)
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Acknowledgements

The Ministry of Healthgratefully acknowledges NikolausHermanspahn for his work in developing this report andthe assistance of MrBruceBuckbyofNorthWeatherLtd,Kaitaia;MrMarkCromptonofWest Weather Ltd, Hokitika; the Rarotonga Meteorological Service, in particular, MrRoro Taia;and Mr Ross Morrison of Roskat EnterprisesLtd, ChathamIslands.

The Managers of the Fonterra Te Rapa, Fonterra Whareroaand Westland Co-operativeDairyCo.(Hokitika)plantsarealsothankedfortheirassistance with themilkmonitoringprogramme.

TheEnvironmentalLaboratoryofNRL organisedthemonitoringandanalysedthe samples.

Disclaimer

The purpose of this publication is to inform discussion and assist policy development. The opinions expressed in the publication do not necessarily reflect the official views of the Ministry of Health.

The Ministry of Health makes no warranty, expressed or implied, nor assumes any legal liability or responsibility for the accuracy, correctness, completeness or use of the information or data in this publication. Further, the Ministry of Health shall not be liable for any loss or damage arising directly or indirectly from the information or data presented in this publication.

The Ministry of Health welcomes comments and suggestions about this publication.

Contents

Acknowledgementsiii

Summary

Introduction

2011 monitoringprogramme

2011 monitoringresults

Atmospheric radioactivity

Radioactive deposition

Radioactivity in milk

Discussion

Quality management

List of tables

Table 1: The annual average concentrations of 7Be and 210Pb in air filters in 2011 at three monitoring stations

Table 2: Annualaverage137Csconcentrationsinmonthlymilkpowdersamples fromWaikato, TaranakiandWestlandfor2011

Environmental Radioactivity in New Zealand and Rarotonga: Annual Report 2011 1

Summary

Theatmospherewasmonitoredforradioactivity atKaitaia,theChathamIslandsand Rarotonga;depositedradioactivity wasmonitoredatHokitika(throughrainwater testing);andradioactivity inmilkwasmonitoredintheWaikato,Taranakiand Westland regions.

Anyartificialradioactivity continuedtobeatlevelsthatarebelowdetection thresholdsinmanycasesandsignificantlybelowlevelsthatwouldgiveriseto healthconcerns.Inparticular,noradioactivecontaminationfromthe Fukushima DaiichinuclearaccidentwasobservedintheNewZealandenvironment.No significantchangein theradioactivitystatus of theenvironmentoccurred in2011.

Introduction

TheNationalRadiationLaboratory (NRL)hasmonitoredenvironmental radioactivity levelsintheNewZealandandSouthPacificregionssince1960,as describedinearlierreportsinthisseries.[1],[2]Monitoringwasinitiallyconductedfor radioactive falloutfromnuclear weaponstestsinthe northernhemisphereand thenforfalloutfromthe Frenchnuclear weaponstesting programmeinthe TuamotuArchipelago.WhentheFrenchatmosphericradiationtesting programme wasterminatedin1974,monitoring continuedforresiduesfromatmospherictests and to detect anyventing from theundergroundtests.

By 1985,levelsofweapons-testdebrisintheatmosphereandrainwaterhad decreased to nearthe limits of detection forthe monitoringtechniques in useat the time,andtheextensivemonitoringnetworkwasscaleddown[3]tothreemonitoring sites–twoinNewZealand(KaitaiaandHokitika)andoneintheCookIslands (Rarotonga).Thesensitivity ofweeklyatmosphericmonitoringatthesesiteswas increased with theinstallation of150 m3/hour high volume air samplers.[4]

FollowingthesigningoftheComprehensiveNuclear-Test-BanTreaty(CTBT)[5]by theUnitedNationsmembercountriesinSeptember1996,verificationoftreaty compliancebecameanimportantinternationalissue.NewZealandsignedthe CTBTon27September1996,andratifiedtheCTBTon19March1999,withthe passingof theNuclear-Test-BanAct.

ToenforcetheCTBT,theInternationalMonitoring Systemwasdesignedto provide,onaglobalscale,passivemonitoringcapableofdetectingandlocating nuclearexplosions.The four monitoring techniquesare seismic,radionuclide, infrasoundandhydro-acoustic.Theplannedradionuclidemonitoringnetwork willconsistof 80particulate radionuclide stations.These stationsaretobe distributedover39countriesandtheirterritories.Asofmid-2010,morethan60 radionuclide stationshad beeninstalled.These include stationslocated atKaitaiaand the ChathamIslands,NewZealand and Rarotonga, CookIslands.

In2000,andinaccordance withtheCTBT,themonitoring stationsatKaitaiaand RarotongawereupgradedandanewstationwascommissionedintheChatham Islands.Thesestationsarenowcapableofdaily monitoringwithagreater sensitivity resultingfromtheinstallationof900m3/hourhigh-volumeair samplers.

Inconjunctionwithradionuclide detection,meteorological“back-tracking” provides information onanyradionuclidesourcelocation through analysisofwind patternsinthepreceding daysandweeksofmeasurement.Meteorologicalstations operatingto World Meteorological Organization standards arelocated at each site.

Thepresentmonitoringprogramme,consistingofwetanddry deposition radioactivitymonitoringandthemonitoringof radioactivityinmilk,isintendedto warnofanyinfluxofradioactivityintotheNewZealandandSouthPacific regionsfromany sourceandtomonitortrendsinlevels.Themonitoring programmeprovidesthebasisforcertificationoftheradioactivity contentof foodstuffs.Italsoservesasthebasisofconsumer andcommercialadvisory servicesconcerning radioactivityandforcomparisonsoftheenvironmental radioactivitystatus of theSouth Pacific region with that ofother regions.

Tomaintainahighstandardofcapabilityinradiochemicalanalysis,NRLtakes partinquality assuranceprogrammesandinternationalanalyticalintercomparisonexercisesrunby theIAEA,theComprehensiveNuclear-Test-BanTreaty Organization(CTBTO),theNationalPhysicalLaboratory (UK)andtheUnited States Department of Energy.

Althoughtheenvironmentalmonitoringprogrammeisdesignedprimarilyto detectandmonitorlevelsofartificialradioactivity,measurementsinclude naturally occurringradioactivematerials,forcomparativeandscientificpurposes. Theatmosphericmonitoring thereforeincludesmeasurementsofconcentrationsof beryllium-7(7Be)andlead-210(210Pb)intheatmosphere.7Beisacosmogenic nuclide(a productofspallationreactionsofcosmicradiationwithintheupper atmosphere),while210Pbisadecay productofgaseousradon-222,whichdiffuses out of soil.

The1993report[6]providedfulldiscussionof trendsinatmosphericcaesium-137 (137Cs) levels,radionuclidesthatcontribute tothe measuredatmospheric beta activity,theageofaerosolscollectedintheNRL monitoringnetwork,current concentrationsof137CsinNewZealandsoilsanddietaryradiationexposuredue to fallout (both natural and artificial).

In2004,NRL stoppedmonitoring levelsofstrontium-90(90Sr)inmilk powders becausetheconcentrations had fallenbelow the detection limit and werefar below thereferencelevelof120Bq/kg.Thepresentfalloutmonitoring programme will detect anynew deposition of90Sr.

2011 monitoringprogramme

Theenvironmentalradioactivity monitoring programmecomprisedthe followingelementsduring2011.

Atmosphericradioactivity:Atmosphericmonitoring isthemostimportant componentofthemonitoring programmebecauseany radioactivepollution reaching theregionwillhavebeentransportedintheatmosphere,andthehigh-sensitivity monitoringwillprovideanearlywarningofany influxorchanging trendinenvironmentalradioactivity levels.Particulateswerecollecteddailyfrom the Kaitaia, ChathamIslands andRarotongastations.

Thestations atKaitaia,the ChathamIslandsandRarotongauseda SENYA “Snow White”airsamplertodrawairthrough2025cm2filters(3Mfilter,polypropylene BMF)ataflowrateofapproximately900 m3/hour,withadailysamplevolumeof approximately20,000m3.Thefilterswereanalysed by high-resolutiongamma spectrometry(Canberrahigh-purity n-typegermaniumBEGE5030detector)for gamma-emitting artificialandnaturalradionuclides.Theminimumdetectable concentrationforthefissionproduct,137Cs,inthedailyfilteranalysesranged from1to5 Bq/m3.

Radioactivedeposition:Thetotalbeta-activity concentrationinthedepositionwas monitoredatHokitikawithweekly (smallarearaincollector0.021m2)sample collection.ThetotalbetaconcentrationwasdeterminedatNRL usingaliquid scintillationcounter.

Thelarge-arearaincollectoratHokitikaallowedthemonitoring ofweekly depositionsof theartificial radionuclidesin rainwater.A stainlesssteelrain collector(1m2) hadanionexchangeresincolumnattachedtoitsbase.The resin retainsany cationicspeciespresentintherainwater,whichpercolatesthroughit. The column remainedattachedtothe collectorfor the1-weeksamplingperiod, afterwhichitwas returnedtoNRLforgammaspectrometric analysis.7Be measurementswereusedasaqualitycontrolfortheperformanceofthesampling system.

Radioactivity inmilk:Iodine-131(131I),caesium-134(134Cs) and137Cs concentrationsweremonitoredinmonthly samplesofdairymilkpowdersby gammaspectrometryfromthreeNewZealandregions–Waikato,Taranakiand Westland.

2011 monitoringresults

Radioactivityunitsusedthroughoutthisreportarebecquerels(Bq), millibecquerels(mBq)andmicrobecquerels(µBq):1Bq=1nuclear transformation persecond.

Theuncertaintiesreportedarestandarddeviationsofthemeanvaluesmultiplied byacoveragefactor(k)=2, providing alevel ofconfidenceof 95%.

Atmospheric radioactivity

Nosignificantconcentrationsofartificialradionuclidesweredetectedby gamma- spectroscopicanalysisofairfilterscollecteddailyfromeachmonitoringstation during2011.

7Becontinuedtobe themostsignificantradionuclidedetectedonthe airfilters during2011.210Pblevelsweresimilaratallthreemonitoringsites.Theannual averageconcentrationsof7Beand210PbontheairfiltersfromKaitaia,the ChathamIslandsandRarotongaarepresented in Table 1.

Table 1:The annual average concentrations of 7Be and 210Pb in air filters in 2011 at three monitoring stations

Sampling site / 7Be (Bq/m3) / 210Pb (Bq/m3)
Kaitaia / 3630± 41 / 99± 10
Chatham Islands / 3485± 46 / 69± 10
Rarotonga / 3892± 41 / 89.1±7.5

Neither131Inoranyotherfissionproductsweredetectedatthesestations.Typical detection limitswerein the range of1 to 5 Bq/m3for131I, 134Cs and137Cs.

Radioactive deposition

TheChristchurchearthquake22February 2011disruptedtheoperation oftheNRLenvironmentallaboratory.Thisdisruption wasmanagedby extending the samplingperiodofthelargeareacollectoruntilthelaboratory wascapableof receivingsamplesagain.Theweeklyrainwatersamplingcontinuedasper schedule. Samples werestored in Hokitika untilNRLwasreadytoaccept them.

Noartificialradionuclidesweredetectedinthedepositionsamplesby gamma- spectrometricanalysis.Thedepositionofbetaemittersfor2011atHokitikawas

485 ± 20 Bq/m2with2600mmofrainfall.Theaverageweeklydepositionwas

9.9±2.3Bq/m2.

Radioactivity in milk

The radioactivity contentofcows’ milkwasassessedby gammaspectrometric analysisofmonthly milksamplesfromthreeregions–Waikato,Taranakiand Westland.137Cswastheonly detectableartificialradionuclide.Resultsare summarised in Table 2.

Table 2:Annualaverage137Csconcentrationsinmonthlymilkpowdersamples fromWaikato, TaranakiandWestlandfor2011

Region / 137Cs(Bq/kg)
Waikato / 0.47±0.19
Taranaki / 0.72±0.37
Westland / 0.33±0.14

Discussion

DespiteinterruptiontoNRL’soperationsinChristchurchinearly 2011,the monitoringprogrammewascontinued without anysignificant disruption.

Neitherdepositionnorairmonitoringshowedanysignsofinfluxofradioactive contamination.

Caesium-137continuestobetheonlyfissionproductdetectableinmilk,andlevels continueto decreaseconsistent with observations from thelast decade.

Nosignificantchangeintheradioactivitystatusoftheenvironmentoccurredin2011.

Environmental Radioactivity in New Zealand and Rarotonga: Annual Report 2011 1

Quality management

Quality managementisanessentialfeatureofany measurementlaboratory’s operations.

InMay 2011,theEnvironmentalLaboratory’saccreditationtotheinternational standard NZS/ISO/IEC17025“Generalrequirementsfor thecompetence oftesting andcalibrationlaboratories” wasreassessedandconfirmed.Thescopeof accreditationincludesenvironmentalmonitoringandtheanalysesoffoodstuffs and waters.

During2011,theEnvironmentalLaboratoryparticipatedinfiveintercomparisonexercises,conducted bytheInternationalAtomicEnergy Agency,theBritish National PhysicalLaboratory,the ComprehensiveNuclear-Test-BanTreaty Organizationandthe USDepartmentof Energy.These exercisesinvolvedthe analyses of air filters, soil, vegetation and water.

Environmental Radioactivity in New Zealand and Rarotonga: Annual Report 2011 1

[1] Environmental RadioactivityAnnual Reports: NRL-F/48 (1971)–NRL-F/52 (1973) summarising previous results, NRL-F/54 (1974)–NRL-F/75 (1995). National RadiationLaboratory,Christchurch.

[2] Environmental Radioactivity: Fallout fromnuclear weapons tests conductedby FranceintheSouthPacificandcomparisonswithprevious testseries.Reports:NRL-F/47(1971),summarisingallmonitoringsince 1966; NRL-F/49 (1972); NRL-F/51 (1973); NRL-F/53 (1974).National RadiationLaboratory, Christchurch.

[3] NationalRadiationLaboratory.1985.EnvironmentalRadioactivity Annual Report 1984. Christchurch:National RadiationLaboratory.

[4] NationalRadiationLaboratory.1986.EnvironmentalRadioactivity Annual Report 1985. Christchurch:National RadiationLaboratory.

[5] Comprehensive Nuclear-Test-BanTreaty (CTBT) and Texton the EstablishmentofaPreparatory CommissionfortheComprehensiveNuclear-Test-Ban Treaty Organization.PreparatoryCommissionforthe Comprehensive Nuclear-Test-Ban Treaty, Vienna,1996.

[6] NationalRadiationLaboratory.1994.EnvironmentalRadioactivity Annual Report 1993. Christchurch: National RadiationLaboratory.