us particulate and xenon measurements made following the fukushima reactor accident

7/31/2019 US Particulate and Xenon Measurements Made Following the Fukushima Reactor Accident

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US Particulate and XenonMeasurements Made Following theFukushima Reactor Accident

1 Pacific Northwest National Laboratory, Richland, Washington, USA2 The University of Texas at Austin, Austin, Texas, USA

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INGE 2011 Yogyakarta Workshop,

Justin McIntyre1, Steve Biegalski2, Ted Bowyer1, Matt Copper1, PaulEslinger1, Jim Hayes1, Derek Haas1, Harry Miley1, J.P. Rishel1, Vincent

Woods1


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2

Views expressed here do not necessarily reflect theopinion of the United States Government, the UnitedStates Department of Energy, or the Pacific NorthwestNational Laboratory


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Event

NetworkAtmospheric Transport

Detections

Isotopic RatiosConclusions

Outline

Material in this presentation is covered in more depth in the following journal submissions.

S. Biegalski, et al., US Particulate and Xenon Measurements Made Following the Fukushima Reactor Accident, acceptedfor publication in Jour. of Envir Radioactivity, 2011

T. Bowyer, et al., Elevated Radioxenon Detected Remotely Following the Fukushima Nuclear Accident. Jour. of Envir.Radioactivity 102 (7):681-687. doi:10.1016/j.jenvrad.2011.04.009

P. Eslinger, et al., Source Term Estimation of Radioxenon Released from the Fukushima Daiichi Nuclear Reactors UsingMeasured Air Concentrations and Atmospheric Transport Modeling, to be submitted in Jour. of Envir. Radioactivity, 2011


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The March 11, 2011 9.0magnitude underseamegathrust earthquake offthe coast of Japan and

subsequent tsunami wavestriggered a major nuclearevent at the FukushimaDaiichi nuclear powerstation.

At the time of the event,units 1, 2, and 3 wereoperating and units 4, 5,and 6 were in a shutdowncondition for maintenance.

Event


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Boiling Water Reactor

Unit Design Containment Electric

Power

Thermal

Power

Fukushima

Daiichi 1

BWR-3 Mark I 460 MW 1,380 MW

Fukushima

Daiichi 2


Fukushima

Daiichi 3



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Following the Fukushima Detection

Evidence of radionuclidereleased reached theJapanese IMS station

within 2-3 days

First evidence of the plumehitting the United States

came to PNNLsexperimental equipmentabout 1 day later (March16)

Fukushima Radioactive Release Timeline


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Melbourne, FL

Charlottesville, VA

Palmer Station

Ashland, KSSacramento, CA

Oahu, HI

Sand Point, AK

Salchaket, AK

Midway Islands

Wake Island

Upi, Guam

US Radionuclide Stations + Richland, WA

Richland, WA


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Our First Results

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Xenon-133 measurementswere x450,000 our detectionlevels using a SAUNA-II

xenon measurement system

Noble gas does not wash-out, and is the first emittedfrom any possible fuel

damage

Levels persisted for weeksand isotopes were ultimatelydetected across the northern

hemisphere and around theworld

First detection of radioxenon in US at Richland WA


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U.S. stations detected bothparticulate and noble gasemitted from the event.

Initial 133Xe detections inRichland, WA (non-IMSstation) were on March 16,2011.

Several volatile radio-isotopeswere detected

Missing were severalisotopes that were highly

indicative of a nuclearexplosion

U.S. IMS Station Detections


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131I Activity Concentration


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133Xe Activity Concentration


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SCALE6/ORIGEN-ARP models were conducted to modelpredicted isotopic ratios (same models used for inventorycalculations).

Comparisons were made between model and measurements.

Good comparison adds validity to models and to

measurements.Shows that all stations are measuring the same event.

Isotopic Ratios


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133I/131I Activity Ratios(Indicative of gaseous releases)


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136Cs/137Cs isotopic activity ratio


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133Xe/131mXe isotopic activity ratioHEU Pulse


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Aerosol Observations/ Lessons LearnedAerosol Network Take Away Points

Network worked as plannedEvent was equivalent to a 20kT above-ground nuclear explosion

Indicates network is capable across at least 5 orders of magnitude for

measured concentrations

Sampling sites were able to report fission products without being overwhelmed,site closest to accident had trouble because of extremely high activity and power

outages.

Radionuclide concentration analysis clearly indicated that this was a reactor

accident/release.

Isotopes measured are consistent with a nuclear reactor

Lack of short-lived refractory isotopes indicative of a reactor

Nearby stations had significant increases in MDCs caused by this event, however

ATM allowed predictive plume hits and impact to down wind stations.

Not all of the network was affected all of the time

Need additional analysis to determine how impacted nearby stations were and

would they still be able to detect a 1kT above ground test

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Aerosol Observations/ Lessons LearnedAerosol Network Take Away Points (2)Potential improvements

Initial RASA measurements were possible before the filter was measured

Detector may need additional shielding from environmental influences

Intermittent power loss was significant at RN-38

Improved mechanisms for recovery from power loss

Takes ~3 days to get sample counted and reported

Need first look early response systems with real time measurements (e.g.,

NaI, CsI) for high activity events

Suggest the need for a emergency situation software script or state to

reduce per-sample activity (sample for 6, 12, or 24 hours)

Potential to incorporate future accident measurements into existing radiological

safety protocols (discussed at ISS-11)

Not unlike the seismic network tie in after the 2005 Tsunami

Clearly outside of the original scope of the network

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Conclusions

Radioxenon Network Take Away PointsNetwork worked as planned

Event was equivalent to a 1Mt below-ground nuclear explosion with

1% leakage

The xenon measurements made by IMS-like equipment were the

highest fidelity measurements made and far superior to what was

available post-Chernobyl

Radionuclide analysis clearly indicates that the plume was from a

nuclear reactor2 of four radioxenon isotopes were easily detected from the

Fukushima event across the globe.

Xe-135 MDC was only slightly elevated by this event, providing key

indicator of nuclear explosionImpacted stations are not blinded to underground nuclear

explosions.

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Gas Observations/ Lessons LearnedRadioxenon Take away points (2)

SAUNA dead time observed in samples with elevated count rate and wassignificant with very high count rates

Sauna dead time corrections needed

Initial high Xe levels saturated the RN-38 detector so no spectral analysis was

possibleNuclear detector electronics needs to be updated to handle high count rate

The MDC of the detector was highly effected from high memory effect

Research and implementation on reduction of memory effect necessary (in

progress).

Inconsistencies with meta-stable ratios.

Need to re-analzye data sets

Need better analysis methods (currently working on SDAT ).

Desire >2X improvement in conversion electron resolution

Xe was first observed at Richland WA which is not part of the IMS networkNeed higher density of Xe systems

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The IMS network demonstrated that it is capable of measuringand reporting radionuclides from a single event across theglobe.

Measurements were significantly above the detection limits formany systems.

Combination of atmospheric transport, radiation detection, andreactor modeling were fused to provide a picture of the event.

Careful analysis mitigates source blinding

More data analysis is required to demonstrate and further

enhance second event detection.

Conclusions


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Background slides


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Atmospheric transport modelswere run to predict transport of

radionuclides.Models predicted that most ofthe radiation traveled east.

First detections were in Japan,

Russia, and the United States.

Initial Atmospheric Transport


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PNNL Aerosol Data

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137Cs Activity Concentration


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Unit 1, 2, and 3 Xe Inventories

Combining atmospheric transport, ground measurements, and inventory

shows that between 85% and 103% of radioxenon inventory was released

from the three reactors.

us particulate and xenon measurements made following the fukushima reactor accident

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