xenon monitoring and the comprehensive nuclear … · how large is our signal? pnnl-sa-98831 2q d...
TRANSCRIPT
PNNL-SA-98831
Dr. Theodore (Ted) W. Bowyer Laboratory Fellow
Pacific Northwest National Laboratory
Chair: CTBT Radionuclide Experts Group
Xenon Monitoring and the Comprehensive Nuclear-Test-Ban
Treaty
PNNL-SA-98831
The views expressed in this presentation do not necessarily reflect those of the Pacific Northwest National Laboratory, the US Department of
Energy, or the United States Government.
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How do you monitor (verify) a CTBT?
It is a difficult challenge to monitor the entire world for nuclear tests, regardless of size
Underground Above ground Underwater
kiloton or more), nuclear tests: Shake the ground Emit large amounts of radioactivity Make loud noises if in the atmosphere (or hydroacoustic waves if underwater)
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International Monitoring System Technologies Seismic sensors
Detecting earth movement Must separate explosions and 100+ earthquakes per day Can pinpoint the location of the event to with 1,000 km2 or better
Infrasound
Low frequency sound waves Affected by wind noise Most useful for atmospheric detonations
Hydroacoustic Underwater blasts
Expensive sensors, but only a few are needed to monitor all of the oceans (and whales) because these pressure/sound waves travel far in water
Radionuclide detection Atmospheric detonations
Huge amount of radioactivity released
Underground detonations Radioactive xenon may be released
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Topics of interest to Nuclear Professionals
Early 1990s Goal: Incredibly sensitive detection of airborne radionuclides in the atmosphere indicative of a nuclear explosion
Equipment ~106 times more sensitive than ordinary sensors 2013 status: Network ~80% completed at sensitivities needed
Issues
Specialized techniques (no commercial off the shelf technology exists) to
processes Customized technology Custom software
Negotiation of on-site inspection techniques that are effective for the detection of nuclear tests, yet do not reveal other unrelated sensitive information to inspectors
For example, national security sensitive information at a former nuclear test site
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Radionuclide Detection in the IMS
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The International Monitoring System The International Monitoring System was
established with 321 stations and consists of Seismic, Airborne radionuclide, Hydroacoustic, Infrasound
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Radionuclide Detection Fission and activation products from a nuclear explosion can be liberated into the atmosphere and detected remotely
4 1018 m3 air
133Xe produced from a 1-kiloton nuclear detonation (after 3 days) ~1016 Bq
= 10 mBq/m3
Easy to
Concentration ~ 0
Station
High Concentration Concentration ~ 0
A dense RN network is needed
PNNL-SA-98831 What Makes a Good Analyte for the Detection of Nuclear Explosions? Should be as definitive as possible
-to- No problems with interpretation
Should be possible to measure using ordinary means
Interpretation we must design idiot- (PhD-) proof technology
Must be robust and have diagnostics Systems or processes used to detect it should adhere to some fiscal reality
1993 Target was $100k per system; $1M is the current estimated cost
Radioactive xenon is the best candidate Is produced in large quantities and is the most likely to be emitted from underground Has reasonable backgrounds most places Has reasonable half-lives
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RN Stations in the International Monitoring System
Airborne radioactive debris can be in the form of radioactive particles or radioactive gases Each completely automatic IMS radionuclide station consists of either
A particulate monitoring system or
A particulate monitoring system and radioactive noble gas (xenon) system
Each IMS radionuclide station may also send the physical debris to one of 16 designated laboratories for confirmatory analysis
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PNNL-SA-98831 General Capability of IMS Radionuclide Systems
Particulates Completely automatic systems available commercially Data sent to the International Data Center Sensitive to gamma emitters only Detection sensitivities in the 1-10 µBq/m3 range Planned 80 stations (>80% complete) 24-hour collection, 24-hr of decay for Rn, then count starts Samples archived onto filter paper Some samples can be sent to a series of labs for reanalysis Measurements are quality controlled and the equipment undergoes a certification process
Noble gases (131mXe, 133Xe, 133mXe, 135Xe) Completely automatic systems available commercially Data sent to the International Data Center Sensitive only to radioactive xenon Detection sensitivities in the 0.1-1 mBq/m3 range Planned 40 stations (~75% complete) with 40 more possible 12-hr collection, followed by 24-hr count Samples archived into bottles for a short period Some samples can be sent to a series of labs for reanalysis Measurements are quality controlled and the equipment undergoes a certification process
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RN Technology General Specifications
PNNL-SA-98831 Particulates (i.e., dust and dirt with non-gaseous radionuclides)
Huge amounts of activity are released in atmospheric detonations
An Aside - Radioactive aerosols (particulates)
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RASA Aerosol Details
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Six Strip Segmented Sample Head
Lead Shield
Polyester Rolls
Drive Rollers
Filte
r Sup
ply
High Purity Germanium Detector
Aerosol collection and measurement
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RASA Filter Paper
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3M SBMF-40VF NaCl Test
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
0 0.1 0.2 0.3
Microns
Trap
ping
Effi
cien
cy
1x120
2x120
3x120
Aerosol Filter
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Radioactive Xenon Detection Systems
Radioactive xenon isotopes 131mXe, 133Xe, 133mXe, 135Xe
Large amounts produced and (likely) released from nuclear explosions Are definitive with the use of isotopic ratios
Still a complex measurement for non-specialists, though high quality, reproducible measurements can be made routinely using specialized equipment Fiscal realities
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Schematic of Xenon System
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Typical xenon monitoring system for the IMS A small chemical engineering plant with a dedicated, specialized nuclear detector
Radioactive Xenon Separation and Detection
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Radioxenon Analysis Uses Correlated Beta and Gamma Measurements
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0 100 200 300 400 500 600 7000
100
200
300
400
500
600
700
Beta Energy (keV)
Gam
ma
Ener
gy (k
eV)
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Totally unfair (but illuminating) example * If all of the activity vented from a 1 kiloton nuclear
atmosphere (1018 m3) it would yield a concentration in the atmosphere of: 5x1017 Bq / 1018 m3 = 0.5 Bq/m3
-> The detection limits of the radionuclide samplers are in the range of 1x10-5 Bq/m3
Amount of Release of Radionuclides The amount of radionuclides released can vary from <10-7 of the test to 100% of those produced
The total amount of activity produced is about 5x1017 Bq (disintegrations per second) per kiloton at t=1 day
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How Large is our Signal?
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The production of 99Mo medical isotopes needed for medical procedures around the world also produces and emits huge amounts (though at very low dose levels) of radioactive Xe Several production locations around the world
Emissions can be tracked across the world Scientific studies are underway to understand the isotopes emissions and ways to avoid or account for them
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Medical Isotope Production Effects*
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*Based on published data and assumptions about release frequency.
Daily Release (Bq) Facility 1.440E+13 Chalk River, Canada 1.600E+12 MDS Nordion, Kanata, Canada 2.500E+09 Mallinckrodt, Petten, Netherlands 4.600E+12 IRE, Fleurus, Belgium 1.300E+13 NECSA, Pelindaba, South Africa 1.665E+12 CNEA, Buenos Aires, Argentina 1.850E+12 ANSTO, Lucas Heights, Australia 7.800E+12 Batan Serpong, Indonesia 6.240E+12 RIAR, Dimitrovgrad, Russia 1.560E+12 Karpov Institute, Obninsk, Russia
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102
100
10-2
10-4
10-6
100 105
Xe-
135/
Xe-
133
X e-133m/Xe-131m
Reactor Operations
Possible Nuclear Explosion
Medical Isotope Production
Discrimination Between Types of Events
If the plume travels over a station, discrimination between event types is possible under some circumstances If 3 or 4 of the isotopes are detected above the detection levels
concentrations lower than possible to detect
Event falls clearly in one part of phase space or the other
happen because of error bars and medical isotope production
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The production of medical isotopes is similar to a nuclear explosion; unlike reactors
Irradiation of uranium, followed by dissolution as soon as possible A constant presence of radioxenon causes a background that can be
therefore the statistical precision to which we can subtract it is affected This effect persists even if the amount at the location can be calculated from stack monitoring data
133m
133 131m
135
Xenon Fog
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On-Site Inspection
Detection of radionuclides in the environment near a presumed ground zero
Isotopes targeted: 37Ar, 95Zr, 95Nb, 99Mo, 99mTc, 103Ru, 106Rh, 132Te, 131I, 132I, 131mXe, 133Xe, 133mXe and others
Techniques to detect radionuclides vary widely
Debris may be expected Above, at, or below the surface Gaseous or particulate forms At low or high levels
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Radionuclide Detection for OSI
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Xenon (and Argon) and On-Site Inspection
Radioxenon and radioargon are often considered one of the smoking guns for an on-site inspection Local (on-site) concentrations of radioactive xenon and argon noble gases are expected to be x1000s or more above remote levels, for months after the detonation
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Important Examples
DPRK-1 Detection of Xe-133 in IMS station in Yellowknife, Canada as well as report of detection of Xe-133m and Xe-133 in the ROK at low levels
DPRK-2 No detections reported
DPRK-3 Detection of Xe-131m and Xe-133 at appropriate ratios, easily observed in two IMS stations, at ~55 days following the seismic event
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Side Example - Fukushima Reactor Accident
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Detected across the IMS at >105 -106
detection level
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Summary - Challenges for the NG Community
Understanding background Atmosphere (IMS): Medical isotope production and nuclear reactors cause a xenon weather in the atmosphere Subsurface (OSI): Complex geologies, atmospheric pumping, and variable crustal elements can cause variable xenon isotopes in the background from spontaneous fission
Density The IMS needs more xenon measurement systems to maximize probability that a plume travels across a station
Data quality The current data quality of NG stations needs to be improved and cross checked it is still a relatively new technology
Data interpretation Understand all the signals, all the time when there are complex backgrounds and venting mechanisms
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