We report on the first measurements of short-lived gaseous fission products detected outside of Japan following the Fukushima nuclear releases, which occurred after a 9.0 magnitude earthquake and ...tsunami on March 11, 2011. The measurements were conducted at the Pacific Northwest National Laboratory (PNNL), (46°16′47″N, 119°16′53″W) located more than 7000 km from the emission point in Fukushima Japan (37°25′17″N, 141°1′57″E). First detections of
133Xe were made starting early March 16, only four days following the earthquake. Maximum concentrations of
133Xe were in excess of 40 Bq/m
3, which is more than ×40,000 the average concentration of this isotope is this part of the United States.
► First measurements of radioactivity detected outside of Japan following the nuclear reactor accident. ► High level description of the accident and the use of noble gas as an isotope that can be detected long range. ► Determination of the inventory of xenon-133 released from the accident.
Systems designed to monitor airborne radionuclides released from underground nuclear explosions detected radioactive fallout across the northern hemisphere resulting from the Fukushima Dai-ichi ...Nuclear Power Plant accident in March 2011. Sampling data from multiple International Modeling System locations are combined with atmospheric transport modeling to estimate the magnitude and time sequence of releases of 133Xe. Modeled dilution factors at five different detection locations were combined with 57 atmospheric concentration measurements of 133Xe taken from March 18 to March 23 to estimate the source term. This analysis suggests that 92% of the 1.24 × 1019 Bq of 133Xe present in the three operating reactors at the time of the earthquake was released to the atmosphere over a 3 d period. An uncertainty analysis bounds the release estimates to 54–129% of available 133Xe inventory.
•We estimate the airborne release of 133Xe from three Fukushima Dai-ichi nuclear power plants.•Combining measurements from multiple locations improves the accuracy of the release estimate.•The estimated time history of releases is consistent with reported reactor venting and explosion times.•Release of 133Xe is 92% of reactor inventory at the time of the earthquake, with a plausible range from 54% to 129%.
The March 11, 2011 9.0 magnitude undersea megathrust earthquake off the coast of Japan and subsequent tsunami waves triggered a major nuclear event at the Fukushima Dai-ichi nuclear power station. At ...the time of the event, units 1, 2, and 3 were operating and units 4, 5, and 6 were in a shutdown condition for maintenance. Loss of cooling capacity to the plants along with structural damage caused by the earthquake and tsunami resulted in a breach of the nuclear fuel integrity and release of radioactive fission products to the environment. Fission products started to arrive in the United States via atmospheric transport on March 15, 2011 and peaked by March 23, 2011. Atmospheric activity concentrations of 131I reached levels of 3.0×10−2Bqm−3 in Melbourne, FL. The noble gas 133Xe reached atmospheric activity concentrations in Ashland, KS of 17Bqm−3. While these levels are not health concerns, they were well above the detection capability of the radionuclide monitoring systems within the International Monitoring System of the Comprehensive Nuclear-Test-Ban Treaty.
A high-sensitivity multidimensional gamma-spectrometer is being developed within the shallow underground laboratory at Pacific Northwest National Laboratory (PNNL, USA). The system consists of two ...broad energy germanium detectors, inside a low-background shield, fitted with a cosmic veto system. The detector has advanced functionality, including operation in single or combined detector mode, with reductions in the cosmic background of 49.6% and Compton suppression of 6.5%. For selected radionuclides this provides increased peak identification, reductions in uncertainty of 27.6% and MDA improvements of 52.7%. The design uses commercially off-the-shelf components to provide a powerful solution for low-level nuclear measurements.
PNNL has developed two low-background gamma-ray spectrometers in a new shallow underground laboratory, thereby significantly improving its ability to detect low levels of gamma-ray emitting fission ...or activation products in airborne particulate in samples from the IMS (International Monitoring System). The combination of cosmic veto panels, dry nitrogen gas to reduce radon and low background shielding results in a reduction of the background count rate by about a factor of 100 compared to detectors operating above ground at our laboratory.
•Two new low-background gamma detectors in shallow underground laboratory at PNNL•The detectors are designed for use with the International Monitoring System•Gamma-ray background about a factor of 100 lower than our surface gamma detectors•Detection limits are about a factor of 10 lower than surface gamma detectors
The monitoring of the radioactive xenon isotopes 131mXe, 133Xe, 133mXe, and 135Xe is important for the detection of nuclear explosions. While backgrounds of the xenon isotopes are short-lived, they ...are constantly replenished from activities dominated by the fission-based production of 99Mo used for medical procedures. At present, one of the most critical locations on earth for the monitoring of nuclear explosions is the Korean peninsula where the Democratic People's Republic of Korea (DPRK) has announced that it conducted three nuclear tests between 2006 and 2013. This paper explores the backgrounds that would be caused by the medium to large scale production of 99Mo in the region of the Korean peninsula.
•Molybdenum-99 production causes emissions that impact nuclear explosion detection.•Large radioxenon emissions in the Korean peninsula significantly affect monitoring.•Radioxenon emissions below 109 Bq/d are possible but will not affect monitoring.
As the world faces a challenging future in maintaining the commercial availability of radioactive isotopes for medical use, new methods of medical isotope production are being pursued. Many of these ...are small in size and could effectively operate continuously. With the potential for much shorter retention times, a new suite of isotopes may soon be found in the environment. The authors estimate that many more aerosols containing low-level isotopes of gas/volatile origin could be detectable at short range and times, and a few at longer ranges and times as compared to those released in more common nuclear reactor operations.
•New Medical Isotope production (MIP) facilities are coming online.•Modeled novel and classical medical isotope production techniques.•MDA values have been calculated for a multidimensional gamma-spectrometer.•New MIP methods may result in the environmental detection of additional isotopes.
We report an improved SIMPLE experiment comprising four superheated droplet detectors with a total exposure of 0.42 kgd. The result yields ∼ factor 10 improvement in the previously-reported results, ...and—despite the low exposure—is seen to provide restrictions on the allowed phase space of spin-dependent coupling strengths almost equivalent to those from the significantly larger exposure NAIAD-CDMS/ZEPLIN searches.
Argon-37 is an environmental signature of an underground nuclear explosion. Producing and quantifying low-level (37)Ar standards is an important step in the development of sensitive field measurement ...instruments. This paper describes progress at Pacific Northwest National Laboratory in developing a process to generate and quantify low-level (37)Ar standards, which can be used to calibrate sensitive field systems at activities consistent with soil background levels. This paper presents a discussion of the measurement analysis, along with assumptions and uncertainty estimates.
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