Carlsbad Environmental Monitoring Research Articles

GEANT4 simulations of cosmic muon background in CEMRC BEGe lung detectors and detection sensitivity optimization of trans-uranic radionuclides

In this work, we discuss two results from GEANT4 simulations of the broad-energy germanium (BEGe) lung counting system used by the Carlsbad Environmental Monitoring and Research Center (CEMRC) inte...

Sources and distribution of 241Am in the vicinity of a deep geologic repository.

The detection, distribution, and long-term behavior of 241Am in the terrestrial environment at the Waste Isolation Pilot Plant (WIPP) site were assessed using historical data from an independent monitoring program conducted by the Carlsbad Environmental Monitoring & Research Center (CEMRC), and its predecessor organization the Environmental Evaluation Group (EEG). An analysis of historical data indicates frequent detections of trace levels of 241Am in the WIPP environment. Positive detections and peaks in 241Am concentrations in ambient air samples generally occur during the March to June timeframe, which is when strong and gusty winds in the area frequently give rise to blowing dust. A study oflong-term measurements of 241Am in the WIPP environment suggest that the resuspension of previously contaminated soils is likely the primary source of americium in the ambient air samples from WIPP and its vicinity. Furthermore, the 241Am/239 + 240Pu ratio in aerosols and soils was reasonably consistent from year to year and was in agreement with the global fallout ratios. Higher than normal activity concentrations of 241Am and 241Am/239 + 240Pu ratios were measured in aerosol samples during 2014 as a result of February 14, 2014 radiation release event from the WIPP underground. However, after a brief spike, the activity concentrations of 241Am have returned to the normal background levels. The long-term monitoring data suggest there is no persistent contamination and no lasting increase in radiological contaminants in the region that can be considered significant by any health-based standard.

Source and long-term behavior of transuranic aerosols in the WIPP environment.

Source and long-term behavior transuranic aerosols ((239+240)Pu, (238)Pu, and (241)Am) in the ambient air samples collected at and near the Waste Isolation Pilot Plant (WIPP) deep geologic repository site were investigated using historical data from an independent monitoring program conducted by the Carlsbad Environmental Monitoring and Research Center and an oversight monitoring program conducted by the management and operating contractor for WIPP at and near the facility. An analysis of historical data indicates frequent detections of (239+240)Pu and (241)Am, whereas (238)Pu is detected infrequently. Peaks in (239+240)Pu and (241)Am concentrations in ambient air generally occur from March to June timeframe, which is when strong and gusty winds in the area frequently give rise to blowing dust. Long-term measurements of plutonium isotopes (1985-2015) in the WIPP environment suggest that the resuspension of previously contaminated soils is likely the primary source of plutonium in the ambient air samples from WIPP and its vicinity. There is no evidence that WIPP is a source of environmental contamination that can be considered significant by any health-based standard.

The magnitude and relevance of the February 2014 radiation release from the Waste Isolation Pilot Plant repository in New Mexico, USA

After almost fifteen years of successful waste disposal operations, the first unambiguous airborne radiation release from the Waste Isolation Pilot Plant (WIPP) was detected beyond the site boundary on February 14, 2014. It was the first accident of its kind in the 15-year operating history of the WIPP. The accident released moderate levels of radioactivity into the underground air. A small but measurable amount of radioactivity also escaped to the surface through the ventilation system and was detected above ground. The dominant radionuclides released were americium and plutonium, in a ratio consistent with the known content of a breached drum. The radiation release was caused by a runaway chemical reaction inside a transuranic (TRU) waste drum which experienced a seal and lid failure, spewing radioactive materials into the repository.According to source-term estimation, approximately 2 to 10Ci of radioactivity was released from the breached drum into the underground, and an undetermined fraction of that source term became airborne, setting off an alarm and triggering the closure of seals designed to force exhausting air through a system of filters including high-efficiency-particulate-air (HEPA) filters. Air monitoring across the WIPP site intensified following the first reports of radiation detection underground to determine the extent of impact to WIPP personnel, the public, and the environment, if any. This article attempts to compile and interpret analytical data collected by an independent monitoring program conducted by the Carlsbad Environmental Monitoring & Research Center (CEMRC) and by a compliance-monitoring program conducted by the WIPP's management and operating contractor, the Nuclear Waste Partnership (NWP), LLC., in response to the accident. Both the independent and the WIPP monitoring efforts concluded that the levels detected were very low and localized, and no radiation-related health effects among local workers or the public would be expected.

Source term estimation and the isotopic ratio of radioactive material released from the WIPP repository in New Mexico, USA

After almost 15 years of operations, the Waste Isolation Pilot Plant (WIPP) had one of its waste drums breach underground as a result of a runaway chemical reaction in the waste it contained. This incident occurred on February 14, 2014. Moderate levels of radioactivity were released into the underground air. A small portion of the contaminated underground air also escaped to the surface through the ventilation system and was detected approximately 1 km away from the facility. According to the source term estimation, the actual amount of radioactivity released from the WIPP site was less than 1.5 mCi. The highest activity detected on the surface was 115.2 μBq/m3 for 241Am and 10.2 μBq/m3 for 239+240Pu at a sampling station located 91 m away from the underground air exhaust point and 81.4 μBq/m3 of 241Am and 5.8 μBq/m3 of 239+240Pu at a monitoring station located approximately 1 km northwest of the WIPP facility. The dominant radionuclides released were americium and plutonium, in a ratio that matches the content of the breached drum.Air monitoring across the WIPP site intensified following the first reports of radiation detection underground to determine the extent of impact to WIPP personnel, the public, and the environment. In this paper, the early stage monitoring data collected by an independent monitoring program conducted by the Carlsbad Environmental Monitoring & Research Center (CEMRC) and an oversight monitoring program conducted by the WIPP's management and operating contractor, the Nuclear Waste Partnership (NWP) LLC were utilized to estimate the actual amount of radioactivity released from the WIPP underground. The Am and Pu isotope ratios were measured and used to support the hypothesis that the release came from one drum identified as having breached that represents a specific waste stream with this radionuclide ratio in its inventory. This failed drum underwent a heat and gas producing reaction that overpowered its vent and lifted its lid to allow release of waste into the underground air.

Environmental and health impacts of February 14, 2014 radiation release from the nation's only deep geologic nuclear waste repository

The environmental impact of the February 14, 2014 radiation release from the nation's only deep geologic nuclear waste repository, the Waste Isolation Pilot Plant (WIPP) was assessed using monitoring data from an independent monitoring program conducted by the Carlsbad Environmental Monitoring & Research Center (CEMRC). After almost 15 years of safe and efficient operations, the WIPP had one of its waste drums rupture underground resulting in the release of moderate levels of radioactivity into the underground air. A small amount of radioactivity also escaped to the surface through the ventilation system and was detected above ground. It was the first unambiguous release from the WIPP repository. The dominant radionuclides released were americium and plutonium, in a ratio that matches the content of the breached drum. The accelerated air monitoring campaign, which began following the accident, indicates that releases were low and localized, and no radiation-related health effects among local workers or the public would be expected. The highest activity detected was 115.2 μBq/m3 for 241Am and 10.2 μBq/m3 for 239+240Pu at a sampling station located 91 m away from the underground air exhaust point and 81.4 μBq/m3 of 241Am and 5.8 μBq/m3 of 239+240Pu at a monitoring station located approximately one kilometer northwest of the WIPP facility.CEMRC's recent monitoring data show that the concentration levels of these radionuclides have returned to normal background levels and in many instances, are not even detectable, demonstrating no long-term environmental impacts of the recent radiation release event at the WIPP. This article presents an evaluation of almost one year of environmental monitoring data that informed the public that the levels of radiation that got out to the environment were very low and did not, and will not harm anyone or have any long-term environmental consequence. In terms of radiological risk at or in the vicinity of the WIPP site, the increased risk from the WIPP releases is exceedingly small, approaching zero.

Radiation release at the nation's only operating deep geological repository--an independent monitoring perspective.

Recent incidents at the nation's only operating deep geologic nuclear waste repository, the Waste Isolation Pilot Plant (WIPP), resulted in the release of americium and plutonium from one or more defense-related transuranic (TRU) waste containers into the environment. WIPP is a U.S. Department of Energy mined geologic repository that has been in operation since March, 1999. Over 85,000 m3 of waste in various vented payload containers have been emplaced in the repository. The primary radionuclides within the disposed waste are 239+240Pu and 241Am, which account for more than 99% of the total TRU radioactivity disposed and scheduled for disposal in the repository. For the first time in its 15 years of operation, there was an airborne radiation release from the WIPP at approximately 11:30 PM Mountain Standard Time (MST) on Friday, February 14, 2014. The radiation release was likely caused by a chemical reaction inside a TRU waste drum that contained nitrate salts and organic sorbent materials. In a recent news release, DOE announced that photos taken of the waste underground showed evidence of heat and gas pressure resulting in a deformed lid, in material expelled through that deformation, and in melted plastic and rubber and polyethylene in the vicinity of that drum. Recent entries into underground Panel 7 have confirmed that at least one waste drum containing a nitrate salt bearing waste stream from Los Alamos National Laboratory was breached underground and was the most likely source of the release. Further investigation is underway to determine if other containers contributed to the release. Air monitoring across the WIPP site intensified following the first reports of radiation detection underground to ascertain whether or not there were releases to the ground surface. Independent analytical results of air filters from sampling stations on and near the WIPP facility have been released by us at the Carlsbad Environmental Monitoring & Research Center and confirmed trace amounts of 241Am and 239+240Pu, at ratios reflecting the suspect waste stream. The highest activity detected offsite was 115.2 μBq/m3 for 241Am and 10.2 μBq/m3 for 239+240 Pu. These concentrations in air were very small, localized, and below any level of public health or environmental concern.

Environmental monitoring of radioactive and non-radioactive constituents in the vicinity of WIP

Abstract The Waste Isolation Pilot Plant (WIPP), a US Department of Energy (DOE) facility, is a deep geologic transuranic waste disposal site designed for the safe disposal of transuranic (TRU) wastes generated from the US defense program. Monitoring is a key component of the development and operation of any nuclear repository and is important to the WIPP performance assessment. Initial concerns over the release of radioactive and chemical contaminants from the WIPP led to various monitoring programs, including the independent, academic-based WIPP environmental monitoring (WIPP-EM) program conducted by the New Mexico State University (NMSU) Carlsbad Environmental Monitoring and Research Center (CEMRC) located in Carlsbad, NM. The mission of CEMRC is to develop and implement an independent health and environmental monitoring program in the vicinity of WIPP and make the results easily accessible to the public and all interested parties. Under the WIPP-EM program constituents monitored include: (1) selected radionuclides, elements, and ions of interest in air, soil, vegetation, drinking water, surface water and sediment from within a 100-mile radius of WIPP as well as in the air exiting the WIPP exhaust shaft, and (2) internally deposited radionuclides in the citizenry living within a 100-mile radius of WIPP. This article presents an evaluation of more than tens years of environmental monitoring data that informed the public that there is no evidence of increases in radiological contaminants in the region that could be attributed to releases from the WIPP. Such an extensive monitoring program and constant public engagement is an ideal model for all nuclear waste repositories anywhere in the world.

What Now for Nuclear Waste?

The article discusses the disposal of nuclear waste in the U.S. The administration of U.S. President Barack Obama canceled the plan to store nuclear waste at the Yucca Mountain site in Las Vegas, Nevada, which is where the federal government had been trying for years to build a waste repository. Topics include the suggestion by the director of the Carlsbad Environmental Monitoring and Research Center at New Mexico University, James L. Conca, to use salt deposits beneath the New Mexican Chihuanhuan desert to store nuclear waste. The debate over storing waste inside salt deposits, why the cancellation may not be a bad thing, and an in-depth examination of the components of nuclear waste are also discussed. An overview of the politics that led to the creation of Yucca Mountain is presented. INSETS: THE COMPONENTS OF NUCLEAR WASTE;END OF AN ERA;Where Will We Put It All?;WHAT CAN BE DONE WITH THE WASTE?

Fingerprinting Fugitive Dust

Finding the sources that contribute to the estimated 1000 tons of so-called “fugitive dust” entering the atmosphere each year is of increasing concern. Scientists at the US Department of Agriculture’s Agricultural Research Service (USDA-ARS) have shown that enzymes produced by soil microorganisms can be an effective tool in tracing the origin of dust. The researchers generated dust in the lab, thereby knowing its exact source, which is often difficult when collecting field data. The set of three soil enzymes used as a collective fingerprint are sensitive to climate, soil properties, and management, making them perfect candidates to profile soils over an entire region. Enzymes can also provide information about specific nutrient cycles or even organic matter decomposition. USDA-ARS soil microbiologist Veronica Acosta-Martinez (Lubbock, Texas) knew enzymes remained active in the soil for some time, but was surprised to find aryl sulfatase, typically the least predominant enzyme in these semi-arid soils, still present in the dust. “Enzymes are able to tell us about biochemical properties and the status of different soil processes”, she explains. Enzymes are the latest in a series of dust profiling tools. Past work has focused on using fatty acid methyl esters (FAME) to profile microbial communities, as well as inorganic factors to profile soil mineral and chemical characteristics. “By layering these measures together, we can get a nice idea of what the biology of a given soil looks like under different management systems”, notes USDA-ARS soil microbiologist Ann Kennedy (Pullman, Washington), who developed soil FAME profiles. By combining both organic and inorganic characteristics, the fingerprint becomes even more robust. “The more you describe a person, the easier it is to trace that person”, points out Acosta-Martinez. “We’re trying to do that with dust also.” Her research partner, soil scientist Ted Zobeck (Lubbock, Texas), is also working with others to develop additional profiling tools. Both Zobeck and Acosta-Martinez agree that enzymes alone can’t do the job. Zobeck is starting a project with Rich Arimoto of the Carlsbad Environmental Monitoring and Research Center (Carlsbad, New Mexico) to develop another tracing method, using radionuclides. “We’re the first ones looking directly at plutonium”, says Arimoto. This method has been overlooked in the past, due to the large sample size requirements and difficult analysis. According to Zobeck, “The overall goal of using these technologies is to identify types of cropping systems that have problems with dust, and to develop strategies to mitigate dust in the atmosphere”.

A Joint HML-CEMRC Project: Testing a Function to Fit Counting Efficiency of a Lung Counting Germanium Detector Array to Muscle Equivalent Chest Wall Thickness and Photon Energy Using a Realistic Torso Phantom over an Extended Energy Range

The previously developed function that fits counting efficiency to chest wall thickness, adipose content of the chest wall, and photon energy was previously shown to be valid only over the energy range 17 keV to 344 keV. The validity of this function has been tested for a wider energy range, 17 keV to 1408 keV by testing it on experimental data sets generated by the Centro de Investigaciones Energeticas Medicambientales y Tecnologicas and by the Carlsbad Environmental Monitoring Research Centre. Both facilities used their Lawrence Livermore National Laboratory torso phantom and associated overlay plates with their germanium detector lung counting systems. The function has been validated over the extended energy range and the ratio of calculated to observed counting efficiency varies from 0.92 to 1.14.

An Evaluation of Recent Lung Counting Technology

The Carlsbad Environmental Monitoring and Research Center (CEMRC), New Mexico State University, began the construction and procurement of a lung and whole-body counting system during the winter of 1996. Through a competitive and technical bid process, Canberra Industries was awarded the contract for the fabrication of the instrument. In collaboration with CEMRC scientists, new technology was developed and tested during the manufacturing of the instrument, including (1) the determination of the appropriate detector thickness for the CEMRC application; (2) the production of 20 mm thick, 3800 mm2 lung counting detectors with broad photon energy response (BEGe, 9-2000 keV); (3) electronic modifications to reduce low energy noise from cosmic ray interactions in the detectors; (4) an optimal alignment for Canberra cryostats to improve lung counting efficiency; and (5) the development and evaluation of a 20 mm thick, 5000 mm2 BEGe detector for lung counting. The results of the technology development and the implications of this technology on lung counting sensitivity are discussed.