Assessment of hydrologic impact of extending exploratory shafts into the Calico Hills nonwelded tuff unit at Yucca Mountain, Nevada

The US Department of Energy (DOE) is performing analyses to address an objection by the US Nuclear Regulatory Commission to plans in the Consultation Draft of the Site Characterization Plan for direct excavation of the Calico Hills nonwelded (CHn) unit within the repository exploration block at Yucca Mountain, Nevada. The excavation was planned as part of site characterization activities for the potential high-level nuclear waste repository at Yucca Mountain. This characterization activities for the potential high-level nuclear waste repository at Yucca Mountain. This characterization activity has been deferred, pending the results of a risk/benefit analysis of alternative methods for obtaining needed characterization data from CHn unit. The benefits from characterizing the CHn unit are generally related to obtaining information leading to improved confidence in predictions of site performance. The risks are generally associated with potential adverse impacts to site performance that result from excavation or other intrusion into the CHn unit. The purpose of the risk/benefit analysis is to produce a recommendation to the Director, Regulatory and Site Evaluation Division. DOE/Yucca Mountain Site Characterization Project Office for a strategy for characterizing the CHn unit. The recommendation will describe characterization activities that are expected to provide the needed information while limiting adverse impacts to site performance to the extent practical. The risk/benefit analysis was supported with scoping calculations to provide a quantitative evaluation of the impacts associated with different strategies. The working group responsible for the risk/benefit analysis requested that these scoping calculations to be supported with more detailed performance assessments for evaluating impacts of different characterization activities. This report summarizes the results of these performance assessment analyses. 9 refs., 30 figs., 1 tab

Pervasive gaps in Amazonian ecological research

Biodiversity loss is one of the main challenges of our time, and attempts to address it require a clear understanding of how ecological communities respond to environmental change across time and space. While the increasing availability of global databases on ecological communities has advanced our knowledge of biodiversity sensitivity to environmental changes, vast areas of the tropics remain understudied. In the American tropics, Amazonia stands out as the world's most diverse rainforest and the primary source of Neotropical biodiversity, but it remains among the least known forests in America and is often underrepresented in biodiversity databases. To worsen this situation, human-induced modifications may eliminate pieces of the Amazon's biodiversity puzzle before we can use them to understand how ecological communities are responding. To increase generalization and applicability of biodiversity knowledge, it is thus crucial to reduce biases in ecological research, particularly in regions projected to face the most pronounced environmental changes. We integrate ecological community metadata of 7,694 sampling sites for multiple organism groups in a machine learning model framework to map the research probability across the Brazilian Amazonia, while identifying the region's vulnerability to environmental change. 15%–18% of the most neglected areas in ecological research are expected to experience severe climate or land use changes by 2050. This means that unless we take immediate action, we will not be able to establish their current status, much less monitor how it is changing and what is being lost

Search for gravitational-wave transients associated with magnetar bursts in advanced LIGO and advanced Virgo data from the third observing run

Gravitational waves are expected to be produced from neutron star oscillations associated with magnetar giant f lares and short bursts. We present the results of a search for short-duration (milliseconds to seconds) and longduration (∼100 s) transient gravitational waves from 13 magnetar short bursts observed during Advanced LIGO, Advanced Virgo, and KAGRA’s third observation run. These 13 bursts come from two magnetars, SGR1935 +2154 and SwiftJ1818.0−1607. We also include three other electromagnetic burst events detected by FermiGBM which were identified as likely coming from one or more magnetars, but they have no association with a known magnetar. No magnetar giant flares were detected during the analysis period. We find no evidence of gravitational waves associated with any of these 16 bursts. We place upper limits on the rms of the integrated incident gravitational-wave strain that reach 3.6 × 10−²³ Hz at 100 Hz for the short-duration search and 1.1 ×10−²² Hz at 450 Hz for the long-duration search. For a ringdown signal at 1590 Hz targeted by the short-duration search the limit is set to 2.3 × 10−²² Hz. Using the estimated distance to each magnetar, we derive upper limits upper limits on the emitted gravitational-wave energy of 1.5 × 1044 erg (1.0 × 1044 erg) for SGR 1935+2154 and 9.4 × 10^43 erg (1.3 × 1044 erg) for Swift J1818.0−1607, for the short-duration (long-duration) search. Assuming isotropic emission of electromagnetic radiation of the burst fluences, we constrain the ratio of gravitational-wave energy to electromagnetic energy for bursts from SGR 1935+2154 with the available fluence information. The lowest of these ratios is 4.5 × 103

Open data from the third observing run of LIGO, Virgo, KAGRA, and GEO

The global network of gravitational-wave observatories now includes five detectors, namely LIGO Hanford, LIGO Livingston, Virgo, KAGRA, and GEO 600. These detectors collected data during their third observing run, O3, composed of three phases: O3a starting in 2019 April and lasting six months, O3b starting in 2019 November and lasting five months, and O3GK starting in 2020 April and lasting two weeks. In this paper we describe these data and various other science products that can be freely accessed through the Gravitational Wave Open Science Center at https://gwosc.org. The main data set, consisting of the gravitational-wave strain time series that contains the astrophysical signals, is released together with supporting data useful for their analysis and documentation, tutorials, as well as analysis software packages

A joint Fermi-GBM and Swift-BAT analysis of gravitational-wave candidates from the third gravitational-wave observing run

We present Fermi Gamma-ray Burst Monitor (Fermi-GBM) and Swift Burst Alert Telescope (Swift-BAT) searches for gamma-ray/X-ray counterparts to gravitational-wave (GW) candidate events identified during the third observing run of the Advanced LIGO and Advanced Virgo detectors. Using Fermi-GBM onboard triggers and subthreshold gamma-ray burst (GRB) candidates found in the Fermi-GBM ground analyses, the Targeted Search and the Untargeted Search, we investigate whether there are any coincident GRBs associated with the GWs. We also search the Swift-BAT rate data around the GW times to determine whether a GRB counterpart is present. No counterparts are found. Using both the Fermi-GBM Targeted Search and the Swift-BAT search, we calculate flux upper limits and present joint upper limits on the gamma-ray luminosity of each GW. Given these limits, we constrain theoretical models for the emission of gamma rays from binary black hole mergers

Comparative simulations of a two-layer landfill barrier using the HELP Version 2. 0 and UNSAT-H Version 2. 0 computer codes

This report documents the results of a simulation of the performance of a two-layer infiltration barrier for a nonradioactive dangerous waste landfill (NRDWL) at the US Department of Energy's Hanford Site in semi-arid southeast Washington State. The performance of the barrier was simulated for a period of 10 years using the UNSAT-H version 2.0 groundwater flow computer code. Pacific Northwest Laboratory performed this simulation to compare results using UNSAT-H 2.0 with those of the US Environmental Protection Agency's Hydrologic Evaluation of Landfill Performance (HELP) version 2.0 code. A conceptualization of the actual landfill barrier design was modeled using both codes. This model was simulated using 10 years of daily meteorological data collected at the Hanford Meteorological Station from 1979 through 1988. The intent of the comparison was to demonstrate that HELP conservatively predicts deep percolation of meteoric water at the Hanford Site. This demonstration required that the two codes be used to simulate the same conceptual model using identical, or at least essentially equivalent, input data. Comparing the results of the 10-year simulations showed that for the meteorological data and soil properties modeled the HELP 2.0 code was more conservative than the UNSAT-H code. HELP predicted a net drainage or deep percolation of 0.3592 cm (0.1556 in.) from the barrier for the 10-year period simulated. None to the UNSAT-H simulations predicted any deep percolation. HELP also predicted a greater proportion of precipitation returned to the atmosphere through evapotranspiration than did the UNSAT-H simulations in spite of the larger precipitation values being provided to HELP through an apparent data entry error. 14 refs., 11 figs., 8 tabs

Sensitivity and uncertainty analyses of unsaturated flow travel time in the CHnz unit of Yucca Mountain, Nevada

This report documents the results of sensitivity and uncertainty analyses conducted to improve understanding of unsaturated zone ground-water travel time distribution at Yucca Mountain, Nevada. The US Department of Energy (DOE) is currently performing detailed studies at Yucca Mountain to determine its suitability as a host for a geologic repository for the containment of high-level nuclear wastes. As part of these studies, DOE is conducting a series of Performance Assessment Calculational Exercises, referred to as the PACE problems. The work documented in this report represents a part of the PACE-90 problems that addresses the effects of natural barriers of the site that will stop or impede the long-term movement of radionuclides from the potential repository to the accessible environment. In particular, analyses described in this report were designed to investigate the sensitivity of the ground-water travel time distribution to different input parameters and the impact of uncertainty associated with those input parameters. Five input parameters were investigated in this study: recharge rate, saturated hydraulic conductivity, matrix porosity, and two curve-fitting parameters used for the van Genuchten relations to quantify the unsaturated moisture-retention and hydraulic characteristics of the matrix. 23 refs., 20 figs., 10 tabs