Srnl All-Pathways Application

The Environmental Analysis and Performance Modeling group of Savannah River National Laboratory (SRNL) performs performance assessments of the Savannah River Site (SRS) low-level waste facilities to meet the requirements of DOE Order 435.1. One of the performance objectives in the DOE Order is that the radiological dose to representative members of the public shall not exceed 25 mrem in a year total effective dose equivalent from all exposure pathways, excluding radon. Analysis to meet this performance objective is generally referred to as all-pathways analysis. SRNL performs detailed transient groundwater transport analysis for the waste disposal units, which has been used as input for the groundwater part of all-pathways analysis. The desire to better integrate all-pathways analysis with the groundwater transport analysis lead to the development of a software application named the SRNL All-Pathways Application. Another requirement of DOE Order 435.1 is to assess the impact of nuclear waste disposal on water resources, which SRS has interpreted for groundwater protection as meeting the EPA regulations for radionuclides in drinking water. EPA specifies four separate criteria as part of their implementation guidance for radionuclides, which are specified as maximum contaminant levels (MCL). (1) Beta/gamma emitters have a combined dose limit of 4 mrem/year. (2) Alpha emitters have a combined concentration limit of 15 pCi/L (called gross alpha), excluding uranium and radon, but including radium-226. (3) Combined radium-226 and radium-228 have a concentration limit of 5 pCi/L. (4) Isotopes of uranium have a combined concentration limit of 30 {micro}g/L. The All-Pathways Application was designed to be an easy-to-use software application that utilizes transient concentration results from groundwater transport analysis to (1) calculate the groundwater part of all-pathways dose and to (2) evaluate the four EPA criteria for groundwater protection

Issues in Performance Assessments for Disposal of U.S. Department of Energy Low-Level Waste

The US Department of Energy (DOE) and its contractors have long been pioneers in the field of radiological performance assessment (PA). Much effort has been expended in developing technology and acquiring data to facilitate the assessment process. This is reflected in DOE Order 5820.2A, Radioactive Waste Management Chapter III of the Order lists policy and requirements to manage the DOEs low-level waste; performance objectives for low-level waste management are stated to ensure the protection of public health and the environment. A radiological PA is also required to demonstrate compliance with the performance objectives. DOE Order 5820.2A further requires that an Oversight and Peer Review Panel be established to ensure consistency and technical quality around the DOE complex in the development and application of PA models that include site-specific geohydrology and waste composition. The DOE has also established a Performance Assessment Task Team (PATT) to integrate the activities of sites that are preparing PAs. The PATT`s purpose is to recommend policy and guidance to DOE on issues that impact PAs so that the approaches taken are as consistent as possible across the DOE complex

Automated Inadvertent Intruder Application

The Environmental Analysis and Performance Modeling group of Savannah River National Laboratory (SRNL) conducts performance assessments of the Savannah River Site (SRS) low-level waste facilities to meet the requirements of DOE Order 435.1. These performance assessments, which result in limits on the amounts of radiological substances that can be placed in the waste disposal facilities, consider numerous potential exposure pathways that could occur in the future. One set of exposure scenarios, known as inadvertent intruder analysis, considers the impact on hypothetical individuals who are assumed to inadvertently intrude onto the waste disposal site. Inadvertent intruder analysis considers three distinct scenarios for exposure referred to as the agriculture scenario, the resident scenario, and the post-drilling scenario. Each of these scenarios has specific exposure pathways that contribute to the overall dose for the scenario. For the inadvertent intruder analysis, the calculation of dose for the exposure pathways is a relatively straightforward algebraic calculation that utilizes dose conversion factors. Prior to 2004, these calculations were performed using an Excel spreadsheet. However, design checks of the spreadsheet calculations revealed that errors could be introduced inadvertently when copying spreadsheet formulas cell by cell and finding these errors was tedious and time consuming. This weakness led to the specification of functional requirements to create a software application that would automate the calculations for inadvertent intruder analysis using a controlled source of input parameters. This software application, named the Automated Inadvertent Intruder Application, has undergone rigorous testing of the internal calculations and meets software QA requirements. The Automated Inadvertent Intruder Application was intended to replace the previous spreadsheet analyses with an automated application that was verified to produce the same calculations and results. The application was extended to calculate full decay chains for a given parent so that an intruder calculation could be performed without any input from transport calculations, i.e. the intruder analysis was decoupled from groundwater analysis. Once this full decay chain capability was in place, the application was extended to perform a transient calculation of the dose to an intruder over a specified time range, from which the maximum dose in time was determined. Use of the transient calculation to find the maximum dose in time was a significant step forward in automating and simplifying the inadvertent intruder analysis

The Evolution of Low-Level Radioactive Waste (LLW) Disposal Practices at the Savannah River Site Coupled with Vigorous Stakeholder Interaction

Low-level radioactive waste (LLW) disposal practices at SRS evolved from trench disposal with little long-term performance basis to disposal in robust concrete vaults, again without modeling long-term performance. Now, based on an assessment of long-term performance of various waste forms and methods of disposal, the LLW disposal program allows for a ''smorgasbord'' of various disposal techniques and waste forms, all modeled to ensure long-term performance is understood. New disposal techniques include components-in-grout, compaction/volume reduction prior to disposal, and trench disposal of extremely low activity waste. Additionally, factoring partition coefficient (Kd) measurements based on waste forms has been factored into performance models. This paper will trace the development of the different disposal methods, and the extensive public communications effort that resulted in endorsement of the changes by the SRS Citizens Advisory Board

Probing Spectroscopic Variability of Galaxies & Narrow-Line Active Galactic Nuclei in the Sloan Digital Sky Survey

Under the unified model for active galactic nuclei (AGNs), narrow-line (Type 2) AGNs are, in fact, broad-line (Type 1) AGNs but each with a heavily obscured accretion disk. We would therefore expect the optical continuum emission from Type 2 AGN to be composed mainly of stellar light and non-variable on the time-scales of months to years. In this work we probe the spectroscopic variability of galaxies and narrow-line AGNs using the multi-epoch data in the Sloan Digital Sky Survey (SDSS) Data Release 6. The sample contains 18,435 sources for which there exist pairs of spectroscopic observations (with a maximum separation in time of ~700 days) covering a wavelength range of 3900-8900 angstrom. To obtain a reliable repeatability measurement between each spectral pair, we consider a number of techniques for spectrophotometric calibration resulting in an improved spectrophotometric calibration of a factor of two. From these data we find no obvious continuum and emission-line variability in the narrow-line AGNs on average -- the spectroscopic variability of the continuum is 0.07+/-0.26 mag in the g band and, for the emission-line ratios log10([NII]/Halpha) and log10([OIII]/Hbeta), the variability is 0.02+/-0.03 dex and 0.06+/-0.08 dex, respectively. From the continuum variability measurement we set an upper limit on the ratio between the flux of varying spectral component, presumably related to AGN activities, and that of host galaxy to be ~30%. We provide the corresponding upper limits for other spectral classes, including those from the BPT diagram, eClass galaxy classification, stars and quasars.Comment: AJ accepte

Energy performance contracting (EPC): a suitable mechanism for achieving energy savings in housing cooperatives? Results from a Norwegian pilot project

The barriers to energy savings in institutions and private homes are well known and include people’s lack of interest, awareness, knowledge and human and financial capacity. Experiences made in several countries show that EPC—energy performance contracting—may be used for overcoming many of these barriers. A typical EPC project is delivered by an energy service company (ESCO) and the contract is accompanied with a guarantee for energy savings. EPC is increasingly taken in use in the professional market (firms and the public sector), but is less common in the residential sector market. It has been suggested that there are several barriers for using EPC in the domestic sector such as the uncertainty involved in estimating forthcoming reductions in private consumption. In this paper, we present the results from a pilot project on the use of EPC in a housing cooperative in Oslo. The project was initiated and observed by the researchers. The research followed a transdisciplinary methodology in that it was conducted by both researcher and practitioner (co-authors) in close collaboration with members of the housing cooperative and the ESCOs, who also contributed to the interpretation of results. We document the process in terms of why the Board decided to join the EPC pilot, the call for offers from ESCOs who guaranteed that purchased annual energy would be reduced by one third, the responses to and negotiations of the offer from the ESCO who became contracted in the initial phase and up to the moment when the General Assembly finally decided to not invest in the proposed energy saving measures. We find that the residents not only had limited interest in energy savings but also lacked confidence in the EPC process. This contributed to the outcome. We discuss the findings in relation to the barriers to using EPC among housing cooperatives. We highlight the need for more knowledge about the client side for understanding how barriers may be overcome. Three specific recommendations for how EPC may successfully be employed among housing cooperatives are suggested as follows: (i) include refurbishment and not only energy savings in the EPC, (ii) identify the residents’ needs in an early phase and (iii) communicate the EPC principle to the residents throughout the process

Evaluating the Current Status of American Shad Stocks in Three Virginia Rivers

Directed commercial fisheries for American shad Alosa sapidissima in the primary Virginia tributaries of the Chesapeake Bay have been under moratorium since 1994. Monitoring of adult American shad within these rivers has been ongoing since 1998 through a cooperative program involving commercial fishers. The monitoring program is designed to mimic traditional commercial fishing practices so that stock status can be inferred by comparing contemporary catch-per-unit-effort levels with those derived from historic logbooks. In this paper, we present analyses of the available monitoring and historic catch rate data along with updated stock status information for American shad in the James, York, and Rappahannock rivers. Two analytical methods were used to derive annual indices of relative abundance; both methods yielded very similar patterns for each river system. Comparisons of contemporary and historic indices of relative abundance suggest that American shad in the James and York rivers continue to persist at low levels of abundance. Measures of stock abundance in the Rappahannock River have been higher than the logbook reference value for much of the monitoring period. However, current moratoria and restoration strategies, which include hatchery releases of fry, the removal of obstructions blocking spawning and nursery habitat, and reductions in bycatch from other fisheries, should continue into the foreseeable future

Broad Absorption Line Variability in Repeat Quasar Observations from the Sloan Digital Sky Survey

We present a time-variability analysis of 29 broad absorption line quasars (BALQSOs) observed in two epochs by the Sloan Digital Sky Survey (SDSS). These spectra are selected from a larger sample of BALQSOs with multiple observations by virtue of exhibiting a broad CIV $\lambda$1549 absorption trough separated from the rest frame of the associated emission peak by more than 3600 km s$^{-1}$. Detached troughs facilitate higher precision variability measurements, since the measurement of the absorption in these objects is not complicated by variation in the emission line flux. We have undertaken a statistical analysis of these detached-trough BALQSO spectra to explore the relationships between BAL features that are seen to vary and the dynamics of emission from the quasar central engine. We have measured variability within our sample, which includes three strongly variable BALs. We have also verified that the statistical behavior of the overall sample agrees with current model predictions and previous studies of BAL variability. Specifically, we observe that the strongest BAL variability occurs among the smallest equivalent width features and at velocities exceeding 12,000 km s$^{-1}$, as predicted by recent disk-wind modeling.Comment: 11 pages, 7 figures. Accepted for publication in Ap

Time delay between images of the lensed quasar UM673

We study brightness variations in the double lensed quasar UM673 (Q0142-100) with the aim of measuring the time delay between its two images. In the paper we combine our previously published observational data of UM673 obtained during the 2003 - 2005 seasons at the Maidanak Observatory with archival and recently observed Maidanak and CTIO UM673 data. We analyze the V, R and I-band light curves of the A and B images of UM673, which cover ten observational seasons from August 2001 to November 2010. We also analyze the time evolution of the difference in magnitudes between images A and B of UM673 over more than ten years. We find that the quasar exhibits both short-term (with amplitude of \sim 0.1 mag in the R band) and high-amplitude (\sim 0.3 mag) long-term variability on timescales of about several months and several years, respectively. These brightness variations are used to constrain the time delay between the images of UM673. From cross-correlation analysis of the A and B quasar light curves and error analysis we measure the mean time delay and its error of 89 \pm11 days. Given the input time delay of 88 days, the most probable value of the delay that can be recovered from light curves with the same statistical properties as the observed R-band light curves of UM673 is 95{+5/-16}{+14/-29} days (68 and 95 % confidence intervals). Analysis of the V - I color variations and V, R and I-band magnitude differences of the quasar images does not show clear evidence of the microlensing variations between 1998 and 2010.Comment: Submitted to A&A, 11 pages, 9 figure