PNNL-16071 Regional Atmospheric Transport Code for Hanford Emission Tracking, Version 2 (RATCHET2) RATCHET2: Modification and Implementation of RATCHET for Use in SAC J. V. Ramsdell, Jr. J. P. Rishel July 2006 Prepared for the U.S. Department of Energy under Contract DE-AC05-76RL01830 DISCLAIMER This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor Battelle Memorial Institute, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof, or Battelle Memorial Institute. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof. PACIFIC NORTHWEST NATIONAL LABORATORY operated by BATTELLE for the UNITED STATES DEPARTMENT OF ENERGY under Contract DE-AC05-76RL01830 Printed in the United States of America Available to DOE and DOE contractors from the Office of Scientific and Technical Information, P.O. Box 62, Oak Ridge, TN 37831-0062; ph: (865) 576-8401 fax: (865) 576-5728 email: [email protected] Available to the public from the National Technical Information Service, U.S. Department of Commerce, 5285 Port Royal Rd., Springfield, VA 22161 ph: (800) 553-6847 fax: (703) 605-6900 email: [email protected] online ordering: http://www.ntis.gov/ordering.htm This document was printed on recycled paper. PNNL-16071 Regional Atmospheric Transport Code for Hanford Emission Tracking, Version 2 (RATCHET2) RATCHET2: Modification and Implementation of RATCHET for Use in SAC J. V. Ramsdell, Jr. J. P. Rishel July 2006 Prepared for the U.S. Department of Energy under Contract DE-AC05-76RL01830 Pacific Northwest National Laboratory Richland, Washington 99352 Summary In 1999, the U.S. Department of Energy initiated the development of an assessment tool that enables users to model the movement of contaminants from all waste sites at Hanford through the vadose zone, groundwater, and Columbia River and estimate the impact of contaminants on human health, ecology, and the local cultures and economy. This tool was named the System Assessment Capability (SAC) and is an integrated system of computer models and databases used to assess the impact of waste remaining on the Hanford Site. This manual describes the atmospheric model and computer code for the Atmospheric Transport Module within SAC. The Atmospheric Transport Module, called RATCHET2, calculates the time- integrated air concentration and surface deposition of airborne contaminants to the soil. The RATCHET2 code is an adaptation of the Regional Atmospheric Transport Code for Hanford Emissions Tracking (RATCHET), as described by Ramsdell et al. (1994). The original RATCHET code was developed to perform the atmospheric transport for the Hanford Environmental Dose Reconstruction Project. Fundamentally, the two sets of codes are identical; no capabilities have been deleted from the original version of RATCHET. Most modifications are generally limited to revision of the run-specification file to streamline the simulation process for SAC. In this regard, many model parameters that were set within the RATCHET run-specification file are now set internally to the RATCHET2 code. New variables have also been added to the RATCHET2 run-specification file to allow for flexibility in implementing the code into SAC. For example, the center of the model domain is now specified in the run-specification file rather than set internally within the RATCHET code. Other notable changes from RATCHET to the RATCHET2 code include: • Meteorological data input has been changed from direct access files to sequential files, and the file format has been modified to accommodate the meteorological data available from the current meteorological data acquisition system at Hanford. • The format of the meteorological station file has been modified so that station locations are specified in latitude and longitude. • The portions of RATCHET that dealt with determining mixing-layer thickness have been changed in RATCHET2. The mixing-layer thickness is determined for each station and then interpolated to nodes following the procedure described for RASCAL Version 3. • For SAC, the RATCHET code has been revised to estimate annual, time-integrated concentrations normalized to the annual release rate for each analyte class (noble gas, iodine, and particle). • The code is run for a single-source with a unit release; SAC scales the results from RATCHET2 to the appropriate emission rate. • Decay calculations have been disabled within RATCHET2; SAC calculates radionuclide decay where appropriate. iii This manual has three major sections: a description of the model, a user’s guide, and a programmer's guide. These sections discuss RATCHET2 from three different perspectives. The first section provides a technical description of the code with emphasis on details such as the representation of the model domain, the data required by the model, and the equations used to make the model calculations. The second section is the user’s guide to the model and provides information on the model input, output, and instruction for running the code. The third and final section is a programmer’s guide to the code. It discusses the hardware and software required to run the code and discusses the program’s code structure and code elements. iv Contents Summary......................................................................................................................................................iii 1.0 Introduction ....................................................................................................................................... 1.1 1.1 Relationship to Other Atmospheric Dispersion Models......................................................... 1.2 1.2 Quality Assurance .................................................................................................................. 1.2 1.3 Manual Organization.............................................................................................................. 1.3 2.0 Technical Description........................................................................................................................ 2.1 2.1 Model Domain........................................................................................................................ 2.1 2.1.1 Cartesian Representation...........................................................................................2.1 2.1.2 Coordinate Transformations......................................................................................2.3 2.2 Topography ............................................................................................................................ 2.4 2.2.1 Surface Roughness ....................................................................................................2.6 2.3 Meteorology ........................................................................................................................... 2.6 2.3.1 Meteorological Stations.............................................................................................2.7 2.3.2 Meteorological Data Input.........................................................................................2.7 2.3.3 Calculated Meteorological Parameters....................................................................2.11 2.3.4 Spatial Representation of Meteorological Conditions.............................................2.15 2.4 Source Term ......................................................................................................................... 2.16 2.4.1 Release Times and Rates.........................................................................................2.16 2.4.2 Plume Rise and Effective Release Height...............................................................2.16 2.5 Transport .............................................................................................................................. 2.19 2.6 Diffusion............................................................................................................................... 2.21 2.6.1 Calculation of Time-Integrated Air Concentrations................................................2.22 2.6.2 Estimation of Diffusion Coefficients ......................................................................2.24 2.6.3 Estimation of Turbulence Parameters .....................................................................2.27 2.7 Transformation, Deposition, and Depletion ......................................................................... 2.28 2.7.1 Chemical and Physical Transformation...................................................................2.28 2.7.2 Dry Deposition ........................................................................................................2.29 2.7.3 Wet Deposition........................................................................................................2.32 2.7.4 Surface Contamination............................................................................................2.33