RAC has been awarded a contract with the Nuclear Regulatory Commission to present up to five training courses from 2015 through 2019 to agency personnel on the topic of “Environmental Risk Assessment Analysis.” RAC’s lectures, discussions, and demonstrations for these courses will be designed to allow participants to use the acquired knowledge for performance evaluations of licensee environmental assessments and to perform environmental impact reviews, inspect licensee programs, and manage environmental projects. RAC presented a similar course for NRC personnel in 2009.
RAC published a paper on a comparison of the MACCS2 Gaussian Plume atmospheric dispersion model with Lagrangian Puff models as applied to deterministic and probabilistic safety assessment. RAC found that at distances greater than 5 km, the Gaussian Plume model implemented in MACCs calculates higher 1-hour average concentrations compared to Lagrangian puff models.
ABSTRACT: The suitability of a new facility in terms of potential impacts from routine and accidental releases is typically evaluated using conservative models and assumptions to assure dose standards are not exceeded. However, overly conservative dose estimates that exceed target doses can result in unnecessary and costly facility design changes. This paper examines one such case involving the U.S. Department of Energy’s pretreatment facility of the Waste Treatment and Immobilization Plant (WTP). The MELCOR Accident Consequence Code System Version 2 (MACCS2) was run using conservative parameter values in prescribed guidance to demonstrate that the dose from a postulated airborne release would not exceed the guideline dose of 0.25 Sv. External review of default model parameters identified the deposition velocity of 1.0 cm s−1 as being nonconservative. The deposition velocity calculated using resistance models was in the range of 0.1 to 0.3 cm s−1. Avalue of 0.1 cm s−1 would result in the dose guideline being exceeded. To test the overall conservatism of the MACCS2 transport model, the 95th percentile hourly average dispersion factor based on one year of meteorological data was compared to dispersion factors generated from two state-of-the-art Lagrangian puff models. The 95th percentile dispersion factor from MACCS2 was a factor of 3 to 6 higher compared to those of the Lagrangian puff models at a distance of 9.3 km and a deposition velocity of 0.1 cm s−1. Thus, the inherent conservatism in MACCS2 more than compensated for the high deposition velocity used in the assessment. Applications of models like MACCS2 with a conservative set of parameters are essentially screening calculations, and failure to meet dose criteria should not trigger facility design changes but prompt a more in-depth analysis using probabilistic methods with a defined margin of safety in the target dose. A sample application of the probabilistic approach is provided.
J.E. Till, A.S. Rood, C.D. Garzon, and R.H. Lagdon. 2014. “Comparison of the MACCS2 Atmospheric Transport Model with Lagrangian Puff Models as Applied to Deterministic and Probabilistic Safety Analysis.” Health Physics, 107, 213-230.
RAC team member, Helen Grogan, was honored with an invitation to be one of the U.S. delegates at the United Nations Scientific Committee on the Effects of Atomic Radiation. Helen traveled to Vienna, Austria, to represent the U.S. at the 61st session of UNSCEAR from 21-25 July 2014.
Data related to potential radiation exposures to U.S. military personnel in Japan following the accident at Fukushima Daiichi Nuclear Power Station (FDNPS) in 2011 have been added to the RACER Data Analysis and Risk Calculation Tools. These data, provided in the Defense Threat Reduction Agency (DTRA) “Operation Tomodachi Registry: Radiation Data Compendium”, include measured concentrations in soil, air, and tap water, as well as dose rates from survey meters.
RAC has published a paper in Radiation Research describing the methodology for the
dosimetry in the Atomic Veterans Study.
ABSTRACT: Methods were developed to calculate individual estimates of exposure and
dose with associated uncertainties for a subcohort (1,857) of 115,329 military veterans
who participated in at least one of seven series of atmospheric nuclear weapons tests or
the TRINITY shot carried out by the United States. The tests were conducted at the
Pacific Proving Grounds and the Nevada Test Site. Dose estimates to specific organs will
be used in an epidemiological study to investigate leukemia and male breast cancer.
Previous doses had been estimated for the purpose of compensation and were generally
high-sided to favor the veteran’s claim for compensation in accordance with public law.
Recent efforts by the U.S. Department of Defense (DOD) to digitize the historical records
supporting the veterans’ compensation assessments make it possible to calculate doses
and associated uncertainties. Our approach builds upon available film badge dosimetry
and other measurement data recorded at the time of the tests and incorporates detailed
scenarios of exposure for each veteran based on personal, unit, and other available
historical records. Film badge results were available for approximately 25% of the
individuals, and these results assisted greatly in reconstructing doses to unbadged persons
and in developing distributions of dose among military units. This article presents the
methodology developed to estimate doses for selected cancer cases and a 1% random
sample of the total cohort of veterans under study.
Till, J.E., H.L. Beck, J.W. Aanenson, H.A. Grogan, H.J. Mohler, S.S. Mohler, P.G.
Voillequé. 2014. Military Participants at U.S. Atmospheric Nuclear Weapons
Testing-Methodology for Estimating Dose and Uncertainty. Radiat Res. 181, 471 –
John E. Till’s 37th Lauriston S. Taylor Lecture at the 2013 Annual Meeting of the National Council on Radiation Protection and Measurements (NCRP) on March 11, 2013 has been published in Health Physics. F. Ward Whicker introduced Dr. Till’s lecture, entitled “When Does Risk Assessment Get Fuzzy?”. The lecture series honors the late Dr. Lauriston S. Taylor, the NCRP founding President.
J.E. Till. 2014. “When Does Risk Assessment Get Fuzzy?” 37th Taylor Lecture
presented at the annual Meeting of the National Council on Radiation Protection and
Measurements, March 11, 2013. Health Physics, 106 (2). February.
John E. Till presented the 37th Lauriston S. Taylor Lecture at the 2013 Annual Meeting
of the National Council on Radiation Protection and Measurements (NCRP) on March
11, 2013. F. Ward Whicker introduced Dr. Till’s lecture, entitled “When Does Risk
Assessment Get Fuzzy?”. The lecture series honors the late Dr. Lauriston S. Taylor, the
NCRP founding President.
RAC returned to Washington, D.C., for a second year to present a comprehensive one
week course in environmental radiological risk assessment, titled “Radiological Risk
Assessment for Decision Making, Compliance, and Emergency Response” from March 4
– 8, 2013. Course topics included: state-of-the-art environmental risk assessment
methods, with an increased emphasis on practical applications; environmental transport
modeling (air, surface water, and groundwater) and pathway analysis; principles, models
and methods, and computer codes; risk assessment software (where to get it and how to
use it); key references for risk assessment data, models, and computer codes; insight and
understanding of relevant regulations and guidelines; how to build credibility and trust in
the assessment process; and guidance on how to succeed in radiation risk communication.
RAC has published a paper in Health Physics describing the RACER methodology.
ABSTRACT: This paper describes a methodology called Risk Analysis, Communication, Evaluation, and Reduction (RACER*) that converts environmental data directly to human health risk to enhance decision making and communication. The methodology was developed and implemented following the Cerro Grande fire in New Mexico that burned approximately 7,500 acres of Los Alamos National Laboratory in May 2000. The absence of a coordinated and comprehensive approach to managing and understanding environmental data was a major weakness in the responding agencies’ ability to make and communicate decisions. RACER consists of three basic elements: managing information, converting information to knowledge, and communicating knowledge to decision makers and stakeholders. Data are maintained in a web-accessible database that accepts data as they are validated and uploaded. The user can select data for evaluation and convert them to knowledge using human health risk as a benchmark for ranking radionuclides, chemicals, pathways, or other criteria needed to make decisions. Knowledge about risk is communicated using graphic and tabular formats. The process is transparent, flexible, and rapid, which enhances credibility and trust among decision makers and stakeholders. The fundamental principles used in RACER can be applied anywhere radionuclides or chemicals are present in the environment.
Till, J.E., H.A. Grogan, H.J. Mohler, J.R. Rocco, S.S. Mohler. 2012. An Integrated Approach to Data Management, Risk Assessment, and Decision Making. Health
Physics, 102 (4), April.
RAC presented a comprehensive one week course in environmental radiological risk assessment, titled “Radiological Risk Assessment for Decision Making, Compliance, and Emergency Response” from March 5 – 9, 2012, in Washington, D.C. Course topics included: state-of-the-art environmental risk assessment methods, environmental transport modeling and pathway analysis, including principles, models and methods, and computer codes, key references; methods for predicting transport in air, surface water, and groundwater; insight and understanding of relevant regulations and guidelines; risk assessment software (where to get it and how to use it); how to build credibility and trust in the assessment process; and guidance in how to succeed in radiation risk communication.