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Englewood, CO, United States

Spitzinger J.,Arcadis | Cohen S.,SENES Consultants | Heuston D.,Arcadis | Moran P.,Arcadis | Gillow J.,Arcadis
2014 SME Annual Meeting and Exhibit, SME 2014: Leadership in Uncertain Times | Year: 2014

In situ recovery (ISR) of uranium alters the baseline groundwater geochemistry in order to mobilize and complex uranium to extract and concentrate it. ISR wellfield restoration is often challenging,and primarily relies on groundwater sweep,reinjection of treated permeate,and/or injection of reductants. Greater focus should be placed on injection-based approaches (using existing infrastructure) based on established engineering concepts used for in situ remediation of groundwater plumes. Such injection-based approaches could shorten restoration timeframes consequently reducing long-term operational costs. This paper addresses various types of injection-based approaches to wellfield restoration based on in-situ remediation success with other constituents that require similar treatment. This paper describes necessary design practices for injecting reactive chemicals (e.g.,reductants or biostimulants),operations and maintenance (O&M) strategies to prevent fouling of the chemical delivery system and well network,and natural constraints to restoration. Best practices for successful biostimulation strategies that minimize residual uranium,radium,oxoanions,and other trace elements are as described. Advantages of such injection-based approaches could include significant reductions in restoration times,and consequently,lower restoration costs. Source

Brown S.H.,SENES Consultants | Chambers D.B.,SENES Consultants
Health Physics | Year: 2014

This paper presents an analysis of the implications of some recent studies performed to characterize uranium products from modern uranium recovery facilities important for worker protection. Assumptions about the solubility (related to the molecular species being produced) of these materials in humans are critical to properly assess radiation dose from intakes, understand chemotoxic implications, and establish protective exposure standards (airborne concentrations, limits on intake, etc.). Recent studies, as well as information in the historical professional literature, were reviewed that address the issue of solubility and related characteristics. These data are important for the design of programs for assessment of both chemical and radiological aspects of worker exposure to the products of modern uranium recovery plants (conventional uranium mills and in situ recovery plants; i.e., ISRs). The data suggest strongly that the oxide form produced by these facilities (and therefore, product solubility) is related to precipitation chemistry and thermal exposure (dryer temperature). Given the peroxide precipitation and low temperature drying methods being used at many modern uranium recovery facilities in the U.S. today, very soluble products are being produced. The dosimetric impacts of these products to the pulmonary system (except perhaps in case of an extreme acute insult) would be small, and any residual pulmonary retention beyond a month or two would most likely be too small to measure by traditional urinalysis sampling or the current state-of-the-art of natural uranium in vivo lung counting techniques. Uranium recovery plants should revisit the adequacy of current bioassay programs in the context of their process and product specifics. Workers potentially exposed to these very soluble yellowcake concentrates should have urine specimens submitted for uranium analysis on an approximately weekly basis, including analysis for the biomarkers associated with potential renal injury [e.g., glucose, lactate dehydrogenase (LDH) and protein albumen]. Additionally, implications for compliance with current U.S. Nuclear Regulatory Commission (NRC) regulations (e.g., 10 CFR20) are discussed. NRC, the applicable Agreement State agencies, and licensees need to recognize the importance of the uranium chemotoxicity versus dose relationship in the interest of worker protection. © 2014 Health Physics Society. Source

Whicker R.,SENES Consultants | Chambers D.,SENES Consultants
Health Physics | Year: 2015

Instruments and methods for normalization of energy-dependent gamma radiation survey data to a less energy-dependent basis of measurement are evaluated based on relevant field data collected at 15 different sites across the western United States along with a site in Mongolia. Normalization performance is assessed relative to measurements with a highpressure ionization chamber (HPIC) due to its "flat" energy response and accurate measurement of the true exposure rate from both cosmic and terrestrial radiation. While analytically ideal for normalization applications, cost and practicality disadvantages have increased demand for alternatives to the HPIC. Regression analysis on paired measurements between energy-dependent sodium iodide (NaI) scintillation detectors (5-cm by 5-cm crystal dimensions) and the HPIC revealed highly consistent relationships among sites not previously impacted by radiological contamination (natural sites). A resulting generalized data normalization factor based on the average sensitivity of NaI detectors to naturally occurring terrestrial radiation (0.56 nGy h-1 HPIC per nGy h-1 NaI), combined with the calculated site-specific estimate of cosmic radiation, produced reasonably accurate predictions of HPIC readings at natural sites. Normalization against two to potential alternative instruments (a tissue-equivalent plastic scintillator and energycompensated NaI detector) did not perform better than the sensitivity adjustment approach at natural sites. Each approach produced unreliable estimates of HPIC readings at radiologically impacted sites, though normalization against the plastic scintillator or energy-compensated NaI detector can address incompatibilities between different energydependent instruments with respect to estimation of soil radionuclide levels. The appropriate data normalization method depends on the nature of the site, expected duration of the project, survey objectives, and considerations of cost and practicality. © Lippincott Williams & Wilkins. Source

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