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Natural diatomite process for removal of radioactivity from liquid waste.

Diatomite has a number of unique physical properties and has found diversified industrial utilization. The filtration characteristics are particularly significant in the purification of liquids. The purpose of this study was to test natural diatomaceous earth (diatomite) as an alternative material that could be used for removal of radioactivity from liquid waste. A pilot-scale column-type device was designed. Natural diatomite samples were ground, sieved and prepared to use as sorption media. In this study, real waste liquid was used as radioactive liquid having special conditions. The liquid waste contained three radionuclides (Cs-137, Cs-134 and Co-60). Following the treatment by diatomite, the radioactivity of liquid waste was reduced from the initial 2.60 Bq/ml to less than 0.40 Bq/ml. The results of this study show that most of the radioactivity was removed from the solution by processing with diatomite.

Diatomaceous Earth↗

Facile access to 154Eu, a new reference source for calibration in gamma ray spectrometry.

Europium-154 can be obtained as a by-product from the large-scale production of Samarium-153 and possesses attractive features (t1/2 8.592 yr; Egamma 0.12-1.6 MeV) for use as a reference source similar to 152Eu (t1/2 13.516 yr; Egamma 0.12-1.4 MeV), which is the gold standard for calibration in gamma ray spectrometry. Thermal neutron irradiation of 5mg of 98% enriched 153Sm2O3 target in the reactor led to approximately 200 GBq 153Sm and 1.26 MBq 154Eu. A typical batch control sample of 153SmCl3 solution and final radiopharmaceutical product formulation of 153Sm-phosphonate (153Sm-EDTMP) pooled together contained about 20% of total yield, requiring post decay disposal of 153Sm as radioactive waste. Such spent solutions pooled on quarterly basis led to availing 756 kBq of 154Eu. The radioactivity content and radionuclide purity (approximately 82%) of the recovered 154Eu sample were envisaged as adequate to prepare reference sources for calibration of gamma ray spectrometers. At present, one batch of 153Sm is handled per month at our institution, with the possibility for weekly processing in future. Access to approximately 3.5 MBq of 154Eu on quarterly basis is envisaged, apart from obviating the need for instituting steps to tackle disposal of the long-lived 154Eu in the spent solution. Up to 60-120 units of 20-100 kBq of 154Eu reference sources per year could thus be available by the proposed strategy.

Calibration↗

Physiologic determinants of radiation resistance in Deinococcus radiodurans.

Immense volumes of radioactive wastes, which were generated during nuclear weapons production, were disposed of directly in the ground during the Cold War, a period when national security priorities often surmounted concerns over the environment. The bacterium Deinococcus radiodurans is the most radiation-resistant organism known and is currently being engineered for remediation of the toxic metal and organic components of these environmental wastes. Understanding the biotic potential of D. radiodurans and its global physiological integrity in nutritionally restricted radioactive environments is important in development of this organism for in situ bioremediation. We have previously shown that D. radiodurans can grow on rich medium in the presence of continuous radiation (6,000 rads/h) without lethality. In this study we developed a chemically defined minimal medium that can be used to analyze growth of this organism in the presence and in the absence of continuous radiation; whereas cell growth was not affected in the absence of radiation, cells did not grow and were killed in the presence of continuous radiation. Under nutrient-limiting conditions, DNA repair was found to be limited by the metabolic capabilities of D. radiodurans and not by any nutritionally induced defect in genetic repair. The results of our growth studies and analysis of the complete D. radiodurans genomic sequence support the hypothesis that there are several defects in D. radiodurans global metabolic regulation that limit carbon, nitrogen, and DNA metabolism. We identified key nutritional constituents that restore growth of D. radiodurans in nutritionally limiting radioactive environments.

Amino Acids↗

Practical methods for reducing radioactive contamination incidents in the nuclear cardiology laboratory.

OBJECTIVE: The purpose of this study was to determine the extent and cause of radioactive contamination in our nuclear cardiology laboratory, and to develop possible solutions to minimize future occurrence. METHODS: We conducted a retrospective review to determine the underlying causes of the 15 minor radioactive contamination events that have occurred in the exercise areas of our laboratory since 1986. Of the 15 documented events, 8 were caused by failure of intravenous apparatus and 7 were due to syringe mishandling. Based on a staff questionnaire, we determined the most prevalent causes of radioactive contamination. Other than problems associated with intravenous setup, the causes were lack of experience by the individual performing the injection, followed closely by radioactive syringe disposal problems, injection technique, and unclear designation of duties during the exercise procedure. RESULTS: Based on these findings, we formulated a 4-part plan: a training program; a closely inspected intravenous apparatus; a mobile radioactive waste container; and a clear designation of duties for personnel to be included in the exercise procedure protocol. CONCLUSION: We have implemented a sensible and practical plan for reducing radioactive contamination, which is currently being evaluated.

Accidents, Occupational↗

Radio-iodination of neurotrophins and their delivery in vivo: advantages of membrane filtration and the use of disposable syringes.

This paper reports two simple improvements for the radio-iodination of neurotrophins and their delivery in vivo. (1) Neurotrophins can be effectively separated from free iodide by using membrane filtration devices. Seven methods for the separation of free iodide are compared, including dialysis, gel filtration, and membrane filtration. Membrane filtration of the iodinated protein has several important advantages over dialysis or gel filtration. These include the precise control over the final concentration; excellent recovery of the neurotrophin; easy and inexpensive procedure; performance of the entire procedure in a fume hood; and reduced volume of radioactive waste. (2) Disposable, inexpensive syringes are suitable for the delivery of small volumes of radio-iodinated or non-radioactive neurotrophins. Plastic disposable insulin syringes are compared with Hamilton syringes. The ejection volume of the disposable syringes is surprisingly reliable in the dose range 2-15 microl. Their in vivo performance was tested by injections in the eyes of chick embryos in ovo. The amounts remaining in the eye varied significantly less with the disposable syringes. Leakage into the surrounding eye-muscles after intraocular injection was significantly more frequent with Hamilton syringes than with the disposable syringes. Thus, disposable syringes can be a reliable and cost-effective alternative for drug delivery of 2-15 microl volumes.

Animals↗

Science, policy, and stakeholders: developing a consensus science plan for Amchitka Island, Aleutians, Alaska.

With the ending of the Cold War, the US Department of Energy is responsible for the remediation of radioactive waste and disposal of land no longer needed for nuclear material production or related national security missions. The task of characterizing the hazards and risks from radionuclides is necessary for assuring the protection of health of humans and the environment. This is a particularly daunting task for those sites that had underground testing of nuclear weapons, where the radioactive contamination is currently inaccessible. Herein we report on the development of a Science Plan to characterize the physical and biological marine environment around Amchitka Island in the Aleutian chain of Alaska, where three underground nuclear tests were conducted (1965-1971). Information on the ecology, geology, and current radionuclide levels in biota, water, and sediment is necessary for evaluating possible current contamination and to serve as a baseline for developing a plan to ensure human and ecosystem health in perpetuity. Other information required includes identifying the location of the salt water/fresh water interface where migration to the ocean might occur in the future and determining groundwater recharge balances, as well as assessing other physical/geological features of Amchitka near the test sites. The Science Plan is needed to address the confusing and conflicting information available to the public about radionuclide risks from underground nuclear blasts in the late 1960s and early 1970s, as well as the potential for volcanic or seismic activity to disrupt shot cavities or accelerate migration of radionuclides into the sea. Developing a Science Plan involved agreement among regulators and other stakeholders, assignment of the task to the Consortium for Risk Evaluation with Stakeholder Participation, and development of a consensus Science Plan that dealt with contentious scientific issues. Involvement of the regulators (State of Alaska), resource trustees (U S Fish and Wildlife Service), representatives of the Aleut and Pribilof Island communities, and other stakeholders was essential for plan development and approval, although this created tensions because of the different objectives of each group. The complicated process of developing a Science Plan involved iterations and interactions with multiple agencies and organizations, scientists in several disciplines, regulators, and the participation of Aleut people in their home communities, as well as the general public. The importance of including all parties in all phases of the development of the Science Plan was critical to its acceptance by a broad range of regulators, agencies, resource trustees, Aleutian/Pribilof communities, and other stakeholders.

Alaska↗

The combined impact on doses to man of multiple, authorized, radionuclide discharges for the year 1999 reaching the upper river thames, uk.

Before issuing a new or revised authorization to discharge liquid radioactive waste to a river, past and current practice has been to assess the impact of each discharge on a site-by-site basis. This paper reports an assessment of the combined impact of all the (year 1999) authorized discharges in the upper River Thames (UK) catchment. A modification of the PC-CREAM model, using parameters specific to the upper River Thames, was used to estimate "potential doses" to the population, using the authorized discharge activity for each of the discharges as the main driving variable. The main purpose of this study was to investigate the difference in doses between single and multiple discharges in the Thames. A partial validation of the model against measurements was also carried out as a secondary investigation. The source term of the upper Thames consisted of 90 authorized discharges for 86 sites, made up of three nuclear licensed sites, 36 industrial discharges, 25 research organizations, 20 hospitals and two miscellaneous organizations. Of the authorized discharges, nuclear sites constituted 67% of the total activity in authorizations to discharge; hospitals 16%, research organizations 13%, and industry only 3%. Three radionuclides made up 96% of the total authorized discharge activity: tritium-74%; Tc-15%, and C-7%. No other single radionuclide constituted more than 1.5% of the total activity. All of the discharges from non-nuclear sites were via a sewage works so that, in total, only 39 discrete discharges to the river were included in the model. For the purposes of the assessments, it was assumed that all discharges were at the authorized limits (rather than using actual discharge). Even with this maximizing assumption, all the calculated potential doses from the combined source terms were significantly less than the radiation dose limit of 1 mSv y for a member of the public. The highest estimated potential doses were investigated further to identify the major pathways. Ingestion of fish was the main pathway in several river stretches and in the highest case constituted 97% of the dose. In a few stretches, external irradiation from the riverbank or ingestion of drinking water were the main pathways, but the potential contribution was a very small percentage (<1%) of the dose limit for members of the public. An investigation of the reasons for the relatively high potential doses resulting from fish showed that the radionuclide with the largest contribution was P. Three factors had a major effect on potential dose estimations in these circumstances: the fish consumption rate, the P concentration factor and the use of P in some cases to represent radionuclides authorized for discharge as "any other radionuclide, except alpha emitters." Using the precautionary principle, all authorized activity in the latter designation was modeled as the radionuclide which would produce the highest dose to humans.

Adult↗

Waste package performance evaluations for the proposed high-level nuclear waste repository at Yucca Mountain.

The evaluation studies of the proposed repository for long-term storage of spent nuclear fuel and high-level nuclear waste at Yucca Mountain, Nevada, are underway. Fulfillment of the requirements for limiting dose to the public, which includes containment of the radioactive waste emplaced in the proposed repository and subsequent slow release of radionuclides from the Engineered Barrier System (EBS) into the geosphere, will rely on a robust waste container design, among other EBS components. Part of the evaluation process involves sensitivity studies aimed at elucidating which model parameters contribute most to the waste package and overlying drip shield degradation characteristics. The model parameters identified for this study include (1) general corrosion rate parameters and (2) stress corrosion cracking (SCC) parameters. Temperature dependence and parameter uncertainty are evaluated for the general corrosion rate model parameters while for the SCC model parameters, uncertainty treatment of stress intensity factor, crack initiation threshold, and manufacturing flaw orientations are evaluated. Based on these evaluations new uncertainty distributions are generated and recommended for future analyses. Also, early waste package failures due to improper heat treatment were added to the waste package degradation model. The results of these investigations indicate that the waste package failure profiles are governed by the manufacturing flaw orientation model parameters.

Journal Article↗

Receptor-ligand binding assays: technologies and applications.

Receptor-ligand interactions play a crucial role in biological systems and their measurement forms an important part of modern pharmaceutical development. Numerous assay formats are available that can be used to screen and quantify receptor ligands. In this review, we give an overview over both radioactive and non-radioactive assay technologies with emphasis on the latter. While radioreceptor assays are fast, easy to use and reproducible, their major disadvantage is that they are hazardous to human health, produce radioactive waste, require special laboratory conditions and are thus rather expensive on a large scale. This has led to the development of non-radioactive assays based on optical methods like fluorescence polarization, fluorescence resonance energy transfer or surface plasmon resonance. In light of their application in high-throughput screening environments, there has been an emphasis on so called "mix-and-measure" assays that do not require separation of bound from free ligand. The advent of recombinant production of receptors has contributed to the increased availability of specific assays and some aspects of the expression of recombinant receptors will be reviewed. Applications of receptor-ligand binding assays described in this review will relate to screening and the quantification of pharmaceuticals in biological matrices.

Ligands↗

[Improved performance of a waste water radiation monitor].

Gamma ray waste water radiation monitor has been improved by using multichannel analyzer. Maximum permissible concentrations of 125I are one thousandth lower than 51Cr. This condition, the radioactive waste water cannot be pumped out occasionally. Gamma ray energy spectrum is measured by microcomputer based multichannel analyzer by which 125I photo-peak counts is separated from other radionuclide counts. Also detecting vessel is washed with pressured fresh water to prevent contamination.

Environmental Monitoring↗

Radioecological impacts of the Techa River contamination.

During the years 1949-1952, the Mayak Production Association (MAYAK), which was processing weapons-grade plutonium, was discharging radioactive wastes into the Techa River. As a result, all components of the river system (water, bottom soils, and flood plains) were exposed to massive radioactive contamination. The protective measures taken in the 1950's resulted in the improvement of the radioecological conditions in the Techa River. After 1952, the radioecological conditions in the area were mostly determined by the long-lived radionuclides 9OSr and 137Cs. This article focuses on the dependencies governing the migration of radionuclides along the vertical and horizontal planes in different components of the river system over a 40-y period. Until the 1990's, a decrease in 90Sr and 137Cs contents was noted in environmental samples and foodstuffs produced in riverside villages. In the subsequent years, the radioecological situation on the Techa stabilized. The sources of the current contamination of the river are represented by the runoffs from by-pass canals and swampy upper reaches.

Cesium Radioisotopes↗

The international atom: evolution of radiation control programs.

Under the Atoms for Peace program, Turkey received a one MWt swimming pool reactor in 1962 that initiated a health physics program for the reactor and a Radiation Control Program (RCP) for the country's use of ionizing radiation. Today, over 13,000 radiation workers, concentrated in the medical field, provide improved medical care with 6,200 x-ray units, including 494 CAT scanners, 222 radioimmunoassay (RIA) labs and 42 radiotherapy centers. Industry has a large stake in the safe use of ionizing radiation with over 1,200 x-ray and gamma radiography and fluoroscopic units, 2,500 gauges in automated process control and five irradiators. A 48-person RCP staff oversees this expanded radiation use. One incident involving a spent 3.3 TBq (88 Ci) 60Co source resulted in 10 overexposures but no fatalities. Taiwan received a 1.6 MWt swimming pool reactor in 1961 and rapidly applied nuclear technology to the medical and industrial fields. Today, there are approximately 24,000 licensed radiation workers in nuclear power field, industry, medicine and academia. Four BWRs and two PWRs supply about 25% of the island's electrical power needs. One traumatic event galvanized the RCP when an undetermined amount of 60Co was accidentally incorporated into reinforcing bars, which in turn were incorporated into residential and commercial buildings. Public exposures were estimated to range up to 15 mSv (1.3 rem) per annum. There were no reported ill effects, except possibly psychological, to date. The RCP now has instituted stringent control measures to ensure radiation-free dwellings and work places. Albania's RCP is described as it evolved since 1972. Regulations were promulgated which followed the IAEA Basic Safety Standards of that era. With 525 licenses and 600 radiation workers, the problem was not in the regulations per se but in their enforcement. The IAEA helped to upgrade the RCP as the economy evolved from one that was centrally planned economy to a free market economy. As this transition takes place, public radiation exposures in the medical field will continue to be high until the old x-ray equipment is phased out. A small conscientious health physics staff works with limited resources to keep radiation exposures at acceptable levels. These three country RCPs, as they have evolved, have some commonality. Today, all radiation installations are licensed, both for radioactive material and x-ray equipment. Radiation workers are individually licensed or registered. All RCPs have, or are striving to have, their radiation regulations conform to ICRP 60 recommendations as spelled out in the Basic Safety Standard (1996). Finally, all three countries have as yet to find a permanent solution for their radioactive waste.

Calibration↗

Stochastic effects of environmental radiation exposure in populations living near the Mayak Industrial Association: preliminary report on study of cancer morbidity.

The Mayak Industrial Association, located in the South Ural Mountains, began operation in 1948 and was the first Russian site for the production and separation of plutonium. During the early days of operation, technological failures resulted in the release of large amounts of radioactive waste into the Techa River. Residents who lived in villages on the banks of the Techa and Iset Rivers were exposed to varying levels of radioactivity. The objective of this study is to assess stochastic (carcinogenic) effects in populations exposed to offsite releases of radioactive materials from the Mayak nuclear facility in Russia. Subjects of the present study are those individuals who lived during the period January 1950 through December 1960 in any of the exposed villages along the Techa River in Chelyabinsk Oblast. Death certificates and cancer incidence data have been routinely collected in the past from a five-rayon catchment area of Chelyabinsk Oblast. The registry of exposed residents along the Techa River assembled and maintained by the Urals Research Center for Radiation Medicine for the past 40 y is the basis for identifying study subjects for this project. Specific study objectives are to evaluate the incidence of cancer among current and former residents of Chelyabinsk Oblast who are in the exposed Techa River cohort; integrate results from the dose-reconstruction study to estimate doses for risk assessment; and develop a structure for maintaining continued follow-up of the cohort for cancer incidence. In the earlier part of our collaborative effort, the focus has been to enhance the cancer morbidity registry by updating it with cancer cases diagnosed through 1997, to conduct a series of validation procedures to ensure completeness and accuracy of the registry, and to reduce the numbers of subjects lost to follow-up. A feasibility study to determine cancer morbidity in migrants from the catchment area has been proposed. Our preliminary analyses of cancer morbidity underscore the importance of examining both cancer mortality and cancer morbidity in conducting a comprehensive analysis of the occurrence of cancer in this important cohort.

Age Distribution↗

A validation test of a model for long-term retention of (129)I in surface soils.

A linear compartment model for global transport of iodine that we previously developed predicted that the mean residence time of iodine in the first 1 m of surface soil is about 4,000 y. An independent test of the model prediction is provided by measured depth profiles of (129)I in soil following atmospheric releases from the Savannah River Plant (SRP) in South Carolina and from the Karlsruhe fuel reprocessing plant in Germany. Previous analyses of these data using a linear compartment model for downward transport through soil indicated that the mean residence time in the first 0.3 m is about 40 y at both locations, which suggests that removal of (129)I from surface soil may be considerably more rapid than predicted by the global transport model. In this paper, a diffusion model is used to describe the measured soil profiles of (129)I at Savannah River. The diffusion coefficient obtained from the analysis corresponds to a mean residence time in the first 1 m of surface soil that agrees semi-quantitatively with the prediction of the global model when the concentration of naturally occurring stable iodine in soil and the flux of iodine from the atmosphere onto surface soil at Savannah River, as they differ from globally averaged values, are considered. This paper also discusses (1) the importance of the mean residence time of (129)I in surface soil for estimates of dose to individuals from near-surface land disposal of low-level radioactive wastes and (2) unresolved issues regarding global cycling of iodine.

Diffusion↗

The radiological exposure of man from radioactivity in the Baltic Sea.

A radiological assessment has been carried out considering discharges of radioactivity to the Baltic Sea marine environment since 1950. The sources of radioactivity that have been evaluated are atmospheric nuclear-weapons fallout, fallout from the Chernobyl accident in 1986, discharges of radionuclides from Sellafield and La Hague transported into the Baltic Sea, and discharges of radionuclides from nuclear installations located in the Baltic Sea area. Dose rates from man-made radioactivity to individual members of the public (critical groups) have been calculated based on annual intake of seafood and beach occupancy time. The dose rates to individuals from the regions of the Bothnian Sea and Gulf of Finland are predicted to be larger than from any other area in the Baltic Sea due to the pattern of Chernobyl fallout. The dose rates are predicted to have peaked in 1986 at a value of 0.2 mSv year-1. Collective committed doses to members of the public have been calculated based on fishery statistics and predicted concentrations of radionuclides in biota and coastal sediments. The total collective dose from man-made radioactivity in the Baltic Sea is estimated at 2600 manSv, of which approximately two-thirds originate from Chernobyl fallout, approximately one-quarter from atmospheric nuclear-weapons fallout, approximately 8% from European reprocessing facilities, and approximately 0.04% from nuclear installations bordering the Baltic Sea area. An assessment of small-scale dumping of low-level radioactive waste in the Baltic Sea in the 1960s by Sweden and the Soviet Union has showed that doses to man from these activities are negligible. Dose rates and doses from natural radioactivity dominate except for the year 1986 where dose rates to individuals from Chernobyl fallout in some regions of the Baltic Sea approached those from natural radioactivity.

Baltic States↗

Intergenerational issues regarding nuclear power, nuclear waste, and nuclear weapons.

Nuclear power, nuclear waste, and nuclear weapons raise substantial public concern in many countries. While new support for nuclear power can be found in arguments concerning greenhouse gases and global warming, the long-term existence of radioactive waste has led to requirements for 10,000-year isolation. Some of the support for such requirements is based on intergenerational equity arguments. This, however, places a very high value on lives far in the future. An alternative is to use discounting, as is applied to other resource applications. Nuclear weapons, even though being dismantled by the major nations, are growing in number due to the increase in the number of countries possessing these weapons of mass destruction. This is an unfortunate legacy for future generations.

Journal Article↗