Decommissioning and decontamination | Ukraine
Optimizing monitoring of a legacy uranium processing site20 April 2012
Lack of site characterization data and incomplete or unreliable environment monitoring studies can significantly limit quality of safety assessment procedures and priority action analyses needed for remediation planning of contaminated legacy uranium production sites. Based on experience establishing monitoring programmes in Ukraine, this paper proposes some practical steps for optimization in sampling strategy planning and analytical procedures. By Oleg V. Voitsekhovych and Tatiana V. Lavrova
As in other former Soviet Republics, Ukraine has been heavily affected by residues arising from mining and milling of uranium ores. The key uranium production sites in Ukraine are described in [1, 2]. One of the largest uranium production facilities in Ukraine was state enterprise “Pridniprovsky Chemical Plant” (SE PChP), which started operations in 1948 processing ores from Ukraine and other central European countries. The plant is situated a few kilometres away from the Dnipro River in the town of Dniprodzerzhinsk. Operation of the plant ceased in 1991. During operation, nine tailings dumps were created containing about 42 million tonnes of uranium ore production residues and radioactive waste with a total activity estimated at about 4 x 1015 Bq. Five of the tailings dumps are located within the territory of the industrial zone of Dniprodzerzhinsk town, and the zone is located close to inhabited areas. Also left behind in the industrial zone are the abandoned production facilities of the former PChP (including buildings, storage facilities, technical structures), most of them heavily contaminated and in a derelict state. The tailings could also cause environmental impacts that extend the risks for radiation exposure to the public living along the Dnipro River due to contamination of the groundwater at the tailing sites, which drain into the Dnipro River.
The Dniprodzerzhinsk site belongs to one of the most devastated and environmentally impacted sites in Ukraine. Remediation of the legacies at the site is on one hand essential for Ukraine in its ambitious plans to expand the national nuclear energy programme. On the other hand, remediation of the site is a big economic as well as a technical challenge for the country. The expected complexity and the scale of remediation of the legacies require know-how, a sound financial basis and the willingness to prioritise this task.
Preparation and implementation of such a large-scale remediation project also requires having established an adequate environmental monitoring programme. Ukraine’s ambitious plans to implement a remediation programme were first developed in 2003, but only were seriously financially supported since 2009. In that year, the “State target ecological programme to bring in a safe condition of the former uranium facilities at the industrial site of the former SE PChP” was established, and Ukraine became participants of the IAEA regional project RER 3010 “Supporting of preparation for remediation of uranium production legacy sites”.
It has became apparent that the successful implementation of such programmes can be effective only if the priorities, sequencing and scope of the necessary remediation actions will be based on an objective analysis of the expected radiation, ecotoxicological, engineering and economic risks. International experience shows that estimates of these risks can be made on the basis of the safety assessment tool, the input data for which are the result of the site characterization, site-specific environment radiation monitoring and surveillance programmes. Therefore from the very beginning of the preparatory activities for the future remediation programme at this site, the tasks to elaborate and establish the regular source term and environment monitoring programmes were priorities for state enterprise “Barrier”, which was specially created by the government authority for management and implementation of the remediation programme. The environment radiation monitoring department of the Ukrainian Hydrometeorological Institute (UHMI), Kiev, is in charge to help SE “Barrier” to develop and establish a site-specific monitoring programme. The experience gained in developing and optimization of this programme during the past five years are described in this paper.
Existing site observation points
A gamma dose survey and screening studies were carried out for the whole site, allowing identification of the most contaminated areas and hazards prior to the design of a basic monitoring network. The basic monitoring network at the uranium legacy site consists of fixed observational points where environmental samples such as soils, aerosols, surface and groundwater are regularly taken, as well as regular sampling of surface water in five locations in the rivers Dnipro and Konoplyanka. Measurement of the aerosol in air and of atmospheric fallout are currently being carried out at seven locations in the former SE PChP site and at the surrounding residential area of Dniprodzerzhinsk. The observations of groundwater quality are carried out once a year at more than 20 monitoring wells, most of which were created when the facility was in operation . Observations on groundwater include the water level as well as in-situ measurement of water temperature, electroconductivity, pH, Eh. The content of chemical ion composition, toxic contaminants and radionuclides in the water are performed in certified analytical laboratories.
The concentration of the toxic metals in the aerosol, soils and water samples such as As, Pb, Cd, Co, Ni, Zn, Mn, Cu, Fe and V are also determined by atom-adsorption spectrometry method as a part of regular monitoring programme. The observation of Rn-222 ambient concentration are carried out using plastic track detectors with exposure period of 1-2 months at more than 50 locations in the territory, mainly at the surface of tailing dumps, on the buildings of the former U-extraction facilities and administrative buildings. Regular sampling (several times a year) of the groundwater in domestic wells, aerosols in domestic lands and food products growing in farmlands are carried out in the surrounding residential areas as well. Most of the samples collected and analysed for the contents of U-Th series radionuclides and some toxic metals were analysed in the laboratories of the Ukrainian Hydrometeorological Institute and its partners.
At the initial phase of observation it was difficult to identify priority for the exposure pathways of the radiation risks, and consequently parameters to be measured due to lack of prior collected data and uncertainties with this site characterization. With the accumulation of the observational data and its analyses, it became possible to optimize the programme and methods of observation at the site by exposure risk.
The start of remediation programme task implementation was the driving force to establish an optimal radiation monitoring programme. The main reason for optimizing the monitoring programme was to collect site data and characterize the source term to develop a realistic scenario for dose assessment and radionuclide transport modelling to support the decision making process in remediation planning.
An IAEA study  has recommended establishing a source monitoring and an environmental monitoring programme. The latter is divided into source-related and person-related monitoring. Each of the types of programmes require different organizational structures, sampling design, sample collection procedures and determination of analytical methods. Both types of monitoring programmes at the site were integrated into a tool to solve the primary tasks:
1. Safety assessment as basis for priority action planning (source monitoring and environmental monitoring)
2. Safety management during and after implementation of remediation programmes (source-related monitoring and person-related monitoring)
3. Environmental and public Safety and public communication (environmental monitoring, monitoring data management and risk communication).
During recent years extended screening site characterization studies have been carried out, resulting in a comprehensive legacy site inventory report, in which the most contaminated locations and facilities at the former uranium production legacy sites were identified, including data on the tailing residues associated with the amount of radioactive and other chemically-toxic materials. The monitoring network was established taking into account that about 20 enterprises are still in operation at the territory of the former Uranium Industrial site, whose employees are most vulnerable to be exposed by radioactive residues stored or dispersed at this territory.
The screening site characterization study covered the industrial site and surrounding areas, and included the following tasks for observation:
a) Gamma dose rate surveys at the territory of industrial sites, and also inventory studies at the U-tailings and also outside and inside of the most contaminated buildings
b) Radionuclide concentrations in aerosols, soils and tailing materials
c) Radon ambient concentrations at the territory and also outside and inside of buildings, using radon radiometers, passive track detectors and liquid scintillation cameras, and radon exhalation surveys from the tailing covers
d) Radionuclide concentrations in soils, ground and surface water and locally-grown food products
e) Background levels were measured in the vicinity and areas that have not been affected by the uranium tailings
f) Baseline monitoring information (meteorology, hydrology, hydrogeology)
g) Chemistry of soils, aerosols, ground and surface water.
The main focus on analytical measurements was on radionuclides including U-238, U-234, Th-230, Ra-226, Pb-210, Po-210 and Th-230.
The results of the extended screening monitoring studies were summarized in  and used as input data for dose assessment to estimate the relative contribution of the different exposure pathways and for most typical averaged and extreme meteorological and hydrological conditions, which have to be prioritized in the design of the source and environment monitoring programme.
Previous assessments showed that under current conditions the influence of uranium facilities on the population and the environment outside of the industrial area are very low.
Our general conclusions were the following:
•The doses for people living in the vicinity of the uranium production legacy site are estimated to be lower than 1 mSv a year for any potentially calculated scenario
•However, an accident scenario that affects the tailing dams and removes the cover may lead to potentially significant radiological consequences which still require assessment and long-term surveillance at least for periods of 100-1000 years.
•For most workers, those whose work places are in non-contaminated buildings or who are mainly working in a non-contaminated area of the legacy site, the total annual dose values are estimated to be in the range of 0.1-0.5 mSv a year
•The maximum annual doses of workers whose workplaces are located nearby the tailing dumps or in and near the contaminated buildings may vary from 1-2 to 8-12 mSv depending upon their specific duties and time spent at the contaminated areas or contaminated premises
•The highest doses (up to 30mSv a year) would be obtained by people who have regular access to the contaminated premises and are involved in remediation activities such as removal and utilization of the tailing materials and/or of the most contaminated equipment (whose exposure is mainly due to high Rn-222 concentration and external gamma exposure).
These estimates also showed that the main radiation risk factor at the former uranium production industrial area is the high level of Rn-222 activity concentration in air due to high radon exhalation rates that have been measured at the many tailings sites exceeding 1 Bq/(m2s), as well as relatively high levels of external gamma radiation, reaching in some locations
10 µSv/h and higher. It was also shown that Rn-222 is variable in time and is very site-specific. The spatial pattern of Rn-222 distribution over the territory and at the specific tailing covers were detected by radon monitors and also passive track detectors.
Despite the presence of significantly contaminated areas within this site the relative effect of dust wind re-suspension and its role on exposure via exhalation pathways was estimated as not significant.
The estimates obtained from the safety assessment study  based on the result of the initial phase of the monitoring programme enabled us to establish priorities for the observation programmes in future phases of the programme, depending on environmental factors and activities at the industrial site. In the near term, the main attention will be paid to the gamma dose rate and to the radon track detector surveys. The observation of activity concentration in aerosols will be carried out by mobile aerosol pumps to be installed only at the site of remediation works. Continuous observation including meteorology will be carried out only in one representative location to characterize general air contamination condition at the site. A second basic aerosol observation system will be established at the meteorological station of Dniprodzerzhinsk town to characterize background conditions in the region of potential impact.
Despite provisional conclusions that radionuclides in surface water and groundwater also pose low radiological risks for population, trend-type monitoring of radionuclides in surface and groundwater will continue. The regular observation of radionuclides originating in uranium production, and of trace elements in drainage waters, in the water of Dnipro River upstream and downstream of the legacy site, as well as in the groundwater monitoring network at the industrial site can help understanding of the environmental impact of this contaminated site in general, and also will indicate the effectiveness of the particular remediation action under implementation. Therefore the regular monitoring programme will be continued. The water samples will be taken once a month at sampling locations close to the site and once a season at the relatively far-flung zones. Ground water monitoring will be continued at all available observational wells once a year.
Thus, the optimization of sampling programme operations has been determined according to ranking performed by a variety of factors influencing exposure pathways and radiation dose factors.
The remediation priorities may vary significantly during the planning and implementation phase of the remediation programme, and may change priorities, sampling designs and analytical methods for the monitoring observations as well. Therefore, optimization is an ongoing (continuous) process, during which the optimal amount of observational data needed depends on what problems need to be solved, such as compliance of the existing releases from the sources or level of environmental contamination with established regulatory safety criteria such as environment security evaluation (trend of radionuclides at the observational points) or justification of site remediation environment strategy and its effectiveness of remediation technology application. Another significant factor in the optimization of plans and procedures of observation that may affect significantly the cost and reliability of monitoring programmes are the methods of sampling and analytical support.
The analytical methods that are essential for this application can be also considered as a part of site-specific monitoring programme optimization procedures. The relatively simple methods for gross alpha activity measurements and also for U-Th radionuclide series determination in water, soil and aerosols were tested, developed and also successfully applied to support the routine environment monitoring programme established at the uranium production legacy site in Dneprodzerzhinsk .
The general scheme of ranking and justification of the monitoring programme tasks as part of a safety assessment and long-term site management process at the uranium production legacy sites is presented in Fig. 1.
The existing monitoring network and the in-situ observation system established at the site require further development and implementation to support large-scale rehabilitation works. According to the “Concept for the state remediation programme at the PChP uranium production legacy site” (2008) the project would be broken into four phases:
Phase 1: Conceptual design development of the regulatory framework (2010)
Phase 2: Implementation of priority remedial actions, completion of inventory and exhaustive safety assessment. Start of decontamination of the contaminated territories and some buildings (2011-2014)
Phase 3: Reclamation of the tailing covers or relocation of tailings to the largest uranium residue tailing “D”, and further remediation actions (2015-2019)
Phase 4: Phytostabilization of the tailing covers subjected to erosion, reclamation and amelioration of the damaged industrial landscapes to environmentally-friendly and socially-acceptable long-term stable state for long-term stewardship (2020-2024).
To support the changing phases of the project, the monitoring programme has to be continuously re-optimized. It requires the following improvements to conduct remediation task mentioned above.
Phases 1 & 2 (Safety assessment and plan)
1. Conduct additional measurements (dose rate, nuclide concentration and specific activities in different environmental media)
2. Assess the safety and functionality of technical barriers
3. Investigate in detail the state of contamination of technical structures (buildings, technical facilities, pipelines, industrial areas, storage facilities)
4. Re-estimate prior inventory of uranium and its physical and chemical speciation as a basis for justification of a request on possible re-working of the residue materials
5. Use inventory data to assess the potential environmental impact along different pathways
6. Conduct special studies of Kd values for uranium and Ra-226 in the tailing residues to reduce uncertainties in long-term prediction of radionuclide transport from tailings to the Dnipro River via groundwater
7. Provide special assessment of activity median aerodynamic diameter (AMAD) in aerosol particles (especially inside the most contaminated buildings which are planned for reuse or demolition, and in the area where first priority actions are planned with large mechanical soil removal at the surface of tailings)
8. Install a regular observational network in line with the modified monitoring programme
9. Develop recommended aerosol sample monitoring network within the territories around most contaminated areas at the site
10. Conduct monitoring according to the optimized programme.
Phase 3 (Monitoring during site work)
1. Implement and conduct person-related environmental monitoring system within the industrial zone; conduct an individual dosimetry programme
2. Develop and conduct an source-related monitoring to survey the environmental impact of the source-related remedial actions
3. Develop and apply release measurement procedures
4. Develop an source inventory study and environment monitoring -related database, which allows complete documentation of remediation works and their impact
5. Communicate with the public through a regular monitoring programme report to demonstrate safety of ongoing work.
Phase 4 (post-remedial monitoring)
1. Develop and conduct monitoring to prove success of remediation (post-remedial monitoring)
2. Develop special measurement methods for the proof of success of remediation measures
3. Develop the existing remediation and baseline monitoring system with an eye towards a long-term monitoring system, remediation action completion report and public communication.
To establish an optimal and efficient monitoring programme, the analytical laboratory of the operator of the Dniprodzerzhinsk Uranium Legacy Site (SE “Barrier”) should to be able conduct the following actions related to monitoring and surveillance programmes:
1. Maintain local site specific observational network and carry out all sampling activities
2. Measure all field parameters such as ambient dose equivalent rates, ambient radon activity concentrations, radon exhalation rates, dust concentration and dust precipitation (aerosol fallout)
3. Determine gross alpha activities in water and aerosol samples and also total beta activities in water, Eh, pH, redox potential and main cations in water
4. Establish person-related individual gamma dose rate monitoring.
5. Measure the key radiological parameters in solid and liquid samples: Unat, U-238, Ra-226 (in particulates and liquid samples), Rn-222 (in water and air), gross alpha and total beta (in water).
In many cases an ecotoxicological assessment is required for uranium production legacy sites. Therefore it is also recommended to establish regular sampling of aerosols and water to identify some toxic metals and other chemicals. The specific set of analyses should be clarified by special screening studies. In the case of the PChP territory, special attention should be paid to As, Pb, Zn, Mn, Ni and V, which are exceeding maximal admissible levels in soil, groundwater and surface water at many observational points at the site. High contamination of the environment is associated with ore processing procedures at uranium production facilities in past.
Expanding sampling in this way requires additional funds for procurement of equipment, for training of staff and for the ongoing improvement of the infrastructure. But it also requires methodological assistance and science-based support.
In general, the importance of an open communication with the local stakeholders (through public relations activities) should be recognized as indispensable to the successful implementation of remediation work at a site like Dneprodzerzhinsk, where people live in the immediate neighbourhood of radioactive legacies and other hazardous industrial residues. The monitoring data should be regularly disseminated to the public as well as via annually-prepared reports, and via the web site of the enterprises involved. Clearly describing the optimization process and the test procedures can help persuade the public to trust the monitoring programme results, that their perception of risk is adequate, and will help them to become involved in remediation planning.
This work was supported by Ministry of Energy and Coal Industry of Ukraine “State target ecological programme to bring in a safe condition of the former uranium facilities at the industrial site of the former SE PChP. Some aspects of this research were funded by USTC Project No. 3290. A significant amount of analytical equipment that has allowed UHMI to carry out reliable monitoring studies at uranium production legacy sites have been obtained with financial support of IAEA UKR 0923 project. Ukrainian experts have also benefited from participation in the IAEA TC RER/3/010 project.
The authors thank these agencies for their support.
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