NORM AND TENORM MANAGEMENT AND DECONTAMINATION PROCEDURES

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1 NORM AND TENORM MANAGEMENT AND DECONTAMINATION PROCEDURES GIACOMO ZAMBELLI DAVIDE DI PIETRANTONIO CARLO OPPICI ALBERTO CIARMATORI FRANCESCO CARNACCINI Protex Italia spa Via Cartesio, Forlì FC ITALY - Abstract: - Some activities and some specific industrial practices can increase concentrations of naturally occurring radioactive materials (NORM) in mineral concentrates, products and waste streams. This so-called TENORM (Technologically Enhanced Naturally Occurring Radioactive Materials) phenomenon can result in small increases of radiation exposures to workers and the public. This paper aims to provide a general description of the problem related to TENORM describing the practices that originate these materials, the management methods of control, remediation and finally disposal. Key-Words: - NORM TENORM management, Technologically Enhanced Naturally Occurring Radioactive Materials, removal, containment solutions, decontamination techniques. 1 Introduction NORM is an acronym for Naturally Occurring Radioactive Material, which potentially includes all radioactive elements found in the environment. Long-lived radioactive elements such as uranium, thorium and potassium and any of their decay products, such as radium and radon are examples of NORM. These elements have always been present in the Earth's crust and atmosphere. The term NORM exists also to distinguish natural radioactive material from anthropogenic sources of radioactive material, such as those produced by nuclear power and used in nuclear medicine. However, from the perspective of radiation doses to people, such a distinction is completely arbitrary. Most of the average person s yearly radiation is due to exposure to radiation present in nature which therefore is usually considered of any special health or safety significance. However, certain industries handle significant quantities of NORM, which usually ends up in their waste streams. Over time, as potential NORM hazards have been identified, these industries have increasingly become subject to monitoring and regulation. However, there is yet little consistency in NORM regulations among industries and countries. This means that material which is considered radioactive waste in one context may not be considered so in another. Therefore, uncontrolled activities associated with enhanced levels of NORM can contaminate the environment and pose a risk to human health. TENORM, or technologically enhanced NORM, is an acronym used to refer to those materials where the amount of radioactivity has actually been increased or concentrated as a result of industrial processes. Issues related to "NORM / TENORM" are therefore of interest for environmental, public protection and occupational health aspects. Moreover, the "NORM" issue is also referred to radon exposure in homes or in mines, the exposure of flight crew to higher levels of cosmic radiation and exposure of workers in the oil & gas and mineral sands industries. 2 Regulations and decrees There are various national and international regulations and guidelines on radiation protection in general and NORM in particular. These are not specific to the oil & gas industry and there are variations in the methods of control adopted. In Italy, the use of NORM is regulated by Chapter III-bis of the Legislative Decree 230/95 (as amended by Legislative Decree 241/2000) "Exposure from working activities with special natural sources of radiation". In particular, in article 10 bis, paragraph 1, letters c) and d) are mentioned ISBN:

2 the work activities involving the use or storage of materials or the production of residues not usually regarded as radioactive but which contain naturally occurring radionuclides and cause a significant increase in exposure of workers and eventually to members of the public. In Annex I-bis are listed the above mentioned activities. The operator of the activities included in the list must make a preliminary assessment of dose based on measurements using a Qualified Expert. If the action level is met, the assessments should be repeated every three years (every year if over 80% of the value). If the action level is exceeded the competent authorities should be advised (ARPA, Servizio Sanitario Nazionale, Direzione provinciale del lavoro), actions to reduce the doses must be realized and a system of radiation protection is to be adopted in case of persistence of exceedances. The Action Levels specified in the Legislative Decree 230/95 are: for employees 1 msv/yr, for members of the public 0.3 msv/yr. Initiated by the European Commission (DG Energy) in 2011, the EU concluded the recast of five EURATOM Directives affecting equipment using ionizing radiation by publishing on 17 January 2014, Directive 2013/59/EURATOM of 5 December 2013 laying down basic safety standards for protection against the dangers arising from exposure to ionizing radiation. This Directive repeals Directives 89/618/Euratom, 90/641/Euratom, 97/43/Euratom, 2003/122/Euratom and in particular 96/29/Euratom. In this Directive, to be adopted within 4 years, there is a list of industrial sectors in which Member States shall ensure the identification of practices involving naturally occurring radioactive materials: Extraction of rare earths from monazite Production of thorium compounds, manufacture of thorium-containing products Processing of niobium/tantalum ore Oil & gas production (Fig.1) Fig. 1 Geothermal energy production TiO2 pigment production (Fig.2) Fig.2 Thermal phosphorus production Zircon and zirconium industry Production of phosphate fertilizers Cement production, maintenance clinker ovens Coal-fired power plants, maintenance of boilers Phosphoric acid production, Primary iron production, Tin/lead/copper smelting, Ground water filtration facilities, Mining of ores other than uranium ore. The new EU Directive introduces many new features in the field of processing NORM: Provides for example a list of activities subject to discipline more updated and extended than that of the current Italian; Activities on NORM materials are considered "practices"; The rules follow a "graded approach" (notification, authorization and appropriate inspections); It is identified a level of exemption/removal of 1 Bq/g for radionuclides of the series of U-238 and Th-232 (in secular equilibrium) and 10 Bq/g for the K-40 (with the exception of NORM processing residues that are used in building materials). 3 NORM producing industries 3.1 Oil & Gas industry During the production process, NORM flows with the oil, gas and water mixture and accumulates in scale, sludge and scrapings. It can also form a thin film on the interior surfaces of gas processing equipment and vessels as the result of radon gas decay. The level of NORM accumulation can vary substantially from one facility to another (radioactive materials are not necessarily present in the soils at every well site) depending on geological formation, operational and other factors. ISBN:

3 The NORM nuclides of primary concern in oil production are Radium-226 and Radium-228. These decay into various radioactive progeny, before becoming stable lead. Radium-226 belongs to the Uranium-238 decay series and Radium-228 to the Thorium-232 decay series. Fig.3 The process does not mobilizes from the rock formations substances such as the long-lived uranium and thorium isotopes but draws Ra-226, Ra-224, Ra-228 and Pb-210, which appear mainly in the water co-produced during oil and gas extraction. These isotopes and their radioactive progeny can then precipitate out of solution, along with sulphate and carbonate deposits as scale or sludge in pipes (Fig.3), storage tanks, filters, sludge pits, wellheads or other related equipment (such as PIGs). Radon-222 is the immediate decay product of Radium-226 and preferentially follows gas lines. It decays (through several rapid steps) to Pb-210 which can therefore build up as a thin film in gas extraction equipment. The level of reported radioactivity varies significantly, depending on the radioactivity of the reservoir rock and the salinity of the water coproduced from the well. The higher the salinity the more NORM is likely to be mobilized. Since salinity often increase with the age of a well, old wells tend to exhibit higher NORM levels than younger ones. Example of concentration activity values, found in recent decontamination operations occurred in oil & gas facilities are: Pb-210 = 120 Bq/g in sludge deposited on pipe inspection gauges and Ra-226 = 40 Bq/g, Ra-228 = 5 Bq/g in scale contained in pipes. However the values of concentrations also depend on the age of the artifact and the frequency with which this is clean and therefore in literature we can find the following higher values: for sludge Ra-226= 800Bq/g, Pb-210= 1.300Bq/g, Ra-228= 50 Bq/g, and for scales Ra-226= Bq/g, Pb-210=75Bq/g, Ra-228= Bq/g. The people most likely to be exposed to this source of radiation are workers at the site. NORM in the oil and gas industry poses a problem particularly during maintenance, waste transport and processing, and decommissioning. In particular, Pb-210 deposits and films, as a beta emitter, is only a concern when pipe internals become exposed. Exposition to alpha and gamma radiation released during the decay of radium-226 and the low-energy gamma radiation and beta particles released by the decay of radium- 228 are generally low enough not to require protective measures to ensure that workers stay beneath their annual dose limits. Internal exposures can be minimized by hygiene practices. Workers may inhale radon gas which is released during drilling and produced by the decay of radium. 3.2 Mineral sands Mineral sands contain zircon, ilmenite (main resource in the production of titanium dioxide), and rutile, with xenotime and monazite. The NORM aspect is due to monazite a rare earth phosphate containing a variety of rare earth minerals. The minerals in the sands are subject to gravity concentration. Most of this NORM ends up in the waste streams from mineral processing (oftenincluding monazite) and so, apart from zircon, the final product is itself devoid of NORM. Waste produced during zirconia/zirconium production can be high in Ra-226, which presents a gamma hazard, and waste must be stored in metal containers in special repositories. Powders from filters used during zirconia manufacture have been assayed as high as 200Bq/g of Pb-210 and 600 Bq/g Po-210. Example of concentration activity values, found in recent decontamination operations occurred in titanium dioxide industrial production facilities are: Ra-226= 40 Bq/g, Ra-228= 50 Bq/g in scale contained in the inner surface of tanks (Fig.4) and Ra-226= 25 Bq/g, Ra-228= 85 Bq/g, Ra-224= 35 Bq/g on scale deposited on filters. Fig.4 ISBN:

4 3.3 Coal Energy The total levels of individual radionuclides contained in coal are normally not great and are generally about the same as in other rocks near the coal. The main radionuclides are uranium and thorium, as well as their decay products and K-40. During combustion, the radionuclides are retained and concentrated in the flyash and bottom ash, with a greater concentration to be found in the flyash. 3.4 Metals and smelting The mining and processing of metal ores, other than uranium, may also generate large quantities of NORM wastes. These wastes include ore tailings and smelter slag, some of which contain elevated concentrations of uranium, thorium, radium and their decay products that were originally part of the process feed ore. The radioactivity in the wastes may reach in the order of thousands of Bq/kg. 3.5 Rare Earth Elements Rare Earth Elements (REEs) are chemically rather similar to uranium and thorium they are often found in conjunction with these radionuclides. The production of REEs has been accompanied by the production of large volumes of thorium hydroxide and residues containing radioactive lead and radium. Monazites form in phosphatic pegmatites and so REE extraction is sometimes in conjunction with phosphate mining. 3.6 Phosphates and fertilizer production Phosphate rock used for fertilizer is a major NORM due to both uranium and thorium. Phosphate is a common chemical constituent of fertilizer. Treatment with sulfuric acid leads to the production of gypsum (phosphogypsum) which retains about 80% of Ra-226 and 30% of Th-232 and 14% of U-238. This means that uranium and thorium are enhanced to about 150% of the value of the beneficiated ore, making it a significant NORM. Gypsum wastes can have radioactivity levels up to 1700 Bq/kg. Scales from the sulfuric acid process are formed in the pipes and filtration systems of plants and need to be cleaned or replaced periodically. 3.7 Building Materials Building materials can contain elevated levels of radionuclides including Ra-226, Th-232 and K-40. Granite, widely used as a cladding on city buildings and architecturally in homes, contains an average of 3 ppm (40 Bq/kg) uranium and 17 ppm (70 Bq/kg) thorium. Radiation measurements on granite surfaces can show levels similar to those from low-grade uranium mine tailings. 3.8 Radon Radium-226 is one of the decay products of uranium-238, which is widespread in most rocks and soils. When this radium decays it produces radon-222, an inert gas with a half-life of almost 4 days. (Radium-224 is a decay product of thorium, and it decays to radon-220, also known as thoron, with a 54-second half-life.) Because radon is so short-lived, and alpha-decays to a number of daughter products which are solid and very shortlived, there is a high probability of its decay when breathed in, or when radon daughter products in dust are breathed in. Alpha particles in the lung are hazardous. Typically exposure to radon and its progeny accounts for half of an individual s radiation dose, making it the single largest contributor. This radon comes from the ground, with exposure affected by factors such as local geography, building construction, and lifestyle. Radon levels in the air range from about 4 to 20 Bq/m3. 4 NORM Monitoring The key steps for a proper management of those activities in which there is a risk of incurring in NORM are: Identification, Strategy, Management, Decontamination, Disposal and Recycle. To reduce the risk to human health and environment controls to identify where NORM is present and control of NORM-contaminated equipment and waste must be regularly performed. Monitoring can both utilize direct measurement instruments to measure the levels of radiation emitted or alternatively, samples can be collected and sent to a laboratory for radiometric analysis. Various components of a monitoring program may include: Baseline surveys, to establish a baseline of the spread and level of NORM accumulation in facilities; Pre-shut-down surveys, to determine the locations of NORM accumulation in facilities where NORM contamination is suspected; Operational assessments, when there is the risk of encountering contamination when workers conduct intrusive work, such as clean up or maintenance on potentially NORM contaminated equipment; ISBN:

5 Legacy contamination surveys, in land disposal sites, areas used for equipment storage, cleaning, and maintenance where NORM contamination was potentially accumulated over time. Personnel who are required to monitor radiation and contamination has to be trained in the use of the instrumentation and the interpretation of the readings/measurements. There are many factors which affect the efficiency of a radiation detector and personnel who are required to monitoring NORM levels should be aware of these. For example, surface coatings of water or oil/grease would attenuate any NORM contamination present on the surface and give a lower than anticipated indication on the detector. Many surfaces may be difficult to directly monitor due to their surface condition or geometry and therefore both direct (probe measurement) and indirect (smear/swab) means of survey are required. The probe must also be held very close to the surface to ensure optimum detection efficiency for the emitted radiation as both alpha and beta particles have relatively short range in air and gamma ray intensity will decrease in line with the inverse square law away from the source of activity. Fig.5 It is unlikely that alpha and/or beta particles will be unsupported and not have associated gamma rays. Unfortunately, there is no detector that measures all three types of radiation, therefore a minimum of two different detectors is be required to characterize the NORM present in facilities adequately. In addition to monitoring, the general principles of radiation protection are primarily implemented by means of good protective measures at the workplaces. Hence, exposure control and adequate dosimetry are the most critical components of a health and safety program. 5 Control of NORM contaminated equipment NORM-contaminated equipment should be decontaminated prior to release for unrestricted use in an approved NORM decontamination facility or according to an approved decontamination protocol. In the meantime, it should be tagged or clearly marked as NORM contaminated and stored only in designated and exclusive storage areas in which the access is prevented by fencing, locking and guarding. Contaminated equipment must be handled only by trained and qualified in NORM hazards employees using the right PPE and must not be sent for maintenance/repair to workshops without informing the workshop that the component is contaminated with NORM. Before storage, is necessary to ensure that all open sections of equipment (like pipe ends) is adequately covered by heavy-gauge UV-stabilized plastic or other suitable materials to ensure that NORM does not leak from the item. 6 NORM removal 6.1 Work sites Depending on the circumstances and needs, remediation activities will be undertaken in situ, On-site or Off-site. In the first case, the operations will take place in the premises where the contaminated equipment is located. In the event that NORM are moved inside specially equipped areas located within the plant that produced them the work area is called On-site. A work area located outside the area in which the NORM material has been enhanced is called Offsite. 6.2 Containment solutions Decontamination of NORM-contaminated equipment such as tubulars, vessels, pipes, filters, pipe inspection gauges or machinery should be undertaken in a controlled manner to ensure worker protection, prevent the spread of NORM contamination, and to minimize the waste arising from the decontamination process. These must be chosen case by case depending on the type of material, the type of contamination and their dimensions. The containment measures most used are listed below: Glovebag/Glovebox Enclosed Area Total containment area (Static and Dynamic) ISBN:

6 A glovebox (or glove box) is a sealed container designed to allow the manipulation of objects where a separate atmosphere is necessary. Built into the sides of the glovebox are gloves so that the user can place their hands into the gloves and perform tasks inside the box without breaking containment. To allow the user to see what is being manipulated, the box is usually transparent. An Enclosed area it is a mobile decontamination unit, partially or completely statically confined which minimizes the waste arising from the decontamination process, providing containment for HPWJ operations and providing also a Liquid recirculation system. These can be modified ISOcontainers or even sealed structures made in plastic manufactured manually on site. The floor and surfaces shall be of an impermeable non-flammable surface capable of withstanding heavy loads. All liquid used are usually filtered and re-used. There should be no connection to any external drainage system. Primary supply tank, filter bank and settling tank will are required in the system in order to obtain a separation of NORM-contaminated sediment and oily waste material from the process water. Fig.6 A total containment is an area where airborne NORM contamination may occur and therefore requires total containment with a HEPA filtered extract ventilation system. Local extract ventilation (ie elephant trunks) will also be available in the area to control/remove dust/contamination at source. Workers will be required to wear respiratory protective equipment (RPE) in this area. As for the enclosed area, this work area can be realized in plastic using both wooden and iron supports or sealing all openings of an environment or otherwise using particular container bodies. To allow access to the radiologically-controlled areas, entry and exit of personnel and materials will only be done through dedicated decontamination units and containers or plastic bags should be provided for discarded protective clothing at the exit of the work area. Boundaries and radiation warning signs need to be erected around the work area. Only essential personnel is allowed in the work areas. Prior to maintenance of contaminated equipment sufficient ground cover made of a plastic or waterproof type material shall be placed below the item in the work area. A safety meeting is hold for all personnel performing work in order to retrace and summarize intervention procedures, protective clothing and respiratory protection requirements, radiation and contamination levels, requirements for waste generated, heat stress, action to be taken in the case of emergencies. Before operations and periodically throughout the maintenance work, any dry material that is NORM-contaminated should be wetted down to prevent the generation of airborne radioactive dust. Operations that may generate dust containing NORM (e.g., cutting, grinding or polishing) are minimized. All contaminated waste generated during maintenance is drummed or put into containers and marked or labelled listing: producer, place and date of manufacture, owner, identification number, category of radioactivity. Upon job completion, the accessible areas of the work area should be surveyed for loose contamination. Once the work area has been verified free of loose surface contamination, the boundary and postings may be taken down. 6.3 Decontamination techniques The effectiveness of decontamination is usually measured with a decontamination factor (DF) defined as DF = initial activity/residual activity. Choosing the right type of intervention must take into account: Type of surface to be decontaminated, including roughness, porosity, coatings, etc. Radiological conditions Capability for treatment and conditioning of any secondary wastes Time available/required for application Potential safety and environmental impacts Cost benefit to the overall decommissioning process Likely nature and volume of secondary waste arisings. The techniques used for the cleaning of materials NORM contaminated such as scale and sludge are mainly: ISBN:

7 Chemical extraction (dissolution) which may use non-corrosive reagents such as detergents, dilute acids or alkalis or aggressive chemicals like strong acids and other corrosive reagents; Mechanical abrasive techniques (brushing, shot blasting, sandblasting (Fig.7), abrasive jetting etc.). The blasting techniques use abrasive materials suspended in a medium that is projected on to the surface being treated. 7 Worker protection requirement Workers entering NORM-contaminated vessels or conducting decontaminating work on NORMcontaminated equipment are trained and qualified in the associated hazards. All NORM operations are planned and organized. All hazards and precautions are evaluated before the beginning of the operations. Appropriate PPE is worn and consists in: Tyvek coveralls, Neoprene, PVC, or NBR gloves, Half-face respirators with HEPA cartridges or Quarter-face HEPA disposable respirators. Eating, drinking, smoking and chewing are not allowed in work areas. The time spent in NORMcontaminated work areas is minimized. Personnel need to wash up thoroughly after working with contaminated equipment, and before eating, drinking and at the end of the workday. Workers are checked for any contamination with NORM before leaving the work area. Fig.7 High pressure water jetting or (ultra) high pressure water (Fig.8) Fig.8 8 NORM disposal options Permanent disposal for NORM should be designed to prevent contamination of natural resources such as underground water or contamination of soil. Here below are listed some methods of NORM disposal: Land based management Reinjection of scale as slurry into suitable disposal formation, etc. Offshore discharge Stabilization and disposal to authorized landfill Underground injection Cement encapsulation References: [1] IAEA, Radiation protection and the Management of Radioactive Waste in the Oil and Gas Industry, No.34, 2003 [2] IAEA, Extent of Environmental Contamination by Naturally Occurring Radioactive Material (NORM) and Technological Options for Mitigation, No.419, 2003 ISBN: