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2 TENORM = Technologically Enhanced NORM. TENORM is encountered in the petroleum & gas industry. Enhanced levels of natural radioactivity in scale, sand and sludge of oil & gas production was first discovered around

3 TENORM is generated in the petroleum industry in the form of scales, sludge and produced water. Scales are formed on the interior surface of pipes, pumps and valves as well as on the walls of separation & storage tanks. Sludge is a mixture of residues left in the process. It contains sand, heavy hydrocarbons plus pieces of detached scale. 3

4 The other type of TENORM waste is produced water the water that comes out with the oil. Produced water is a combination of formation water, which occurs naturally in the reservoir, and the water injected into the well to increase the pressure in order to extract the oil. 4

5 The primordial radioactive nuclides 238 U and 232 Th are distributed throughout underground rock formations from which oil and gas are extracted. These radionuclides are part of the matrix of the rock, essentially insoluble in the reservoir fluids (fresh water, salt water, oil, gas or condensate), and therefore immobile. 5

6 The radium isotopes 226 Ra, and 228 Ra, which are daughters of respectively 238 U and 232 Th, are somewhat soluble in water and are therefore mobile. Consequently, radium will be present in any water pumped out of subterranean petroleum reserves. 6

7 Formation water may be rich in chloride and sulphate salts and alkaline earths such as calcium (Ca), barium (Ba), strontium (Sr) that dissolve from the rocks that surround the reservoir. Radium will be one of the cation species leached from the rocks into the formation water. 7

8 Produced water and other available water is re-injected back into the process well. When injected water and formation water are brought together, the chemical equilibrium is disturbed and salt precipitation may occur. When produced water is brought to the surface, radium comes along with it. 8

9 Precipitation is enhanced when the oil/gas/water mixture is pumped up to the surface and temperature changes are encountered. This results in the precipitation of sulphates of barium and strontium, as well as calcium sulphate and calcium carbonate BaSO 4, SrSO 4, CaSO 4 and CaCO 3. 9

10 The 226 Ra and 228 Ra concentrations in produced water typically vary between 0.3 Bq/kg 10.5 Bq/kg. Mean concentrations: 226 Ra ~ 4.0 Bq/kg 228 Ra ~ 2.1 Bq/kg. These concentrations are approximately 1000 times higher than the mean concentration in sea water. 10

11 Radium is mixed with Ca, Ba and Sr cations, which are much more abundant and possess similar chemical properties they are all part of group IIA in the periodic system, i.e. in the same vertical column of the periodic table, and have similar chemical properties. Consequently, when produced water is brought to the surface along with oil and gas, radium, which is dissolved in the produced water, co-precipitates with Ca, Ba & Sr sulphates as radium sulphate (RaSO 4 ) and radium carbonate (RaCO 3 ) complexes. 11

12 These precipitates will concentrate and accumulate in different parts of the process, forming scales and sludges. Turbulent flow in the production system will enhance the attachment of precipitated salts to the walls or sand to form deposits with enhanced levels of radioactivity. Radioactively contaminated sand and sludge can be found inside all types of equipment in oil & gas production that has been in contact with the produced water. 12

13 Scale deposits in oil and gas production facilities can usually be divided into 2 main categories: sulphate and carbonate deposits. Sulphate deposits consists mainly of barium sulphate (BaSO 4 ), while carbonate deposits consists of calcium carbonate (CaCO 3 ). Scale deposits containing 226 Ra and 228 Ra and their progeny are found as hard or porous layers on the inside of production equipment that have been in direct contact with the production stream (oil & gas mixed with production water). 13

14 The highest concentrations of radionuclides are found on the inner surfaces of produced water pipelines NORM concentrations in the petroleum industry is usually highest in the scales & sludges that form in water-handling equipment. 14

15 Country Material 226 Ra concentration (Bq/g) Brazil Brazil Algeria Norway Norway 228 Ra concentration (Bq/g) scale sludge as high as 3060 scale as high as 2570 scale sludge

16 The formation of scales and sludges can impair the oil extraction process. Scale reduces the cross-sectional sectional area of pipes and impairs flow; it may even plug pipes, causing considerable production losses. Expensive cleaning procedures may be required once these residues form. Scale removal is a common practice in the petroleum industry. It can be done either by mechanical means, or by the addition of chemicals, or both. 16

17 210 Another major pathway in which radioactive contamination of oil & gas installations occurs, is through the diffusion of the radon isotopes, 220 Rn and 222 Rn, that are either dissolved in the produced fluids or mixed with natural gas. Radon can be produced either at the surface or in the formation daughter of radium. Gas plants can have very high radiation levels, especially where large volumes of gas are stored or compressed. 17

18 The most significant radionuclide remaining at the internal surface of the installation, is 210 Pb, which originates from 222 Rn, and its daughter product, 210 Po. 210 Pb has a relatively long half-life. life. 210 Pb is mostly present as a thin lead-film on the inside of gas transport pipelines & gas storage vessels. 18

19 One can distinguish between deposits containing radium ( 226 Ra & 228 Ra), and deposits containing lead ( 210 Pb). The activity concentrations in radium deposits in production installations, typically range form 1 Bq/g to 500 Bq/g for 226Ra, and from 0 Bq/g to 300 Bq/g for 228Ra and 210Pb. In well equipment 226 Ra concentrations up to several thousand Bq/g were observed. 19

20 The activity concentration in lead deposits can be as high as 3000 Bq/g for 210 Pb. The activity per unit mass of 210 Pb is relatively low in hard scale deposits, but may reach thousands of Bq/g in the very thin layers found on the inner surfaces of gas production, gas transport and gas storage equipment. 20

21 Measured dose rates outside process equipment used in petroleum production, range between 2 µsv/h to 160 µsv/h. This is significantly above background, which is typically 0.15 µsv/h. Care must be taken during cleaning operations in order to reduce the exposure to maintenance personnel as well as to avoid contamination of the environment. 21

22 The two primary routes of personnel exposure are inhalation and external exposure to ionising photons from bulk storage of the material. Dose from the ingestion pathway is insignificant. The main routes of exposure are: Inhalation of dusts during equipment cleaning; Exposure to ionising photons close to pipelines and vessels, which concentrate radionuclides. 22

23 226 Ra is an α-particle emitter and poses a potential inhalation hazard to workers from the dust produced when pipelines are cleaned. Dose rates as high as 140 µsv/h have been measured on the surface of water pipelines, mainly close to valves or elbows, where solid particles tend to accumulate. In storage areas, dose rates up to 700 µsv/hr may be encountered on the external surfaces of barrels

24 Significant external dose rates are only observed at the outside of installation parts that are internally contaminated with radium deposits. The 46 kev ionising photons emitted by 210 Pb are not penetrating enough to cause any significant dose rate at the outside of an installation that is internally contaminated with 210 Pb deposits. 24

25 The external dose rate depends on the activity concentration of the radium deposit, its volume, its geometry and on the shielding capability of the walls, but is typically in the order of several µsv/h. Only in some extreme cases, are dose rates of several tens of µsv/h observed. 25

26 Once a process plant is opened for maintenance or inspection, workers are faced with unsealed radioactive material. Radium is almost as chemically toxic as plutonium, which is the most chemically toxic element to humans. When radium is present, there may consequently be a risk of chemical toxicity, in addition to the health risk from ionising radiation. 26

27 Investigations done on the exposure of workers in the oil and gas industry to NORM, indicate that worker doses are generally well below 10 msv per year. Calculations performed for several scenarios, under the assumption that no special precautions were taken with regard to NORM contamination, show: 27

28 1. For routinely performed maintenance on components at a production location, the yearly dose was calculated to be 0.03 msv under normal conditions, and 0.5 msv under unfavourable conditions. 2. For jobs on components performed by a specialised company on its own location, the yearly dose was calculated to be 0.3 msv under normal conditions, and 7.0 msv under unfavourable conditions. 3. Appropriate safety measures should be taken when work is performed on open NORM- contaminated installations. 28

29 Radiation doses to workers in the petroleum industry are usually below 100 µsv/yr, i.e. about 100 times lower than occupational dose limits The main radiological problems are inhalation and waste disposal. 29

30 In Europe, petroleum industry materials contaminated with NORM, is classified as radioactive waste if the activity concentrations of 226 Ra, 228 Ra or 210 Pb exceeds 10 Bq/g. As a result, the petroleum industry in Europe has to deal with a significant TENORM waste burden. 30