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"190": {
"pageid": 190,
"ns": 0,
"title": "Safety Rules in Radio Chemistry",
"revisions": [
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"*": "[[Basic Laboratory Procedures for Radio-Chemistry|Return]] \n\n<br> Before any of the students start to work in the lab they should have completed the following: \n\n*Answer and deliver the question sheet with pre-lab questions.\n*Read, understand and sign the safety instructions for working in a [[Radio chemistry laboratory|Radiochemistry laboratory]].<br><br><br>\n\n===== Safety Rules =====\n\nIn the laboratory there are measurement instruments that can to be used to check the amount of radioactivity and where it is. Hence you can verify that neither you nor your fellow students are exposed to irradiation above the safe limits. \n\nFor people who are pregnant the rules for exposure are especially strict, nevertheless the amount of activity in most student course exercises are so small that there are no health concerns. In exercises which use larger amount of radioactivity, you will be specially briefed and this will be made quite clear to everybody participating. Do not hesitate to discuss any safety concerns with either your supervisor or radiation protection officer. \n\nThe ALARA (As Low As Reasonably Achievable) principle is the main guideline for all rad. work and should be followed at all times: No person should be exposed to more radiation than absolutely necessary to carry out the work. Therefore all work done with radioactivity should be done meticulous and planned in advance. Mistakes or carelessness could easily contaminate yourself and/or persons around you. To avoid this keep equipment that has been in contact with activity separated from equipment that is not contaminated and keep workbenches etc. tidy and clean. \n\nWhen planning the exercise one should always think about the precautions one must use so that no active material is spread. Therefore certain rules must be followed: \n\n==== Laboratory rules ====\n\n* A special lab-coat (not your own) shall be used during all work in the laboratory and it shall not be used or carried out of the laboratory. \n* There shall be no eating or smoking in the laboratory, this includes chewing gum or sweets of any kind. \n* Only needed papers and writing material shall be taken into the laboratory. \n* Purses and other personal effects shall be put in the wardrobe. \n* Before an exercise starts all the equipment needed must be at the work station. \n* Always test your equipment with non-active material (\"cold run\") first to ensure that everything works as intended before actually performing the experiment (\"warm run\"). \n* Gloves must be used when there is danger of contamination and spilling, i.e. whenever you handle radioactive material or equipment which has been in contact with the radioactive material. \n* All work with radioactive material shall be done in safety trays with absorbing paper in the bottom. \n* At regular intervals and when needed check (with the hand monitor) for contamination on equipment or work space(s) which are supposed to be clean. \n* In case of any accident, minor or major, immediately inform your supervisor or the radiation protection officer. An accident includes all cases when there is contamination on persons, equipment or work spaces which should be clean. \n* All solid active-waste shall be put in specially labeled waste containers. Glass and metal shall not be mixed with paper and plastic. Liquid waste is collected in designated containers. Flammable organic liquids are to be kept separated from aquatic liquids, etc. Radioactive solutes shall not, under any circumstances be poured uncontrolled into the sink. If you work with several different radio nuclei avoid mixing them, but use separate waste containers. All waste containers shall have waste accumulation logs \u2013 make sure to update the logs! \n* When you have finished the radioactive work make sure to clean and tidy up your work station. Clean all the equipment and control it and the work space for contamination. This should be noted down in your journal and signed. In case of contaminated material or equipment, put it in a plastic bag (zip-lock), label it carefully and confer with your supervisor about what you should do with it. \n* When leaving the laboratory, hands should be checked for contamination (without gloves) and thoroughly washed as an extra precaution. If your lab or lab area is equipped with a hand/feet monitor always use it before leaving the restricted are. \n\n\n==== Risk evaluation ====\nBefore you start your exercise, you are required to think through the work and operations you are going to perform and evaluate the associated likelihood of having an accident and how serious such an accident could be. This evaluation is required to be written in your journal and signed by yourself and your supervisor before you start any practical work. \n\n\n[[Category:Radiation_protection]] [[Category:Laboratory_exercise]] [[Category:Radio_chemistry]]"
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"148": {
"pageid": 148,
"ns": 0,
"title": "Scale and Radioactivity",
"revisions": [
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"*": "Written and developed by [http://www.mn.uio.no/kjemi/personer/vit/torbjor/index.html Prof. Tor Bj\u00f8rnstad] (IFE/UiO) \n\nReturn to [[Naturally Occuring Radioactivity - NORM and TENORM | Main]] \n\n<br> \n\n==== What is scale? ====\n\nOne might say that \"scaling is the result of chemical precipitation becoming immobilised in a flowing system\". In petroleum production, the produced water, gas and oil streams define the \u201cflowing system\u201d. These streams carry the chemical components that can precipitate. \n\nScaling in production systems becomes a growing problem in reservoirs where the pressure balance is maintained by injection of waters that are not compatible with the formation waters, and the problem increases, as the reservoir grows more and more mature. In the North Sea most of the injection water has so far been composed of filtered and deoxygenated seawater. The seawater contains considerable amounts of sulphate (2-3000 ppm) while the formation waters often have a relatively high concentration of heavy alkaline earth metals calcium, strontium and barium. See table below for typical analysis of seawater ionic composition and a few examples of formation water compositions both from the North Sea and from other parts of the world. \n\nObvious from the examples given is that there may be a large variation in formation water salinity from one reservoir to another, and the relations between concentrations of the dissolved ions may change dramatically. Therefore, contact between injection and formation waters may entail precipitation and scale formation because the solubility products of the various actual chemical compounds may be superseded (see table below). The main components in scales are found to be BaSO<sub>4</sub> (+ SrSO<sub>4</sub>) and CaCO<sub>3</sub>.<br> \n\n<br> Concentrations of the main ionic components in seawater and a few formation are given in the table below, as well as solubility products.<br> \n\n{| cellspacing=\"1\" cellpadding=\"1\" border=\"1\" style=\"width: 551px; height: 255px;\"\n|-\n| Ions<br> \n| Sea water mg/l1)<br> \n| Format. water I<br>mg/l<br><br> \n| Format. water II<br>mg/l<br><br> \n| Format. water III<br>mg/l<br><br> \n| Format. water IV<br>mg/l<br><br> \n| Format. water V<br>mg/l<br><br> \n| Format. water VI<br>mg/l<br><br> \n| Format. water VII<br>mg/l<br><br>\n|-\n| Cations:<br> \n| <br> \n| <br> \n| <br> \n| <br> \n| <br> \n| <br> \n| <br> \n| <br>\n|-\n| Na<sup>+</sup><br> \n| align=\"right\" | 12.100<br> \n| align=\"right\" | 9.220<br> \n| align=\"right\" | 8.440<br> \n| align=\"right\" | 19.000<br> \n| align=\"right\" | 16.800<br> \n| align=\"right\" | 33.500<br> \n| align=\"right\" | 39.100<br> \n| align=\"right\" | 6.300<br>\n|-\n| K<sup>+</sup><br> \n| align=\"right\" | 460<br> \n| align=\"right\" | 164<br> \n| align=\"right\" | 159<br> \n| align=\"right\" | -<br> \n| align=\"right\" | 24<br> \n| align=\"right\" | 554<br> \n| align=\"right\" | 1.750<br> \n| align=\"right\" | 330<br>\n|-\n| Mg<sup>2+</sup><br> \n| align=\"right\" | 1.130<br> \n| align=\"right\" | 61<br> \n| align=\"right\" | 25<br> \n| align=\"right\" | 380<br> \n| align=\"right\" | 131<br> \n| align=\"right\" | 374<br> \n| align=\"right\" | 2.400<br> \n| align=\"right\" | 330<br>\n|-\n| Ca<sup>2+</sup><br> \n| align=\"right\" | 450<br> \n| align=\"right\" | 325<br> \n| align=\"right\" | 150<br> \n| align=\"right\" | 2.400<br> \n| align=\"right\" | 547<br> \n| align=\"right\" | 2.760<br> \n| align=\"right\" | 31.000<br> \n| align=\"right\" | 4.050<br>\n|-\n| Sr<sup>2+</sup><br> \n| align=\"right\" | 9<br> \n| align=\"right\" | 36<br> \n| align=\"right\" | 44<br> \n| align=\"right\" | 920<br> \n| align=\"right\" | -<br> \n| align=\"right\" | 415<br> \n| align=\"right\" | 850<br> \n| align=\"right\" | 90<br>\n|-\n| Ba<sup>2+</sup><br> \n| align=\"right\" | nd<br> \n| align=\"right\" | 59<br> \n| align=\"right\" | 20<br> \n| align=\"right\" | 1.420<br> \n| align=\"right\" | 6.3<br> \n| align=\"right\" | 229<br> \n| align=\"right\" | 900<br> \n| align=\"right\" | -<br>\n|-\n| Anions:<br> \n| align=\"right\" | <br> \n| align=\"right\" | <br> \n| align=\"right\" | <br> \n| align=\"right\" | <br> \n| align=\"right\" | <br> \n| align=\"right\" | <br> \n| align=\"right\" | <br> \n| align=\"right\" | <br>\n|-\n| Cl<sup>-</sup><br> \n| align=\"right\" | 20.950<br> \n| align=\"right\" | 14.409<br> \n| align=\"right\" | 12.555<br> \n| align=\"right\" | 36.800<br> \n| align=\"right\" | 28.000<br> \n| align=\"right\" | 59.100<br> \n| align=\"right\" | 123.895<br> \n| align=\"right\" | 14.980<br>\n|-\n| SO<sub>4</sub><sup>2-</sup> \n| align=\"right\" | 2.300<br> \n| align=\"right\" | nd<br> \n| align=\"right\" | 14<br> \n| align=\"right\" | nd<br> \n| align=\"right\" | 13<br> \n| align=\"right\" | 14<br> \n| align=\"right\" | -<br> \n| align=\"right\" | 823<br>\n|-\n| HCO<sub>3</sub><sup>-</sup><br> \n| align=\"right\" | 170<br> \n| align=\"right\" | 1.310<br> \n| align=\"right\" | 1.418<br> \n| align=\"right\" | 600<br> \n| align=\"right\" | 552<br> \n| align=\"right\" | 968<br> \n| align=\"right\" | 110<br> \n| align=\"right\" | 230<br>\n|}\n\n<br> \n\n{| cellspacing=\"1\" cellpadding=\"1\" border=\"1\" style=\"width: 548px; height: 24px;\"\n|-\n| valign=\"top\" | \n{| cellspacing=\"1\" cellpadding=\"1\" border=\"1\" style=\"width: 252px; height: 200px;\"\n|-\n| valign=\"middle\" align=\"left\" colspan=\"2\" | <br>Solubility products K<sub>sp</sub> of <br>SCALE salts<br>\n|-\n| Compound<br> \n| Ksp<br>\n|-\n| CaSO<sub>4</sub><br> \n| align=\"right\" | 3.73 <math>\\cdot</math>10<sup>-5</sup><br>\n|-\n| SrSO<sub>4</sub><br> \n| align=\"right\" | 3.42 <math>\\cdot</math>10<sup>-7</sup><br>\n|-\n| BaSO<sub>4</sub><br> \n| align=\"right\" | 1.05 <math>\\cdot</math>10<sup>-10</sup><br>\n|-\n| RaSO<sub>4</sub><br> \n| align=\"right\" | 4.30 <math>\\cdot</math>10<sup>-11</sup><br>\n|-\n| CaCO<sub>3</sub><br> \n| align=\"right\" | 4.95 <math>\\cdot</math>10<sup>-9</sup><br>\n|-\n| FeS<br> \n| align=\"right\" | 1.57 <math>\\cdot</math>10<sup>-19</sup><br>\n|}\n\n<br> \n\n| valign=\"baseline\" | \n <br> \n\n<br> \n\nCa<sup>2+</sup> + SO<sub>4</sub><sup>2-</sup> <math>\\cdot</math> CaSO<sub>4</sub><br> Ba<sup>2+</sup> + SO<sub>4</sub><sup>2-</sup> <math>\\cdot</math> BaSO<sub>4</sub><br> Sr<sub>2</sub><sup>+</sup> + SO<sub>4</sub><sup>2-</sup> <math>\\cdot</math> SrSO<sub>4</sub> <br>(Ra<sup>2+</sup>)<sub>x</sub> + (Ba<sup>2+</sup>)<sub>y</sub> + (SO<sub>4</sub><sup>2-</sup>)<sub>z</sub> <math>\\rightarrow</math> [Ba(Ra)SO<sub>4</sub>]<sub>z</sub> \n\nwhere x + y = z and x \u226a y. Radium is co-precipitated with barium sulphate and the other sulphates and carbonates.<br> \n\n<br> \n\n<br> \n\n|}\n\n<br> \n\n<br>\n\n==== What is radioactive scale, LRA? ====\n\nUranium and Thorium in rocks are not easily dissolved and transported by the moving waters. Their decay products are easily dissolvable. These are Radium (<sup>226</sup>Ra from the <sup>238</sup>U-series and <sup>228</sup>Ra and <sup>224</sup>Ra from the <sup>232</sup>Th-series) and Radon (<sup>222</sup>Rn from the <sup>238</sup>U-series and <sup>220</sup>Rn from the <sup>232</sup>Th-series). In brines with high chloride concentration also Lead isotopes (<sup>214</sup>Pb and <sup>210</sup>Pb from the <sup>238</sup>U-series and <sup>212</sup>Pb from the <sup>232</sup>Th-series) dissolve as chloride complexes and are easily transported in the water systems. \n\nThese radionuclides are the main sources for radioactivity in scales, in waters, oils and gases and in internal surface coating of production equipment. \n\nLRA may be roughly classified into two basically different types: <br> \n\n{| width=\"200\" cellspacing=\"1\" cellpadding=\"1\" border=\"0\"\n|-\n| [[Image:Nat activity KJM5911 lab1 4.png]]\n|-\n| ''Decay sequence for the <sup>238</sup>U natural series ending in stable <sup>208</sup>Pb. Number in the squares: Element and mass number (upper) and half-life (lower)''<br>\n|}\n\n<br> \n\nThe Radium-based LRA that is found in fields with water production. This scale is predominantly containing <sup>226</sup>Ra and <sup>228</sup>Ra and their progeny (may also contain some primary transported <sup>210</sup>Pb). Since the concentration of Radium in formation waters is much too low for precipitation with available anions on its own (i.e. the solubility product is not exceeded), the radioactivity concentration in scale is due to co-precipitation with analogues alkaline earth elements present in macro-amounts. These are mainly Ca, Sr and Ba, and the main precipitates are BaSO<sub>4</sub>, SrSO<sub>4</sub> and CaCO<sub>3</sub> according to the general equation <br> \n\nxBa<sup>2+</sup> + yRa<sup>2+</sup> (x+y)SO<sub>4</sub><sup>2-</sup>\u21c4 Ba<sub>x</sub>(Ra)<sub>y</sub>[SO<sub>4</sub>]<sub>(x+y)</sub><br> \n\nContaminated equipment may be production tubing, valves, pumps, separators, storage tanks etc.<br> \n\n2. Radon-based deposit that is also found in oil-handling facilities and most importantly in gas-producing facilities. This latter deposit is composed of thin (invisible) layers of <sup>210</sup>Pb and its decay products <sup>210</sup>Bi and <sup>210</sup>Po. Contaminated equipment may be those mentioned above and in addition gas transportation tubing, gas handling equipment (refineries), gas storage tanks etc.<br> \n\n[[Image:Nat activity KJM5911 lab1 7.png]]<br> \n\n<br> \n\n<br>\n\n==== '''Analysis of radioactive scale''' ====\n\nAnalysis of radioactivity in scale is best carried out with gamma spectroscopy. For this purpose one may for instance use NaI(Tl)-scintillation detectors. An example of the lower portion of a gamma spectrum (< 550 keV) accumulated with a NaI(Tl)-detector is given in the fig. below.<br><br> \n\n{| width=\"200\" cellspacing=\"1\" cellpadding=\"1\" border=\"0\"\n|-\n| [[Image:Nat activity KJM5911 lab1 8.png]]\n|-\n| ''NaI(Tl)-solid scintillation gamma-spectrum of <sup>228</sup>Ra and its decay products inclusice <sup>210</sup>Pb''<br>\n|}\n\n<br> \n\nSince the gamma spectrum is relatively complex, it is recommended to use a high-resolution HpGe-detector in order to resolve the photopeaks and obtain better accuracy in the analysis. An example of a gamma spectrum accumulated with a HpGe-detector in the same energy range is given in the fig. below.<br> \n\n{| width=\"200\" cellspacing=\"1\" cellpadding=\"1\" border=\"0\"\n|-\n| [[Image:Nat activity KJM5911 lab1 9.png]]\n|-\n| ''HpGe gamma-spectrum of <sup>228</sup>Ra and its decay products inclusive<sup>210</sup>Pb''<br>\n|}\n\n\nDecay schemes, gammaspectra and relevant gamma energies for NORM nuclides in radioactive scale are given as attachment to this text. \n\nThe degree of scaling in production equipment can be so heavy that flow is seriously reduced or even hindered. In such cases equipment, like production tubing in production wells have to be replaced. \n\nThe used tubing is treated specially because of the radioactivity in the scale. The first procedure on the offshore production platforms is to separate the \u201cradioactive\u201d from the \u201cnon-radioactive\u201d. For this purpose, simple detection procedures have been established that are capable of deciding whether the activity concentration is below or above the exemption level. \n\nThe practiced exemption level in Norway is \n\n10 Bq/g for <sup>226</sup>Ra<br>10 Bq/g for <sup>228</sup>Ra<br>10 Bq/g for <sup>210</sup>Pb \n\ni.e. if the activity concentration of one of these radionuclides supercedes this limit, the material will have to be treated as low-activity waste. \n\nThe scale which shows an activity concentration above the exemption level is then subject to closer and detailed analysis by gamma spectrometry in the laboratory. \n\nIn this exercise we will determine the activity concentration in examples of radioactive scale originating from the Norwegian petroleum production.<br><br> \n\n<br> \n\n<br> \n\n[[Category:Nuclear_Properties]] [[Category:Natural_activity]] [[Category:Laboratory_exercise]] [[Category:Germanium_detector]] [[Category:Gamma_Detector]] [[Category:NaI_Detector]] [[Category:Semiconductor_detector]] [[Category:Gamma_spectroscopy]] [[Category:Master]]"
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