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Radiation protection in NORM industries

Radiation protection in NORM industries. Karin Wichterey Federal Office for Radiation Protection, Germany. IRPA13, Refresher Course (RC 12), 16.05.2012, Glasgow. Content. Natural radioactivity: new field of regulations Contents of NORM regulations in Germany

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Radiation protection in NORM industries

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  1. Radiation protection in NORM industries Karin Wichterey Federal Office for Radiation Protection, Germany IRPA13, Refresher Course (RC 12), 16.05.2012, Glasgow

  2. Content • Natural radioactivity: new field of regulations • Contents of NORM regulations in Germany • Materials / scenarios / pathways • Dose calculations • Impact on industries • Practical experience

  3. Natural radioactivity – RP regulations development • May 1996: Directive 96/29/EURATOM (EU-Basic Safety Standards) first regulations on NORM - different from usual RP (now: „work activities“ vs. „practices“) • implementation into national law till 2000  Germany 2001 (StrlSchV) Radiation Protection Ordinance (RPO) • Radiological criterion: 1 mSv/a (in addition to natural background) to members of the public • now: 10 years experience in industries, authorities

  4. Natural radioactivity – RP regulations development • IAEA/EU: new development  more specific regulations on natural RA and included in regular RP system, • 29.09.2011: Proposal Council Directive (Basic Safety Standards)http://ec.europa.eu/energy/nuclear/radiation_protection/doc/com_2011_0593.pdf under discussion • more stringent requirements concerning natural RA • NORM regarded as planned situation  regulatory control, but graded approach • stricter dose values (0.3 mSv/a for public in case of clearance of NORM)

  5. Implementation of EU-BSS ‘96: Example Germany Comprehensive analysis of existing informationon: • Branches of possibly relevant industries • Masses of materials / residues, their reuse or disposal options • Mass specific activities of materials and residues • Effective doses to workers and members of the public (literature) • Calculation of doses and derived limits of specific activities Materials considered: slags ashes sands wasterock, stone Reuse / disposal options: heaps, disposal use for road construction, backfilling building material (additive), others

  6. Contents of the regulations (1)Radiation Protection Ordinance (RPO) – Part 3 • Subject • Protection of humans and the environment from natural radiation sources (work activities) • Basics • level of protection: 1 mSv/a in addition to natural background (as reference level for the public*) • selectivity (‚Positive list‘ Annex XII, Part A) • no licensing – surveillance only • self-control of industries concerned (to a large extent) • if > 2.000 t of materials arising per year: declaration to authority *Workers without exposure category as well

  7. Contents of the Regulations (2) Appendix XII – List of Residues to be considered (shortened) • Sludges and scales from oil and natural gas extraction, • Impure phosphorgypsum; sludges, dust, slags from the production / processing of raw phosphate, • waste rock, sludges, sands, slags and dusts from the extraction and preparation of bauxite, columbit, copper shale, tin, ... • Dust and sludges from the off-gas cleaning of blast furnaces in raw iron and non- ferrous metal processing • Excemptions: • if used in the processes as raw material • C < 0.2 Bq/g for each RN of the U-238 sec/Th-232 sec series (= upper range of mass specific activity in soils in Germany  unamenable to control!), U-235 series considered in models only

  8. Contents of the Regulations (3) Appendix XII – Surveillance limits No residue requiring control / surveillance! • CU238max + CTh232max < C

  9. Contents of the Regulations (4) Release of Residues from control Release on application of the Legally Responsible Person • precondition: < 1 mSv/y, public (without specific measures) • other preconditions: • no obligations regarding (conventional) waste law • Declaration of the whereabouts (applicant) • Declaration of acceptance (re-user / disposal facility) formal release from control if

  10. Contents of the Regulations (5) Proof of compliance with dose criteria on release of residues • Dose assessment according to priciples layed down in Appendix XII Part D • Realism (Parameters) • inclusion of all relevant paths/ exposures Demonstration of compliance also possible by demonstrating (in case of joint disposal with other residues and waste), if conditions according to Annex XII Part C fulfilled: If proof fails: Residues should remain under surveillance! (mean specific activities of all materials disposed of within 12 months)

  11. Contents of the regulations (6)Values for CM (Annex XII Part C) Disposal of residues together with other waste (“mixing”) If C >10 Bq/g (50 Bq/g for special disposal sites)  dose assessment obligatory

  12. Contents of the regulations (7)Surveillance of other materials • Materials: (§ 3 (2) No. 20): Substances comprising natural radioactivity (if not subject to ‚practices‘) • only applicable in case of significantly enhanced exposures • authority may direct: • protective measures • that the materials are to be kept / stored at a specific place • kind of disposal • not specific, need for guidelines of application

  13. Example of check for the need of surveillance • Bauxite processing - red mud • Assumption: > 5,000 t in calender year; Disposal within catchment area of a usable aquifer CU238max + CTh232max < 0.5 Bq/g 0 + 0.34 = 0.34 < 0.5  no residue requiring control!

  14. What are representative measurements? • Definition of batches • Statistical procedures (confidence limits) • Software support!

  15. Scenarios re-use disposal other re-use road-/landscape construction sportsfields etc. house construction public workers public workers public

  16. disposal aboveground underground (disposal / backfill) public worker worker other use of slags as abrasives

  17. Pathways • external -radiation • inhalation of radon / radon DP / dust • ingestion of contaminated food (incl. drinking water) • ingestion of contaminated material Radionuclides • U-238 sec • U-235 sec (fixed natural ratio to U-238) • Th-232 sec • K-40 (found to be not relevant, not regulated) • Pb-210 + (important in case of thermal processes)

  18. Pathways according to ‚Calculation Guide‘

  19. Calculation bases for determination of the effective dose due to NORM in Germany First edition 1999 Second edition 2010 English version2011 Calculation Bases for the Determination of Radiation Exposure due to Mining-caused Environmental Radioactivity (Calculation Bases Mining) Monitoring of Radiation Exposure at Working Activities (Guidance for the implementation of legal provisions of German RPO, Part 3)

  20. „Calculation Bases Mining“ (BfS, 1999/2011) • First paper to specify calculation models and parameters enabling „realistic, but sufficiently conservative“ dose assessments • special guide for mining-related exposures with generic assumptions (formulas, parameter, reference person, background values…) • made for exposures from mining (uranium, copper) and U-milling/ Cu-smelting  has to be adapted to NORM residues, if known (scenarios, leaching rates, radionuclide vector…) • Dose calculations for members of the public and workers different scenarios and parameter • english version:http://doris.bfs.de/jspui/handle/urn:nbn:de:0221-201109056212

  21. External exposure Measurements (work place) • ambient dose rate measurement H*(10) (µSv/h) to estimate external exposure by -radiation in 1 m above ground • calibration of rate meter with Ra-226 • effective dose calculation according to „Monitoring of radiation exposure at work activities“ Calculation using models • known activities and geometry • house-scenario: equivalent to RP 112 model room • dose factors (mSv/h)/(Bq/g) • calculation according to „Calculation Guide“

  22. Inhalation of dust • calculation according to „Calculation Guide“ dust concentration dependent on scenario and kind of material (0.05 … 3 mg/m³)  concentration factor 4 for some materials (soil, waste rock, sand) due to enrichment in fine particles Berner-Impactor with dust collectors Inhalation of Radon/Radon DP • calculation according to „Calculation Guide“ • dose conversion coefficient: ICRP 65 diffusion from soil, rock, building materials  air (indoor/outdoor) using models / empirical data

  23. Waterpath / groundwater • leading scenario: private well, with paths • drinking water • cattle watering cow – milk – milkproducts meat • irrigation of forage plants & vegetables … • for six age groups according to EU-BSS (1996) In case of surface water contamination: same paths like „well scenario“, except drinking water

  24. Consumption of contaminated food • via: - irrigation of vegetables / forage plants • - deposition of dust on plants • calculation according to „Calculation Guide“ Ingestion of contaminated material (direct) • stay on / work with contaminated material • ingestion rates according to the „Calculation Guide“ • concentration factor 2 for some materials (soil, waste rock, sand) Reference person, critical group • six age groups according to EU-BSS (1996)

  25. . Eext = f ∙ H*(10) ∙ tW Example Zircon-Sand: Estimate of effektive dose* Effective dose = external dose + internal dose E = Eext + EInh EInh = b ∙ e ∙ c ∙ tW + cRn∙ F ∙ g ∙ tW . f Conversion factor of ambient dose to effective dose (default?) H*(10) Ambient dose rate, 1.5 µSv/h (maximum of measured rate) b Standard breathing rate of a person, 1.2 m3/h (default) e Inhalation dose coefficient in µSv/Bq (default?) c Average total alpha activity conc. at work place, x mBq/m3 (measured) cRn Radon-222 concentration in Bq/m³ (calculated) F Equilibrium factor, 0.4 (default) g Dose conversion, 7.8E-03 (µSv/h) / (Bq/m³) (default) tW Working hours at work place in h/a (to investigate) *See Guidance „Überwachung von Strahlenexpositionen bei Arbeiten“

  26. Estimate of effective dose Which conversion factor? • Conversion factor of ambient dose to effective dose depending on irradiation geometry/ photonenergy • Conversion factor for adults: 0.4 to 0.9 for (0.1 … 3) MeV •  For unknown irradation geometry: conversion factor = 1 • In comparison to “Calculation Bases Mining“: Semi-infinite volume source for U-238- or Th-232 series • Age group Conversion factor • > 12 a 0.6 • 1 - 12 a 0.7 ≤ 1 a 0.8

  27. Dose-coefficient for inhalation Which lung absorption class? (1/2) • Default values in the Guidance „Monitoring for radiation exposures of work activities“, BfS 2006: (slowest lung absorption class)(IAEA Safety Guide RS-G-1.6 “Occupational Radiation Protection in the Mining and Processingof Raw Materials“, 2004): • U – class S (highly insoluble compounds) • Th, Pa, Ac – class S (oxide and hydroxide) • Ra – class M (one value for all compounds) • Po – class M (oxide, hydroxide and nitrate) • Pb – class F (one value for all compounds) • ICRP 71: (Age-Dependent Doses to members of the public…): If NO information about the chemical compound (solubility) → class M should be used (except thorium (class S) and actinium (class F))  Conforms to default values in “Calculation Bases Mining”, BfS 2010

  28. Dose-coefficient for Inhalation Lung absorption class (2/2) For environmental exposure, the physico-chemical form of inhaled radionuclides is generally less well defined than in case of workplace exposure (radioactive element often is a minor component of the inhaled particles). Absorption of the radionuclide to body fluids then may be well controlled by dissolution of the particle matrix  Procedure for unspecified compounds after ICRP 71 (mainly class M) In airborne particles at work places the dissolution often is governed by the (generally known) chemical compound of the radionuclide  For work places coefficient for known compound should be used (for unknown compound: slowest absorption class)

  29. Dose-coefficient for inhalation Which AMAD (Activity Median Aerodynamic Diameter) should be used? • ICRP recommended a default AMAD for occupational exposure of 5 µm = analysis of measurements at different types of work places: nuclear power industry, research centres, uranium mills, other U-facilities, fuel handling and other facilities (only few places with monazite or mineral sand taken into account) • BfS measurement by cascade impactor in zircon sand milling room (not representative): alpha-activity in a range of 0.3 – 3.0 µm • In compliance with literature data for milled zircon sand: Dose calculation with AMAD = 1 µm and assumption of NO enrichment of radioactivity in the fine-grained fraction (for the public: always AMAD = 1 µm)

  30. Dose-coefficient for inhalation of dust Dose estimation from total-alpha-activity Effective dose-coefficient is the dose coefficient for the mixture divided by the number of alpha-emitting nuclides in the series (for U-nat: 5 and Th-nat: 3)  For U-nat: 8.2 µSv/Bq  For Th-nat: 22 µSv/Bq Results of γ-spectrometric measurements of zircon sand: Fraction of nuclides: U-nat / Th-nat ≈ 2 : 1 Effective dose coefficient: 8.2 µSv/Bq x 0.67 + 22 µSv/Bq x 0.33 ≈ 13 µSv/Bq

  31. Impacts on industries • — Usually, no personnel qualified in radiation protection; • assistance provided by consultants, authorities (guidelines etc.), • industrial associations  industries can solve problems ! • — Reduction of doses – reasons: • specific measures to reduce exposures (working regime, H&S) • technical progress (automation) • substitution of radioactive additives • — Increasing public awareness  also industries not directly • concerned with the regulations are forced to deal with RP: • portal monitors at disposals • quality certificates of materials containing radioactivity • fears of image loss  Example: water works

  32. Experience - water works — 20 tons gravel filter — C Ra-226 > 1 Bq/g No controlled residue, but operator insisted on formal release (food supplier, fears of image loss)

  33. Experience – residues from oil / gas — scales and sludges with C Ra-226 up to 1,000 Bq/g — in Germany: 10,000 t of scrap per year, containing 1,000 t of scales — C >> Control limits to be released from control! — different disposal options new technology: removal of scales, immobilisation (geopolymers) D < 1 mSv/a

  34. Support by Industrial Associations: Code of Practice

  35. Example: Thoriated gas mantles • Trend: Th replaced by Y • Working regime at change of mantles: clearly reduced internal exposure when not done overhead

  36. Water works: Reduction of radon exposure (1) Organisation of work, remediation measures, technical development (automation)

  37. Water works: Reduction of radon exposure (2)

  38. Experience - practical problems (1) — specification of residues to be controlled is suitable to confine regulatory and practical effort Problem: changing industries, raw materials, processes (e. g. geothermal energy)  need for updates !? — some possibly important materials are not listed (e.g. filter gravel) — specification of residues partly not precise enough examples: ‚scales from oil production‘ – and if enclosed in pipes ( = scrap?) ‚residues from the extraction and preparation of bauxite‘

  39. Problems with selectivity – Example bauxite Sludges from processing of bauxite to aluminium oxide red mud — 630,000 t/a — Ra-226 up to 1.6 Bq/g But: Blast bauxite also within the scope ?

  40. Experience - practical problems (2) — some disposal operators reluctant to accept radioactive materials (although released residues are not radioactivein the meaning of law) — regulatory inconsistencies with ADR (European regulations on the carriage of dangerous goods by road): exceedance of ADR limits  class 7 transport as „radioactive material“, but not in the sense of RPO (released from surveillance) Some further poblems: — standardisation of methods, models, parameters — NORM specific calculation guide for dose assessments — simple measurement methods (dosemeters, contamination monitors)

  41. Conclusions • Regulations on NORM partly lead to a considerable decrease of exposures of workers • In other fields exposures turned out to have been overestimated in the past  realistic rather than conservative dose estimates •  Guideline for dose assessments necessary • Regulated workplaces / residues partly not up to date •  more flexibility desirable! • Concept of self-control has proven itself to be adequate (no authorization necessary), but needs assistence by RP professionals

  42. Good luck with the implementation of radiation protection in NORM industries! • Thank you for your attention! • For questions: • Bundesamt für Strahlenschutz • SW 1.2: Natürlich vorkommende radioaktive Materialien, radiologische Altlasten • Karin Wichterey • +49-3018 - 333-4249 • kwichterey@bfs.de

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