Dietmar Weiss. Exposure of Workers from the Transport of NORM in Germany

Transcription

1 Dietmar Weiss Exposure of Workers from the Transport of NORM in Germany

2 Content Objectives Methodological Approach Definition and description of scenarios Results Summary and conclusions

3 Objectives GRS services under the IAEA CRP on Transport of NORM Overall status review and categorization of most relevant NORM in Germany Status review, analysis and evaluation of NORM shipments and expected radiation exposure of the shipment staff, taking into account the usual shipment manner and package forms Development and checks of evaluation criteria and safety requirements to provide adequate safety standards for the transportation of NORM Procedures to determine the limits for exempt materials or consignments for transportation according to ADR for NORM in non-equilibrium, the applicability of homogeneity criteria and relevance of associated conventional harmful substances

4 Methodological Approach Principal legal basis for the status review and transport of NORM: German Radiation Protection Ordinance (StrlSchV), 97 with Annex XII and 102 IAEA TS-R-1 or Annex A of ADR, especially No e (nonequilibrium) and use of 10fold-value (No b) Annex XII Part A of StrlSchV contains only NORM residues (wastes), but no raw materials and by-products Raw materials and by-products which apply to the definition of NORM are considered in relation to their corresponding residues (Annex XII Part A of StrlSchV)

5 Definition and description of scenarios (1) Transport scenarios were defined for the following NORM Tantalum raw materials (Microlyte, Tantalite, Columbite, Tin slag) Raw phosphate Pipe scales and sludge from oil and gas exploitation Coal ash Waste rock material from Uranium mining Zircon raw materials (Pegmatite, Baddeleyite) Titanium dioxide raw materials (Ilmenite, Rutile) Filter gravel from waterworks

6 Definition and description of scenarios (2) Exemption conditions for non equilibrium: The derived A1 or A2 value or the limit of total activity / specific activity according to TS-R-1 para. 404 is : X m i 1 f X i i f(i) X(i) X(m) portion of activity /concentration of nuclide i in mixture corresponding A1 or A2 value or exempt value of nuclide i derived value of A1 or A2 value or exempt limit for mixture

7 Definition and description of scenarios (3) Examples for calculation of exempt limits for natural gas scales X m i 1 f X based on measured data (EEG) based on data of /KOL 85/ f Ra226 = Bq/g f Ra226 = Bq/g f Pb210 = Bq/g f Pb210 = Bq/g f Po210 = Bq/g f Po210 = Bq/g f Ra228 = Bq/g f Ra228 = Bq/g f Th228 = Bq/g f Th228 = Bq/g i i = 0.84/ /10 = = 0.995/ /10 = / /

8 Definition and description of scenarios (4) Exempt value vs. Th 228-portion f % (Th228) 60,00 50,00 40,00 30,00 20,00 Rechnerisch Exemplarische gemessene Werte 10,00 0, FG (Bq/g) Min.: 16 Bq/g (only Ra 228) Max.: 100 Bq/g (only Ra 226)

9 Definition and description of scenarios (5) Gamma dose rate around small freight containers Distance (m) Ratio -DR in distance x [m] : -DR at surface mean S.D. minimum maximum Recomm

10 Activity concentration for exempt material (1) Branch / Process Crude oil exploitation Natural gas exploitation Residue / Product Exempt value FG (Reference Nuclide) [Bq/g] sludge (36) 1, (5.8) 3 (Ra 228) Separated scales (36) 1, (5.8) 3 (Ra 228) scrap (180) 1, (29.0) 3 (Ra 228) sludge (67) 1, (30.2) 3 (Ra 226) Separated scales (67) 1, (30.2) 3 (Ra 226) scrap ( (150) (Ra 226) Amount for ADR transport [t/a] Remarks ~ 150 FG depends on 228Ra/226Ra-ratio of the deposit; data from /KOL 85/ ~ 20 ~ 1,000 mass related ratio tube/scale = 5 ~ 100 FG depends on 228Ra/226Ra-ratio of the deposit; data from /KOL 85/ ~ 30 ~ 3,000 mass related ratio tube/scale = 5

11 Activity concentration for exempt material (2) Branch / Process Niobium / tantalum manufacure Uranium mining Residue / Product Exempt value FG (Reference Nuclide) [Bq/g] Tinn slag 10 U238 + Th 232 Microlyte, Tantalite, 10 U238 + Th 232 Columbite 10 U238 + Th 232 Waste rock material 10 U238 Amount for ADR transport [t/a] Remarks ~ 10 depending on portion of U 238 ~ 60 80% share of total import of ~ 80,000 t/yr ~ 10 Huge amount from remediation of former Uranium mining sites

12 Activity concentration for exempt material (3) Branch / Process Coal combustion Titanium pigment industry Zirconium industry Residue / Product Exempt value FG (Reference Nuclide) [Bq/g] Fly ash 10 U238 + Th 232 or Pb 210 Bottom ash 10 U238 + Th 232 Ilmenite, Rutile 10 U238 + Th 232 Pegmatite, baddeleyite 10 U238 + Th 232 waterworks Filter gravel Ra 226 Amount for ADR transport [t/a] no no Remarks Mean activity concentratin < 0.5 Bq/g Mean activity concentratin < 0.5 Bq/g ~ 420,000 Importet raw material per year ~ 15,000 Milled raw material for further processing? Sporadically; depending on portion of Ra 228

13 Bulk cargo of Tantalum raw materials (1) Scenario description 1. Loading of the truck with tantalum raw materials from storage silo at railcar yard 2. Transport of bulk material from yard to plant Values of specific activities used for dose calculation Material Specific activity [Bq/g] U nat Th nat Microlyte Tantalite 15 5 Columbite 15 5 Tin slag 3 1

14 Bulk cargo of Tantalum raw materials (2) Exposure of transport workers Material U nat [Bq/kg] Th nat [Bq/kg] Personnel Hours worked per year Dust, H (Inh,j) [msv/yr] Radon, H (Inh,j) [msv/yr] external, H (E,j) [msv/yr] Microlyte Yard worker Tantalum Raw Materials E E E E E E-01 Microlyte Truck driver Tantalum Raw Materials E E E E E E-01

15 Bulk cargo of raw phosphate (1) Scenario description 1. Debarkation of raw phosphate by means of belt loader and interim storage at storage area 2. Loading of trucks with raw phosphate by means of Front-End Loader from storage silo 3. Transport of bulk material from storage area to plant Values of specific activities used for dose calculation Material Specific activity [Bq/g] U nat Th nat Raw phosphate

16 Bulk cargo of raw phosphate (2) Exposure of transport workers Material U nat [Bq/kg] Th nat [Bq/kg] Personnel Hours worked per year Hours with enh. dust conc. External, H (E,j) [msv/yr] Dust, H (Inh,j) [msv/yr] Radon, H (Inh,j) [msv/yr] Raw phosphate Belt Loader Operator Front-End Loader Driver ,96E-02 7,96E-03 6,85E ,07E-02 1,99E-02 1,71E-03 Truck driver ,90E-04 3,98E-03 3,43E-04 Truck driver ,61E-02

17 Shipment of contaminated pipes in freight container (1) Scenario description 1. Manual loading of containers with tubes at interim storage area 2. Loading of low-loading truck by fork lift truck 3. Transport of containers from storage area to repository 4. Unloading of containers at above ground warehouse by fork lift truck Ratio between specific activity of Ra 226 and Ra 228, resp. in scales at the inner wall of tubes and -dose rate at container surface: 10 Bq/g Ra 226 (scales in tubes) ~ 190 nsv/h (container surface) 10 Bq/g Ra 228 (scales in tubes) ~ 300 nsv/h (container surface)

18 Shipment of contaminated pipes in freight container (2) Exposure of transport workers Personnel Hours worked per year Shielding (steel), [cm] Distance, [m] External, H (E,j) [msv/yr] Fork Lift Truck Driver E-03 Truck Driver E-02 Warehouseman at / E-02 container Warehouseman at tubes / E-02 Warehouseman, total E-01

19 Shipment of waste rock material from uranium mining (1) Scenario description 1. Loading of dump truck by front-end loader 2. Bulk cargo shipment with dump truck from waste rock pile to open pit Mean activity of nuclides of U-Ra decay chain in waste rock material: 0.5 Bq/g ( Bq/g) 0.5 Bq/g Ra 226 ~ 250 nsv/h at a hight above ground of 1.00 m Dose calculation without exposure by inhalation of Rn 222 and decay products (only access to this area by occupationally exposed personnel) Less than 0.5 msv/yr for 1,200 hours per year working time

20 Shipment of waste rock material from uranium mining (2) Exposure of transport workers Personnel Hours worked per year Shielding (steel) [cm] Distance [m] Dust concentratio n [mg/m³] Hours with enh. dust conc. External H (E,j) [msv/yr] Dust H (Inh,j) [msv/yr] Total dose [msv/yr] Front-end loader driver 1, , E E E-02 Dump truck driver 1, / / E E E-02 Labourer (at storage site) E E E-02

21 Shipment of Titanium Dioxide Raw Materials (1) Scenario description 1. Debarkation of raw materials by means of belt loader and interim storage at storage area 2. Loading of trucks with raw materials by means of front-end loader from storage area at harbour 3. Transport of bulk material from storage area to plant Values of specific activities used for dose calculation Material Specific activity [Bq/g] U nat Th nat Ilmenite Rutile

22 Shipment of Titanium Dioxide Raw Materials (2) Exposure of transport workers Material U nat [Bq/kg] Th nat [Bq/kg] Personnel Hours worked per year Shielding (steel), [cm] Distance, [m] Hours with enh. dust conc. external, H (E,j) [msv/yr] Dust, H (Inh,j) [msv/yr] Baddele yite 7, Front-End Loader Driver Truck Driver Belt Loader Operator Dock Worker (bulk shipment) E E / / E E E E E E-02

23 Summary and Conclusions (1) The transport scenarions included both, the drivers of vehicles and the staff dealing with loading and unloading The scenarios concerned bulky or unpackaged transport and packaged transport The dose by inhalation of dust must only be taken into account for bulky transport scenarions in addition to the external dose by -radiation Special attention was paid on calculation of exposure resulting from transport of materials with non-equilibrium of radionuclides of U-Ra-chain and Th-chain

24 Summary and Conclusions (2) The 10fold limit for exempt materials containing only natural radionuclides, e.g. 100 Bq/g for Radium isotopes, is only a theoratical value due to the need for derivation of this limit by means of the formula given in para. 404 of TS-R-1 As the value for activity concentration of e.g. Th228 is by factor 10 lower than for Radium isotopes or Pb/Po210 the limit of activity concentration decisively depends on the share of Th228 (fth 228 ) The external dose by -radiation depends solely from the activity concentration of Ra226 and/or Ra228 independent on the equlibrium status because no -emitters appear before Ra226 and Ra228 in the decay chains

25 Summary and Conclusions (3) For all scenarios on transport of packaged materials only the external dose must be considered while the dose by dust inhalation is neglegible in that case. Accordingly, the application of the 10fold value for U nat and Th nat is non-restrictive for transport of packaged material. The resulting external dose is less than about 0.3 msv/yr, in most cases less than 0.1 msv/yr. Contrary, the application of the 10fold value for U nat and Th nat is restrictive for transport of unpackaged material due to the consideration of the dust inhalation path. A 5fold value for U nat and Th nat is proposed.

26 Summary and Conclusions (4) The activity concentration of Ra226 and Ra228 is linearly correlated to the external dose independent on the kind and indented use of the shipped material The application of the 10fold value for materials of radioactive non-equilibrium with a Ra226/Ra228 ratio > 5 and subsequently a gross activity concentration of exempt material of > 75 Bq/g could cause a dose > 1 msv/yr. Therefore the following limitation for the activity concentration of Ra isotopes of 15 Bq g -1 for Ra 226 and 10 Bq g -1 for Ra 228 is proposed The 10fold exempt limit of 100 Bq g -1 for Pb 210 and Po 210, each in non-equilibrium is thoroughly applicable regardless there limitation to 50 Bq g -1 of each by application of the formula in para 404 of TS-R-1.

27 Thank you for your attention!