CLEARANCE IN THE FRAMEWORK OF DECOMMISSIONING OF NUCLEAR POWER PLANTS IN GERMANY. Thomas Pöhlsen Clearance of Radioactive Material

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1 CLEARANCE IN THE FRAMEWORK OF DECOMMISSIONING OF NUCLEAR POWER PLANTS IN GERMANY Clearance of Radioactive Material

2 Mg Mg WHY IS CLEARENCE OF IMPORTANCE IN GERMANY? IN THE FRAMEWORK OF DECOMMISSIONING Masses in a NPP example: Supervised area Control area 2

3 Mg Mg WHY IS CLEARENCE OF IMPORTANCE IN GERMANY? IN THE FRAMEWORK OF DECOMMISSIONING Masses in a NPP example: Supervised area Control area 97,2% 2,4% Clearance options: unconditional clearance clearance for disposal (landfills / incinerators) clearance for recycling (melting of metals) clearance of buildings for demolition clearance of ground area rad. waste 0,4% further use under a licence 3

4 CLEARANCE IN THE REGULATORY FRAMEWORK Atomic Energy Act (AtG) Radiation Protection Ordinance (StrlSchV) Licences State-of-the-art technology rules (ISO, DIN ), Guidelines, Radiation Protection Ordinance (StrlSchV), 29: radioactive / contaminated material may only be used as non-radioactive material if clearance is granted by the competent authority clearence <-> 10 µsv/a criterion for individuals of the population (in math. models: expectation value 10 µsv) nuclide-specific clearance levels for eight different clearing paths for different materials and different restrictions (in Bq/g, Bq/cm²). Competent authorities may call in an independent expert (AtG 20) TÜV NORD works as an independed expert for several Nuclear Licencing and Supervisory Authorities in Germany Internationally TN is a full service provider in the field of nuclear safety. 4 in preparation: a new ordinance for clearance to transpose the Council Directive 2013/59/Euratom into national law

5 CLEARING PATH: CLEARANCE FOR DISPOSAL OF SOLID MATERIAL ON LANDFILLS Restrictions: Material to be disposed on a landfill, up to 1000 t/a, Higher clearance values than for unrestriced clearance (e.g. Co-60: 2 Bq/g instead of 0.1 Bq/g) 5

6 CLEARANCE PATHS IN GERMANY Unconditional clearance of Solid material, oils, coolants Demolition waste > 1000 t/a Ground area Buildings for further use Clearance values for Co Bq/g 0.09 Bq/g 0.03 Bq/g 0.4 Bq/cm² Surface contamination: averaging up to 1000 cm² 1 Bq/cm² Averaging up to: 300 kg 1000 kg 1000 kg 1 m² Clearance for disposal of Solid material on landfills Solid and liquid material in incinerators up to 100 t/a / 1000 t/a 6 Bq/g / 2 Bq/g (1 Bq/cm²) 7 Bq/g / 2 Bq/g (1 Bq/cm²) 300 kg 300 kg Clearance of buildings for demolition 3 Bq/cm² 1 m² (or more) Clearance of scrap metal for recycling (melting) 0.6 Bq/g (1 Bq/cm²) 300 kg 6

7 HOW IS COMPLIANCE WITH CLEARANCE LEVELS DEMONSTRATED? CLEARANCE PLAN chronological list of the treatment and monitoring steps Rules for participation for independent experts / supervisory authority further applicable documents giving detailed description of the step personnel involved in treatment or monitoring 7

8 HOW ARE CLEARANCE MEASUREMENTS PERFORMED Characterization Dismantling Decontamination Screening Final Measurements Approval / control by supervisory authority Performing measurements in compliance with state-of-the-art technology rules (ISO 11929, DIN to -7) Combined measurements may be used: e.g. radioactive surface contamination monitor + gammasensitive measuring system Key results: Activity concentration < clearance levels with 95 % conf. lev. 8 typically 100 % of material measured

9 CURRENT APPLICATIONS, EXAMPLES Buildings for demolition Laborious procedures Every wall area to be measured Infiltration of contamination to be taken into account Special structures to be evaluated 9

10 CURRENT APPLICATIONS, EXAMPLES: CLEARANCE OF A GENERATOR (BWR) Approx. 23 m x 5 m Approx. 650 Mg Stator: Center & end caps Rotor Auxiliary units Steel body Lamination Windings Cooling systems (gas & liquid) Painted in the control area Aim: non-destructive demonstration of compliance with clearing levels Image: Vattenfall Europe Nuclear Energy GmbH 10

11 CURRENT APPLICATIONS, EXAMPLES: CLEARANCE OF A GENERATOR (BWR) Non-destructive demonstration of compliance with clearing levels considering: Outer surface Liquid cooling system Gas compartments Combination of considering the operational history, measuring accumulation points sampling (paint) measuring the outer surface (in-situ) 11 Image: Vattenfall Europe Nuclear Energy GmbH

12 CLEARANCE FOR DISPOSAL A TOPIC OF PUBLIC INTEREST Clearance for disposal in landfills often causes public interest: the 10 µsv/a criterium may be checked for every individual disposal facility Real conditions at the location of the disposal facility Model parameters for the conduction of clearance values 12

13 NEEDS FOR FURTHER IMPROVEMENTS, IAEA ASSISTANCE / TOPICS FOR INT. COOPERATION International guidance on surface contamination values SR 44 chapter 3.5: it has to be recognized that for specific situations such as the clearance of metal or the reuse of buildings from nuclear installations, additional criteria relating to the surface contamination may have to be applied that are not reflected in the derived activity concentration values. International guidance on averaging masses (and averaging surfaces) also taking into account confidence levels to be reached due to measurement uncertainties for each sample and for larger amounts of material, e.g.: for clearance it turns out that the consideration of uncertainties (measurement uncertainties / natural background / initial level of polution) often contributes significantly to conservatism and can be a challenge when compliance with clearance values is demonstrated. especially for H-3 and C-14 with clearance values from SR 44 and required confidence levels of 95 % for each sample, clearance procedures are more complex and costly than radiologically necessary. An international recommendation and clearance values for deposition of material on landfills. 13

14 SUMMARY In Germany clearance is regulated in the Radiation Protection Ordinance, 29 (StrlSchV). Radiological basis: eff. dose max. in the order of 10 µsv/a for individuals Clearance is of importance because about 97 % of the total mass in the control area is cleared. Clearance paths exist for solid and liquid materials conditional (landfills, incinarators, smelting, buildings for demolishion) and unconditional clearance (material, buildings, ground, rubble) International guidance for surface contamination values, averaging masses / surfaces and confidence levels to be reached would be helpful. TÜV NORD has a wide experience in clearance in Germany working as independed experts for several Nuclear Licencing and Supervisory Authorities. Internationally TN is a full service provider in the field of nuclear safety. 14, tpoehlsen@tuev-nord.de