Activation of equipment - overview Chris Theis, Helmut Vincke - DGS/RP

Contents How does material become activated and what drives activation levels? Legal criteria to classify material as “conventional” or as “radioactive” How can we minimize the amount of activated material?

Creation of radioactivity Material being placed in an accelerator environment can become radioactive  undesirable but unavoidable Interaction with the beam produces lot of different radioisotopes which have different levels of radiotoxicity and different half-lives Radioactivity decays but this depends on the half-life of the produced isotopes

Creation of radioactivity Energy (machine) & beam loss Position in accelerator Radioactivity levels a 1, a 2, a 3,… for different isotopes Time of material present in accelerator & in storage Chemical composition

When is a material legally radioactive? Surface contamination: 1 Bq/cm2 in case of unidentified beta- and gamma emitters and 0.1 Bq/cm2 in case of unidentified alpha emitters. Once a radio-nuclide has been identified then the CS- values given in Table 4 of EDMS doc can be used. Activity: Specific activity exceeds the CH exemption limits as given in Table 2 (column 2) of EDMS doc AND total activity exceeds the CH exemption limits as given in Table 2 (column 2) of EDMS doc OR Dose rate: (  additional criterion used for practical reasons) Ambient dose equivalent rate measured in 10 cm distance of the item exceeds 0.1 uSv/h after subtraction of the background. Safety code F:

Design studies... the minimum of the exemption limits proposed in Refs. [5,7,8] which will be adopted by future European Directives and national legislations. When is a material legally radioactive?

Legally it is ONLY the ratio of activity / LE which defines if a material is conventional or radioactive*: The dose rate criterion > 100 nSv/h is an auxiliary practical criterion. Equipment might be radioactive even if the dose rate is < 100 nSv/h! *surface contamination is not considered here as equipment can often be decontaminated

How do you determine the activity levels? Dose rate measurement a)If DR > 100 nSv/h  radioactive b)If DR < 100 nSv/h  requires detailed analysis with gamma spectroscopy which yields activity levels Gamma spectroscopy is very accurate but time consuming and usually requires destructive sampling!

Why detailed material composition data is crucial for rad. waste characterization?

Example – 3 types of steel CERN Stainless steel 304L Density: 8 g/cm3 CARBON 0.03 wt% CHROMIUM 18.5 wt% COBALT 0.1 wt% IRON 67.1 wt% MANGANESE 2.0 wt% NICKEL 11.3 wt% PHOSPHORUS wt% SILICON 1.0 wt% SULFUR wt% Magnet steel - MAGNETIL Density: 7.8 g/cm3 CARBON wt% IRON 99.7 wt% MANGANESE wt% PHOSPHORUS wt% SILICON wt% SULFUR wt% Exposed as magnets in the SPS for 20 years Storage time% of isotopes contributing to radiotoxicity that cannot be directly measured via dose rate or gamma spec 5 years29% - stainless steel, 93% - MAGNETIL steel, 76% - KHMN steel, 10 years19% - stainless steel, 95% - MAGNETIL steel, 77% - KHMN steel, 20 years10% - stainless steel, 68% - MAGNETIL steel, 41% - KHMN steel, Steel KHMN – LHC endyoke laminations Density: 8 g/cm3 CARBON 0.1 wt% CHROMIUM 6.7 wt% IRON 63.6 wt% MANGANESE 28 wt% MOLYBDENUM 0.1 wt% NICKEL 0.82 wt% NITROGEN 0.1 wt% PHOSPHORUS wt% SILICON 0.6 wt% SULFUR wt% Different steel types show considerable differences in radiotoxicity & measurable dose rate

Cooling time dependence Ti-44 dominant, Fe-55 is disappearing Fe-55 dominant

Cooling time dependence

Radiological characterization without detailed knowledge about chemical composition and radiation history is like searching a haystack to prove that there is no needle.

What can we do to avoid or minimize activation?

Reduction of radioactive waste Safety benefit Lower dose rates and committed doses Operational benefit Reduced downtime due to faster access Less restrictions for manipulation & access End of life-cycle benefit Smaller amount and less critical radioactive waste Smaller financial burden 15 Optimization already crucial during the design phase Beside other aspects also the radiological consequences of the implementation of a material have to be considered Level of activation depends on the type of the material

Material catalogue Material catalogue produced with ActiWiz EDMS or Classification of most common materials by the use of global operational and waste hazard factors 16 Catalogue provides guidelines for selection of materials to be used in CERN’s accelerator environment Authors: Robert Froeschl, Stefano Sgobba, Chris Theis, Francesco La Torre, Helmut Vincke and Nick Walter Acknowledgements: J. Gulley, D. Forkel-Wirth, S. Roesler, M. Silari and M. Magistris

Catalogue consists of three parts: Catalogue for the radiological hazard classification of materials Introduction List of critical materials in terms of handling & waste disposal* Appendix with data 17 * Many thanks to Luisa Ulrici (DGS-RP-RW) for elaborating and providing the waste disposal guidelines Materials not contained can be very easily assessed by the equipment designer/producer with the ActiWiz software –

Thank you for your attention