Minimizing Activation, Size and Costs and yet Maximizing Efficiency

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1 Minimizing Activation, Size and Costs and yet Maximizing Efficiency An Engineering Challenge for Neutron Research Instruments Elbio Calzada MLZ is a cooperation between:

2 Outline Introduction: Neutron Source FRM II Experimental Halls Experiences with Materials: the Good and the Ugly. Experiences with Shielding Elements Developement of a Reusable Shielding Material for Neutron and Gamma Radiation Conclusions 15th May, 2018 CREMLIN - Engineering for Advanced Neutron Instrumentation and Sample Environment 2

3 Research Center Garching 15th May, 2018 CREMLIN - Engineering for Advanced Neutron Instrumentation and Sample Environment 3

4 Research Center Garching 15th May, 2018 CREMLIN - Engineering for Advanced Neutron Instrumentation and Sample Environment 4

5 Neutron Source FRM II 15th May, 2018 CREMLIN - Engineering for Advanced Neutron Instrumentation and Sample Environment 5

6 Neutron Source FRM II 15th May, 2018 CREMLIN - Engineering for Advanced Neutron Instrumentation and Sample Environment 6

7 Experimental Hall at FRM II 15th May, 2018 CREMLIN - Engineering for Advanced Neutron Instrumentation and Sample Environment 7

8 Neutron Guide Hall West at FRM II 15th May, 2018 CREMLIN - Engineering for Advanced Neutron Instrumentation and Sample Environment 8

9 Neutron Guide Hall East at FRM II 15th May, 2018 CREMLIN - Engineering for Advanced Neutron Instrumentation and Sample Environment 9

10 Activation in Materials Core Biological shield Elements in the biological shield Elements in the biological shield and in the neutron beam Elements in the neutron beam Shielding elements 15th May, 2018 CREMLIN - Engineering for Advanced Neutron Instrumentation and Sample Environment 10

11 Activation: Elements in the Biological Shield Core Biological shield Elements in the biological shield All materials in contact with neutrons become radioactive. One of the most uncomfortable material is Cobalt. It is present mostly in stainless steels and has a half life of 5 years. 15th May, 2018 CREMLIN - Engineering for Advanced Neutron Instrumentation and Sample Environment 11

12 Example 1: Elements in the Biological Shield of the Reactor Plate made of stainless steel (Co) after 10 years in operation the front part gets a dose rate of 5 Sv/h 15th May, 2018 CREMLIN - Engineering for Advanced Neutron Instrumentation and Sample Environment 12

13 Example 1: Elements in the Biological Shield of the Reactor Coating made of borated aluminum 15th May, 2018 CREMLIN - Engineering for Advanced Neutron Instrumentation and Sample Environment 13

14 Example 2: Elements in the Biological Shield of the Reactor Coating made of borated aluminum Coating made of boron carbide plates 15th May, 2018 CREMLIN - Engineering for Advanced Neutron Instrumentation and Sample Environment 14

Screws shielded with boron carbide plates 15th May, 2018 CREMLIN -

15 Example 2: Elements in the Biological Shield of the Reactor Fasteners made of titanium Coating made of boron carbide plates Screws shielded with boron carbide plates 15th May, 2018 CREMLIN - Engineering for Advanced Neutron Instrumentation and Sample Environment 15

16 Activation in Materials Core Biological shield Elements in the biological shield Elements in the biological shield and in neutron beam 15th May, 2018 CREMLIN - Engineering for Advanced Neutron Instrumentation and Sample Environment 16

17 Example 3: Elements Placed in Neutron Beam Collimator made of low cobalt steel 15th May, 2018 CREMLIN - Engineering for Advanced Neutron Instrumentation and Sample Environment 17

18 Example 3: Elements Placed in Neutron Beam Collimator made of low cobalt steel 15th May, 2018 CREMLIN - Engineering for Advanced Neutron Instrumentation and Sample Environment 18

19 Example 3: Elements Placed in Neutron Beam A hot cell was necessary to handle the activated collimators 15th May, 2018 CREMLIN - Engineering for Advanced Neutron Instrumentation and Sample Environment 19

Example 3: Elements Placed in Neutron Beam Even small amounts of Cobalt contained in every steel become activated so much during operation that a later handling and removal becomes a major problem.

20 Example 3: Elements Placed in Neutron Beam Even small amounts of Cobalt contained in every steel become activated so much during operation that a later handling and removal becomes a major problem. The new collimators are therefore manufactured from borated steel plates as they are used for nuclear power plant shielding. The cross section of the contained boron overshadows the iron cross section in order to decrease the activation. 15th May, 2018 CREMLIN - Engineering for Advanced Neutron Instrumentation and Sample Environment 20

88 wt% boron in granular form, encased in the rolling process of steel plates.

21 Example 3: Elements Placed in Neutron Beam For the manufacture of the new collimators a steel alloy was used. An Austrian company produces borated steel plates that contain up to 1.88 wt% boron in granular form, encased in the rolling process of steel plates. Since the boron is encased during the rolling process, this material is not available as semi-finished blocks, but only as sheet metal with a maximum thickness of 3.4 mm or less. 15th May, 2018 CREMLIN - Engineering for Advanced Neutron Instrumentation and Sample Environment 21

process These blocks were placed in a milling machine and reduced to the required cross

22 Example 3: Elements Placed in Neutron Beam The cut-out pieces were stacked and aligned in a press, then welded together in the pre-fabricated grooves, forming a solid block in the process These blocks were placed in a milling machine and reduced to the required cross section 15th May, 2018 CREMLIN - Engineering for Advanced Neutron Instrumentation and Sample Environment 22

Wire-cut electric discharge machining (wire EDM) with a threaded wire was the best way to cut the

23 Example 3: Elements Placed in Neutron Beam To produce the conical channels in the collimators, stepped layering by laser cutting of varying diameter holes had been considered. Wire-cut electric discharge machining (wire EDM) with a threaded wire was the best way to cut the complicated contours of the pinhole camera projection. 15th May, 2018 CREMLIN - Engineering for Advanced Neutron Instrumentation and Sample Environment 23

24 Activation in Materials Core Biological shield Elements in the biological shield Elements in the biological shield and in neutron beam Elements in the neutron beam 15th May, 2018 CREMLIN - Engineering for Advanced Neutron Instrumentation and Sample Environment 24

25 Example 4: Elements Placed in Neutron Beam Neutron guides with vacuum tubes made of stainless steel (Co) 15th May, 2018 CREMLIN - Engineering for Advanced Neutron Instrumentation and Sample Environment 25

of aluminum 15th May, 2018 CREMLIN - Engineering for

26 Example 4: Elements Placed in Neutron Beam Vacuum tubes made of stainless steel (Co) Vacuum tubes made of aluminum 15th May, 2018 CREMLIN - Engineering for Advanced Neutron Instrumentation and Sample Environment 26

27 Example 5: Elements Placed in Neutron Beam Neutron guides with cobalt coating 15th May, 2018 CREMLIN - Engineering for Advanced Neutron Instrumentation and Sample Environment 27

28 Activation in Materials Core Biological shield Elements in the biological shield Elements in the biological shield and in neutron beam Elements in the neutron beam Shielding elements 15th May, 2018 CREMLIN - Engineering for Advanced Neutron Instrumentation and Sample Environment 28

Shielding Elements for Neutron and Gamma Radiation Some properties to be considered in the design of shielding elements: Whenever the areas of

The elements must be lighter than the capacity of the crane.

The dose rate on the outer surface of the shielding must be lower than the dose rate stipulated by the local authorities in these controlled

29 Shielding Elements for Neutron and Gamma Radiation Some properties to be considered in the design of shielding elements: Whenever the areas of the reactor need to be accessed, the shielding elements must be able to be disassembled. The elements must be lighter than the capacity of the crane. The joint between components should not have a direct view to the interior of the instrument. The dose rate on the outer surface of the shielding must be lower than the dose rate stipulated by the local authorities in these controlled area. Shielding elements must be designed to minimize background. Shielding elements must not be inflammable. The surface must be able to be decontaminated. The activation in shielding elements should be be as low as possible. 15th May, 2018 CREMLIN - Engineering for Advanced Neutron Instrumentation and Sample Environment 29

30 Shielding Elements for Neutron and Gamma Radiation Manufacturing Cost Installation Cost / Time Decommissioning Cost 15th May, 2018 CREMLIN - Engineering for Advanced Neutron Instrumentation and Sample Environment 30

Shielding Elements for Neutron and Gamma Radiation Typical challenges in places with limited space: With a limited wall thickness, the possible shielding properties may fall below the

31 Shielding Elements for Neutron and Gamma Radiation Typical challenges in places with limited space: With a limited wall thickness, the possible shielding properties may fall below the required value. For the required thickness, the load on the floor may be greater than allowed. 15th May, 2018 CREMLIN - Engineering for Advanced Neutron Instrumentation and Sample Environment 31

32 Shielding Elements for Neutron and Gamma Radiation Material for typical shielding elements for neutron and gamma radiation Heavy concrete with or without formwork. Combination of steel and polyethylene plates 15th May, 2018 CREMLIN - Engineering for Advanced Neutron Instrumentation and Sample Environment 32

33 Shielding Elements for Neutron and Gamma Radiation Disadvantages of heavy concrete shieldings: Not all contained elements attenuate neutron- and gamma-radiation Available space at facility may be an issue Weight of shielding element may be an issue Processing difficult in winter time Decommissioning of concrete in steel containers is complex, costly and time consuming. Reusable shielding material will have to consist of a neutron moderator based on hydrocarbon a neutron absorber based on B a gamma absorber based on Fe 15th May, 2018 CREMLIN - Engineering for Advanced Neutron Instrumentation and Sample Environment 33

Shielding Elements for Neutron and Gamma Radiation First approach Calculations Monte Carlo Model Detector Source Objectives Explore the optimal proportion of polyethylene, iron and boron carbide to

34 Shielding Elements for Neutron and Gamma Radiation First approach Calculations Monte Carlo Model Detector Source Objectives Explore the optimal proportion of polyethylene, iron and boron carbide to reach the lowest dose rate Explore the ideal powder density to reach the same shielding quality as concrete Parameters Use of a sphere with a 60 cm radius and a theoretical powder density of 100% Use of two radiation sources for neutron- and gamma-radiation 15th May, 2018 CREMLIN - Engineering for Advanced Neutron Instrumentation and Sample Environment 34

Dose [psv] First Approach Total dose per source neutron on the surface of the sphere R=60cm [psv] Result of Montecxarlo Simulations: The lowest total dose rate at the surface of the simulation model

35 Dose [psv] First Approach Total dose per source neutron on the surface of the sphere R=60cm [psv] Result of Montecxarlo Simulations: The lowest total dose rate at the surface of the simulation model assuming 100% powder density is reached with a mixture of 60 % Iron 35 % Polyethylene 5% Boron Carbide 15th May, 2018 CREMLIN - Engineering for Advanced Neutron Instrumentation and Sample Environment 35

Three alternative models Polyethylene pellets

paraffin 15th May, 2018 CREMLIN - Engineering

36 Three alternative models Polyethylene pellets with boron and iron powder Steel granulate with a layer of wax and boron powder A mixture of iron powder, ferroboron powder and liquid paraffin 15th May, 2018 CREMLIN - Engineering for Advanced Neutron Instrumentation and Sample Environment 36

37 Ideal Powder Density Dose rate on the surface of MC model Dose rate psv 1,E-05 1,E-06 1,E-07 1,E-08 1,11E-07 1,01E-07 1,15E-07 3,27E-07 4,23E-08 5,20E-08 5,74E-08 1,52E-07 1,63E-08 2,60E-08 2,87E-08 7,10E-08 3,87E-07 1,02E-07 2,01E-08 5,09E-07 Dosis Neutrons Dosis secondary Gamma Dosis primary Gamma Dosis Total radiation 1,E-09 Fe/FeB/Paraffin- Mixture Powder density 80% Fe/FeB/Paraffin- Mixture Powder density 90% Fe/FeB/Paraffin- Mixture Powder density 100% Heavy concrete (4,5g/ccm) Result: A powder density of 80% is sufficient to reach the same shielding quality as heavy concrete. 15th May, 2018 CREMLIN - Engineering for Advanced Neutron Instrumentation and Sample Environment 37

holes 15th May, 2018 CREMLIN - Engineering for

38 Practical Implementation Borated polyethylene Iron beam filled with shielding material Filling holes 15th May, 2018 CREMLIN - Engineering for Advanced Neutron Instrumentation and Sample Environment 38

39 Improvements: 15th May, 2018 CREMLIN - Engineering for Advanced Neutron Instrumentation and Sample Environment 39

Inserts with screw thread can be mounted with precision.

40 Possible Applications: Mixture of Fe + FeB casted with epoxy resin Density 4.7g/cm³ This material can be finished with machine tools. Inserts with screw thread can be mounted with precision. 15th May, 2018 CREMLIN - Engineering for Advanced Neutron Instrumentation and Sample Environment 40

41 Possible Applications: Collimator components made of Fe + FeB + Epoxy resin 15th May, 2018 CREMLIN - Engineering for Advanced Neutron Instrumentation and Sample Environment 41

42 Conclusions: The selection of suitable materials is essential to guarantee the required functionality in each component of an instrument and to minimize its activation at the same time. The best choice of materials guarantees the efficient operation of the components of an instrument but also minimizes radioactive waste. In the long term, that choice can be the most cost-efficient. About Shielding material: We have successfully developed a truly innovative shielding material for neutron- and gamma-radiation at FRM II. This new shielding material is reusable, has a better shielding quality than heavy concrete and is cost-efficient. Shielding elements with the same shielding effect that heavy concrete are 10 % to 20 % thinner. This innovative shielding material is being implemented at the new facilities at FRM II. TU-München holds a patent for this innovative shielding material. 15th May, 2018 CREMLIN - Engineering for Advanced Neutron Instrumentation and Sample Environment 42

43 Thank you for your attention! Questions are welcome... 15th May, 2018 CREMLIN - Engineering for Advanced Neutron Instrumentation and Sample Environment 43

SAMPLING AND RADIOLOGICAL ANALYSIS OF COMPONENTS OF THE TRIGA REACTOR AT THE MEDICAL UNIVERSITY OF HANNOVER

SAMPLING AND RADIOLOGICAL ANALYSIS OF COMPONENTS OF THE TRIGA REACTOR AT THE MEDICAL UNIVERSITY OF HANNOVER ABSTRACT Gabriele Hampel, Heinrich Harke, Medical University of Hanover, Germany Uwe Klaus, Wieland