TAPIRO fast spectrum research reactor for neutron radiation damage analyses M. Carta*, K. W. Burn, P. Console Camprini, V. Fabrizio, L. Falconi, A. Santagata ( ENEA – Italy ) S. Dulla, P. Ravetto ( Politecnico di Torino – Italy ) * mario.carta@enea.it IGORR 18 3-7 December 2017, Sydney Australia
Layout of the presentation 1. Introduction 2. ASTM standard damage functions 3. The TAPIRO reactor 4. TAPIRO neutronic characterization 5. TAPIRO damage parameters 6. Roundup 2 IGORR 18 3-7 December 2017, Sydney, Australia
Introduction Although Material Testing Reactors (MTRs), having powers greater than 5 ÷ 10 MW, are usually selected as radiation fields for neutron radiation damage analysis, nowadays an increasing attention is paid also to low power research reactors because they can provide very qualified, in terms of both intensity and energy spectrum, neutron radiation fields. The ENEA low power fast spectrum TAPIRO research reactor, located in the Casaccia Research Center near Rome, Italy, complies with the above quality requirements. This paper describes how the neutron flux characterization has been performed in the past at TAPIRO. Characteristics of some main ASTM standard damage parameters, such as 1 MeV equivalent neutron flux and hardness parameter, are provided for different positions along the main irradiation channels. 3 IGORR 18 3-7 December 2017, Sydney, Australia
ASTM standard damage functions The damage mechanism Rate of displacements produced by a Primary Knock-on Atom (PKA) after elastic (for example) collision with neutrons having energy E n A A A A A A n E n A A A PKA 4 IGORR 18 3-7 December 2017, Sydney, Australia
ASTM standard damage functions The damage mechanism dpa ( E ) ( E ) ( E ) n el n n A A A A A A n E n ( E ) el n A A A 5 IGORR 18 3-7 December 2017, Sydney, Australia
ASTM standard damage functions The damage mechanism dpa ( E ) ( E ) ( E ) n el n n A A A A A R T θ n A A A 1 1 4 A T E 1 cos E 1 cos n n 2 2 2 ( 1 A ) 4 A 0 T E E n n 2 ( 1 A ) 6 IGORR 18 3-7 December 2017, Sydney, Australia
ASTM standard damage functions The damage mechanism Mean transferred energy <T> to an atom by elastic collision <T>/E n with a neutron having energy E n 0.50 0.45 0.40 0.35 0.30 0.25 0.20 0.15 0.10 0.05 0.00 0 50 100 150 200 250 A 7 IGORR 18 3-7 December 2017, Sydney, Australia
ASTM standard damage functions The damage mechanism dpa ( E ) ( E ) ( E ) n el n n A A A A R D T E d A A A E T 2 E d d average threshold displacement energy for an atom 8 IGORR 18 3-7 December 2017, Sydney, Australia
ASTM standard damage functions The damage mechanism E n dpa ( E ) ( E ) ( E ) P E ; T ( T ) dT n el n n n E d A A A … R ( T ) D D T E d A A A T 2 E d average threshold displacement energy for an atom 9 IGORR 18 3-7 December 2017, Sydney, Australia
ASTM standard damage functions The damage mechanism ν (T) ν ( T ) 25.0 En = 1 keV En = 10 keV 20.0 15.0 10.0 5.0 0.0 0.00E+00 2.00E+02 4.00E+02 6.00E+02 8.00E+02 1.00E+03 1.20E+03 1.40E+03 T (eV) 0 for T E d 2 ( T ) 1 for E T E d d 0 . 8 T 2 0 . 8 for E T E d n 2 E 0 . 8 d 10 IGORR 18 3-7 December 2017, Sydney, Australia
ASTM standard damage functions The damage mechanism An approximate relation is: E n dpa ( t ) t el 4 E d For example, assuming for 27 Al < σ el > = 3 barn, <E n > = 0.5 MeV, E d = 25 eV, Δ t = 1 year we obtain the figure below for different flux intensities. dpa*year 100.00 10.00 TRIGA 1 MW 1.00 JHR 100 MW 0.10 0.01 1.00E+11 1.00E+12 1.00E+13 1.00E+14 1.00E+15 φ (n∙cm -2 ∙s -1 ) 11 IGORR 18 3-7 December 2017, Sydney, Australia
ASTM standard damage functions KERMA functions In general a PKA will generate a cascade of ν displacements. This cascade will deposit in the lattice a damage energy E D (T), also indicated as partition energy, proportional to the PKA energy T, given by: E D ( T ) T L ( T ) where L(T) is the Lindhard partition function. It can be defined a displacement KERMA (Kinetic Energy Released in MAterials) function (units [ barn∙eV ]) for neutron collisions. This function F D provides the rate, following neutron collisions, of deposit in the lattice of a damage energy E D (T), for unit atom and unit flux. F ( E ) ( E ) P ( E ; T ) T L ( T ) dT [barn eV] D n el n n ASTM Standards 12 IGORR 18 3-7 December 2017, Sydney, Australia
ASTM standard damage functions KERMA functions 28 Si Damage functions Fd (mb·MeV) 1.E+03 JANIS JEFF 3.1 ASTM 1.E+02 1.E+01 1.E+00 1.E-01 1.E-02 1.E-03 1.E-05 1.E-04 1.E-03 1.E-02 1.E-01 1.E+00 1.E+01 1.E+02 1.E+03 1.E+04 1.E+05 1.E+06 1.E+07 1.E+08 E (eV) 13 IGORR 18 3-7 December 2017, Sydney, Australia
ASTM standard damage functions KERMA functions In general we’ll have for a certain neutron flux, being N the atomic density of the material: -3 -1 w N F ( E ) ( E ) dE [eV cm s ] D D n n n where w D is the rate, following neutron collisions, of deposit in the lattice of the damage energy density. w D has units [eV∙cm -3 ∙s -1 ]. It can be noticed that w D is a “damage” power density. For an interval time Δt we have: -3 D N t F ( E ) ( E ) dE [eV cm ] D n n n 14 IGORR 18 3-7 December 2017, Sydney, Australia
ASTM standard damage functions 1 MeV equivalent flux For a certain position of the system we can define a monochromatic flux with energy E ref given by : ( , E ) ( E E ) r eq n n ref having the properties to produce the same damage power at the same position of the system: W ( ) F ( E ) ( , E ) W ( ) F ( E ) ( , E ) dE r r r r D , eq , ref D ref eq ref D D n n n This flux it’s named the E ref equivalent flux. In particular, if E ref =1 MeV , we’ll have: F ( 1 MeV ) ( , 1 MeV ) F ( E ) ( , E ) dE r r D eq D n n n Or: F ( E ) ( , E ) dE r D n n n ( , 1 MeV ) r eq F ( 1 MeV ) D and this flux it’s named the 1 MeV equivalent flux. 15 IGORR 18 3-7 December 2017, Sydney, Australia
ASTM standard damage functions Spectrum hardness parameter We can define a neutron spectrum hardness parameter as: ( , 1 MeV ) r eq H ( ) r ( , E ) dE r n n We need less 1 MeV neutrons to produce the same damage produced by the system neutron H 1 ( , 1 MeV ) ( , E ) dE r r spectrum. The system neutron spectrum tends eq n n to be “softer ” respect 1 MeV eq. The same 1 MeV or system neutron spectrum neutrons are needed to produce the same H 1 ( , 1 MeV ) ( , E ) dE r r eq n n damage. The system neutron spectrum tends to be “damage analogous” respect 1 MeV eq. We need more 1 MeV neutrons to produce the same damage produced by the system H 1 ( , 1 MeV ) ( , E ) dE r r neutron spectrum. The system neutron eq n n spectrum tends to be harder ” respect 1 MeV eq. 16 IGORR 18 3-7 December 2017, Sydney, Australia
ASTM standard damage functions The role of low power research reactors (LPPRs) To accurately evaluate these damage parameter we have to accurately know: • Reactor spectrum, which in turns dpa ( t ) t k k depends on reactor materials and k geometrical complexity, plus nuclear data -3 -1 w N F ( E ) ( E ) dE [eV cm s ] D D , k n n n k • Damage mechanisms, including annealing times -3 D N t F ( E ) ( E ) dE [eV cm ] D , k n n n k The challenge for LPRRs, providing largely less damage respect to High Power Research Reactors, is to try to compensate this lack in damage level by a higher accuracy in experimental data. 17 IGORR 18 3-7 December 2017, Sydney, Australia
The TAPIRO reactor What it means TAPIRO? TAPIRO (Tapir in English)? Taratura Pila Rapida a potenza zerO at Zero Power Fast Pile Calibration 18 IGORR 18 3-7 December 2017, Sydney, Australia
The TAPIRO reactor Origins 19 IGORR 18 3-7 December 2017, Sydney, Australia
The TAPIRO reactor Core layout 20 IGORR 18 3-7 December 2017, Sydney, Australia
The TAPIRO reactor Experimental channels 21 IGORR 18 3-7 December 2017, Sydney, Australia
The TAPIRO reactor Neutronic features Φ ≈ 2∙10 10 n/cm 2 ∙s @ 5 kW Φ ≈ 5∙10 11 n/cm 2 ∙s @ 5 kW Φ ≈ 3∙10 12 n/cm 2 ∙s @ 5 kW 22 IGORR 18 3-7 December 2017, Sydney, Australia
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