Neutron Activation Cross Sections for Fusion
Adelle Hay
The University of York/Culham Centre for Fusion Energy
March 30, 2015
Adelle Hay (UoY/CCFE) Neutron activation cross sections March 30, 2015 1 / 17
Overview
1 Introduction
2 Validating Cross-section DataDifferential and Integral Data
3 Experimental Procedure and Activation AnalysisExperimental ProcedureAnalysis of ASP data
4 Current Work
Adelle Hay (UoY/CCFE) Neutron activation cross sections March 30, 2015 2 / 17
Motivation for Determination of Cross-sections
Single D-T reaction releases a 14 MeV-neutron, which can activatefirst wall components.
Neutron activation cross sections must therefore be known to a highprecision to aid in the design of first wall components.
Inventory code (FISPACT) used to determine how long materials canbe left in the tokamak until they need replacing.
Results from FISPACT also help determine the safest way ofconducting maintenance.
Adelle Hay (UoY/CCFE) Neutron activation cross sections March 30, 2015 3 / 17
Aim: To Validate Existing Cross-section Data
Ÿ2233 nuclidesŸStable and isomeric states (T ½ > 1s)
EAF-201066256 neutron induced reactions
5096 important reactions
2265 major reactions
1728 reactions with any experimental data
470 reactions with integral data
European Activation File (EAF): neutron cross sections
Cross sections
Validation: SACS
Validation: C/E
Decay data
Ÿ816 targets (H-1 to Fm-257)Ÿ86 reaction types
21282
21283
21284
20881
20882
Pb
Bi
Po
Pb
Tl
0
0
0
0
0
493
328
40
β
β
β
α
α
γ
γ
γ3 mins
stable
10.64 hours
0.3 μs
60.55 mins
Adelle Hay (UoY/CCFE) Neutron activation cross sections March 30, 2015 4 / 17
Experimental and Theoretical Cross-Section Data
Validation of EASY-2007 using integral measurements UKAEA FUS 547 (2008)
Adelle Hay (UoY/CCFE) Neutron activation cross sections March 30, 2015 5 / 17
C/E values
Validation of EASY-2007 using integral measurements UKAEA FUS 547 (2008)
Adelle Hay (UoY/CCFE) Neutron activation cross sections March 30, 2015 6 / 17
Differential and Integral Data
To validate cross-section data, require:
Integral results in several complementary neutron spectra.
Adequate experimental differential data.
Differential Data:
Cross-section measurements taken at a single, well-defined incidentneutron energy.
E.g. Neutron time-of-flight data.
Adelle Hay (UoY/CCFE) Neutron activation cross sections March 30, 2015 7 / 17
Integral Data
Neutron energy spectrum with wide peaks, eg:
Validation of EASY-2007 using integral measurements UKAEA FUS 547 (2008)
Adelle Hay (UoY/CCFE) Neutron activation cross sections March 30, 2015 8 / 17
Experimental Procedure
ASP facility at AWE. Fusion Engineering and Design 87 (2012) 662666
Deuterons accelerated towards a tritiated target.
D-T fusion reaction releases 14 MeV-neutrons.
14 MeV-neutron beam irradiates a thin (0.5mm), cylindrical(diameter 5 - 12mm) foil of chosen material.
The foil is moved (remotely) from the irradiation site to the HPGedetector.
Adelle Hay (UoY/CCFE) Neutron activation cross sections March 30, 2015 9 / 17
Experimental Procedure
ASP facility at AWE.
Adelle Hay (UoY/CCFE) Neutron activation cross sections March 30, 2015 10 / 17
Experimental Procedure
Data from the ASP neutron generator is considered integral at theposition of the rabbit system.
Due to a broad neutron energy peak.
Beam is roughly the same diameter as the foil.
Foil further away = consider the data differential. Too much flux lostat this distance.
Adelle Hay (UoY/CCFE) Neutron activation cross sections March 30, 2015 11 / 17
Reactions
Adelle Hay (UoY/CCFE) Neutron activation cross sections March 30, 2015 12 / 17
Activation Analysis
,
A0
time, t (s)
activity, A (Bq)
t = delay time (transfer time) t = measurement timed m
t = irradiation time0
A0 = Nφσ(
1 − e−λt0)
σ =A0
Nφ (1 − e−λt0)
A0 = activity at time t0
N= no. of atoms in sample
σ = neutron activation cross section
φ = neutron flux
λ = decay constant
Glenn F. Knoll, Radiation Detection and Measurment, John Wiley and Sons
Adelle Hay (UoY/CCFE) Neutron activation cross sections March 30, 2015 13 / 17
Activation Analysis
,
A0
time, t (s)
activity, A (Bq)
t = delay time (transfer time) t = measurement timed m
t = irradiation time0
A0 = Nφσ(
1 − e−λt0)
σ =A0
Nφ (1 − e−λt0)
A0 = activity at time t0
N= no. of atoms in sample
σ = neutron activation cross section
φ = neutron flux
λ = decay constant
Glenn F. Knoll, Radiation Detection and Measurment, John Wiley and Sons
Adelle Hay (UoY/CCFE) Neutron activation cross sections March 30, 2015 13 / 17
Activation Analysis
,
A0
time, t (s)
activity, A (Bq)
t = delay time (transfer time) t = measurement timed m
t = irradiation time0
A0 = Nφσ(
1 − e−λt0)
σ =A0
Nφ (1 − e−λt0)
A0 = activity at time t0
N= no. of atoms in sample
σ = neutron activation cross section
φ = neutron flux
λ = decay constant
Glenn F. Knoll, Radiation Detection and Measurment, John Wiley and Sons
Adelle Hay (UoY/CCFE) Neutron activation cross sections March 30, 2015 13 / 17
Experimental Determination of Cross Section
,
C0
time, t (s)
counts per live second, C
t = delay time (transfer time) t = measurement timed m
t = irradiation time0
C (t) = C0exp
(− ln2
T 12
[t + td ]
)
A =C
Iγε
C0 = count rate at time t0
T 12
= half life of radioactive daughter
Iγ = intensity of γ peak
ε = absolute efficiency of detector
M. R. Gilbert, L.W. Packer, and S. Lilley, Nuclear Data Sheets, Article DC8, 2013
Adelle Hay (UoY/CCFE) Neutron activation cross sections March 30, 2015 14 / 17
Experimental Determination of Cross Section
,
C0
time, t (s)
counts per live second, C
t = delay time (transfer time) t = measurement timed m
t = irradiation time0
C (t) = C0exp
(− ln2
T 12
[t + td ]
)
A =C
Iγε
C0 = count rate at time t0
T 12
= half life of radioactive daughter
Iγ = intensity of γ peak
ε = absolute efficiency of detector
M. R. Gilbert, L.W. Packer, and S. Lilley, Nuclear Data Sheets, Article DC8, 2013
Adelle Hay (UoY/CCFE) Neutron activation cross sections March 30, 2015 14 / 17
Experimental Determination of Cross Section
,
C0
time, t (s)
counts per live second, C
t = delay time (transfer time) t = measurement timed m
t = irradiation time0
C (t) = C0exp
(− ln2
T 12
[t + td ]
)
A =C
Iγε
C0 = count rate at time t0
T 12
= half life of radioactive daughter
Iγ = intensity of γ peak
ε = absolute efficiency of detector
M. R. Gilbert, L.W. Packer, and S. Lilley, Nuclear Data Sheets, Article DC8, 2013
Adelle Hay (UoY/CCFE) Neutron activation cross sections March 30, 2015 14 / 17
Corrections to Data Analysis and Automated Processing
True coincidence summing effects.
Consderation of errors, and how to correctly carry these through the dataanalysis.
Making the equations used for calculating differential cross-sectionssuitable for integral data:
Variation of neutron energy with time.
Variation of flux with time.
Aim: to produce a robust, standard method of calculating cross-sectionsand associated error using integral data.
Adelle Hay (UoY/CCFE) Neutron activation cross sections March 30, 2015 15 / 17
Corrections to Data Analysis and Automated Processing
True coincidence summing effects.
Consderation of errors, and how to correctly carry these through the dataanalysis.
Making the equations used for calculating differential cross-sectionssuitable for integral data:
Variation of neutron energy with time.
Variation of flux with time.
Aim: to produce a robust, standard method of calculating cross-sectionsand associated error using integral data.
Adelle Hay (UoY/CCFE) Neutron activation cross sections March 30, 2015 15 / 17
Corrections to Data Analysis and Automated Processing
True coincidence summing effects.
Consderation of errors, and how to correctly carry these through the dataanalysis.
Making the equations used for calculating differential cross-sectionssuitable for integral data:
Variation of neutron energy with time.
Variation of flux with time.
Aim: to produce a robust, standard method of calculating cross-sectionsand associated error using integral data.
Adelle Hay (UoY/CCFE) Neutron activation cross sections March 30, 2015 15 / 17
Corrections to Data Analysis and Automated Processing
True coincidence summing effects.
Consderation of errors, and how to correctly carry these through the dataanalysis.
Making the equations used for calculating differential cross-sectionssuitable for integral data:
Variation of neutron energy with time.
Variation of flux with time.
Aim: to produce a robust, standard method of calculating cross-sectionsand associated error using integral data.
Adelle Hay (UoY/CCFE) Neutron activation cross sections March 30, 2015 15 / 17
Gamma Spectroscopy at Culham
Characterisation of detectors recently available at Culham:
Well detector
Compton-suppressed BEGe detector
Co-axial HPGe detector
Adelle Hay (UoY/CCFE) Neutron activation cross sections March 30, 2015 16 / 17
Acknowledgements
Supervisor: David JenkinsThe Nuclear Physics Group, The University of York
Supervisor: Steven LilleyThe Applied Radiation Physics Group, CCFEAndrew Simons, and the ASP team at AWE
Adelle Hay (UoY/CCFE) Neutron activation cross sections March 30, 2015 17 / 17