Status and needs of activation data for fusion Robin Forrest 1 and Jura Kopecky 2 1 Euratom/UKAEA Fusion Association Culham Science Centre, UK 2 JUKO Research, Alkmaar, The Netherlands This work, supported by the European Communities under the contract of Association between EURATOM/UKAEA, was carried out within the framework of EFDA

Outline Introduction - activation data EAF data libraries, used in JEFF and FENDL EAF-2007  Suitable for ITER, IFMIF  Contents Validation and testing  EXFOR  Integral data  SACS Which nuclides and reactions are important? Importance diagrams Uncertainty data Decay data Needs Questions

Introduction Fusion technology requires good nuclear data for activation calculations Addressed in Europe by EAF and for ITER by FENDL What about needs for IFMIF? Focus is on cross sections, but also need decay data Uncertainty data also needed, what form should these be, are covariances required? ‘Issues’ to do with formats for E > 20 MeV Can subsets of important nuclei and reactions be defined? How are data validated and tested? Are new data libraries required or should existing ones be extended and improved?

EAF data libraries Long history of EAF libraries (> 20 years) Becoming larger and more comprehensive Part of an activation ‘package’ (EASY) EAF-2003 is the recommended FENDL/A-2.1 and JEFF- 3.1/A special purpose files Since then:  EAF-2005 (60 MeV)  EAF (60 MeV, d-induced)  EAF-2007 (60 MeV, d-induced, p-induced) EAF contains (simple) uncertainty data for all n-induced reactions Decay data (consistent with cross sections) Documentation Validation reports

EAF-2007 Distributed beginning 2007 Builds on EAF Details:  65,565 n-induced reactions (10 -5 eV - 60 MeV)  Isotopes with T ½ > 6 hours as targets  66,864 d-induced reactions  67,925 p-induced reactions  Decay data for 2,231 nuclides  Uncertainty data for all n-induced reactions  Part of EASY-2007 Documentation available on web site ( Cross section data > 20 MeV and d- and p- induced data  suitable for IFMIF

Validating and testing EAF libraries Consider only the n-induced data in EAF-2007 Huge number (65,565) of reactions All methods of testing are built into SAFEPAQ-II Compare with EXFOR (~1,700 reactions) Compare to integral data (~ 450 reactions) Only a small fraction of library can be compared to exp. Statistical Analysis of Cross Sections (SACS) method  Look at all reactions for each reaction type  Uses various statistics in scatter plots  Trend lines, identify outliers  Used to test reactions with no experimental data

Integral measurements Existing methods of comparison of activation measurements with calculations proceed as follows:  Measure amount of activity by  detector, assign it to particular daughter nuclides  Calculate with an inventory code the predicted activity using the correct materials, irradiation history and neutron spectrum  At a time where a radionuclide dominates calculate C/E for the activity  Present C/E for a range of radionuclides This can only be done once a data library exists to provide input to the code

EASY method As before measure amount of activity by  detector, run inventory code and calculate (C/E) activity Use the FISPACT pathways method to determine the pathways that are responsible for the production of each radionuclide If one pathway is responsible (can be extended) then find the value of the library cross section averaged in the neutron spectrum (  C ) Find  E =  C / (C/E) activity this is the measured value of the effective cross section  E is input into SAFEPAQ-II in the same way as other experimental data During the development of the next data library the preliminary data can be adjusted using the integral data

89 Y(n,2n) 88 Y – integral (EAF-2005) New data Ignore?

89 Y(n,2n) 88 Y – differential Region probed by rez_DF Remains validated

182 W(n,p) 182 Ta - integral (EAF-2007 prelim) Ignore? New data

182 W(n,p) 182 Ta - differential (EAF-2007 prelim) Remains validated (as sum) Region probed by fzk_ss316 & rez_DF

Testing large activation libraries – EAF ,565 reactions 448 reactions with integral data 1,715 reactions with differential or integral data How to test?

Statistical analysis of cross sections (SACS) Systematics show that measured cross sections at particular energies have a good correlation with parameters such as A or s = (N - Z) / A Work on maximum cross sections by Manokhin for (n,2n) shows similar trend Such data easily extracted from EAF-2007 or one of the data sources and displayed as scatter plot against A, Z or s Trend lines can be added and reactions discrepant from the trend identified

Definition of statistics  max E max ½½

EAF –  max (s) for (n,p) Trend line Discrepant reactions

EAF-2007 –  max (s) for (n,p) Improvement

EAF-2007 –  ½ (s) for (n,p) Backed by exp 10 MeV 30 MeV

EAF-2007 –  ½ (s) for (n,  ) Trend Outlier

EAF-2007 –  max (s) for (n,2n) new options Can display reactions that are ‘important’ (based on EAF-2003 analysis)

EAF-2007 –  30keV (aU) for (n,  ) Odd and Even Z targets New systematic?

Importance diagrams A neutron spectrum needed for activation calculations FISPACT output files contain a large amount of data How to summarize – ideally as a picture? Importance diagrams give a picture of the dominant nuclides for all neutron energies and all decay times They are largely independent of the neutron flux Set of activation calculations for mono-energetic neutrons Identify dominant nuclides for a quantity e.g. activity Find regions in (decay time, energy) space where a nuclide contributes more than 50% Now able to cover energy < 60 MeV

Dose rate importance diagram for Cu Zn-65 contributes > 50% E > 20 MeV new. New dominant nuclides?

Heat output importance diagram for Cr 52 V produced by 50 Cr(n,  ) 51 Cr(   ) 51 V(n,  ) 52 V 52 V produced by 52 Cr(n,p) 52 V and 53 Cr(n,d) 52 V

Importance diagrams Diagrams for all elements (EAF-2003) in ‘Activation Handbook’ (544 pages) Analysis shows:  754 of the 1,917 nuclides describes activation properties of all elements < 20 MeV  1,314 of the 12,617 reactions needed for all dominant nuclides  Allows focus on important nuclides and reactions Currently updating with EAF-2007 data Energy now includes 20 – 55 MeV Search for new dominant nuclides Identification of important reactions This allows a focus on the most relevant nuclides and reactions hence the most significant improvement in data

Importance diagrams for EAF-2007 New primary nuclides are seen for E > 20 MeV  For V: 48 V, 44 Sc and 40 K So far data for H – Xe analysed  15 new primary nuclides  109 new secondary nuclides  Some swapping of primary ↔ secondary New primary nuclides  7 Be, 11 C, 48 Ca, 50 Cr, 66 Ga, 72 As, 76 Br, 82m Rb, 86 Y, 108 Cd, 114 Cd, 109 Sn, 124 Sn, 124 I and 124 Xe ‘Exotic’ reactions seen for E > 20 MeV  54 Fe(n,d  ) 49 V in pathways → 39 Ar, 42 Ar and 44 Sc  18% of 39 Ar formed has 54 Fe(n,d  ) 49 V as first step For Fe irradiation  EAF-2003, 3 reactions on 54 Fe  EAF-2007, 10 reactions on 54 Fe

Uncertainty in EAF Only for n-induced data 2 – 4 variance values per reaction No covariance data Also use  T ½ Can be used by FISPACT → uncertainty on activity etc Plans to extend this in future (using calculated uncertainties from TALYS by varying parameters) Are covariances needed? Large extension to FISPACT so covariances could be used No data for d- and p-induced libraries At present no JEFF/A or FENDL/A data

Uncertainties - 60 Ni(n,  ) 61 Ni  =0.4  =0.3  =0.1

Decay data Decay data for all nuclides produced in reactions/decays needed for activation calculations Ongoing work in evaluation of fusion relevant nuclides Results → JEFF and EAF Carried out by Serco (Alan Nichols) Currently 21 nuclides are being evaluated: 45m Sc, 70 Ga, 71 Ge, 75 Ge, 75m Ge, 79 Se, 90 Y, 90m Y, 90 Nb, 90m Nb, 98 Tc, 113 Cd, 113m Cd, 121 Sn, 121m Sn, 166 Dy, 170 Tm, 176m Yb, 184 Re, 189m Os, 190 Pt Results will be included in EAF-2009

Format issues EAF-2003 converted to ENDF format = JEFF-3.1/A This can also be done for EAF-2007 but  What about data E > 20 MeV?  At present ~ 50 ‘non-standard’ MT  Could lump to total cross section  Several ways of converting EAF → ENDF  What about uncertainty data?

Development needs (activation) Include uncertainties for d- and p-induced libraries Improve uncertainties (more groups) for n-induced library More differential data especially ~ 20 MeV for n More integral measurements > 20 MeV for n Better model calculations for important reactions

Questions Do we need a FENDL/A-3 library? EAF-2007 available, should this be recommended for a new FENDL activation library? Should d- and p-induced data be included? Should uncertainty data be included? Should FENDL ‘add value’ by improving a subset of reactions or uncertainty data? New measurements? Formats? What about validation? Time scale?