NEA/WPEC–2

International Evaluation Co-operation

VOLUME 2
GENERATION OF COVARIANCE FILESFOR IRON-56 AND NATURAL IRON

A report by the Working Partyon International Evaluation Co-operationof the NEA Nuclear Science Committee

CO-ORDINATORMONITOR

H. VonachH. Gruppelaar

Institut für Radiumforschung und
Kernphysik der Universität Wien
Austria

Nehterlands Energy Research
Foundation, ECN
The Netherlands

NUCLEAR ENERGY AGENCY
ORGANISATION FOR ECONOMIC CO-OPERATION AND DEVELOPMENTORGANISATION FOR ECONOMIC CO-OPERATION AND DEVELOPMENT
Pursuant to Article 1 of the Convention signed in Paris on 14th December 1960, and which cameinto force on 30th September 1961, the Organisation for Economic Co-operation and Development (OECD)shall promote policies designed:−−−to achieve the highest sustainable economic growth and employment and a rising standard ofliving in Member countries, while maintaining financial stability, and thus to contribute to
the development of the world economy;
to contribute to sound economic expansion in Member as well as non-member countries in
the process of economic development; andto contribute to the expansion of world trade on a multilateral, non-discriminatory basis inaccordance with international obligations.

The original Member countries of the OECD are Austria, Belgium, Canada, Denmark, France,
Germany, Greece, Iceland, Ireland, Italy, Luxembourg, the Netherlands, Norway, Portugal, Spain, Sweden,
Switzerland, Turkey, the United Kingdom and the United States. The following countries became Members
subsequently through accession at the dates indicated hereafter: Japan (28th April 1964), Finland (28thJanuary 1969), Australia (7th June 1971), New Zealand (29th May 1973), Mexico (18th May 1994), the Czech
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Communities takes part in the work of the OECD (Article 13 of the OECD Convention).
NUCLEAR ENERGY AGENCYThe OECD Nuclear Energy Agency (NEA) was established on 1st February 1958 under thename of the OEEC European Nuclear Energy Agency. It received its present designation on 20th April 1972,
when Japan became its first non-European full Member. NEA membership today consists of 27 OECD
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The Commission of the European Communities also takes part in the work of the Agency.
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to assist its Member countries in maintaining and further developing, through international
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FOREWORD

A Working Party on International Evaluation Co-operation was establishedunder the sponsorship of the OECD/NEA Nuclear Science Committee (NSC)
to promote the exchange of information on nuclear data evaluations, validation,and related topics. Its aim is also to provide a framework for co-operative
activities between members of the major nuclear data evaluation projects.
This includes the possible exchange of scientists in order to encourage
co-operation. Requirements for experimental data resulting from this activity
are compiled. The Working Party determines common criteria for evaluatednuclear data files with a view to assessing and improving the quality andcompleteness of evaluated data.
The Parties to the project are: ENDF (United States), JEF/EFF (NEA Data
Bank Member countries), and JENDL (Japan). Co-operation with evaluation
projects of non-OECD countries are organised through the Nuclear Data Sectionof the International Atomic Energy Agency (IAEA).
The following report was issued by a Subgroup investigating different
methodologies to produce covariance data. These data are required to assess
uncertainties in design parameters and to refine the use of nuclear data bothin fission and fusion reactor applications. It was agreed to limit the scope
to covariance data for Iron-56 and natural iron in view of their importance as
structural materials in reactors and particularly for fusion reactor shielding
applications.
The opinions expressed in this report are those of the authors only and do not
represent the position of any Member country or international organisation.
This report is published on the responsibility of the Secretary-General of the
OECD.

3

Members of Subgroup 2

AUSTRIA

THE NETHERLANDSVONACH, Herbert
Inst. f. Radiumforschung und
Kernphysik der Univ. Wien

GRUPPELAAR, Harm
Head, Nuclear Analysis Group
Netherlands Energy Research
Foundation ECNPettenFRANCESANTAMARINA, Alain
Commissariat à l’Energie Atomique
C.E. - Cadarache

KOPECKY, J.
Stichting Energieonderzoekcentrum
NederlandPettenGERMANY

UNITED STATES OF AMERICAFRÖHNER, Fritz
Institut für Neutronenphysik undReactortechnik
Kernforschungszentrum Karlsruhe

FU, C.Y.
Oak Ridge National LaboratoryJAPAN

LARSON, Duane C.
Eng. Physics & Math Div.
Oak Ridge National Laboratory

HETRICK, David M.
Eng.Physics & Maths. Division
Oak Ridge National Laboratory

HASEGAWA, Akira
Applied Radiation Laboratory
Dept. of Reactor Engineering
JAERI, Tokai-Mura

PEELLE, R.W.
Oak Ridge National Laboratory

KANDA, Yukinori
Dept. of Energy Conversion Eng.
Kyushu University
SUGIMOTO, Masayoshi
Nuclear Data Center
Department of Physics
JAERI, Tokai-Mura

4

CONTENTS

1. Work within the Subgroup............................................................................

7

2. Open problems.............................................................................................. 10
2.1. Representation of covariance information in the ENDF/B-VI format ... 10
2.2. Covariances of calculated cross-sections ............................................. 10
Appendix A. Report of the initiation of Subgroup 2 on
the generation of covariance files for 56Fe and natural Fe........... 13
Appendix B. List of documents originating from the work of Subgroup 2 ...... 255

GENERATION OF COVARIANCE FILESFOR IRON-56 AND NATURAL IRON

1. Work within the Subgroup
Considerable work has been done on most of the topics assigned to
the Subgroup in the report on its initiation (NFA-FUS-90-03). In detailthe following subjects have been addressed:a) Sensitivity calculations especially for fusion reactor shielding problems –Papers A 1-10;b) Generation of covariances for evaluated cross-sections of 56Fe frommodel calculations by means of simple qualitative methods for crosssections, elastic angular distributions and total gamma-production crosssections – Papers A 9-10, 23-25;c) Generation of covariances for 56Fe cross-sections evaluated from model
calculations and experimental data combined by least squares procedures– Papers A 11-12;d) Detailed comparison of evaluated 56Fe cross-sections and uncertainties
derived by different methods with each other and with precise
experimental data – Papers A 11-13;e) Derivation of an accurate set of 14-MeV cross-sections for 56Fe by
quantitative evaluation of the experimental data base in order to provide
a sensitive test for evaluated cross-sections and uncertainties –Papers A 14-15;f) Work on proposals for formats for cross-section types not yet describableby ENDF/B format rules, such as coupled energy-angle distributions forsecondary neutrons, and charged particle emission and total and energydifferential gamma-emission cross-sections – Papers A 16-17;

7g) Derivation of cross-section covariances in the resonance range –Paper A 26;

In the course of this work among others the following results have beenobtained:a) Extensive sensitivity calculations have been performed for the shieldingof the superconducting coils of a tokamak fusion reactor; andthe sensitivity of the calculations to the different cross-section types andto the various energy ranges of each cross-section has been obtained
in detail. Also the sensitivity of the shielding calculations to the P1-P3
coefficient of the elastic scattering distributions was investigated andproven to be important – Papers A 1-7.
b) The approximate methods for generation of covariances of cross-sections
from model calculations used at ORNL and IRK have been documented –Papers A 8-10 – compared with each other – Paper A 13 –,with precisionexperimental data – Papers A 14-15 – and with results from a moreaccurate evaluation – Papers A 11-12. From this comparison it can beconcluded that the approximate methods for generation of covariancesused in ENDF/B-VI and EFF have provided reliable uncertainty estimates
and thus can be recommended for further use.
c) The method of estimating covariances from the dispersion of different
evaluations has been extended from cross-sections (file 33 data) to elastic
angular distributions, secondary energy distributions, and total andenergy-differential gamma-production cross-sections – Papers A 11-12.
d) Two formats (MF 30 and 36) – Papers A 16-17 – have been worked out
in detail and proposed for proper dealing with covariances of coupled
angle-energy distributions of secondary neutrons and charged particles,
and total and energy-differential gamma-production cross-sections.
e) A new evaluation of all important cross-sections of 56Fe has been
performed using all available experimental information and combining itwith the EFF-2 evaluation based model calculations using quantitative
Bayesian methods – Papers A 11-14. It has been demonstrated thata large reduction of uncertainties (typically by factors 2-3) can beobtained in this way compared with evaluations completely based onmodel calculations. After two years this evaluation has been updated in
1994 by adding new accurate experimental data for a number of cross-8

sections – Paper A 22. This has resulted in considerable further reductionof the cross-section uncertainties and – even more important – has fully
confirmed the original evaluation within its stated uncertainties. Thus itappears that the approach developed in Papers A 11-14 may be usedgenerally for important materials in order to create accurate and easily
updateable evaluations including reliable uncertainty information.
f) The problem of deriving covariances of cross-sections from nuclear
model calculations from uncertainties of the model parameters wasinvestigated in some detail. As yet, however, results tend to seriously
underestimate the cross-section uncertainties – Papers A 18-19. This may
be partly due to the use of too restricted parameter spaces and in part tothe neglect of the inherent model deficiencies. More work on this –in principle promising method – is needed.
g) A complete set of covariances for the resonance parameters of 56Fe wasderived by F. Fröhner and put into ENDF format (file 32). There are,however, serious problems in the use of this information as the important
potential scattering radii cannot at present be stored in the ENDF-6
format. Therefore also the existing codes neglect the uncertainties of thepotential scattering radii and thus lead to unrealistically small crosssection uncertainties. In addition comparisons of cross-sections in
the resonance range both between different recent experiments and withthe reconstructions from the resonance parameters given in the mostrecent evaluations have revealed considerably larger discrepancies than
expected from the estimated accuracies of both the data and the resonanceparameters. Thus it appears that in file 32, uncertainties of the crosssections in the resonance range need to be supplemented at present by
file 33 information estimated by qualitative methods.
h) As a consequence of the work described in b-e), there exist now
four evaluations, EFF-2.2, ENDF/B-VI, Vienna-Obninsk and CENDL-2
with complete file-33 information – Paper A 8-12 – which have been
compared in detail and found to agree within stated uncertainties.
i) As a result of the work for the new Vienna-Obninsk evaluation
the experimental data base for 56Fe has been compiled and thoroughly
checked, and – unless given by authors – covariance matrices were
estimated for each data set.

9j) Most members of the Subgroup participated in the NSC Specialists’Meeting and Subgroup members acted as working group members andchairmen of this meeting. Thus the recommendations and conclusions of
this meeting – Paper A 20 – summarise to a large extent the conclusionsof the Subgroup concerning generation and processing of covariances.
k) Based on the experience gained by the work within the Subgroup,
H. Vonach, the co-ordinator, gave an overview at the Brookhavenmeeting on Evaluation Methodology – Paper A 21.

2. Open problems
2.1 Representation of covariance information in the ENDF/B-VI format
The work of the Subgroup has demonstrated on the example of 56Fe thatthe goal of generating reliable and rather complete covariance information canbe obtained with reasonable effort. The actual use of this information, however,is today severely limited by the existing processing and sensitivity codes.
At present only the information on cross-section covariances (file-33 data) andcovariances of angular distributions for elastic and inelastic scattering todiscrete levels (file-34 data) can be used in neutronics calculations. In order toalso consider the effects of covariances of coupled energy-angle distributions ofsecondary neutrons, and total and energy-differential gamma-production crosssections, considerable extensions of the present processing and sensitivity codes
would be needed in order to handle the proposed new formats MF 30 and
MF 36. Likewise the processing codes for transforming file-32 information(covariances of resonances) into covariances of group cross-sections have to beamended to include the covariances of all parameters especially those of
the potential scattering radii. While this work is rather straightforward andshould not pose major problems, it exceeds the resources available tothe members of the Subgroup.

2.2 Covariances of calculated cross-sections
The problem of estimating the covariances of calculated cross-sections used
so far – Paper A 8-12 – is still rather crude and development of more rigorous
methods is urgently needed. Attempts in this direction – Papers A 18-19 – haveshown that the consideration of the uncertainties of the model parameters is
insufficient to explain the uncertainties of the theoretically calculated crosssections and an explicit inclusion of the uncertainties due to the model

10

deficiencies is necessary for realistic uncertainties estimates. These, however,cannot be quantified easily. This is probably the most important, however, also
most difficult open question concerning the generation of reliable covarianceinformation of evaluated nuclear data.

11

Appendix A

Report of the initiation of Subgroup 2 on the generation
covariance files for 56Fe and natural Fe
H. Gruppelaar

1. Introduction
The NEANDC/NEACRP Working Group on International Evaluation
Co-operation was founded at a joint session of NEANDC and NEACRP
members at the NEACRP meeting in Argonne, October 9-13, 1989. A report isgiven in document NEACRP-A-1011/NEANDC-A-257. Six high-priority tasks
were defined of which the first two are relevant to this paper:
1. Intercomparison of the files for Cr-52, Fe-56 and Ni-58,
2. Generation of covariance files for Fe-56 and natural Fe
For each task a Sub Working Group had to be initiated by D. Larson and
H. Gruppelaar, respectively. This paper reports the progress in the initiation of
Subgroup 2.
The task was described shortly as follows:“Covariance data are required to assess uncertainties in design parameters(e.g., in the design of shields for the superconducting magnets of fusion
reactors) and to refine the use of nuclear data in reactor applications. It is notalways clear how much detail is required in the covariance files for different
applications, the requirements being related to the sensitivity calculations.
Collaboration in the general area of covariance files is beneficial to all parties.
Initially it is proposed to concentrate on covariance data for Fe-56 and natural
Fe in view of their importance in reactors, particularly for fusion shielding
applications. The JEF-2/EFF-2 and ENDF/B-VI covariance data (files 32 and33) should be intercompared and the methodology to produce these data should

be discussed. Possible improvements should be indicated. A study is also
recommended of the methods used to evaluate and store covariance information
for double-differential and photon production cross-sections.”
I like to stress here that the proposed task has the rather wide purpose toimprove the methods, to derive covariance files in general with special
emphasis on Fe. Fe was chosen as an example to start with and to illustrate
the various problems. It was also chosen to concentrate on one application andto avoid an open-ended activity. Still the participants should bear in mind thatthe final goal is to obtain methods to generate a general purpose file withcovariance data for all materials.

2. Invitation to participate
After consultation with the chairmen of the various nuclear data projects in
the OECD area, an invitation letter to participate in Subgroup 2 was sent out on
December 18, 1989 to potential participants in Europe, Japan and the U.S.A.
A copy was sent to the above-mentioned chairmen. This letter contained
a proposal for a chairman (Dr. H. Vonach) and the following suggestions for
activities:
2.1.

Sensitivity studies. Which data are most important?
a.
b.
c.
d.

energy and angle-integrated cross-sections
energy distributions
angular distributions
coupled energy-angle distributions

These studies depend on the applications, e.g., the shielding ofsuperconducting magnets in a fusion reactor
2.2.

Exchange of information on codes and methods for sensitivity
calculations

2.3.

Exchange of information on methods for the evaluation of covariance
data

a.
b.
c.

from experimental datafrom theory and uncertainties in model parametersfrom a combination of experimental data and models.

14

2.4.

Exchange of information on formats and how to use these formats inpractical applications

2.5.

Simple methods to generate covariance files

2.6.

Inspection of previous results with regard to covariance data for Fe.
Comparison of (preliminary) EFF-2/JEF-2, JENDL-3 and ENDF/B-VI
files and (as far as available) covariance files

2.7.

Evaluation of covariance data for cross-sections in broad energy ranges(stored in file 33)

2.8.

Evaluation of covariance data for resolved resonances, or only forimportant resolved resonance

2.9.

Evaluation of covariance data for energy-angle distributions

2.10. Evaluation of covariance data for photon production
2.11. Evaluation of covariance data for the natural element
2.12. Evaluation of covariance data for group constants and transfer matricies

It was asked to indicate which topics were of most interest to the potential
members and also, to mention possible other items and ideas for a working planand time-schedule. Also any material relevant to these points was requested forgeneral distribution: Annexes of the invitation letter, including mailing lists andNEACRP-A-1011.

3. Received answers
Most scientists invited to Subgroup 2 have reacted in a positive way.
Some have not explicitly answered, but it may be assumed that those listed in
Section 4 will actively participate. There may be further interest from the users’side and from the non-OECD region. A name that has been suggested isProf. Dr. Zhou Deling (CNDC, P.R. China). All invited scientists agreed withthe choice of Prof. Vonach as a chairman of Subgroup 2.

15

It is noted that the present task is also of interest to the community of
dosimetry users. However, the emphasis of Subgroup 2 is more directed togeneral purposes. Nevertheless, contacts with colleagues working in
the dosimetry field are recommended. This is already guaranteed by
the participation of some members of the group.
The received reactions are summarised below.

3.1. NEA Data Bank/ NNDC/ RSIC/ Subgroup 1
Some very useful assistance could be given by the NEA Data Bankin relation to graphical intercomparisons or recent evaluations for iron(Dr. C. Nordborg) and the provision of (utility and sensitivity) codes andderived (covariance) libraries (Dr. E. Sartori). Similar services could be
performed by NNDC (Dr C. Dunford). With respect to shielding sensitivity andcovariance codes the RSIC could also play an important role. Furthermore,with respect to the possibility to derive some information on uncertainties fromthe dispersion between different data files, it is important to keep in good
contact with the chairman of Subgroup 1 (contact Dr. D. Larson).

3.2. Europe (EFF/JEF)
Positive reactions were obtained from Dr. H. Vonach (IRK-Vienna),
Dr. F. Fröhner (KfK) and Dr. J. Kopecky (ECN-Petten). A new name was alsosuggested: Dr. A. Hogenbirk from ECN-Petten.
Furthermore, there is considerable interest in applications of covariance data
to shielding problems: e.g., at the NET team in Garching, at PSI-Würenlingen,at CEA-Saclay (Mr. I. Kodeli; see his contribution on PWR shielding to theMarseille PHYSOR-90 meeting), at CEA-Cadarache (Dr. M.A. Santamarina)
and ECN-Petten (Dr. A. Hogenbirk, who is performing sensitivity andcovariance calculations for the NET shielding). Contact with these users is
recommended.
All invited participants are involved in the EFF-2 project (coordinator:
Dr. Gruppelaar). The main emphasis of this project has recently been redirectedto the calculation of a shielding data base for the NET fusion reactor, including
covariance data. The strategy of EFF-2 with respect to covariance data is asfollows:

16

a. Determine sensitivities of NET shielding parameters to cross-sections.
Include studies with respect to energy and angular distributions (SED and
SAD).
b. Use presently available methods and data to make a first estimate of
the uncertainties in the shielding parameters.
c. Improve covariance data base with priorities taken from studies a.,b.
Some approximate methods could be used initially (i.e., only file 33 andapproximate methods for SED/SAD).
Drs. Fröhner and Kopecky are involved in the JEF-2 project (chairman:
Dr. Salvatores as well). The EFF-2 and JEF-2 projects are closely linked
together; a common meeting is scheduled at the NEA Data Bank in the last
week of May 1990
Dr. Vonach is specialised in the high-energy range (above 1 MeV) and has
considerable experience in covariance evaluation for the international dosimetry
file. Dr. Fröhner is an expert in the resolved resonance region. Dr. J. Kopecky
and Dr. A. Hogenbirk are involved in the EFF-2 project and are currently
working on the formatting of the evaluations for structural materials both for
JEF-2 and EFF-2. The high-energy range of the EFF-2 evaluations for the major
isotopes of Fe, Cr and Ni are contributed by Prof. M. Uhl (IRK, Vienna).
The present status of JEF-2 with respect to Fe is that the-file (only for
isotopic data) is ready for benchmark testing. The EFF-2 file for Fe will beequal to JEF-2 except for the energy part of Fe-56 above 1 MeV, which has
been evaluated by Dr. M. Uhl. The EFF-2 file for Fe is assembled at ECN,
Petten and will be ready before summer 1990. (covariance files for Fe will be
constructed by simple means as soon as possible, starting with diagonalcovariances for the most important reactions and for the strongest S-wave
resonances.

3.3. Japan
Three names have been suggested from the JENDL project by Dr. Kikuchi.
Two scientists from JAERI were mentioned: Dr. A. Hasegawa (Shielding
laboratory) and Dr M. Sugimoto (LINAC laboratory) and Prof. Y. Kanda from
Kyushu University. At present JENDL-3 does not yet contain covariance data.
As this is considered for the near future, there is considerable interest to study
methods for implementing these data.

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Dr. Kanda has specified to be interested in topics 2.3, 2.6 and 2.8, mentioned
in Section 2. A discussion with regard to topic 2.3 – Exchange on information
on methods to evaluate covariance data – is given in a contribution of Y. Kanda
and Y. Uenohara to the Mito conference (1988) – p. 1041 of the proceedings“Covariance matrices evaluated by different methods for someneutron-dosimetry reactions”. Prof. Kanda intends to estimate covariances forsome reactions of Fe by applying the methods mentioned in this reference andthen intercomparing his results and comparing them with those from otherevaluations. He is also interested to see the developments in assigningcovariances to resolved resonances. He stresses that also the data files should beintercompared (Subgroup 1).
The status of JENDL-3 for Fe is that it has been released in Japan forbenchmark testing. There are no covariance data included as yet.

3.4. U.S.A.
Dr. C.Y. Fu has written that he is interested in the co-operation on this task
force. From a recent summary of the November 1989 Cross-Section Evaluation
Working Group (CSEWG) meeting (distributed on February 1, 1990),
two names for Subgroup 2 were proposed:
Dr. C.Y. Fu and Dr. D. Hetrick, both from Oak Ridge National Laboratory.
It may be of interest to note that both are also participating in Subgroup 1.
Some preliminary covariance data for the structural materials were alreadypresented at the afore-mentioned CSEWG meeting. They consisted of diagonal
uncertainties for most reactions in file 3 of ENDF/B-VI. Some ideas to create
these files were presented. To represent the resolved resonance region, it ispossible to assign errors to the “background” cross-section in file 3, even if thiscross-section is zero. Thus, for a fast and preliminary evaluation of errors only
file 33 is necessary. The inclusion of correlations is complicated because
the covariance matrices should be positive definite. This can be accomplishedby using the LB=8 law, but it is questioned whether the use of this law might
introduce artificial features into the covariance matrices. Thus, further work isnecessary on this item.

18

The checking and processing capabilities for files 32 and 33 are in a good
shape (latest versions of BNL checking codes and NJOY). For file MF=30
these possibilities are lacking (also for MF=34,35?). The advanced options of
MF=30 could be used to represent covariances by means of sensitivities andcovariances of parameters which represent the compiled data. This could bea future option to represent uncertainties in double-differential data (MF6).
The next CSEWG meeting takes place in May 1990. Several Subgroup 2
members will participate. Dr. Vonach will also be present. At that meeting morenews about the covariance file of Fe has to be expected.
The status of ENDF/B-VI for Fe is that the file will be released very soon,
probably with some covariance data. Otherwise the file will be released without
covariance data and further testing of the covariance data follows.

4. Establishment of Subgroup 2
From the above-mentioned reactions it is clear that there is interest andenthusiasm to establish Subgroup 2 with the following members:
Prof. Dr. Y. Kanda (Kyushu University)
Dr. A. Hasegawa (JAERI)
Dr. M. Sugimoto (JAERI)
Dr. C.Y. Fu (ORNL)
Dr. D. Hetrick (ORNL)
Prof. Dr. H. Vonach (IRK, Vienna; chairman)
Dr. F. Fröhner (KfK, Karlsruhe)
Dr. J. Kopecky / Dr. A. Hogenbirk (ECN, Petten)
The initiator of Subgroup 2 has sent a letter containing this report to thesemembers. Starting from May 1, 1990 the working group has been establishedand Dr. Vonach will co-ordinate the further activities. My task will be tomonitor the progress and to report the progress to the Working Group on
International Evaluation Co-operation.

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Important progress should be communicated to the following persons:Dr. C. Nordborg / Dr. E. Sartori (NEA Data Bank)
Dr. Y. Kikuchi (JAERI)
Dr. M. Salvatores (CEA, Cadarache)
Dr. C.L. Dunford (BNL, Brookhaven)Dr. H. Gruppelaar (ECN, Petten)

4. Programme of Subgroup 2
A programme to start the work of Subgroup 2 has been discussed
at an ad-hoc meeting in Petten on April 9, 10 with Drs. H. Vonach, J. Kopecky,
A. Hogenbirk and K.A. Verschuur. It is based upon the suggestions ofSections 2 and 3 and the opinions of the participants of the above-mentioned
ad-hoc meeting.
The programme contains four elements:
A. Investigation why covariance data are important and how the user applies
these data to real problems.
This includes essentially items 2.1. and 2.2.
4.1. Sensitivity studies. Which data are most important?
a. energy and angle-integrated cross-sections
b. energy distributions
c. angular distributions
d. coupled energy-angle distributions
These studies depend on the applications, e.g., the shielding ofsuperconducting magnets in a fusion reactor or shielding problems ofa PWR. Dosimetry problems should not be emphasised in this study.
4.2. Exchange of information on methods and codes for sensitivity calculations
Point 4.1 is performed at Petten (Hogenbirk). Interesting results show,that for the inboard shielding, the energy range below a few hundred keV
are unimportant in contrast to the 14 MeV elastic and inelastic crosssections. A paper on this subject is being prepared. There are also results
forthcoming from I. Kodeli (CEA-Saclay) on PWR shielding.

20

Point 4.2 could be an action for the NDB and RSIC. Codes that could be
used are SENSIT and SUSD. Further developments may be necessary,in particular for SED/SAD treatment.

B. Investigation of methods and formats to produce covariance data
This includes items 2.3, 2.4, 2.5.
4.3. Exchange of information on methods for the evaluation of covariance dataa. from experimental datab. from theory and uncertainties in model parametersc. from a combination of experimental data and models
4.4. Exchange of information on formats and how to use these formats forpractical applications (files 30-35)
4.5. Simple methods to generate covariance files, e.g., to obtain immediate
results or to obtain results that can be processed and used immediately
Existing literature should be compiled and scanned. Format information
should come from CSEWG, LANL, BNL, ORNL, etc.
There are problems with LB8 and uncertainties about MF30, MF34, MF35.
Can the processing codes treat advanced options? Do the users know how
to use these advanced options? Are there sensitivity/covariance codes totreat these options? (NDB, RSIC)
There is interest from Drs. Vonach and Kanda to work on problems 4.3 and4.5. A very simple method is to derive uncertainty information from intercomparison of new evaluations, see next point.

C. Comparison of existing data and covariancesThis includes item 2.6, which is also part of Subgroup 1.

21

4.6. Inspection of previous results with regard to covariance data for Fe.
Comparison of (preliminary) EFF-2/JEF-2, JENDL-3 and ENDF/B-VI filesand (as far as available) covariance files
Following the work of Subgroup 1 (with priority for Fe!) useful
uncertainty information can be derived from the spread in the data.
Distribution of the new files is of high priority. Also graphicalintercomparisons are desired. (NDB, BNL, JAERI).
Dr. Vonach would like to use this information.
There is also some information from existing covariance data,e.g., COVFILS (ENDF/B-V) and the work of the NEA Data Bank andperhaps soon the preliminary covariance data from ENDF/B-VI. These
data could be inspected or reviewed (distr. NDB, BNL, RSIC).
Participation in the review of ENDF/B-VI could be a good suggestion. At
Petten the NDB covariance data are used to perform test calculations of
the uncertainty in NET shielding calculations. Further work withpreliminary data if available is considered.
A good plotting option for covariance data is required (NJOY, BNL?).
Probably the NJOY code contains or will contain these features.
In view of the importance of 14 MeV data for fusion reactor applicationsa re-evaluation of experimental 14 MeV data could be considered(H Vonach).

D. Construction of covariance data for each file
This includes items 2.7 to 2.12.
4.7. Evaluation of covariance data for cross-sections in broad energy ranges(stored in file 33)
4.8. Evaluation of covariance data for resolved resonances, or only forimportant resolved resonances
4.9. Evaluation of covariance data for energy-angle distributions
4.10. Evaluation of covariance data for photon-production22

4.11. Evaluation of covariance data for the natural element
4.12. Evaluation of covariance data for group constants and transfer matrices

This is an action for all three parties.
The easiest way is to start with point 4.7, also for the resolved range.
For fusion application the high-energy range is clearly very important.
The next priority could be point 4.8, starting with the most important S-wave
resonances (Fröhner, etc.).
Point 4.9 is too complex at present and should be simplified.
First the uncertainty in the elastic angular distributions should be
investigated. It is not yet clear how important this is and how this should be
dealt with. A simple solution is to evaluate the uncertainty in the P1 term.
The evaluation of uncertainties in secondary energy distributions is anotherproblem. Sensitivity codes can use the “median” approach. If this is effective
it is simple, but there is now a way to store this information in ENDF format.
New developments are necessary to store energy-angle correlated covariancedata and uncertainties in photon production spectra (4.10). This may be possible
with MF30 in the near future. With respect to point 4.11 one should think about
the problems related with the fact that Fe-56 is only one isotope of the naturalelement. A simple solution is to assume that the uncertainties for Fe-56 arerepresentative for natural Fe. The evaluation of covariance data for groupconstants and transfer matrices could be done with the processing code (NJOY),
only as far as the information is available on the basic files. If this is notpractical (perhaps in the case of SED/SAD) other input should be given to
the users’ codes (e g. uncertainty in the median in the case SENSIT is used).
This could be a practical solution now (use of code ANGELO for change ofgroup structure), but is not attractive on the long run.

E. Intercomparison of covariance data for Fe-56
Finally, the three (new) covariance data should be compared and some
calculations of applications should be made.

23

5. Time schedule
It is rather difficult to give a detailed time schedule at present. An optimistic
time schedule is to finish the work for A and B within one year and to haveat least some covariance files for Fe-56 ready as well. After about one year
the programme should be re-evaluated and new priorities should be set.

24

Appendix B

List of documents originating from the work of Subgroup 2

1)

A. Hogenbirk“Self-Shielding in the Net Fusion Reactor Blanket and Effects ofUncertainty Calculations”, Report ECN-R-90-007 (1990).

2)

A. Hogenbirk, H. Gruppelaar and K.A. Verchunv“Sensitivity and Uncertainty Analysis of Net/ITER Shielding Blankets”,
Report ECN-RX-90-062 (1990).

3)

A. Hogenbirk“Sensitivity and Uncertainty Analysis of the Nuclear Heating in the Coilsof a Fusion Reactor”, Report ECN-RX-90-34 (1990).

4)

A. Hogenbirk“Energy Self-Shielding and SED/SAD Effects in Sensitivity Calculationsof a Net Shielding Blanket”, Report ECN-RX-91-038 (1991).

5)

A. Hogenbirk“Extensive Sensitivity/Uncertainty Analysis of a Net Fusion Reactor
Blanket”, EFF-DOC-128 (1991).

6)

A. Santamarina and T. Parish“Uncertainty Analysis of the Net/ITER S.C. Coil Shielding Parameters to
Cross Section Data Uncertainties”, Contribution to International Workshop
on Fusion Neutronics, June 5, 1992, Los Angeles, U.S.A.

7)

A. Hogenbirk“New Sources of Uncertainties in Sensitivity/Uncertainty Studies”,
Proceedings of the 17th Symposium on Fusion Technology, September
14-18, 1992, Rome, Italy.

25

8)

A. Hogenbirk“Uncertainty Calculations Made Easier”, Contribution to 8th International
Conference on Radiation Shielding, April 24-28, 1994, Arlington, Texas,
U.S.A., Report ECN-RX-94-035.

9)

A. Hogenbirk“Calculation of Design Uncertainties for the Development of Fusion
Reactor Blankets Taking into Account Uncertainties in Nuclear Data”,
Contribution to Int. Conf. on Nuclear Data for Science and Technology,
May 9-13 1994, Gatlinburg, Tennessee, U.S.A.

10) A. Hogenbirk“Extensive Neutronic Sensitivity/Uncertainty Analysis of a Fusion Reactor
Shielding Blanket”, Fusion Engineering and Design 24 (1994) 275-286.
11) T. Parish and A. Santamarina“Sensitivity and Uncertainty Analysis of the Net Magnet Neutronic Design
Parameters to Uncertainties in Cross Section Data” (pre-print).
12) H. Vonach et al.
“Uncertainty Estimates for the Fast Neutron Cross Sections for theEuropean Fusion File EFF-2 for 52Cr, 56Fe, 58Ni and 60Ni”, EFF-DOC.85(1990).
13) S. Tagesen and H. Vonach“Uncertainty Estimates for the EFF-files for 52Cr, 56Fe, 58Ni and 60Ni”,
Proc. Int. Conf. on Nuclear Data for Science and Technology, Jülich,
Germany, May 12-17, 1991, Springer Berlin Ed. S. Qaim, p. 871.
14) D.M. Hetrick, D.C. Larson and C.Y. Fu“Generation of Covariance Files for the Isotopes of Cr, Fe, Ni, Ca and Pb
in ENDF/B-VI”, Report ORNL/TM-11763 Oak Ridge (1991).
15) H. Vonach et al.
“Evaluations of the Fast Neutron Cross Sections of 56Fe including
Complete
Covariance
Information”,
Physics
Data
13-7
Fachinformationszentrum Karlsruhe (1992).

2616) V. Pronyaev et al.
“Updating of a Theoretical Evaluation by Experimental Data in the Case of
56Fe”, Proc. of the NSC Specialists' Meeting on Generation and Processingof Covariance Data, October 7-9 1992, Oak Ridge, U.S.A.,
NEA/NSC/DOC(93)3 p.135.
17) S. Tagesen and D.C. Larson“Approximate Methods for Derivation of Covariance Data”,
Proc. International Symposium on Evaluation Methodology, October
12-16 1992, Brookhaven, U.S.A. (in press).
18) H. Vonach et al.
“Evaluation of 14 MeV Cross Sections for the Main Isotopes of theStructural Materials Fe, Cr and Ni”, Proc. Int. Conf. on Nuclear Data for
Science and Technology”, Jülich, May 12-17, 1991, Springer Berlin Ed.
S. Qaim, p. 906.
19) A. Pavlik et al.
“Evaluation of 14 MeV Cross Sections for the Main Isotopes of theStructural Materials Cr, Fe and Ni”, Physics Data 13-6,
Fachinformationszentrum Karlsruhe (1991).
20) D.W. Muir
“Description of Covariances of Emission Spectra using ENDF File 30”,
Proc. of the NSC Specialists' Meeting on Generation and Processing of
Covariance Data, 7-9 Oct. 1992, Oak Ridge, U.S.A., NEA/NSC/DOC(93)3
p.195.
21) H. Vonach“Direct Covariance Data for Coupled Energy-angle Distributions”, Proc. of
the NSC Specialists' Meeting on Generation and Processing of Covariance
Data, 7-9 Oct. 1992, Oak Ridge, U.S.A., NEA/NSC/DOC(93)3 p.183.
22) Y. Kanda“Generation of Covariance Data from Combined Experimental andTheoretical Data”, Proc. of the NSC Specialists' Meeting on Generation
and Processing of Covariance Data, 7-9 Oct. 1992, Oak Ridge, U.S.A.,
NEA/NSC/DOC(93)3 p.119

2723) T. Kawano et al.
“Estimation of Nuclear Reaction Model Parameters for 59Co, 58Ni and
60Ni. Proc.Int.Conf. on Nuclear Data for Science and Technology,
May 12-17, 1991, Jülich, Germany, , Springer Berlin Ed. S. Qaim, p. 974.
24) Report of Working Group A “Generation of Covariances to meet User
Needs” and,Report of Working Group B “Covariance File Formats and Processing”
Proc. of the NSC Specialists' Meeting on Generation and Processing of
Covariance Data, 7-9 Oct. 1992, Oak Ridge, U.S.A., NEA/NSC/DOC(93)3
p. 289.
25) H. Vonach“Covariances of Evaluated Nuclear Data - Present Status and prospects for
the Future”, Proc. International Symposium on Evaluation Methodology,
12.-16. October 1992, Brookhaven, U.S.A. (in press).
26) V.G. Pronyaev, S. Tagesen and H. Vonach
Update and Improvement of the IRK Evaluation for 56Fe, Proc. Int. Conf.
on Nuclear Data for Science and Technology, May 9-13 1994, Gatlinburg,
U.S.A. (in press).
27) Zhao Zhixiang and Lin Tong
“Uncertainty Files for Neutron Cross Sections and Elastic Angular
Distributions on 56Fe”, EFF-DOC-266 (1993).
28) Lin Tingjin et al.
“Intercomparison of Fe, Cr, Ni Neutron Data from CENDL-2, BROND-2
and ENDF/B-VI and JENDL-3”, Proc. Int. Conf. on Nuclear Data for
Science and Technology, May 9-13 1994, Gatlinburg, U.S.A. (in press).
29) Zhao Xiang et al.
“Evaluation of Neutron Induced Data on 56Fe”, Comm. Nucl. Data
Progress, Vol. 11, 56 (1994).
30) F. Fröhner
“On Uncertainty Evaluation and Fluctuations in the resolved andunresolved Resonance Regions”, Proc. Int. Conf. on Nuclear Data for
Science and Technology, May 9-13 1994, Gatlinburg, U.S.A. (in press).

28

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