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High-Priority Nuclear Data Request List For Intermediate Energies

Version: December 11, 1996

NEA/NSC Subgroup 13 of the WPEC

Arjan Koning

Netherlands Energy Research Foundation ECN, BU - Nuclear Energy,
P.O. Box 1, 1755 ZG Petten, The Netherlands
email: koning@ecn.nl

The new High-Priority Request List (HPRL) for Intermediate Energy Nuclear Data (IEND) deviates considerably from the first, preliminary versions. The initiative for maintaining this HPRL was taken about three years ago,as a guideline for necessary measurements for accelerator-based transmutation research.

As expected, the most difficult aspect of maintaining a HPRL turned out to be keeping it within bounds: Several suggestions from both the applied and fundamental community were added to the list until the last version (see proceedings of the Kalmar conference) provided enough experimental work for the next few centuries. Clearly, the adjective "high-priority" was no longer appropriate. On the other hand, several conferences in the field and personal communications between scientists have arguably led to more consensus on the required data. Accordingly, I have created a new HPRL by means of a threefold reduction:

• fewer nuclides.
• a smaller energy region (for evaluated data files only: $E<200$ MeV).
• fewer types of cross sections to be measured.

As usual, you are invited to criticize my choice and to argue that other nuclides or reactionsare more, or at least equally, important. Keep in mind however that this should remain a HIGH-PRIORITY list. If it gets too big by new additions, other nuclides/cross-sections should be left out to keep this project focussed.

Nuclides

My proposal is to include 10 nuclides in this list, which cover both the periodic table and various applications. They are the most abundant (apart from 100Mo) isotopes of:

• one material for medical purposes: O.
• three structural materials: Al, Fe and Ni.
• one fission product: Mo.
• one "nuclear model" material: Zr.
• two target materials: W and Pb.
• two actinides: Th and U.

Energies

The highest energy in the HPRL is now 200 MeV. Not only does this coincide with the new upper limit of intermediate energy evaluated data files (Los Alamos has chosen 150 MeV), it is also near the maximum energy of some of the remaining experimental facilities (AGOR-KVI, Groningen, Holland; university of Uppsala, Sweden; Louvain-la-Neuve, Belgium and NAC, Faure, South Africa are laboratories that come to mind). The proposed energy grid for neutron and proton production cross sections has been chosen so that it may overlap with existing measured cross sections for other nuclides or incident particles.

Cross sections

Another reason to keep the number of isotopes limited is that we may eventually obtain "complete" sets of experimental nuclear data. This is of critical importance to nuclear model calculations. If elastic and total (reaction) cross sections for both neutrons and protons (to construct a 0-200 MeV optical model) as well as a complete set of (p,xn),(p,xp),(n,xn) and (n,xp) cross sections are available, code developers can narrow down the uncertainties in their calculations, which has an immediate, positive impact on predictions for other nuclides where no experimental data exist. Of the whole periodic table, 90Zr is the closest to this ideal situation. Therefore, the remaining measurements for this nuclide are included in the list.

There are three important quantities not on the list, which may need explanation:

• Neutron total cross sections. Los Alamos National Laboratory has announced, and partially completed, a very extensive experimental program for neutron total cross sections measurements in the 5-600 MeV region. The results will be presented at the Nuclear Data Conference in Trieste, May 1997. I suggest that we look at what is left to be measured after completion of this experimental program.

• Residual production cross sections. A lot of these requirements have been or will be met by the experimental group of Dr. Michel, Hannover. Since the total collection of measured data is so large, it is difficult to see on short notice (for me at least) where particular shortcomings exist for the ten selected nuclei.

• Deuteron up to alpha production cross sections. Although these cross sections are much smaller than the neutron and proton production cross sections (for heavier targets at least), they are still important for e.g. damage, heating and gas production. Since the measurements are very scarce, both for incident neutrons and protons, the requirements for these quantities apply to almost every nuclide. In first instance however, they are not considered as top-priority.

Conclusions and your participation

This is a request list for experiments and indirectly for evaluations. At present, there is a 100 % overlap between experiment and evaluated data requirements. High-energy evaluations completely consist of results from nuclear model calculations that have been tuned to experimental data. An exception to this may be residual production cross sections: these are so difficult to predict (see recent NEA Benchmark by Michel - a factor of 2 on average is considered good!) that it may be more appropriate to directly include experimental data in activation data files. This however, needs further discussion.

In the last column of the HPRL, I give the possible applications of the measured cross sections, thereby attempting to give a priority order as well. Optical model and nuclear reaction model requirements have an indirect character: The quality of these data determines the quality of the evaluated data files.

In sum, the HPRL for IEND is now much shorter than it was before, though still quite substantial. I stress that the new HPRL is my, and therefore a subjective, view of the situation and I would be very grateful to learn about additions, or better, replacements, or even better, omissions. In particular:

• If you were allowed to choose only ten nuclides, covering both the periodic table and applications, would your choice coincide with the one given here?
• Are there still reactions in the list that should have been left out because they have already been measured?
• Other suggestions?

Finally, it is hoped that maintaining this list may contribute to the justification of the existence of experimental facilities in the next century.

I wish to thank Olivier Bersillon and Jean-Paul Delaroche of CEA, Bruyères-le-Châtel and Mark Chadwick of Los Alamos National Laboratory for their valuable comments.

I thank you in advance for your cooperation.

High-Priority Nuclear Data Request List for Intermediate Energies

A: Accelerator-Driver Systems, F: Fusion (E_n 50 MeV), M:Medical, N: Nuclear Reaction Models, O: Optical Models, A_y: Analyzing Power

Last reviewed: 3 February 2012