Energy-Balance Tests for ENDF/B-VII.1

Robert E. MacFarlane
Los Alamos National Laboratory

Energy-Balance Methods

Nuclear heating can be defined using the energy-balance method; that is, the energy released by charged-particles and the recoil nucleus from a nuclear reaction is given by E + Q - E-bar-neutron - E-bar-gamma. However, not all nuclear data evaluations have perfect energy balance, and in those cases, this formula can give strange results. For example, if the E-bar-gamma value is too large, the energy release can be negative. In a large enough system, this negative value will be cancelled out by the excess energy deposited by the over-large gamma field, and energy will be perfectly conserved. For a system small with respect to photon mean-free-paths, one could see cooling instead of heating! Of course, if E-bar-gamma were too small, it would be possible to get an absurdly high value of the energy-balance heating.

The HEATR module of the NJOY Nuclear Data Processing System can be used to study these energy-balance problems. In addition to computing the heating, it computes some kinematic limits that should bracket the energy-balance heating. If the computed heating falls outside this range, there are problems with the evaluation that could be fixed. The code prepares graphs showing the computed heating and its kinematic limits, and it also prepares graphs showing the photon energy production with its kinematic limits. The graphs are given using both log and linear scales to highlight the low-energy and high-energy regimes.

We have gone through these graphs and prepared qualitative summaries of whether the energy balance is good, fair, or poor for each evaluation from ENDF/B-VII.1. In most cases, "good" means that the deviations of the heating values are less than a factor of 2 from the kinematic limits. Some comments on the graphs are usually given in the summary also.

It should be noted that the heating for the heavier targets is small with respect to E+Q; thus, we are computing it as a differece between large numbers. Fairly small percentage errors in the photon energy can often lead to large percent errors in the computed heating. These kinds of small errors are inevitable when using model codes to prepare the evaluation because of things like binning and the choice of grids. Evaluators should really adjust their results to smooth out these problems, but this hasn't always been done. Therefore, we use a more relaxed definition of "good" for the heavier targets.

Some of the isotopes for 150-MeV materials also have "expanded" pictures to better show the problems below 20 MeV.

More information of the kinematic checks done by HEATR can be found in the NJOY manual, and the printed outputs from the NJOY runs contain lots of additional information that can be used to help find the sources of the energy-balance problems demonstrated by these graphs.

Comments on VII.1 vs VII.0

For the light isotopes (Z<=29), most of the energy-balance problems seen for VII.0 were not fixed for VII.1. However, titanium was greatly improved, and all the isotopes now satisfy the tests. Vanadium was upgraded from an elemental evaluation to V-50 and V-51. Both of these satisfy the tests, so this is an improvement. The tests for Sc-45 were omitted from the VII.0 table. They are now included here. They show modest problems in the .5 to 1 MeV range.

In the range Z=30 to 39, there is not much change. There was an error in the table for VII.0. Rb-87 actually has no gammas, and that has been fixed here. Y-89 has a new peak in the heating around 4.5 MeV.

In the important Zr-Nb-Mo range, Zr-90 is now worse for VII.1 above 4.5 MeV. Zr-91 has been improved quite a lot, but it still only rates as fair from 10 to 15 MeV. Zr-92 has maybe been improved a bit, but it now has negative heating in the 7 MeV range. Zr-94 is the same story--some improvement overall with negative heating around 6 and 7 MeV. Ditto for Zr-96 with negative heating between 5 and 6 MeV. Nb-93 looks a little better, but it still rates as poor with negative kermas.

In range range Z=43 to 54, there weren't many changes. The large glitch for Sn-125 has been fixed, and it now rates as good. It could stand some additional improvement in the 5 to 7 MeV range.

In the range Z=55 to 71, most problems remain the same. However, Ba-133 now has gammas. It rates as good, except fair from 11 to 16 MeV.

In the range Z=72 to 78, there were a number of changes to evaluations. The hafnium isotopes were not given in the VII.0 tables, and they have been added here. Their energy balance is generally poor with lots of negative kermas. The tungstens were reevaluated, but the energy balance is still poor in general from 1 to 20 MeV. The renium isotopes now have gammas. They have some energy-balance problems in the 1 to 4 MeV range. The iridium isotopes also have gammas. Ir-191 has problems above 500 keV. Ir-193 is not too bad, but it could use some improvement between 1 and 7 MeV.

There were no changes in the energy balance for the range Z=79 to 83, but we did change some of the ratings.

Table of Energy-Balance Tests

Click on the desired isotope links to view the energy-balance testing graphs.

H-1 Good.

H-2 Good.

H-3 No gammas.

He-3 No gammas.

He-4 No gammas.

Li-6 Good.

Li-7 Good.

Be-7 No gammas.

Be-9 Good heating. Some small deviations in photon production above 1 MeV.

B-10 Good.

B-11 Good below 11 MeV, fair above.

C-nat Good.

N-14 Good.

N-15 Good.

O-16 Good.

O-17 No gammas.

F-19 Good.

Na-22 No gammas.

Na-23 Good to 4 MeV. Fair to 10 MeV. Poor above 10 MeV.

Mg-24 Good.

Mg-25 Good.

Mg-26 Some modest problems between 8 and 14 MeV. For MT=91 between 8.3 and 9 MeV, MF=3 uses int=3 and MF=12 uses int=2, resulting in a sharp peak in the heating. From 9 to 20 MeV, the problems seem to come from MT=91.

Al-27 Good.

Si-28 Good.

Si-29 Good.

Si-30 Good.

P-31 Good below 2 MeV. Poor from 2 to 20 MeV. Good above 20 MeV.

S-32 Good.

S-33 Good, except for a glitch between 4 and 5 MeV caused by using int=3 in MF3/MT91 and int=2 in MF12/MT91. Negative heating there.

S-34 Good below 5 MeV. Fair from 5 to MeV. Good above 10 MeV. The glitch between 5 and 6 MeV comes from using int=3 in MF3/MT91 and int=2 in MF12/MT91.

S-36 Good below 5 MeV. Poor above 5 MeV. The big problem between 5 and 9 MeV comes from MT=91.

Cl-35 Good.

Cl-37 Good.

Ar-36 No gammas.

Ar-38 No gammas.

Ar-40 No gammas.

K-39 Good, except for a feature between 4 and 5 MeV coming from using int=3 in MF=3 and int=2 in MF=12 for MT=91.

K-40 Good.

K-41 Good, except fair between 1 and 10 MeV.

Ca-40 Good.

Ca-42 Good, except fair between 2 and 20 MeV.

Ca-43 Good, except fair between 2 and 20 MeV.

Ca-44 Good, except poor between 2 and 20 MeV.

Ca-46 Good, except poor between 2 and 20 MeV.

Sc-45 Good, except only fair from 0.5 to 1 MeV.

Ti-46 Good.

Ti-47 Good.

Ti-48 Good.

Ti-49 Good.

Ti-50 Good.

V-50 Good.

V-51 Good.

Cr-50 Good.

Cr-52 Good.

Cr-53 Good.

Cr-54 Good.

Mn-55 Good.

Fe-54 Good.

Fe-56 Good.

Fe-57 Good.

Fe-58 Good.

Co-58 Good.

Co-58m1 No gammas.

Co-59 Fair from 3 to 5 MeV, OK elsewhere.

Ni-58 Good.

Ni-59 Good except for negative kermas around 1 MeV.

Ni-60 Good.

Ni-61 Good.

Ni-62 Good.

Ni-64 Good.

Cu-63 Good.

Cu-65 Good.

Zn-64 Good, except for some strange histogram shapes in the 100 eV to 10 keV range.

Zn-65 Good.

Zn-66 Good.

Zn-67 Good. Could use slightly tighter grids.

Zn-68 Good. Could use slightly tighter grids.

Zn-70 Good. Could use slightly tighter grids.

Ga-69 No gammas.

Ga-71 No gammas.

Ge-70 Good.

Ge-72 Good.

Ge-73 Fair for 4 to 20 MeV.

Ge-74 Good.

Ge-76 Good.

As-74 Fair above 2 MeV, OK below.

As-75 Good.

Se-74 No gammas.

Se-76 No gammas.

Se-77 No gammas.

Se-78 No gammas.

Se-79 No gammas.

Se-80 No gammas.

Se-82 No gammas.

Br-79 No gammas.

Br-81 No gammas.

Kr-78 Poor above 2.5 MeV.

Kr-80 No gammas.

Kr-82 No gammas.

Kr-83 No gammas.

Kr-84 No gammas.

Kr-85 Good to 9 MeV, fair above.

Kr-86 No gammas.

Rb-85 No gammas.

Rb-86 Good to 2 MeV, fair above.

Rb-87 No gammas.

Sr-84 Good.

Sr-86 No gammas.

Sr-87 No gammas.

Sr-88 No gammas.

Sr-89 No gammas.

Sr-90 No gammas.

Y-89 Good to 12 MeV, fair above.

Y-90 Good.

Y-91 No gammas.

Zr-90 Good below 4.5 Mev, fair above.

Zr-91 Fairly good except only fair from 10 to 15 MeV.

Zr-92 Fair above 3 MeV. Negative kermas.

Zr-93 No gammas.

Zr-94 Fair to poor above 3 MeV. Negative kermas

Zr-95 No gammas.

Zr-96 Fair to poor above 3 MeV. Negative kermas.

Nb-93 Nb-93-expanded Good below 800 keV, poor to 20 MeV. Negative kermas.

Nb-94 No gammas.

Nb-95 No gammas.

Mo-92 Poor above 500 keV. Negative kermas. Strange gamma shapes.

Mo-94 Poor above 500 keV. Negative kermas. Strange gamma shapes.

Mo-95 Good.

Mo-96 Poor abov 500 keV. Negative kermas. Strange gamma shapes.

Mo-97 Poor abov 500 keV. Negative kermas. Strange gamma shapes.

Mo-98 Poor abov 500 keV. Negative kermas. Strange gamma shapes.

Mo-99 No gammas.

Mo-100 No gammas.

Tc-99 Good.

Ru-96 No gammas.

Ru-98 No gammas.

Ru-99 No gammas.

Ru-100 No gammas.

Ru-101 Good to 8 MeV, poor above.

Ru-102 No gammas.

Ru-103 No gammas.

Ru-104 No gammas.

Ru-105 No gammas.

Ru-106 No gammas.

Rh-103 Good.

Rh-105 No gammas.

Pd-102 Good.

Pd-104 Good.

Pd-105 Good.

Pd-106 Good.

Pd-107 No gammas.

Pd-108 Good.

Pd-110 Good.

Ag-107 Good.

Ag-109 Fair.

Ag-110m1 No gammas.

Ag-111 Good below 10 MeV, fair above.

Cd-106 Good to 2.5 MeV, poor above.

Cd-108 No gammas.

Cd-110 No gammas.

Cd-111 Poor above 1.5 MeV.

Cd-112 No gammas.

Cd-113 No gammas.

Cd-114 No gammas.

Cd-115m1 Poor from .5 to 10 MeV. Negative kermas.

Cd-116 No gammas.

In-113 No gammas.

In-115 No gammas.

Sn-112 No gammas.

Sn-113 Good.

Sn-114 No gammas.

Sn-115 No gammas.

Sn-116 No gammas.

Sn-117 No gammas.

Sn-118 No gammas.

Sn-119 No gammas.

Sn-120 No gammas.

Sn-122 No gammas.

Sn-123 No gammas.

Sn-124 No gammas.

Sn-125 Good.

Sn-126 No gammas.

Sb-121 No gammas.

Sb-123 No gammas.

Sb-124 No gammas.

Sb-125 No gammas.

Sb-126 Good.

Te-120 No gammas.

Te-122 No gammas.

Te-123 No gammas.

Te-124 No gammas.

Te-125 No gammas.

Te-126 No gammas.

Te-127m No gammas.

Te-128 No gammas.

Te-129m No gammas.

Te-130 No gammas.

Te-132 Good, except for a sharp glitch at 16 MeV. Negative kermas. The sharp problem in the heating is due to faulty angular distributions in MF=6, MT=91 at 16 MeV.

I-127 Good.

I-129 No gammas.

I-130 Good. Could use a little improvement at 6 MeV.

I-131 No gammas.

I-135 No gammas.

Xe-123 Poor below 1 keV. Poor above 1 MeV.

Xe-124 Poor above 2.5 MeV.

Xe-126 No gammas.

Xe-128 No gammas.

Xe-129 No gammas.

Xe-130 No gammas.

Xe-131 Good to 8 MeV, poor above.

Xe-132 No gammas.

Xe-133 No gammas.

Xe-134 No gammas.

Xe-135 No gammas.

Xe-136 No gammas.

Cs-133 Good, except for a sharp glitch at 16 MeV. Negative kermas.

Cs-135 No gammas.

Cs-136 No gammas.

Cs-137 No gammas.

Ba-130 No gammas.

Ba-132 No gammas.

Ba-133 Good below 10 Mev, poor above.

Ba-134 No gammas.

Ba-135 No gammas.

Ba-136 No gammas.

Ba-137 No gammas.

Ba-138 No gammas.

Ba-140 No gammas.

La-138 No gammas.

La-139 No gammas.

La-140 Good. Could use a little improvement around 4 to 6 MeV.

Ce-136 Good.

Ce-138 Good.

Ce-139 Good.

Ce-140 No gammas.

Ce-141 No gammas.

Ce-141 No gammas.

Ce-142 No gammas.

Ce-143 Good to 1.5 MeV, poor above. Negative kermas.

Ce-144 No gammas.

Pr-141 Good.

Pr-142 Good.

Pr-143 No gammas.

Nd-142 Good.

Nd-143 Good.

Nd-144 Good.

Nd-145 Good to 8 MeV, poor above. Negative kermas.

Nd-146 Good.

Nd-147 Good to 6 MeV, poor above. Negative kermas.

Nd-148 Good.

Nd-150 Good.

Pm-147 No gammas.

Pm-148 No gammas.

Pm-148m1 No gammas.

Pm-149 No gammas.

Pm-151 Good, except for a poor region from 4 to 8 MeV.

Sm-144 Good.

Sm-147 Good to 10 Mev, poor above. Negative heating.

Sm-148 Good to 10 MeV, poor above.

Sm-149 Good below 7.5 MeV, poor above. Negative heating.

Sm-150 Good to 10 MeV, fair above.

Sm-151 Good to 6 MeV, poor above. Negative heating.

Sm-152 Good to 14 MeV, fair above.

Sm-153 Good to 9 MeV, fair above.

Sm-154 Good.

Eu-151 No gammas.

Eu-152 No gammas.

Eu-153 Good to 17 MeV, fair above.

Eu-154 No gammas.

Eu-155 No gammas.

Eu-156 No gammas.

Eu-157 Good to 5 MeV, fair above.

Gd-152 Good.

Gd-153 Good to 7.5 MeV, poor above. Negative heating.

Gd-154 Good to 10 MeV, poor above.

Gd-155 Good to 7.5 MeV, poor above. Negative heating.

Gd-156 Good.

Gd-157 Good to 10 MeV, poor above.

Gd-158 Good.

Gd-160 Good to 10 MeV, fair above.

Tb-160 Good, except for a poor region at 5 to 7 MeV.

Dy-156 Good.

Dy-158 Good.

Dy-160 Good.

Dy-161 Good below 8 MeV, fair above.

Dy-162 Good.

Dy-163 Good below 8 MeV, fair above.

Dy-164 Good below 8 MeV, fair above.

Ho-165 Good. Some negative kermas.

Ho-166m1 A sharp spike at 4 MeV. Fair above there. Negative kermas at 1 MeV.

Er-162 Poor above 1.5 MeV.

Er-164 Poor above 1.5 MeV.

Er-166 Poor above 1.5 MeV.

Er-167 Poor above 1 MeV.

Er-168 Poor above 1.5 MeV

Er-169 Poor above 1.5 MeV

Er-170 Poor above 1.5 MeV

Tm-168 Some problems between 1 and 7 MeV. Negative kermas.

Tm-169 Some problems between 2 and 10 MeV. Fair above.

Tm-170 Some problems between 2 and 13 MeV. Fair above. Lu-175 No gammas.

Lu-176 No gammas.

Hf-174 Good to 2 MeV. Poor above. Negative kermas.

Hf-176 Good to 2 MeV. Poor above. Negative kermas.

Hf-177 Good to 1 MeV. Poor above. Negative kermas.

Hf-178 Good to 2 MeV. Poor above. Negative kermas.

Hf-179 Good to 1 MeV. Poor above. Negative kermas.

Hf-180 Good to 2 MeV. Poor above. Negative kermas.

Ta-181 Good to 1 Mev. Poor above.

Ta-182 No gammas.

W-182 W-182 expanded Good to 1 MeV. Poor from 1 to 20 MeV. Good above.

W-183 W-183 expanded Good to 800 800 keV. Poor from there to 10 MeV, OK above 10 MeV.

W-184 W-184 expanded Good to 1 MeV. Poor between 1 and 20 MeV.

W-186 W-186 expanded Good to 1 MeV. Poor between 1 and 20 MeV.

Re-185 Good to 1 MeV. Poor from 1 to 4 MeV. Good above.

Re-187 Good to 1 MeV. Poor from 1 to 4 MeV. Good above.

Ir-191 Good to 500 keV, poor above.

Ir-193 Good to 1 Mev. Fair from 1 to 7 MeV. Good above.

Au-197 Good. Some negative kermas.

Hg-196 Hg-196 expanded Good to 8 MeV except for a glitch near 3 MeV. Poor between 8 to 20 MeV. Good above there. Negative kermas.

Hg-198 Good, except for some problems between 8 and 20 MeV.

Hg-199 Hg-199 expanded Good to 8 MeV except for some problems around 1 MeV to 8 MeV except for some problems around 1 MeV. Poor from 8 to 20 MeV. OK above.

Hg-200 Good to about 8 MeV. Poor between 8 and 20 Mev. OK above.

Hg-201 Good to about 8 MeV. Poor between 8 and 20 Mev. OK above.

Hg-202 Hg-202 expanded Good to about 8 MeV. Poor between 8 and 20 Mev. OK above. Negative kermas.

Hg-204 Good to about 8 MeV. Poor between 8 and 20 Mev. OK above.

Tl-203 OK to 2.5 MeV, poor above. Negative kermas.

Tl-205 OK to 2.5 MeV, poor above. Negative kermas.

Pb-204 Pb-204 expanded Good to 2.5 MeV. Poor from 5 to 20 MeV. OK above.

Pb-206 Pb-206 expanded Good to 3 Mev. Poor around 5 MeV. Fair between 7 and 20 MeV. OK above.

Pb-207 Pb-207 expanded Good to 3 MeV. Poor from 4 to 8 MeV. Fair between 8 and 20 MeV. OK above.

Pb-208 Pb-208 expanded Good to 3 MeV. Poor from 4 to 8 MeV. Fair between 8 and 20 MeV. OK above.

Bi-209 Bi-209 expanded Good. Negative kermas.