Thermal Scattering Data

User Support
1

How can I get thermal scattering data for H in H20 at 300 and 1027 K? I do not get the accurate answer using interpolation method for temperature treatment.

While using NJOY, I received following error

  • S (alpha, beta) are included for H in H20 at 293.6 350 400 450 500 550 600 650 800 [ ENDF/ B-7 ]
  • S (alpha, beta) are included for H in H20 at 293.6, 323.6, 373.6, 423.6, 473.6, 523.6, 573.6, 623.6, 647.2, 800, 1000 [ JEFF 3.2 ]
2

Unfortunately it’s not simple to generate S(a,b) data at temperatures that don’t already exist on the ENDF evaluation. For these two libraries (ENDF/B-VII.1 and JEFF 3.2), the evaluations are based on the work of Keinert and Mattes and were generated using the LEAPR module from NJOY. This means you would have to generate new LEAPR inputs corresponding to the desired temperatures. You can find some of the LEAPR inputs from the original work in this report:

https://www.oecd-nea.org/science/wpec/sg42/Files/Report_mattes2005.pdf

3

Thanks for the docs Paul

4

Ariful,

I agree with Paul, you need to include LEAPR in your calculation.

But, I would like you to think about this: how much sense does make water at 1027 K?. Already all the values above the critical point are just extrapolations, because you need to consider not only temperature but pressure for supercritical water.

Best,
Ignacio

5

It could be usefull.

LA-UR-20-24456.pdf (1.59 MB)

6

Thanks Nacho Marquez for your help. Could you please explain a little bit about pressure consideration for supercritical water? In which part I should pay more attention to LEAPR module in context of pressure? How do I choose (alpha, beta) grid value?

7

Thanks Tarek EI Bardouni

8

The thermal scattering libraries for hydrogen bound in light water are valid for liquid light water. If you have water under other conditions (ice, steam, supercritical water) thermal scattering is different.

Also, properties in liquid water do not change significantly with pressure (at least from a TSL perspective), but they do in supercritical water.

If you are simulating a thermal supercritical reactor I recommend this:

https://elib.uni-stuttgart.de/handle/11682/1999

Best,
Ignacio

9

I have a question regarding ! card 12 -- rho(energy) (order of increasing ev) in LEAPR module.

293.6/  temperature (K)
0.00215 68/  frequency distribution
0.00000E+00  1.04170E-02  4.16710E-02  9.37490E-02  1.66682E-01
2.60457E-01  3.74972E-01  5.10341E-01  6.66586E-01  8.43707E-01
1.04169E+00  1.26039E+00  1.49991E+00  1.76047E+00  2.04172E+00
2.34379E+00  2.66665E+00  3.01045E+00  3.33873E+00  3.72164E+00
4.10441E+00  4.54222E+00  4.98019E+00  5.47328E+00  5.91196E+00
6.24071E+00  6.45971E+00  6.56965E+00  6.56980E+00  6.35010E+00
5.91059E+00  5.58143E+00  5.19738E+00  4.86852E+00  4.53952E+00
4.26544E+00  3.99124E+00  3.71714E+00  3.49814E+00  3.27889E+00
3.11484E+00  2.95067E+00  2.84650E+00  2.74784E+00  2.65469E+00
2.56706E+00  2.48495E+00  2.40835E+00  2.33727E+00  2.27169E+00
2.21165E+00  2.15711E+00  2.12732E+00  2.11543E+00  2.10353E+00
2.09165E+00  2.07975E+00  2.06786E+00  2.05596E+00  2.04408E+00
2.03218E+00  2.02029E+00  2.00839E+00  1.99651E+00  1.98461E+00
1.97272E+00  9.86360E-01  0.00000E+00/

How did you calculate these values? If I want to know for let’s say 1027 K, How do I calculate these values?

10

These values represent the phonon frequency distribution. Typically this would come from a molecular dynamics code, so it’s not an easy task to come up with it for some new condition.

11

Thanks @paulromano

Ah, I see. But worried about it.

12

Hi all,

I found this old post and would like your recommendations on an issue I am having.

I am conducting a study on nuclear data uncertainty propagation. For this purpose, I am interested in creating my nuclear data library from ENDF and am using the ThermalScattering.from_njoy() method to generate the thermal scattering data; I need data at 500 and 800 K.

With that method, I noted that when the list of temperatures is not included, the thermal scattering file is generated (at room temperature). However, when the list of temperatures [500.,800.] is considered, there is an error after some seconds of running NJOY (please see “Error.txt”). I tried with both NJOY21 and NJOY2016 and got the same error.

My script, the “Error.txt” file, the ENDF incident neutron sub-library file and the thermal neutron scattering sub-library file are here

Please, any suggestion?
Javier

13

Thermal scattering behaves a little bit differently from incident neutron data in this respect. ENDF thermal scattering files have data listed for specific temperatures and there’s no straightforward way to “Doppler broaden” them to other temperatures. Instead, what you’ve have to do is run LEAPR (or an equivalent code) to generate a new ENDF file with data at the temperatures you need. I know some organizations do this when the ENDF file provided in the main library only has data on a very coarse temperature grid. If you have access to the underlying phonon frequency spectra, they can be interpolated to the desired temperatures and fed through LEAPR to give a new ENDF file.

In your particular case, when you run from_njoy with no temperatures listed, it will use all available temperatures in the ENDF file. This means that whatever data you are processing, they only have data listed at room temperature unfortunately.

14

I got it @paulromano, thanks for your quick reply.