Input error: Continuous S(a,b) format not supported

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gavin.ridley.utk
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Input error: Continuous S(a,b) format not supported

Post by gavin.ridley.utk » Tue Oct 30, 2018 4:15 pm

Hi all,

I was hoping to try out some of the new ENDF/B-VIII S(a,b) data but it seems Serpent doesn't support it, giving:
Input error:

Continuous S(a,b) format not supported
Is there any preprocessing of this data that has to be done? Or is using this just not really an option now?

Thanks very much,
Gavin Ridley

Yellowstone Energy

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Jaakko Leppänen
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Re: Input error: Continuous S(a,b) format not supported

Post by Jaakko Leppänen » Wed Oct 31, 2018 11:26 am

The problem is that the new data format has not been documented and therefore cannot implement the sampling routines in Serpent either. Right now the only option is to use older S(a,b) libraries. There maybe some options in NJOY for choosing the format, but I haven't looked into that.
- Jaakko

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Re: Input error: Continuous S(a,b) format not supported

Post by gavin.ridley.utk » Thu Nov 01, 2018 1:46 am

Thanks very much Dr. Leppänen. As a note for anyone else running into this, you can obtain S(a,b) in the serpent-compatible format by specifying iwt=1 in card 9 of the ACER sequence.
Gavin Ridley

Yellowstone Energy

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Re: Input error: Continuous S(a,b) format not supported

Post by Jaakko Leppänen » Thu Nov 01, 2018 10:35 am

Also, if you come across any documentation on the new S(a,b) data format, please let us know.
- Jaakko

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Re: Input error: Continuous S(a,b) format not supported

Post by gavin.ridley.utk » Fri Nov 09, 2018 10:03 pm

As a followup to this, Dr. Leppanen, do you remember the number of NJOY THERMR "icoh" bins and number of discrete cosines used to generate the S(a,b) data distributed with Serpent 1? I've tried to match lwe6.00t k_eff values for a pin cell problem and found the following:

Code: Select all

nbins | keff +/- sigma
----------------------
1     | 1.05036 +/- 0.00019
2     | 1.05173 +/- 0.00022
3     | 1.05259 +/- 0.00018
5     | 1.05263 +/- 0.00020

Serpent reference value (lwe6.00t):
1.05097 +/- 0.00021
This was generated using the ENDF/B8 data, which may explain some of the discrepancy, but a 200 pcm change in the result is a little unsettling just from changing an input parameter to NJOY.
Gavin Ridley

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Re: Input error: Continuous S(a,b) format not supported

Post by danshen15 » Tue Jun 25, 2019 7:08 am

Hi Dr. Leppanen, will Serpert 2.1.31 support the new ENDF/B-VIII S(a, b) data format? Thank you very much.
Jaakko Leppänen wrote:
Wed Oct 31, 2018 11:26 am
The problem is that the new data format has not been documented and therefore cannot implement the sampling routines in Serpent either. Right now the only option is to use older S(a,b) libraries. There maybe some options in NJOY for choosing the format, but I haven't looked into that.

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Re: Input error: Continuous S(a,b) format not supported

Post by Jaakko Leppänen » Wed Jun 26, 2019 1:06 pm

No. Unfortunately we haven't been able to implement the continuous S(a,b) formalism yet.
- Jaakko

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Re: Input error: Continuous S(a,b) format not supported

Post by paulromano » Mon Nov 11, 2019 7:03 pm

The ACE format documentation is now openly available (work in progress): https://github.com/NuclearData/ACEFormat

I recently added a section describing the continuous S(a,b) format and LANL has blessed it. It would be nice to have another code that supports it for cross-code comparison purposes.

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Re: Input error: Continuous S(a,b) format not supported

Post by Ville Valtavirta » Wed Nov 13, 2019 2:06 pm

Thank you Paul,

we'll look into implementing the support.

-Ville

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Re: Input error: Continuous S(a,b) format not supported

Post by Jaakko Leppänen » Wed Nov 20, 2019 6:51 pm

Is there any documentation on how to perform the sampling? Or is it just similar to ENDF law 61 with linear interpolation?
- Jaakko

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