Delayed neutrons - coupled variable pre1 was not found (3d_auto_diff_rho)

[M. Pater]

Hello, I am attempting to run some 3d cases for MSRE that are available on GitHub and I encountered a few difficulties. For instance, with regard to a delayed neutron source:

In the 'problems/033117_nts_temp_pre_parsed_mat/3d_auto_diff_rho.i' file

Kernels\delayed_group1 the DelayedNeutronSource lacks a 'group_number' parameter, I believe. But after adding 'variable = group1' in this block, the following error appears:

delayed_group1: Coupled variable 'pre1' was not found

Would anyone have any idea for solving this problem after having a look at the input file?

There are more issues with other files there, but let's focus on one problem at a time...

Kind regards,

Matt

[Huff, Kathryn D]

Hi Matt,

You said you believe the DelayedNeutronSource lacks a 'group_number' parameter. Why? did you see an error? If so what was the error?

You then said you added 'variable = group1' in this block, and saw the following error:

delayed_group1: Coupled variable 'pre1' was not found

That's confusing to me, because, in the current repository, that file already includes `variable = group1` ... so you shouldn't have had to add it.

https://github.com/arfc/moltres/blob/devel/problems/033117_nts_temp_pre_parsed_mat/3d_auto_diff_rho.i#L92 

This may be cleared up when you confirm the version (git hash) of moltres that you are using. 

On some other notes:

I'm glad you're using Moltres. We are enthusiastic about users trying to adopt moltres and we appreciate users like you reporting bugs because it helps us make moltres more robust. Also, it's important that you feel welcome and included so that we can form collaborations in the longer term.

However, I'd like to make some requests. Though the moltres-users group is a fine place to put some of this, your bug reports might be more appropriately placed on github itself, in a new issue. GitHub is a better place for a lot of these bug reports because more members of the Moltres community see these issues and anyone on earth can respond there on GitHub. Also, it's a clearer location for future users to find past bug reports and their solutions (hopefully solved once someone is looking for it).  

Finally, without discouraging you, I'd like to temper your expectations with regard to user support. Moltres is research software, mostly used and developed by graduate students at the moment, and as such, you may find it moves a bit quickly for us to garuntee backwards compatibility. So, please keep that in mind. 

Katy

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The University of Illinois at Urbana-Champaign

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[M. Pater]

Hi, I'm sorry, I made a mistake - I added 'group number = 1' because what was missing was CHID, if I remember well - the group into which the delayed neutrons are born. So after analysing the input file I decided to add that line but then another error that I mentioned appeared.

Thank you for your message, I understand you completely and appreciate everything you said.

[Huff, Kathryn D]

Hi Matt,

Thanks. I'm not sure I'm understanding. Maybe someone else is following this better. Or -- maybe to clarify, you can share (e.g., in a gist) the current input file that you're trying to get to run, in the state that it is when it throws this error?

Katy

On Mon, May 13, 2019 at 8:53 AM M. Pater <mateusz...@gmail.com> wrote:

Hi, I'm sorry, I made a mistake - I added 'group number = 1' because what was missing was CHID, if I remember well - the group into which the delayed neutrons are born. So after analysing the input file I decided to add that line but then another error that I mentioned appeared.

Thank you for your message, I understand you completely and appreciate everything you said.

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[M. Pater]

Dear Katy, this is the file: https://gist.github.com/MateuszPater/ff2ef3b34292f5b10b0e7167cbcb9810

I took it from this repository: https://github.com/arfc/moltres/blob/devel/problems/033117_nts_temp_pre_parsed_mat/3d_auto_diff_rho.i and since Moltres told me that there was a missing parameter, I added the above mentioned line 95 to the code, which produced another error. According to the DelayedNeutronSource.C it seemed to be what was needed, so I don't know why a "coupled variable 'pre1' was not found".

Matt

[Alexander Lindsay]

I need to actually generate a mesh before I can run this input...but try adding `block = fuel` in any of the blocks corresponding to `DelayedNeutronSource` since the precursors only live in the fuel and hence any kernels that use them should only exist in the fuel...

Also, was that the complete error message?

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[M. Pater]

I added "block = 'fuel'" to the .delayed_group1 kernel but it also needed a group_number for the CHI:

*** ERROR ***

/home/peppe/projects/moltres/tutorial/3d/3d_auto_diff_rho.i:94: missing required parameter 'Kernels/delayed_group1/group_number'

        Doc String: "neutron energy group number for chi_d"

After adding the 'group_number = 1', another error appears:

*** ERROR ***

Material property 'chi_d', requested by 'delayed_group1' is not defined on block fuel

When I define the chi_d as a property of the fuel material and give it value 1, I am getting:

*** ERROR ***
Material has no property named: chi_d

Any idea? The input file does not use any Serpent-generated txt files for the properties, the material type is MsreFuelTwoGrpXSFunctionMaterial and it seems to specify the chi...

Best, Matt

[Alexander Lindsay]

I feel like we just had a discussion on our moltres issues/prs about this...it would be great if an ARFC student chimed in here...

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[Gavin Ridley]

The first issue is due to the fact that, at first, all delayed neutrons were assumed to be born in group 1. The Material object MsreFuelTwoGrpXSFunctionMaterial was written during this time. A good bit after that, I wrote in some functionality to make sure delayed neutrons were born in their correct physical groups. Since most calculations used only two groups in the early days of moltres, the original assumption was good. Go to four or more groups though, and delayed neutrons should certainly be born with their own spectrum.

You should be getting an error because the precursor setup action, by default, will tell the precursors to be emitted according to a spectrum specified by GenericMoltresMaterial; MsreFuelTwoGrpXSFunctionMaterial likely does not provide that data. This is the root of the problem. Looks like if you want to use that older Material object now, some code updating will be required. It's likely the easiest route to set up MsreTwoGrpXSFunctionMaterial to provide CHI_D data, since CHI_D should just be [1, 0] for all temperatures.

There was another question over email about why the radially outermost boundary condition for temperature is about 25 kelvin hotter than the actual MSRE inlet. IIRC, Alex did this so that we didn't have to model precursor formation in the downcomer and subsequent mixing in the lower plenum. Instead, all the Moltres models end at the active core boundary and just treat the downcomer as a constant temperature zone. The temperature which is 25 kelvin hotter than the inlet temperature should correspond to the average downcomer temperature, IIRC.

On Thursday, May 16, 2019 at 9:39:09 AM UTC-4, Alexander Lindsay wrote:

I feel like we just had a discussion on our moltres issues/prs about this...it would be great if an ARFC student chimed in here...

On Thu, May 16, 2019 at 2:35 AM M. Pater <mateusz...@gmail.com> wrote:

I added "block = 'fuel'" to the .delayed_group1 kernel but it also needed a group_number for the CHI:

*** ERROR ***

/home/peppe/projects/moltres/tutorial/3d/3d_auto_diff_rho.i:94: missing required parameter 'Kernels/delayed_group1/group_number'

        Doc String: "neutron energy group number for chi_d"

After adding the 'group_number = 1', another error appears:

*** ERROR ***

Material property 'chi_d', requested by 'delayed_group1' is not defined on block fuel

When I define the chi_d as a property of the fuel material and give it value 1, I am getting:

*** ERROR ***
Material has no property named: chi_d

Any idea? The input file does not use any Serpent-generated txt files for the properties, the material type is MsreFuelTwoGrpXSFunctionMaterial and it seems to specify the chi...

Best, Matt

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[M. Pater]

Thank you all so much for the replies! It helps my work a lot. I'm going to tinker with the code since now I know where the problem lies