Large volume of water

Questions and discussion about applications, input, output and general user topics
Post Reply
knevhor
Posts: 7
Joined: Thu Apr 09, 2020 7:45 pm
Security question 1: No
Security question 2: 7

Large volume of water

Post by knevhor » Mon Jun 01, 2020 6:46 pm

When modeling a single pin, I get large volume of water (1.00000E+37 cm3) in the materials section of the .out file but what when I run the checkvolumes routine I get 1.97648E-01 cm3 which is a lot closer to the 1.93678157E-01 cm3 that I expect for water.

This is my geometry:

pin 1
Fuel 0.4095
Gap 0.418
Clad 0.4750
Water

surf 1 sqc 0.0 0.0 0.4750
cell 2 0 fill 1 -1
cell 3 0 outside 1

What is causing this?
thanks

PRoux
Posts: 5
Joined: Thu Oct 06, 2016 11:24 pm
Security question 1: No
Security question 2: 84

Re: Large volume of water

Post by PRoux » Tue Jun 02, 2020 3:27 am

Hello Serpent users,

The issue was resolved.
To make Serpent print the actual volume of the material in the case of "filler" materials (by "filler", I mean a material that is occupying the outside universe), in that case Water, the volume of the material actually needs to be specified.

For instance, the material line could be for you, knevhor:
mat Water sum tmp 585 vol 2.00E+2

The manual suggests to provide the volumes for all materials, not only the "fillers". I made a (very) quick check on cross sections for a pin cell, both inputs (with and without the vol entry) provided identical cross sections.

Out of curiosity if users/developers run into this thread, I would be interested to know if users/developers noticed significant differences in the results if the vol entry is not specified, for example in terms of isotopic inventory in burn up mode? flux in detectors? cross sections? k-inf?).

Cheers

Pascal

Riku Tuominen
Posts: 63
Joined: Tue Feb 27, 2018 10:52 am
Security question 1: No
Security question 2: 93

Re: Large volume of water

Post by Riku Tuominen » Tue Jun 02, 2020 10:27 am

Hi! In general you should not trust that the code calculates the volumes correctly. You can calculate and define the volumes yourself or use the Monte Carlo volume-checker routine (set mcvol card or checkvolumes command line option). More information on defining the volumes is available here. Incorrect volumes can cause notable differences in burnup calculations since the reaction rates are incorrect. As another example, in case of detectors the results are divided by the volume which by default is set to 1. Global parameters such as kinf and keff are not affected by the volumes directly, but of course in burnup calculations incorrect volumes result in incorrect reaction rates which in turn result in incorrect nuclide compositions and incorrect multiplication factors.

knevhor
Posts: 7
Joined: Thu Apr 09, 2020 7:45 pm
Security question 1: No
Security question 2: 7

Re: Large volume of water

Post by knevhor » Fri Jun 05, 2020 8:00 pm

Thanks Riku and Pascal

mishraa
Posts: 1
Joined: Mon Jun 29, 2020 8:03 pm
Security question 1: No
Security question 2: 7

Re: Large volume of water

Post by mishraa » Mon Jun 29, 2020 8:07 pm

NICE explanation #pascal
I am Field Maintenance Technician at field engineer

User avatar
Jaakko Leppänen
Site Admin
Posts: 2378
Joined: Thu Mar 18, 2010 10:43 pm
Security question 2: 0
Location: Espoo, Finland
Contact:

Re: Large volume of water

Post by Jaakko Leppänen » Tue Jun 30, 2020 11:42 am

Calculating analytical solutions for material volumes in a general 3D geometry is practically impossible. The fuel pin universes are truncated by the lattice cells, and even though it is possible to determine which material is located at position (x,y,z), it is not as straightforward to figure out where a specific material is, let alone its volume.
- Jaakko

Kaizes
Posts: 1
Joined: Mon Jul 20, 2020 6:16 am
Security question 1: No
Security question 2: 7

Re: Large volume of water

Post by Kaizes » Mon Jul 20, 2020 6:20 am

Jaakko Leppänen wrote:
Tue Jun 30, 2020 11:42 am
Calculating analytical solutions for material volumes in a general 3D geometry is practically impossible. The fuel pin universes are truncated by the lattice cells, and even though it is possible to determine which material is located at position (x,y,z), it is not as straightforward to figure out where a specific material is, let alone its volume.
this is great answers.You can consult

Post Reply