# How to specify the boron concentration (ppm) in calculation

**URL:** <https://openmc.discourse.group/t/how-to-specify-the-boron-concentration-ppm-in-calculation/877>\
**Category:** User Support\
**Created:** [November 29, 2020, 8:56am UTC](https://openmc.discourse.group/t/how-to-specify-the-boron-concentration-ppm-in-calculation/877 "2020-11-29T08:56:20Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![wangyahui](https://avatars.discourse-cdn.com/v4/letter/w/df705f/32.png) [@wangyahui](https://openmc.discourse.group/u/wangyahui)\
**Post date:** [November 29, 2020, 8:56am UTC](https://openmc.discourse.group/t/how-to-specify-the-boron-concentration-ppm-in-calculation/877/1 "2020-11-29T08:56:20Z")

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Hi all,

I try to calculate the pin cell multi-group cross-section under different boron concentrations, but I don’t know how to set the boron concentration in ppm. Should it be specified in the moderator by using “material.add\_nuclide” or “material.nuclide\_element”? For different boron concentrations, does the density of water need to be recalculated manually using H, O and B?

Below is what I did:

* * *

boron\_ppm=500

#borated water  
water = openmc.Material(name=‘Borated Water’)  
water.add\_nuclide(‘H1’, 2)  
water.add\_nuclide(‘O16’, 1) #is it right? or how can I calculate the ‘atomic percentage’ from the atomic density？  
water.add\_element(‘B’,boron\_ppm\*1e6,‘wo’)  
water.set\_density(‘g/cm3’, 0.740582)

* * *

I found a python API " [openmc.model.borated\_water](https://docs.openmc.org/en/stable/pythonapi/generated/openmc.model.borated_water.html?highlight=borated_water#openmc.model.borated_water)" that can specify the boron concentration in ppm, but no examples of using it were found.

Sincerely yours,  
Yahui Wang

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**Author:** ![mkreher13](https://yyz2.discourse-cdn.com/free1/user_avatar/openmc.discourse.group/mkreher13/32/4093_2.png) [@mkreher13](https://openmc.discourse.group/u/mkreher13)\
**Post date:** [December 2, 2020, 12:22am UTC](https://openmc.discourse.group/t/how-to-specify-the-boron-concentration-ppm-in-calculation/877/2 "2020-12-02T00:22:30Z")

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Using openmc.model.borated\_water() is probably the way to go. Here is an example:

water = openmc.model.borated\_water(boron\_ppm=432.473,temperature=566,pressure=15)

Using the temperature and pressure you give, it automatically calculates the density. If you specify the density, it overrides the temperature and pressure.

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**Author:** ![wangyahui](https://avatars.discourse-cdn.com/v4/letter/w/df705f/32.png) [@wangyahui](https://openmc.discourse.group/u/wangyahui)\
**Post date:** [December 2, 2020, 2:36am UTC](https://openmc.discourse.group/t/how-to-specify-the-boron-concentration-ppm-in-calculation/877/3 "2020-12-02T02:36:09Z")

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Hi mkreher，

Thank you for your kind reply. I have another problem. Does ‘openmc.model.borated\_water’ include S(α,β) table? Thank you again.

Sincerely yours,  
Yahui Wang

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**Author:** ![mkreher13](https://yyz2.discourse-cdn.com/free1/user_avatar/openmc.discourse.group/mkreher13/32/4093_2.png) [@mkreher13](https://openmc.discourse.group/u/mkreher13)\
**Post date:** [December 2, 2020, 3:52am UTC](https://openmc.discourse.group/t/how-to-specify-the-boron-concentration-ppm-in-calculation/877/4 "2020-12-02T03:52:09Z")

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Yes, it does! I see it in the source code.