# Maximum number of lost particles has been reached.

**URL:** <https://openmc.discourse.group/t/maximum-number-of-lost-particles-has-been-reached/3545>\
**Category:** User Support\
**Created:** [October 23, 2023, 2:59pm UTC](https://openmc.discourse.group/t/maximum-number-of-lost-particles-has-been-reached/3545 "2023-10-23T14:59:07Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![ann22](https://avatars.discourse-cdn.com/v4/letter/a/e47c2d/32.png) [@ann22](https://openmc.discourse.group/u/ann22)\
**Post date:** [October 23, 2023, 2:59pm UTC](https://openmc.discourse.group/t/maximum-number-of-lost-particles-has-been-reached/3545/1 "2023-10-23T14:59:07Z")

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Hello, I’m getting this error, and I don’t quite understand what the problem is. Perhaps you need to register another surface or another boundary condition…Thank you in advance for your help

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**Author:** ![Sabyasachi](https://avatars.discourse-cdn.com/v4/letter/s/58956e/32.png) [@Sabyasachi](https://openmc.discourse.group/u/Sabyasachi)\
**Post date:** [October 23, 2023, 3:49pm UTC](https://openmc.discourse.group/t/maximum-number-of-lost-particles-has-been-reached/3545/2 "2023-10-23T15:49:22Z")

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Try the code with boundary type reflective.