# My leakage fration too high in result

**URL:** <https://openmc.discourse.group/t/my-leakage-fration-too-high-in-result/2021>\
**Category:** User Support\
**Created:** [May 5, 2022, 2:58pm UTC](https://openmc.discourse.group/t/my-leakage-fration-too-high-in-result/2021 "2022-05-05T14:58:45Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![lz152](https://yyz2.discourse-cdn.com/free1/user_avatar/openmc.discourse.group/lz152/32/1547_2.png) [@lz152](https://openmc.discourse.group/u/lz152)\
**Post date:** [May 5, 2022, 2:58pm UTC](https://openmc.discourse.group/t/my-leakage-fration-too-high-in-result/2021/1 "2022-05-05T14:58:45Z")

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Hi guys,  
I am running a pwr pincell with reflective B.C. the running mode is k-eigenvalue calculation. and I got the result follow:

```auto
 ============================> RESULTS <============================

 k-effective (Collision) = 1.00843 +/- 0.00033
 k-effective (Track-length) = 1.00843 +/- 0.00033
 k-effective (Absorption) = 1.00898 +/- 0.00027
 Combined k-effective = 1.00877 +/- 0.00023
 Leakage Fraction = 0.73030 +/- 0.00030

```

because of the leakage fraction is too high to unbelievable, I think it is non-physical result, but I do not know how to solve it.  
I need some help from you guys!  
Thank you in advance~

* * *

Best regard!  
ZhuangL

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**Author:** ![paulromano](https://yyz2.discourse-cdn.com/free1/user_avatar/openmc.discourse.group/paulromano/32/486_2.png) [@paulromano](https://openmc.discourse.group/u/paulromano)\
**Post date:** [May 10, 2022, 12:06pm UTC](https://openmc.discourse.group/t/my-leakage-fration-too-high-in-result/2021/2 "2022-05-10T12:06:49Z")

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The only thing I can think of is if you are applying vacuum boundary conditions in the z direction. For particles to leak, there must be a vacuum boundary somewhere.

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<div class="post-metadata">

**Author:** ![lz152](https://yyz2.discourse-cdn.com/free1/user_avatar/openmc.discourse.group/lz152/32/1547_2.png) [@lz152](https://openmc.discourse.group/u/lz152)\
**Post date:** [May 10, 2022, 12:11pm UTC](https://openmc.discourse.group/t/my-leakage-fration-too-high-in-result/2021/3 "2022-05-10T12:11:39Z")

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Thank you Paul!  
Thank you for your effort!  
You clear my doubt.  
(I have much to learn, Than you!)

* * *

Best regards!  
Zhuangli