# Fast reactor depletion caculate

**URL:** <https://openmc.discourse.group/t/fast-reactor-depletion-caculate/3762>\
**Category:** User Support\
**Created:** [December 20, 2023, 1:18am UTC](https://openmc.discourse.group/t/fast-reactor-depletion-caculate/3762 "2023-12-20T01:18:19Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![wzrone](https://avatars.discourse-cdn.com/v4/letter/w/8491ac/32.png) [@wzrone](https://openmc.discourse.group/u/wzrone)\
**Post date:** [December 20, 2023, 1:18am UTC](https://openmc.discourse.group/t/fast-reactor-depletion-caculate/3762/1 "2023-12-20T01:18:19Z")

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When I calculate the burn-up of the reactor, the power is set to about 1e7, and the Keff will gradually decrease. However, when the set power value is less than 1e7, the keff change is not regular. How should I handle the situation, please? I would appreciate it if anyone answered the question.  
Here’s my code:  
_model = openmc.Model(geometry=geom, settings=settings)_  
_operator = openmc.deplete.CoupledOperator(model, “./chain\_casl\_sfr.xml”)_  
_power = 1e6_  
_time\_steps = [30] \* 12_  
_integrator = openmc.deplete.LEQIIntegrator(operator, time\_steps, power, timestep\_units=‘d’)_  
_integrator.integrate()_

computational results  
 ![image](https://global.discourse-cdn.com/free1/uploads/openmc/original/2X/b/b29091a616e29e116c319fef8538f240cc0b9f58.png)

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**Author:** ![Awww](https://avatars.discourse-cdn.com/v4/letter/a/c6cbf5/32.png) [@Awww](https://openmc.discourse.group/u/Awww)\
**Post date:** [March 27, 2024, 3:02am UTC](https://openmc.discourse.group/t/fast-reactor-depletion-caculate/3762/2 "2024-03-27T03:02:06Z")

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I have the same problem with you  
😔 have you solved this problem?

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<div class="post-metadata">

**Author:** ![wzrone](https://avatars.discourse-cdn.com/v4/letter/w/8491ac/32.png) [@wzrone](https://openmc.discourse.group/u/wzrone)\
**Post date:** [April 2, 2024, 12:37am UTC](https://openmc.discourse.group/t/fast-reactor-depletion-caculate/3762/3 "2024-04-02T00:37:48Z")

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Hi, my power does not match the core design, and when my power is scaled up, the problem is solved.