[fluka-discuss]: A puzzled neutron shielding problem

From: YANG Tao <yangt_at_ihep.ac.cn>
Date: Thu, 23 Jun 2016 23:41:28 +0800 (GMT+08:00)

Hello, everyone!

I simulated the neutron shielding effect by three layers as shown in fig1, the first layer is 4-cm-thick iron, the second layer is 4-cm-thick borated polyethylene(BPE), and the last one is 2.5-cm-thick lead. Neutrons of 1 MeV injects on the iron layer from left to light. Now I set three scoring cards(USRBDX, one-way current) at the interface of iron to BPE, BPE to lead and lead to the right vacuum to obtain the neutron fluence. However, I obtain the strange results as shown in fig2, it seems that the neutron number becomes greater after they penetrate the BPE layer since the red line is higher than the black line. But when I check the corresponding sum.lis files, the Tot. resp. is respectively 0.7257115, 0.3018902, 0.1735702 , which are reasonable for the neutron counting decreases as they penetrate the layers. However, how to explain the inconformity of fig2 and the total response (neutron counting) in sum.lis files?

Could someone help me in this question please?
Thank you.
With the best regards,

Tao Yang



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(image/png attachment: fig2.png)

Received on Thu Jun 23 2016 - 19:46:55 CEST

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