Skyshine vs Direct Dose in MCNP5

In summary, "Skyshine" refers to radiation scattered by the sky and outside of any radiological shielding. This can be calculated using an importance value of 0 in the primary barrier. It is a faster and almost identical alternative to using a high fictitious density slab in the middle of the shield. When there is no shielding, "skyshine" refers to the radiation scattered by the sky air that is 50 yards away from the dose point. This term is also referenced in the book "Radiation Problems: From Analytical to Monte-Carlo Solutions."
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Will_007
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TL;DR Summary
how to calculate skyshine dose with mcnp?
Hello - what is an accepted definition of the skyshinne dose in MCNP and how would you calculate this? If you have a source and a shield a few meters away between the dose point, the contribution that goes around the shield would be skyshine....but..what if you have a big source region (e.g., a building) and your dose point is a mile away - how would you separate skyshine component?

Thanks
 
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Hi, you can consider an importance (imp:p 0) 0, in the primary barrier
 
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PSRB191921 said:
Hi, you can consider an importance (imp:p 0) 0, in the primary barrier
Hey - yeah. This was my ultimate choice. Initially I put in a slab with really high fictitious density in the middle of my shield (to allow stuff to scatter back and around to the dose location), but ran a test case and imp=0 was way faster and almost identical results.

if there is no shield (other than air), and source is 50 yards away from the dose point, what does skyshine mean to you?
 
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"Skyshine" is a radiation scattered by sky air, outside the radiological
shielding.
In the first figure (geometry definition) in the second results with MCNP (reference Radiation Problems : From Analytical to Monte-Carlo Solutions ) :
skyshine.jpg
skyshineMCNP.jpg
 
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thanks
 

FAQ: Skyshine vs Direct Dose in MCNP5

What is the difference between skyshine and direct dose in MCNP5 simulations?

Skyshine refers to radiation that has been scattered in the atmosphere and then reaches a detector, while direct dose refers to radiation that travels directly from the source to the detector without significant scattering. In MCNP5 simulations, skyshine typically involves modeling the scattering processes in the air, whereas direct dose calculations focus on the unscattered radiation path.

How do you model skyshine radiation in MCNP5?

To model skyshine radiation in MCNP5, you need to define the air volume surrounding the radiation source and the detector. This involves setting up an appropriate geometry and material definitions for the air, and using tallies that can capture scattered radiation, such as F2 (surface flux) or F4 (cell flux) tallies with appropriate energy bins and scattering physics enabled.

What are the common challenges in calculating skyshine radiation?

Common challenges in calculating skyshine radiation include accurately modeling the atmospheric conditions, dealing with the large computational resources required for simulating scattering processes, and ensuring that the simulation boundaries are sufficiently far from the source and detector to capture all relevant scattering events. Additionally, achieving statistical convergence in the results can be difficult due to the low probability of scattered radiation reaching the detector.

Why is it important to differentiate between skyshine and direct dose in radiation protection studies?

Differentiating between skyshine and direct dose is important because they have different implications for radiation protection. Direct dose typically represents a higher intensity of radiation over a shorter distance, posing immediate health risks. Skyshine, on the other hand, can extend the area of radiation exposure over larger distances, potentially affecting more people and requiring different shielding and mitigation strategies.

Can MCNP5 handle both skyshine and direct dose calculations simultaneously?

Yes, MCNP5 can handle both skyshine and direct dose calculations simultaneously. This is achieved by setting up the geometry, source, and tally definitions in a way that both direct and scattered radiation paths are considered. Using multiple tallies and energy bins, you can separately analyze the contributions of direct and scattered radiation to the total dose received by a detector.

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