The analysis of skyshine caused by X-γ ray

Objective: To analyse the variation of the radiation dose in the atmosphere outside of the shielding enclosures caused by X-γ ray's skyshine and the monitoring method in daily radiation monitoring. Method: By using the monte carlo softwave mcnp4c for calculating many kinds of the skyshine models. Results: Giving the shandow radius's empirical formula of the large space. Conclusion: The variation of the radiation dose in the atmosphere outside of the shielding enclosures is not monotonously decreasing, it will get the maximal value when reaching the shandow radius of the shielding enclosures. Monitoring at the shandow radius is suggested. (authors)