A new approach of shielding technique due to a leakage of radiation exposure outside a 10 MEV Linac room in a facility designed for 6 MEV

At the national cancer institute - Cairo - Egypt. A decision of upgrading a linear accelerator of 6 MeV, Elekta machine, to high energy 10 MeV is taken. Because of advances in radiation sources and techniques, shielding and room design considerations for radiation oncology and such upgrade, are not covered by the NCRP reports. A problem has arises due to limited room size that was previously shielded based upon the 6 MeV energy, there was no other spaces for additional shielding in the treatment room which creates a problem of radiation leakage. This work presents an appraisal of radiation leakage and calculations of doses which vary from 65μSv/hr to 7.5 mSv/hr. We discuss the particular shielding problems related to high energy machines. Finally a new shielding methodology is presented merging more than two materials shows to be effective and reduce shielding cost.