Three gamma sources S, S2 and S3 are located at the center of 3 identical circles with diameter of ( 100+LDSN)cm. The 3 sources are mono energetic, their activities are A-30 mCi, A=15 mCi and A3=10 mCi, and their conversion factor Cf=1.8 pSv.cm2 /y, Cf= 0.9 pSv.cm2 /y and Cf3-0.6 pSv.cm2 /y, respectively. S3 S1 52 Figure 1: Locations of 3 Gamma Sources (Radius of the circle is 100+LDSN cm) 1. What is the equivalent dose rate H at a point P from the 3 sources source, where P is the intersection of the 3 circles as shown in Figure 1? 2. What is the total equivalent dose rate from all sources at the point P? 3. If a person spent 5 hours at point P, what is his total dose equivalent? 4. What is the maximum time allowed to a person to spend at point P to meet the CNS requirements of 1mSv/year?