The use of granite stones as building materials in homes or offices can result in the residents’ long-term whole-body exposure to gamma radiation. Although the whole-body annual dose has been investigated in the literature, it is obvious that different human organs receive different equivalent dose due to different position respect to the walls and floor covered by granite stones. In this paper, the effect of distance from the walls and floor of a room on the equivalent dose is investigated by using MCNPX code. An “ORNL” phantom is simulated in three situations; standing (P1), sleeping one meter above the floor (P2) and sleeping on the floor (P3) and the equivalent dose in different organs is calculated. Excess lifetime cancer risk (ELCR) is calculated in the whole of the body for these three positions. By the results, the value of ELCR in the third position is more than the average world value (2.9 × 10⁻⁴). The results show the importance of considering body position in dose determination, especially in some organs such as the brain and eyes which are close to the granite stones in certain positions such as sleeping.

在家庭或办公室使用花岗岩石作为建筑材料可能会导致居民长期全身暴露在伽马辐射下。虽然文献中已经对全身年剂量进行了调查，但很明显，不同的人体器官由于相对于花岗岩石覆盖的墙壁和地板的不同位置而受到不同的当量剂量。本文利用MCNPX代码研究了距房间墙壁和地板的距离对等效剂量的影响。“ORNL”模型在三种情况下进行模拟；站立（P1）、离地一米睡觉（P2）和趴地睡觉（P3）并计算不同器官的当量剂量。计算这三个位置的整个身体的超额终生癌症风险 (ELCR)。从结果来看，第三位的ELCR值超过了世界平均值（2.9×10 ^-4）。结果表明，在确定剂量时考虑身体位置的重要性，特别是在某些器官（例如大脑和眼睛）在某些位置（例如睡觉）靠近花岗岩石的器官中。