When a radiation detector is applied to the measurement of the radioactivity of high-level of radioactive materials or the rapid response to the nuclear accident, several collimators with the different inner radii should be prepared according to the level of dose rate. This makes the in-situ measurement impractical, because of the heavy weight of the collimator. In this study, an IRIS collimator was developed so as to have a function of controlling the inner radius, with the same method used in optical camera, to vary the attenuation ratio of radiation. The shutter was made to have the double tungsten layers with different phase angles to prevent the radiation from penetrating owing to the mechanical tolerance. The performance evaluation through the MCNP code was conducted by calculating the attenuation ratio according to the inner radius of the collimator. The attenuation ratio was marked on the outer scale ring of the collimator. It is expected that when a radiation detector with the IRIS collimator is used for the in-situ measurement, it can change the attenuation ratio of the incident photon to the detector without replacing the collimator.

• 지영용(한국원자력연구원, 대전광역시 유성구 대덕대로 989번길 111) | Young-Yong Ji Corresponding author
• 정근호(한국원자력연구원, 대전광역시 유성구 대덕대로 989번길 111) | Kun Ho Chung
• 이완로(한국원자력연구원, 대전광역시 유성구 대덕대로 989번길 111) | Wanno Lee
• 최상도(한국원자력연구원, 대전광역시 유성구 대덕대로 989번길 111) | Sang-Do Choi
• 김창종(한국원자력연구원, 대전광역시 유성구 대덕대로 989번길 111) | Change-Jong Kim
• 강문자(한국원자력연구원, 대전광역시 유성구 대덕대로 989번길 111) | Mun Ja Kang
• 박상태(공주대학교, 충청남도 공주시 공주대학로 56번길) | Sang Tae Park