RADIATION HAZARDS FROM CRITICALITY ACCIDENT IN OPEN POOL TYPE REACTOR.

In this study, a hypothetical nuclear criticality accident has occurred in open pool type reactor due to ejection of the control rod during loss of coolant accident. Dose rate distribution was determined for prompt neutrons and gamma rays resulting from first radiation pulse of the criticality accident. MCNP code has been used to determine the dose rate in different positions that the worker may locate inside the reactor during the accident. The results show that the maximum radiation dose is 2.52 Sv which located at the center of the top of the main pool. The worker located in the control room, the first floor and the ground floor will receive a dose of 68.2, 11.6 and 0.85 mSv, respectively. The worker located in the underground floor will receive a dose of 35 μSv. SKYDOSE and SKYNEUT codes were used to determine the dose distribution outside the reactor building resulting from skyshine effect where the shielding around the reactor core is sufficient to attenuate the radiation in the radial direction. MCNP code was used to verify the SKYDOSE and SKYNEUT results along the distance of 1200 m from the reactor. The results show that the person around the reactor would receive an accumulated dose ranged between 1776.7 and 0.02 μSv along the distance between 20 and 1200 m.