[en] Activity in the primary coolant water and pool water of an open tank-in-pool type research reactor is a key problem from operation and radiological safety points of view. Saturation activities of different radio-nuclides in primary coolant loop and pool water of the upcoming 30 MW High Flux Research Reactor (HFRR) have been estimated based on the proposed design. The activation products of aluminium ("2"4Na, "2"7Mg and "2"8Al) are estimated by using an effective thickness (ET) of aluminium for each product. This ET takes into account the formation of oxide layer and its dissolution in water. These estimated values are compared with those obtained using flight lengths of different activation products in aluminium as the effective thickness. It is found that ignoring the oxide layer formation and its removal by moving coolant may underestimate the activity in coolant and pool water. Activity of "4"1Ar is calculated using a saturation value of argon in water at 45°C. Calculations are also carried out to find the activities of "1"9O, "1"6N, and "1"7N in primary loop. The half-lives of "1"9O, "1"6N, "1"7N, "2"7Mg and "2"8Al are much less than the time involved in mixing of bypass flow into pool water. Therefore the activity of pool water is mainly governed by "2"4Na and "4"1Ar. To calculate the activity of pool water, nuclide balance is used in a model of core and pool flow schemes. This model is similar to that used in Hanaro for source estimation. The consistency of this model is ensured by calculating the activities of different nuclides in Hanaro by giving their estimated sources and flow characteristics as inputs and finding the calculated values in agreement with the measured ones. (author)