International Conference on Research Reactors:
Safe Management and Effective Utilization

14-18 November 2011, Rabat, Morocco

Reactor pool water was found to be leaking through the Radial Beam Port-1 (RBP-1) of the 3MW TRIGA Mark II research reactor (RR) of Bangladesh Atomic Energy Commission (BAEC) when the graphite shield plug of the beam port (BP) was removed after about 23 years for installation of the collimator of the newly procured high resolution powder diffractometer (HRPD). The leak was found in the aluminium part of the RBP 1, which is located inside the reactor pool at a depth of about 8 m. Investigation showed that an installation defect caused moisture from the heavy concrete shielding to seep into beam port and initiate the corrosion. As a result of such corrosion, the 1.016 m long graphite shield plug got jammed inside the BP very tightly. While trying to remove the plug, it got broken leaving a segment having a length of about 33 cm inside the aluminium part of the BP. This segment of the BP plug was removed by using special hand tools designed and fabricated locally. Leakage of water at a rate of about 500 ml/day came to the notice of the reactor operators a couple of days after the graphite BP plug had been totally removed from the RBP-1. Immediately a rubber strap was installed around the leaking part of the BP by using a temporary arrangement so as to stop drainage of reactor pool water. Detailed investigations were carried out using remote handling cameras including an underwater camera supplied by the International Atomic Energy Agency (IAEA). Corrosion products were collected from the surface of the BP plug and analyzed using scanning electron microscopy and energy dispersive X-ray (EDX) analysis techniques. Results showed the presence of oxygen, carbon, lead, silicon and aluminum. The friable and porous nature of some of the samples indicated the presence of hydroxides in it. The investigation and analysis results were found to be useful in identifying the root cause of the leakage problem. Water leakage was eventually prevented by installing a split type encirclement aluminium clam around the damaged part of the RBP 1 by using innovative remote handling fastening devices, designed and fabricated locally. The paper presents details of the leakage problem, root cause analysis and the corrective measures implemented so as to prevent any further leakage of pool water through the beam port and thus make the reactor ready again for normal operations.

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