Beam port leakage problem in the BAEC TRIGA Mark-II research reactor and the corrective measures implemented

The 3MW TRIGA Mark-II research reactor (RR) of Bangladesh Atomic Energy Commission (BAEC), which has been in operation since 1986, has four Beam Ports (BPs). One of the BPs, which remained plugged with the beam port plugs (mainly a graphite shield plug) for about 23 years, was found to be leaking when its plugs were removed for installation of a high resolution powder diffractometer in it. The leak, which was developed because of corrosion, was found in the aluminum part of the BP, which is located inside the reactor pool at a depth of about 8 m. Condensate accumulated in the annular space between the graphite plug and inner wall of the aluminum beam port initiated the corrosion. The graphite plug, which got stuck very tightly inside the BP, was removed using locally designed and fabricated hand tools. Leakage of water came to the notice of the reactor operation personnel a couple of days after the beam port had been cleared. Water leakage was stopped by installing a split type encirclement clam around the damaged part of the BP by some remote handling mechanisms, designed and fabricated locally. The paper presents in detail the description of the leakage problem and the remedial measures implemented so as to make the reactor operational again after about 16 months. (author)