Biofouling and microbial corrosion problem in the thermo-fluid heat exchanger and cooling water system of a nuclear test reactor |
| |
Authors: | T S Rao Aruna Jyothi Kora P Chandramohan B S Panigrahi S V Narasimhan |
| |
Institution: | 1. Water and Steam Chemistry Division , Bhabha Atomic Research Centre Facilities , Kalpakkam , 603 102 , Tamil Nadu , India subbarao@igcar.gov.in;3. National Centre for Compositional Characterisation of Materials , Hyderabad , 500 062 , India;4. Water and Steam Chemistry Division , Bhabha Atomic Research Centre Facilities , Kalpakkam , 603 102 , Tamil Nadu , India;5. Reactor Chemistry Section, Indira Gandhi Centre for Atomic Research , Kalpakkam , 603 102 , Tamil Nadu , India |
| |
Abstract: | This article discusses aspects of biofouling and corrosion in the thermo-fluid heat exchanger (TFHX) and in the cooling water system of a nuclear test reactor. During inspection, it was observed that >90% of the TFHX tube bundle was clogged with thick fouling deposits. Both X-ray diffraction and Mössbauer analyses of the fouling deposit demonstrated iron corrosion products. The exterior of the tubercle showed the presence of a calcium and magnesium carbonate mixture along with iron oxides. Raman spectroscopy analysis confirmed the presence of calcium carbonate scale in the calcite phase. The interior of the tubercle contained significant iron sulphide, magnetite and iron-oxy-hydroxide. A microbiological assay showed a considerable population of iron oxidizing bacteria and sulphate reducing bacteria (105 to 106 cfu g?1 of deposit). As the temperature of the TFHX is in the range of 45–50°C, the microbiota isolated/assayed from the fouling deposit are designated as thermo-tolerant bacteria. The mean corrosion rate of the CS coupons exposed online was ~2.0 mpy and the microbial counts of various corrosion causing bacteria were in the range 103 to 105 cfu ml?1 in the cooling water and 106 to 108 cfu ml?1 in the biofilm. |
| |
Keywords: | heat exchanger biofouling microbial corrosion iron bacteria SRB thermo-tolerant |
|
|