|Year : 2010 | Volume
| Issue : 4 | Page : 185-188
Use of specific resins to minimise release of activity at ETP, Trombay
MB Yadav, BN Singh, S.V.S. Rao, RK Badhwar, Gabriel Johnson, Surender Kumar, Kanwar Raj
Waste Management Division, Bhabha Atomic Research Centre, Trombay, Mumbai, India
|Date of Web Publication||1-Dec-2011|
M B Yadav
Waste Management Division, Bhabha Atomic Research Centre, Trombay, Mumbai
Source of Support: None, Conflict of Interest: None
Selective sorbent resins have been developed and are being used extensively for decontamination of radioactive effluents received from reactor at CWMF, Kalpakkam. These materials were evaluated for their suitability in treatment of effluents generated at ETP Trombay to minimise release of activity to the environment. An ion exchange column of capacity 80 litre was fabricated and filled with Copper ferrocyanide (CFC) and Hydrous manganese dioxide (HMO) supported on polyurethane foam. The former is selective for Cesium and the later for strontium. The feed effluent gross βγ activity was in the range of 10-15 Bq/ml. About 130 m 3 (1550 Bed Volume) of effluent was treated resulting a Decontamination Factor (DF) of about 7-9. This has demonstrated the effectiveness of specific resins for treatment of low level radioactive liquid effluents. It is desired to introduce prefiltration systems to enhance the life of the resin.
Keywords: Specific activity, decontamination, ion exchange, Copper Ferro cyanide, Hydrous manganese dioxide, 137 Cs
|How to cite this article:|
Yadav M B, Singh B N, Rao S, Badhwar R K, Johnson G, Kumar S, Raj K. Use of specific resins to minimise release of activity at ETP, Trombay. Radiat Prot Environ 2010;33:185-8
|How to cite this URL:|
Yadav M B, Singh B N, Rao S, Badhwar R K, Johnson G, Kumar S, Raj K. Use of specific resins to minimise release of activity at ETP, Trombay. Radiat Prot Environ [serial online] 2010 [cited 2023 Jun 2];33:185-8. Available from: https://www.rpe.org.in/text.asp?2010/33/4/185/90461
| 1. Introduction|| |
At effluent treatment plant (ETP) Trombay, radioactive liquid effluents are received from reactor operation, fuel reprocessing, research laboratories and other plants. The major radio nuclides present in the effluents are 137 Cs and 90 Sr. The effluents having specific activity above 10 Bq/ml are given specific chemical treatment in a clariflloculator. The supernatant is monitored and discharged to sea as per authorized limits. The radioactive sludges are centrifuged and immobilized in cement matrix prior to disposal in engineered trenches. About 70,000-90,000 m 3 of effluents are managed annually. Bulk of the effluents received at ETP is having activity below 10 Bq/ml and are not subjected to any kind of treatment. Though chemical treatment is not effective, ion exchange methods are capable of decontaminating such effluents. To bring down the activity discharge to the environment by more effective methods of decontamination, ion exchange treatment using selective sorbents with high throughput and economy are employed in the present work. The Copper ferrocyanide (CFC) and Hydrous manganese dioxide (HMO) supported on polyurethane foam, selective for cesium and strontium respectively, are employed in the 80 liter column (Rao et al, 1999; 2003). The flow rate was maintained at 20 lpm through a rotameter. Initial gross βγ activity was in the range of 10-15 Bq/ml. 130m 3 (1550 Bed Volume) effluent was treated resulting in a decontamination factor (DF) about 7-9.
| 2. Column Preparation|| |
A carbon steel column having 430 mm diameter and 630 mm height of capacity 80 litre was fabricated for the experimental studies. The column is designed to provide flow from bottom to the top. Strainers of 200 mesh are provided in the bottom and top of the column. CFC coated and HMO coated polyurethane foam in quantity was made available by Centralised Waste Management Facility (CWMF), Kalpakkam using the indigenously developed process (Rao, et al, 1999 & 2003). A nylon bag of diameter 45 cms and height 80 cms with hooks was utilized for the studies. About 5 nos of fresh PU foam sheets having 5-6 mm thickness were placed at the bottom of the bag. Thereafter, layers of 7.5 kg of CFC, 7.5 kg of HMO and 2.5 kg of CFC resin were filled in the bag. Subsequently, additional 5 nos of PU foam sheets were placed to avoid carry over of the resin and the bag was tied properly. Three layers of PU foam sheets were provided in the bottom of the column and the nylon bag was firmly inserted in the column. Subsequently three layers of PU foam sheets were placed on the top of the bag in the column and the column was closed by the top lid. The column is provided with easy removable lid to minimize exposure during handling.
| 3. Experimental|| |
The column [Figure 1] was installed near the receipt tanks at ETP, Trombay. Process schematic flow diagram is given in [Figure 2] The effluents were drawn from the near by low level liquid Tank (LLT) using a submersible pump of capacity 300 lpm. The characteristics of the waste employed for the studies are given in [Table 1]. The flow rate through the column was monitored by a rotameter installed in the line and was maintained at about 20 lpm (about 15 bed volume per hour) throughout the experiment. The effluent samples were collected from the upstream and downstream of the column periodically using the sampling points. During the operations various parameters such as flow rate, pressure drop, radiation field etc. were also monitored periodically.
|Table 1: Characterization of effluents for IX Column at ETP, Trombay Source: Effluents from CIRUS, Dhruva and Research labs|
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About 128 m 3 of effluent was passed through the column during the studies. The pressure drop across the column increased steadily to about 1.0 kg/cm 2 and the flowrate was dropped down to 12-13 lpm. The radiation field on contact of the column also increased to 0.5 mGy/h. The inlet and outlet effluent samples collected periodically were analysed for gross βγ activity using GM counter and for 137 Cs, 125 Sb, 106 Ru using gamma spectrometry. Strontium was measured using low background liquid scintillation counter (Cerenkov counting system). The experimental results are summarized in [Table 2].
3.1 Disposal of used resin
The top lid of the column was opened and removed using a crane. The nylon bag and foam sheets were pulled out from the column and collected in a standard 200 litre MS drum. The contents of the drum were immobilized in cement and the drum was disposed in Near Surface Disposal Facility (NSDF) as per standard practices.
| 4. Results and Conclusions|| |
The initial pressure drop across the column was below 0.1 kg/cm 2 which indicates that the resin coated on foam has high throughput. During the studies, about 128 m 3 (1550 BV) of effluent was passed through the column. It is realized that higher volume could have been treated if the effluents were pretreated for removal of suspended matter. A decontamination factor of about 7-9 for gross βγ activity was achieved at low concentrations and hence the process can be effective to minimize the release of activity to the environment. The results also indicate that the specific resin does not pick up 125 Sb/ 106 Ru. The feed effluent was changed after passing about 90 m 3 of liquid effluent. A lower DF was obtained subsequently due to the presence of antimonite (SbO3 - ) in the feed effluent. The residual activity in the outlet samples is mainly due to the presence of these radionuclides. The column should be run to exhaust the entire capacity of the resin. Suitable shielding can be provided to the column to maintain the radiation fields within limits in working areas. Treatment may be required for Sb and Ru for further minimizing the release of activity.
| 5. References|| |
- Rao S.V.S. Lal K.B., Narsimhan S.V. and Jaleel Ahmed (1999), Copper ferrocyanide- polyurethane foam as a composite ion exchanger for removal of radioactive Cesium, Journel of Radioanalytical and Nuclear Chemistry, Vol. 240, No.1, 269-276.
- Rao S.V.S., Narsimhan S.V. and Lal K.B. (2003), Composite CFC-PU foam ion Exchanger in the removal of Radioactive cesium pilot plant scale studies using simulated and actual waste, Journal of Radioanalytical and Nuclear Chemistry, Vol. 256, No.1, 137-141.
[Figure 1], [Figure 2]
[Table 1], [Table 2]