|Year : 2010 | Volume
| Issue : 3 | Page : 109-111
Regulatory aspects in liquid effluent generated during the production of the novel 99m Tc gel generator system developed at BRIT
NV Choughule1, AK Devi1, SK Suman1, Rekha Anilkumar1, DK Patre1, S Murali1, P Saraswathy2
1 Radiation Safety Systems Division, BARC, Mumbai, India
2 Radio-Pharmaceuticals Laboratory, BRIT, Vashi, India
|Date of Web Publication||22-Oct-2011|
N V Choughule
Radiation Safety Systems Division, BARC, Mumbai
Source of Support: None, Conflict of Interest: None
Radioactive process liquid waste is generated during production of 99m Tc gel generator at Radiopharmaceutical Laboratory, BRIT, Vashi. The wastes were transferred to Waste Management Division, BARC, in carbuoys after assessment of activity content, to ensure that the activity limit set by the regulatory authority is complied with. A study was taken up for the optimization of decay time of effluent generated during the production of Tc-Gel generator. Study on the identification of the radio nuclides present in the liquid waste, to plan for disposal is discussed in this paper. Liquid waste aliquots were counted by different techniques and were followed for decay of activity over long duration. The analysis of the samples led to identify the long lived radio nuclides like 60 Co, 134 Cs and 65 Zn in liquid waste generated from 99m Tc gel generator production facility.
Keywords: Liquid effluent, activity, waste disposal
|How to cite this article:|
Choughule N V, Devi A K, Suman S K, Anilkumar R, Patre D K, Murali S, Saraswathy P. Regulatory aspects in liquid effluent generated during the production of the novel 99m Tc gel generator system developed at BRIT. Radiat Prot Environ 2010;33:109-11
|How to cite this URL:|
Choughule N V, Devi A K, Suman S K, Anilkumar R, Patre D K, Murali S, Saraswathy P. Regulatory aspects in liquid effluent generated during the production of the novel 99m Tc gel generator system developed at BRIT. Radiat Prot Environ [serial online] 2010 [cited 2022 May 20];33:109-11. Available from: https://www.rpe.org.in/text.asp?2010/33/3/109/86273
| 1. Introduction|| |
Board of Radiation and Isotope Technology (BRIT) is engaged in the promotion of radioisotope applications in healthcare, industry, agriculture and research. 99m Tc is the workhorse of nuclear medicine. More than 90% of nuclear medicine studies are carried on with radio-pharmaceuticals based on 99m Tc such as imaging and assessment of the functional status of heart, brain, liver, kidney and bone.
Radio-pharmaceutical laboratories, BRIT supplies 99 Mo in the form of sodium molybdate solution to hospitals for 99m Tc generation. 99m Tc is separated from 99 Mo by solvent extraction using methyl ethyl ketone. But the solvent extraction method is time consuming, operator dependant and involves wet chemical operations. To make available user friendly generator system, gel generators from indigenous resources was developed at BRIT, containing a column matrix of zirconium molybdate- 99 Mo gel. 99m Tc can be eluted from gel column using physiological saline. The gel generator can be operated instantly and has superior radiological and pharmaceutical safety features compared to solvent extraction generators.
Up to a maximum of 925 GBq of the radioisotope 99 Mo (T 1/2 -67h) in radioactive equilibrium with it's daughter 99m Tc (T 1/2 -6 h) is handled per batch in a single day on a weekly basis to meet the demand. Due to short half lives of radioisotopes to be handled, the guiding principle of 'Decay and Dispose' will be generally followed. The regulatory aspect in liquid waste management of the new generator system developed is discussed in this paper.
| Method of Effluent Sample Collection and Analysis|| |
The liquid waste generated during the processing, a white turbid solution, was collected in glass bottles inside the plant and transferred by gravity to HDPE carboys (10 L) kept in lower shielded compartment. Transfers were effected through pneumatic drain valves operated using switches in control console. Liquid waste from each batch was collected in separate carboys. Generally about 5 to 8 L of liquid waste was generated per batch.
Soluble, unreacted 99 Mo, precipitate fines, container rinsing- carried over in liquid streams of filtrate, column bed washings are the likely sources of activity concentration in the liquid waste. A representative liquid waste drawn from the carboys and known volume of sample was plancheted, dried under infra red lamp and gross β-γ activity was estimated by counting in an end window Geiger Mueller (GM) set-up. The same planchets of effluent samples were then analyzed in HPGe based gamma spectrometer to identify the radionuclides and to find out the activity. The radioactive content and level were analyzed prior to handing over to waste management agency for disposal.
| 3. Results and Discussion|| |
Liquid effluent samples (19 no.) of 2008 decayed for one year, after planchetting were analyzed by GM counting setup and gross β-γ activity varied from 2.57±0.14 Bq/ml to 54.21±0.41 Bq/ml. The same planchets of samples were then analyzed in HPGe based gamma spectrometer. The result indicated the presence of 60 Co, in all nineteen liquid samples, 65 Zn in sixteen samples and 134 Cs in five samples. The γ activity of 60 Co varied from 4.07±0.25 to 108.17±1.62 Bq/ml, the γ activity of 65 Zn varied from 0.71±0.25 to 4.79±1.29 Bq/ml and the γ activity of 134 Cs varied from 0.35±0.11 to 34.66±1.17 Bq/ml.
The 99 Mo used for the processing of gel generators is obtained from two sources-i) (n,γ) produced by neutron activation of natural MoO 3 targets ii) (n,f) produced by separation from other fission products. Apart from the chief radionuclides, 99 Mo and 99m Tc, any other radionuclides detected in the waste stream could accrue from the elemental impurities present in traces in the target MoO 3 that are likely to give rise to activation products. Traces of Re, Sb, Cs, Co, Zn, Zr, Cr, Fe etc are reported to be probable contaminants in the target MoO 3 . Another probable source is traces of radionuclides impurities present in the fission 99 Mo. Of these, the short (days) and intermediate (months) halflife radionuclides would have decayed during the periods of storage. This is borne out in the results obtained above
Liquid effluent samples of years 2006 and 2007 (total 33 nos.) were also counted for gross β-γ activity using the calibrated G-M set up. Gross β-γ activity varied from 0.18±0.038 Bq/ml to 6.31±0.061 Bq/ml. The same planchets of samples were then analyzed in HPGe based gamma spectrometer. The result indicated the presence of 60 Co, a single radionuclide in thirty liquid samples and 65 Zn in one of the thirty three samples. The γ activity varied from BDL to 15.21±0.79 Bq/ml.
Chemical analysis of the above liquid samples was performed for estimation of any long lived β emitters such as 90 Sr- 90 Y. The result indicated the absence of 90 Sr- 90 Y.
A four days liquid effluent sample after suitable dilution when analyzed by gamma spectrometer showed the presence of 99 Mo radionuclide only with activity level of 1.7×10 5 Bq/ml whereas gross β-γ counting showed activity level to be 3.04×10 5 Bq/ml. Due to short half lives of 99 Mo radionuclide, a quarantine period of two months ~20 half lives of 99 Mo could bring down the activity by 10 -6 times of it's original activity.
The liquid wastes generated from this facility after adequate decay were categorized as Cat-II/III, based on activity level present in it [Table 1] and [Table 2].
|Table 2: Activity of 99mTc Gel Generator Liquid Effluent (Year 2008) Samples|
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| 4. Regulatory Aspects in Liquid Effluent Management|| |
The BRIT complex at Vashi comprises of several units that produce Radiopharmaceuticals and Labeled Compounds and in the process generate liquid effluent containing different radionuclides. The effluents are collected in sump tanks, diluted and are discharged through sewer channels to Thane creek coastal marine environment. Atomic Energy Regulatory Board (AERB) has specified discharge concentration limits and total gross β activity limits for liquid effluent based on the different apportioned dose limits and radiological exposure pathways.
AERB has authorized Radio Pharmaceutical Laboratory, BRIT, Vashi for annual disposal of 1500 m 3 liquid waste containing 131 I radionuclide of concentration less than 2.22 Bq/ml and total gross β activity 330 MBq into NMMC sewers. It has also authorized for annual transfer of 0.2 m 3 liquid waste containing 131 I & 125 I radionuclides with total gross β less than 15 GBq to Waste Management Division (WMD), BARC.
| 5. Conclusions|| |
From the above studies it is evident that the radio nuclides present in 99m Tc gel generator liquid effluent contained long lived β-γ emitters, 60 Co, 134 Cs, 65 Zn. The decay pattern of effluent samples of year 2008 was followed [Table 3] and [Figure 1]. It indicated that 65 Zn (T 1/2 =244 days) and 134 Cs (T 1/2 =2.062 years) could be negligible after two more year of decay. The total decay of the long lived radio-nuclide 60 Co in the effluent is not feasible. Since, the radiopharmaceutical laboratory at BRIT, Vashi is not authorized to discharge long lived radionuclides 60 Co, 134 Cs, and 65 Zn in NMMC sewers, the liquid effluent wastes generated during production of 99m Tc gel generator were handed over to WMD, BARC for necessary treatment. To effect the transfer of the liquid effluent wastes to WMD, BARC within permissible limits, the liquid effluent wastes generated will have to be stored at the facility for about a year.
|Table 3: Estimated Activity of 99mTc Gel Generator Liquid Effluent (Bq/ml)|
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| 6. Acknowledgements|| |
Authors are grateful to Dr. D.N. Sharma, Head, RSSD for his keen interest in carrying out this work. The discussion held with Dr. S. Anilkumar, RSSD and the valuable suggestion is greatly acknowledged. Authors would like to place on record the encouragement rendered by Dr. N. Sivaprasad, SGM, RPhP.
| 7. References|| |
- AERB Authorization for safe disposal/transfer of radioactive waste, Auth. No. 0031, dated 31 st March 1992.
- Dey A.C., Saraswathy P. and Meera V. (2005), Safety analysis report on 99m Tc- Column generator production facility, BRIT, Vashi, dated 31 st Aug.2005.
[Table 1], [Table 2], [Table 3]