|Year : 2010 | Volume
| Issue : 4 | Page : 211-212
Control of internal exposure during event in glove box releasing of α - activity
Sunil Yadav1, Atul Gavalkar1, Govinda Mukherjee1, Anand Gavankar1, DP Rath1, Pramila Sawant2, S Murali1
1 Radiation Safety Systems Division, BARC, Mumbai, India
2 Health Physics Division, BARC, Mumbai, India
|Date of Web Publication||1-Dec-2011|
Radiation Safety Systems Division, BARC, Mumbai
Source of Support: None, Conflict of Interest: None
Facilities handling large amounts of α-emitters viz., isotopes of Pu and other actinides, make use of containment systems viz., Glove Boxes with leak tightness that have very low leak rates. During normal operations, the internal hazard to the lab personnel is practically negligible. However, some operations/events in the glove boxes may lead to loss of integrity of the containment. This could result in release of airborne α - activity inside the glove box into the working environment. Depending on the release of α - activity, the internal hazard may be significant. The assessment of intake and the estimate of CED in suspected cases are carried out. The paper describes the assessment of lab air activity, personnel contamination, intake and internal exposure during an event in glove box that had resulted in release of α-activity. The intake of the S - Class of Pu compound was followed up and the administration of chelating agent to the person was found to have resulted in the reduction of CED to the individual.
Keywords: CED, internal exposure, Pu intake
|How to cite this article:|
Yadav S, Gavalkar A, Mukherjee G, Gavankar A, Rath D P, Sawant P, Murali S. Control of internal exposure during event in glove box releasing of α - activity. Radiat Prot Environ 2010;33:211-2
|How to cite this URL:|
Yadav S, Gavalkar A, Mukherjee G, Gavankar A, Rath D P, Sawant P, Murali S. Control of internal exposure during event in glove box releasing of α - activity. Radiat Prot Environ [serial online] 2010 [cited 2023 Jun 2];33:211-2. Available from: https://www.rpe.org.in/text.asp?2010/33/4/211/90475
| 1. Introduction|| |
The Radiochemical laboratories, Reprocessing facilities and Fuel fabrication plants that handle isotopes of Pu and other actinides make use of containment systems viz., Glove Boxes with leak tight systems that have very low leak rates. Such glove boxes are "lab-in-lab" type, and the activity handled is in highly contained form. The glove box has a negative pressure of ~ 40 mm WG and the ventilation to glove box is provided through special exhaust line. During normal operations in the glove boxes, due to their high leak tightness, there is neither α-air activity (< 0.02 DAC) nor any α-contamination at the workplace. However, during the gauntlet rupture or pin hole in gloves / rupture of gloves and / or exhaust line malfunctioning, the α-air activity in the workplace causes potential internal hazard to lab personnel. Use of protective equipments and decontamination of the area result in bringing the situation to normalcy. The paper describes the operational experience gained during one such event in glove box that had resulted in release of α-activity into work places.
| 2. Containment Systems|| |
The laboratories have containment systems such as - Fume hoods, Glove boxes and Hot cells housed with proper engineering safety features for the safe handling authorized amounts of activity. Especially, the glove boxes find a mention in the containment systems since they are "lab-in-lab" containment systems. The glove boxes made of SS material, have definite volume 1 m 3 or 2 m 3 or train of glove boxes have higher volume depending on the requirement of the facility. They are leak tight in nature with high leak tightness of the order of 0.05 % box volume/h. The glove boxes are designed to have external mobile shields based on the type and amount of activity held in. The radiological surveillance provided for operations in such glove boxes in the laboratory includes continuous radiation field monitoring, estimation of air activity (continuous air monitor and instant high volume sampler) and the alpha contamination check of the area (Radiation Safety Manual for RMD-2006 and Technical Specification of RMD-2007). [Figure 1] gives detail of the glove box at our facility.
2.1 Radiological safety aspects
Glove boxes are designed for handling more than mCi amount of α-activity; however, the higher limit of activity is restricted based on the critical mass of the material. Presently in the labs during analysis the limit of α-activity held in the glove box is restricted to < 100 gm per batch of solution or < 500 gm per batch of solid material. The leak rate of the glove box is periodically checked for validations. The Pu air activity in the lab is measured by continuous air monitor present in each of the labs, suction of air by the sample header designed at 50 lpm, filter paper periodically assessed for Pu activity, Pu-in-air monitor placed in the lab (MGP make ABPM 302) and centripeter air sampler for assessing Pu air activity in presence of natural α-activity. Personnel monitoring programme to the lab persons include the external exposure assessment & control, periodic bio-assay monitoring and acute exposure assessment during suspected events. Whenever, any suspected Pu air activity in the lab is detected, the lab personnel are checked for possible intake by inhalation route by collection of nasal swabs. The personnel are referred for bio-assay sampling to confirm and assess intake of Pu, if any. Based on the solubility class of Pu isotope that was handled during the event in the lab, the personnel based on their bio-assay results are assigned Committed Effective Dose (CED) receivable.
2.2 Glove rupture in glove box
The glove box pertaining to the event discussed presently had been train of glove boxes, inter-connected with facilities such as balance, de-waxing unit, compaction unit and storage units etc. During the shifting of balance through the tunnel inside the glove boxes from one box to another box (De-waxing box to Granulator box), the Pu-air monitor gave alarm. The persons, involved in the operations had reportedly come out of the lab immediately. The Pu air activity was assessed and estimated as 20 DAC of 239 Pu. The persons were checked for bodily contamination and by the nasal swab for suspected intake by inhalation. Though the body contamination was detected in all the persons, the nasal swab of one of the persons was found higher than the threshold value (8 Bq). After decontamination and bath, the person with positive nasal swab result was referred to medicos for administration of Ca-DTPA for quick de-corporation of Pu intake. The person was administered ~ 1 gm of Ca-DTPA intravenously.
2.3 Assessment of intake of Pu
Bio-assay monitoring of the persons was carried out and the follow up by bioassay samples of the persons to assign the CED receivable by the person. From the different bioassay sampling measurements (fecal, urine), the CED estimate was made based on Pu-S class and aerosol size 1 μ AMAD value. The CED estimates for the person had been arrived for isotopes of U (nat), 239+240 Pu and 241 Am. The total exposure during the year, cumulative exposure during the period 2005 - 2009 and the life-time exposure of the person (including the CED values) were scrutinized.
| 3. Results and Discussion|| |
The CED estimates were carried out for the S - class of Pu compound. The CED results had been found matching with the various bio-assay follow up estimates. The case study has led to the conclusion that administration of Ca - DTPA for internal exposures of S - class related Pu compounds were found to have led to minimizing the internal exposures. The external exposure of the lab person during the year was reported as 2.15 mSv, the cumulative exposure during the period 2005 - 2009 was reported as 33.95 mSv and lifetime dose was reported as 161.95 mSv. The internal exposure CED had been accounted in the personal dose record of the individual. The person had been kept away from the active job assignments for the remaining period of the calendar year. The remedial measures presently followed to prevent recurrence of such exposure are - a) Periodic checking on the integrity of gloves and its checking prior to start of any work, b) Nasal swab analysis for suspected inhalation exposure, c) use of respirators, COMFO respirator during cleaning / decontamination operations and fresh airline respirators in planned / glove change operations.
| 4. Conclusions|| |
While handling activity in glove boxes, during few unusual events viz., - the gauntlet rupture / pinhole in gloves / rupture of gloves and / or exhaust line malfunctioning, the internal hazard becomes significant depending on the release of α-activity. The assessment of lab air activity, personnel contamination, intake and internal exposure during events in glove box resulting in release of α-activity had given insight to the potential internal hazard. In the present case, due to the alarm indication given by the Pu-in-air monitor placed in the lab, the immediate suspension of the operation became feasible, which resulted in control of intake of the lab personnel. Besides, the administration of Ca-DTPA to the person with positive nasal swab has resulted in sizeable reduction of CED.
| 5. References|| |
- Radiation Safety Manual for Radiometallurgy Wing, BARC/2006/R/003, BARC, 2006.
- Technical Specifications of Radiometallurgy Division, RMD, BARC, 2007.