Some differences may exist between french and english regulations. Lessons learned are only a translation of those of french incident and are not adapt to english regulation.
Description of the incident
Research work, involving the dispensing of aliquots of a sulphur-35 solution (total activity 259 MBq (7mCi)), was being undertaken in in a laminar flow hood used for the culture of cells. During this work, Mr. A spilled some of the stock solution. Unaware of the significance of the contamination, Mr. A did not undertake any decontamination measures, and did not advise the supervisor about this incident. Because of this, the contamination remained in place and no one knew about it. Some hours later, Mrs. B was called upon to work at this station for approximately 15 minutes.
The radiation protection supervisor was only notified of the incident the next day, and immediately banned access to the contaminated hood. A decontamination procedure was undertaken - some time after the incident, to allow for radioactive decay (the half-life of S-35 is 88 days).
Because of the low energy (167 KeV) beta radiation emitted by sulphur-35, the main potential risk is from internal contamination. 24-hour urine tests were undertaken: no significant residual radioactivity was detected in the urine of either of the persons concerned.
Lessons to be learned from the incident
In this case, Mr A was aware of the spill and should have taken appropriate actions immediately, eg a contamination check, notifying the supervisor, and then planning appropriate decontamination measures. Training for users of open sources should stress the importance of taking prompt actions to prevent the further spread of contamination.
Procedures should be drawn to describe the actions to be taken in the event of contamination spills, and to allow for the demarcation of the contaminated area to prevent it being used by other persons.
Spills may not always be apparent at the time, and users of open soures should be encouraged to regularly check their workspace for contamination, especially where other persons may also be working in the area.
The use of colored solutions (as already exist for some radioisotopes) would have allowed the contamination of the workstation to be visually identified.