Bordeaux university hospital – Haut-Lévêque Hospital: uncontrolled release of radioactive effluents into the public sewerage system. ASN reclassifies the event level 2 on the INES scale and remains attentive to the implementation of corrective measures

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Following a series of events in 2012 and 2013 (see table below) involving leaks from the radioactive effluents collection network (mainly iodine 131) in the nuclear medicine unit of the Haut-Lévêque hospital in Pessac, ASN reclassifies the most significant of these events (notified in August 2013) level 2 on the INES scale, owing to insufficient monitoring of the effluents network and the absence of safety culture. ASN remains attentive to the implementation of the corrective measures.

On 2^nd August 2013, ASN was informed by the Haut-Lévêque hospital in Pessac that an abnormal level of radioactivity had been discovered in a wastewater drain pipe. Investigations showed that radioactive effluents from the vectorised internal radiotherapy¹ rooms were being discharged directly into the public sewerage network instead of being routed to the radioactive decay tanks, between August 2012 and 27^th July 2013, owing to a piping connection error. The connection had been defective since works were carried out in August 2012.

This abnormal level of radioactivity was detected by the hospital by chance, on 27^th July 2013, during a contamination check on a puddle of water (rainwater leak during a storm) present in a room located under the metabolic radiotherapy rooms. This check was the result of a previous event, on 21^st July 2013, during which a leak of radioactive effluents had been discovered in the same sector.

As soon as this contamination was discovered, the hospital suspended the treatments, until the piping had been correctly repaired. This was completed on 9^th August 2013.

On 16^th September 2013, ASN thus asked the hospital to submit it a programme for complete renovation of the radioactive effluents evacuation networks. It asked that this plan specify the steps taken to ensure technical monitoring of the works and check correct performance. ASN also requested that a programme of regular dose rate checks in the vicinity of the pipes be set up.

The hospital sent ASN its action plan on 13^th February 2014. ASN nonetheless asked the hospital on 28^th March 2014 to also carry out an assessment of the impact of the discharges on persons liable to be carrying out an activity exposing them to the wastewater (sewerage workers, wastewater treatment plant personnel). ASN also requested the hospital to specify the technical solutions adopted for renovation of the network, and the schedule of the related works. ASN will in particular check the performance of the corrective measures to be implemented by the hospital. On 16^th May 2014, ASN thus called the hospital management and the head of the nuclear medicine unit to a meeting.

Moreover, in response to an ASN request of 21^st November 2013, the hospital stated on 13^th February 2014 that the total activity released was estimated at 244 gigabecquerels (GBq) of iodine 131. According to the hospital, the doses received by the hospital staff working in the sector affected did not exceed 1 millisievert (mSv), which is the annual dose limit admissible for a member of the public.

ASN observes that this incident occurred, even though two other events concerning the storage of radioactive effluents had been notified to ASN by the hospital in April and August 2012. These two events were examined by ASN, which conducted an inspection of the hospital’s nuclear medicine department in August 2012. It in particular raised the problem of the ageing of the radioactive effluent drainage pipes. ASN requested that all the radioactive effluent collection and decay systems be secured.

Owing to inadequate monitoring of the radioactive effluents network, the repetition of events on this subject and an absence of safety culture, ASN reclassified this event level 2 on the INES scale.

ASN has been notified of numerous significant radiation protection events concerning the management of effluents from nuclear medicine units in recent years and a circular letter was sent out on 17^th April 2012 to all nuclear medicine units, presenting the lessons learned from experience feedback from this type of event.

ASN recalls the need to anticipate these problematical situations and define response procedures in advance. Nuclear medicine comprises all uses of unsealed sources of radionuclides for diagnostic or therapeutic purposes.