21 février 2011
Un niveau élevé de radioactivité a été détecté lors de l’échantillonnage de routine d’un prélèvement des eaux souterraines via un forage sur le site.
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Elevated level of radioactivity was detected during routine sampling of a groundwater sampling borehole on the site
Tritiated effluent arises as part of normal reactor operation, and it is collected in tanks which are safely discharged periodically to sea, via the site liquid effluent discharge culverts. These discharges are authorised under the site discharge authorisation, issued by the Scottish Environment Protection Agency (SEPA).
BEGL reported on 21 February 2011 that an elevated level of radioactivity was detected during routine sampling of a groundwater sampling borehole on the site. This led to an investigation, which suggests that the source of the activity is likely to be leakage from two flanges in tritiated effluent discharge lines 1&2, which lead from the tritiated effluent tanks to the discharge culverts.
The licensee has reported that the activity levels detected in the borehole samples is very small, and in the sump of the secondary containment for the discharge lines it is less than 0.1% of the activity level of the liquid authorised for discharge.
On discovery of the elevated activity levels, BEGL suspended use of the affected discharge lines until measures to prevent further leakage were put in place, and interim operational safety improvements were implemented. Following their remedial work, they have produced a safety case to allow further use of the lines until their investigations are complete.
ONR carried out with SEPA a joint inspection of the event, which found that the licensee’s initial response to the event has been appropriate. However, letters from ONR and SEPA have been sent to Torness requesting further information relating to the circumstances of the event and their proposed response in the longer term.
Currently, we await completion of the licensee’s investigation and a response to the regulators’ letters, and in the interim will continue to monitor the outcome from further use of the site tritiated effluent discharge lines.
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