INES-event
INES 2

UNCONTROLLED POWER TRANSIENT IN A TEST REACTOR WITH DEGRADATION OF THE TESTED IRRADIATED FUEL NEEDLE

During start-up of the reactor, the power unwillingly increased outside the test specification limits to the nominal conditions.
The reactor was manually stopped before actuation of the protection at nominal power.
The fuel needle under test was badly damaged and induced locally a significant irradiation rate in the experimental area around the reactor (a few R/hr). However no release of radioactivity to the environment, nor any abnormal irradiation of the personnel occurred.
The rating by the utility is initially based upon the explanation "extreme deviations from important safety procedures".
After examination, a on-site criterion seems more appropriate.
The incident induced a degradation of the experimental element leading to an irradiation rate of a few R/hr.
Based on the manual p. 17, if the dose rate is such that the statutory dose limit is exceeded within one hour the level is 3. Apparently, the irradiation level does not reach such a value, but is not too far away. This justifies a level 2.

Location: BR2
Event date: Sat, 13-11-1993
Nuclear event report
Legenda & explanation