OREANDA-NEWS. On August 09, 2007 the committee formed by Mayak Production Association for analyzing the incident registered at the plant 235 a month ago completed its work on Aug 3 2007, reported the press-centre of Mayak PA.

To remind, on June 22–24 2007 the personnel of the plant deactivated the pneumatic transporter of solid radioactive waste (chopped metal cladding of fuel elements) and prepared it for repairs.

The on-site individual radiation exposure inspection detected no deviations from the norm. However, the final inspection, on July 2 2007, found out that five operators had received a bit more radiation than was allowed. The management of Mayak immediately released a press statement on the incident and set up a special committee.

The findings of the committee, led by the chief engineer of Mayak A.Suslov, are as follows:

In Mar 2007 the sensors of the plant 235 detected growing gamma radiation at the place where the protective trench (a concrete structure protecting the steel pipe of the pneumatic transporter) goes into the wall of one of the buildings.

Without notifying the management of Mayak, the director of the plant 235 V.Ushakov sent his men to inspect the scene and to remove the problem. The inspection had shown that the steel pipe had a 20mm crack.

June 22–24 the personnel washed the canyon and leaded the fuel element cladding for reducing possible radiation during the repairs of the pipe.

So, the final inspection might have neglected the possibility of high measurement error in the high intensity fields. 

As a result, five people revealed exposure that was higher than the principal dose limit but lower than the limit potentially dangerous for human health.
 
The principal radiation dose limit for nuclear power engineers is 100 mSv wihtin five years.

One of the operators involved in the incident received 77,3 mSv and the other four — 52–55 mSv. 18 more people received 20–50 mSv.

According to the nuclear safety rules-1999, the potentially dangerous dose is 200 mSv, so, any exposure within this limit does not require medical treatment.

However, the committee has decided that this year the irradiated employees will be no longer engaged in potentially dangerous activities and in the following four years their radiation exposure will be kept within admissible 100 mSv.

Based on the committee’s findings, the acting director of Mayak PA S.Baranov has dismissed the director of the plant 235 V.Ushakov and reprimanded the shift manager of the plant A.Tungusov.

Rostekhnadzor has instituted administrative proceedings against the director, the head of the department 5 and the head of the radiation safety service of the plant 235.

The incident has been classified as of local significance.