VVER-1000 Incidents and Accidents (2006 to 2013)
Dr Anisur Rahman
CRadP MSRP FNucI(Author
of 'Decommissioning and Radioactive Waste Management' which is one of the
text books for graduate and post-graduate studies in Nuclear Science in
British, European and Chinese Universities)
......................................................................
On
April 15, 2013 in Kazloduy Unit 6 a leak of primary
coolant (highly radioactive) to secondary system was detected. Excess
radiation level had led to the shutdown of the turbo-generator and consequent
reduction of the generated power. Although the plant manager said that there
was no undue radiation exposure (which is disputed as lot of workers work
around the turbo-generator), the final report is yet to come out.
Rostov,
near Volgodonsk, in Russia had been earmarked in
1970s to have four VVER-1000 reactors. The construction work on Unit 1
started in 1977 and operations began in 2001 (after 24 years); while the Unit
2 construction started in 1983 and operation began in 2009 (after 26 years).
Just after two years of operation, Unit 2 started to show all sorts of
problems requiring frequent shutdowns. A serious incident occurred when the
turbo-generator failed causing the reactor to be taken off-grid. Almost
similar problem was experienced in Kalinin (in Russia) nuclear power plant.
The failure of the turbo-generator led to the reactor scram. Although
automatic protection system did kick in, but the plant availability was
severely reduced.
On
March 1 2006, Unit 5 of Kozloduy NPP (VVER-1000)
had one of the MCPs failed which required emergency shutdown to operate. But
22 out of 60 control rods failed to insert which necessitated secondary
shutdown mechanism to be activated. This was identified as INES-2. Should
there be one additional fault like another MCP failing or more control rods
failing to insert or secondary shutdown failing to suppress reactivity, there
could easily be an uncontrolled reactivity accident resulting in core meltdown.The worst part was that it was not disclosed by
the Kozloduy NPP management for fear of
repercussions on the safety of the reactor. When a whistle blower disclosed
it, the technical manager was sacked and the EU ordered a thorough review of
operational safety of the plant.
These
are only a very few incident/accidents in only 6 reactors over the 7 year
period. A rigorous study will reveal the full extent of these accidents.
Link below for the article as
published in Prothom Alo
in Bangladesh.
http://www.prothom-alo.com/detail/date/2013-07-05/news/365363
