I reblog this information originally from the Barents Observer :

the water-cooled Reactor No. 4 developing a capacity of 411 MgW automatically disconnected from the Russian electric grid Tuesday morning at the Kola Nuclear Power Plant (KAES in Russian) situated in the Region of Murmansk in the Republic of Karelia.

The article did not mention an explanation of the incident which was under investigation and stated that there is no report of a violation of the radiation levels limits. See more recent articles below

Rosenergoatom, the company which runs the power plant, presents more information about this arctic nuclear power plant on its website (English and Russian).

Source: Reactor shutdown at Kola

The Kola nuclear power plant 
(source : By КольскаяАЭС (Own work) [Public domain], via Wikimedia Commons)

Complementary informations about the history of reactor n°4 at Kola Nuclear Power Plant:

COMMENT: Russia gives up on “boosting” Chernobyl-type reactors – but still eyes VVER-running stations for further experiments, from Bellona, 04-16-2012

Kola nuclear plant gets go-ahead to run its No 4 reactor for a record breaking 25 more years, from Bellona, 10-13-2014

Kola NPP: load reduced in connection with the repair of 330 kV “HPP Putkinskaya – Louhi-1”, from Rosenergoatom, 10-26-2015

Russia’s Kola nuclear plant reactor shutdown spooks environmentalists, from Bellona, 02-09-2016

Кольская АЭС: энергоблок №4 включен в сеть, press-release from the Nuclear Power Plant press-centre, in Russian, 02-10-2016

Kola nuclear plant shutdown blamed on deteriorated cable, ending silence on the malfunction, from Bellona, 02-11-2016

 

cover picture : The Kola nuclear Power Plant in the Kola Peninsula, Federation of Russia
source : RIA Novosti archive, image #146342 / Roman Denisov / CC-BY-SA 3.0 [CC BY-SA 3.0 (http://creativecommons.org/licenses/by-sa/3.0)%5D, via Wikimedia Commons