Identify a Russian region based on the description and answer additional questions. This is a border region

Identify a Russian region based on the description and answer additional questions. This is a border region of Russia. During the Russian Empire, the modern regional center was the third most populous city among those located in the territory of modern Russia, trailing only behind St. Petersburg and Moscow. During the Soviet era, a national autonomy was located in the modern territory, which was subsequently abolished. The region is almost evenly divided by a major river, with the regional center located on its banks. Also on the banks of this river is a city that is one of the two in Russia where both a large nuclear power plant and a large nuclear power plant are located. In agriculture, the region is known for growing a particular type of grain, some varieties of which are named after the region. Agriculture in the region is also developed due to the presence of a certain type of fertile soil in the western part of the region. The region is also home to a large enterprise that manufactures a type of urban transportation. The regional center is also known for producing a certain type of household appliances under a brand name that coincides with the name of the city.