In the 1990s, alterations to the original design were made by Westinghouse, in conjunction with SUJB and the IAEA, to bring reliability and safety levels into conformance with Western European standards.

As part of the alterations, information and control systems were added, electrical modifications carried out, and cabling, reactor core, and fuel elements were replaced.

[10] In September and October 2000, Austrian anti-nuclear protesters demonstrated against the Temelín Nuclear Power Plant and at one stage temporarily blocked all 26 border crossings between Austria and the Czech Republic.

[16] The Melk Protocol, signed on 12 December 2000 in Melk, Austria, is the result of negotiations between the Czech and Austrian governments, led by Czech prime minister Miloš Zeman and Austrian chancellor Wolfgang Schüssel, with the participation of European Commissioner Günter Verheugen.

[17] The aim of the protocol was to resolve disputes over the Temelín plant, with Austria raising several concerns about its safety and procedures.

[18] The Czech Republic committed itself to some above-standard procedures (e.g., notification of events at Temelín to Austria, and a more stringent environmental impact assessment).

Consequently, Austria recognised the importance of EU enlargement and agreed that the free movement of goods and people must be preserved (this clause was a response to the blockade of Czech–Austrian border crossings by Austrian anti-nuclear activists).

However, in July 2008, ČEZ requested the Ministry of the Environment conduct an environmental impact assessment for two additional reactors.

[32] Shortly after the Fukushima nuclear accident, prime minister Petr Nečas announced that the construction of new reactors would continue according to original plans[33] but with the tender selection delayed until 2013.

[37] In April 2014, ČEZ cancelled the project after the Czech government stated it did not plan to provide guarantees or other mechanisms to support the construction of low-emission power plants following discussions in the EU.