Electrical Systems at Laguna Verde Nuclear Power Plant (LVNPP) after the Fukushima accident

During the accident occurred in Fukushima Daiichi Nuclear Power Station in Japan, the onsite and offsite electrical systems were affected and lost for a long time with irreversible consequences, therefore, the Mexican Regulatory Body known as the National Commission for Nuclear Safety and Safeguards (CNSNS: for its acronym in Spanish) has taken several actions to review the current capacity of the electrical systems installed at Laguna Verde NPP to cope with an event beyond of the design basis. The first action was to require to Laguna Verde NPP the compliance with Information Notice 2011-05 'Tohoku-Taiheiyou-Oki earthquake effects on Japanese Nuclear Power Plants' and with 10 CFR 50.54 'Conditions of licenses' section 'hh', both documents were issued by the United States Nuclear Regulatory Commission (USNRC). Additionally, CNSNS has taken into account the response actions emitted by other countries after the Fukushima accident. This involved the review of documents generated by Germany, Canada, United Arab Emirates, Finland, France, the United Kingdom and the Western European Nuclear Regulator's Association (WENRA). CNSNS made special inspections to verify the current capacity of the electrical systems of AC and DC. As a result of these inspections, CNSNS issued requirements that must be addressed by Laguna Verde NPP to demonstrate that it has the capacity to cope with events beyond the design basis. Parallel to the above, Mexico has participated in the Ibero-american Forum to address matters related to the 'Resistance Tests', the evaluations of the Forum have reached similar conclusions to those required by European Nuclear Safety Regulators Group (ENSREG), under the format proposed by WENRA. The actions carried out here are closely linked to the requirements established by the USNRC. It is also important to mention that: 1) the Extended Power Up-rate project was implemented in both Units of the Laguna Verde NPP before the accident in Fukushima Daiichi, for this reason the main electrical equipment belonging to the offsite power system was changed and the electrical analysis was reviewed (such as: short-circuit, load flow, electrical stability analysis, etc.), 2) Generic Letter 2006-02 'Grid Reliability and the Impact on Plant Risk and the Operability of Offsite Power' is in process of implementation, this aims to verify that it maintains compliance with regulatory requirements which govern electrical systems and 3) the USNRC is in the process of reviewing the 10 CFR 50.63 and Regulatory Guide 1.155 'Station Blackout', once issued, CNSNS will require its implementation at Laguna Verde NPP. Based on the above, CNSNS concludes that all actions are being taken to enhance the robustness of Laguna Verde NPP's electrical systems, in order to increase their reliability, safety and operation as required in order to cope with events beyond design basis as that occurred at Fukushima Daiichi and avoid as far as possible damage to the reactor core. (authors)