TIRUNELVELI: The long-awaited Unit-2 (Reactor-2) of the Koodankulam Nuclear Power Project (KKNPP) attained criticality at 8.56 pm on Sunday. Speaking to reporters at Koodankulam, Nuclear Power Corporation of India Ltd (NPCIL) Chairman and Managing Director S K Sharma said the KKNPP Unit-2 is the 22nd reactor in the country to attain criticality.
The 163 uranium assemblies in Unit-2 (Reactor-2) were loaded in May. The process took eight days. Following this, containment leak test, reactor pressure vessel, piping line and system equipment test, hydro test and steam generation test were conducted. The test results were submitted to the Atomic Energy Regulatory Board (AERB) for clearance. The clearance for conducting the First Approach to Criticality (FAC) was received in June end. The Tamil Nadu Pollution Control Board also gave its clearance.
After visiting the nuclear plant to inspect Unit-2 on July 1 and 2, a team from the Ministry of Environment and Forests submitted its affidavit in the apex court on July 8. At 7.52 pm the same day, the criticality process (FAC) began.
Reactor-2 was monitored by Russian experts and specialists from the NPCIL and AERB as it marched towards attaining criticality.
Boron (a neutron absorber) was used in the form of boric acid solution in the primary coolant to keep the reactor in a sub-critical state before attaining criticality. The process of approach to criticality involved gradual dilution of Boron, which allows neutrons in the nuclear fuel matrix to multiply till a controlled self-sustaining nuclear fission reaction was attained.
“Criticality means starting of controlled self-sustaining fission chain reaction (neutron chain reaction). The ground breaking ceremony of the Unit-2 was conducted in 2001 and pouring of concrete was done the next year. After around 15 years, Unit-2 attained criticality for the first time today,” the NPCIL officials said.
As 562.50 MWe power generated from Unit-1 of KKNPP is being allotted to Tamil Nadu, it is expected that the same amount of power will be allotted to the home state from Unit-2. The twin VVER reactors, each of 1,000 MWe electricity generation capacity, were set up in technical collaboration with the Russian Federation. Presently, Unit-1 is in its second cycle of power production.
The AERB had granted clearance for FAC of Unit-1 on July 11, 2013. The plant attained criticality on July 13, 2013, within 48 hours. Unit-1 was synchronised with the Southern Grid on October 22 the same year.