KKNPP in Trouble Again

V T Padmanabhan & Sankar Ray

Two 1000 MW Voda-Vodyanoi Energetichesky Reaktors (VVER), built by the Nuclear Power Corporation of India Ltd (NPCIL) with equipment and drawings from the Russian company Rosatom at the Kudankulam Nuclear Power Plant (KKNPP) in South India are again in trouble, as apprehended by well-informed environmental activists. The VVER or Water-Water Energetic Reactor is a series of pressurised water reactor designs originally developed in the erstwhile Soviet Union. The KKNPP-II tripped once again on 3 April, 2017. Trip is forced outage and the World Nuclear Association (WNA) states categorically that, trip is a rare event in modern reactors. A trip in three years happens in the best performing reactors the world over. The KKNPP-2 had six trips right from its grid connection. Its elder brother, KKNPP-1 has a world record for highest number of trips – 16 during commissioning period, 8 during warranty period and 4 after the transfer of the unit to NPCIL by Rosatom.

According to the NPCIL, trips are initiated as part of the commissioning drill. This explanation is a mis-match with international experience. There are three tests which involve disconnection of the turbine from the grid and in all these; the generator will be reconnected within hours. Advance information about such tests is provided to the grid manager and also to the IAEA. The Southern Region Load Despatch Centre (SRLDC) grouped all the trips mentioned above in the category of forced outage. The NPCIL declared the commercial commissioning of the second reactors on 31 December 2014 and 31 March 2017 respectively despite having failed to be through in the the commissioning tests prescribed by the Atomic Energy Regulatory Board (AERB). The repeated trips are a proof that the authorities keep pooh-poohing the regulatory apex.During 225 days of its grid connection (29 Aug 2016 - 10 April 2017), the reactor was on forced outage for 74 days, on partial outage 2 for 125 days and on full power (990 MW) for 27 days. During the past 11 days, the reactor was under forced outage for 7 days and on partial outage for 4 days.

The construction of two AES-92 version 1000 MWe VVER reactors at Kudankulam began in 2001. The reactor was certified as Generation-Ill pressurised water reactor (PWR) by the European Utility Requirement (EUR) club in 2006. As per the original plan, both the units were to be commercial-commissioned before 2008, 65 months after the first concrete pouring. However, the initial fuel loading (IFL) of the first unit (KKNPP-1) was completed in October 2012. The grid connection was done a year later. It was declared commercial on 31 Dec 2014. KKNPP-2 was fuel-loaded in July 2016, grid connected on 29 August 2016 and declared commercial on 31 March 2017.

Needless to stress, commissioning is the most important milestone in the life of a nuclear reactor. The safety code, prescribed by the AERB states unequivocally, “the commissioning programme shall assure that, after construction, the nuclear power plant (NPP) is made operational in a systematic, informative and safe manner, shall verify that the performance criteria, design intent and quality assurance (QA) requirements are satisfied and demonstrate that the plant can be operated in a safe manner through integrated testing of the plant system(s).” Furthermore, “commissioning of pressurised water reactor (is) based nuclear power plants”, while the commissioning is conducted in three phases; the fuel loading is done only after the completion of the second phase.

In the C-Phase, known as power ascension phase, there are 45 different tests in three sub-phases – C-1, C-2 and C-3. (Page 66, Ref 2). After synchronisation with grid, the reactor power is gradually raised from 200 MW to its design output of 1000 MW. It is performed in a systematic sequence so that the plant is progressively subjected from less onerous to more onerous conditions. In C-l and C-2 sub-phases, reactor power is raised to 50 % and to 75% of Full Power (FP) respectively. The main tests of C-3 sub-phase are non-stop operation for 7 days at 90% FP and non-stop operation for 100 days at 100%FP. Non-stop operation means there should be no outage or decline in output during the period.

The NPCIL failed to comply with the “100 day non-stop 100%FP” after repeated trials during the commissioning of the first unit (KKNPP-1) in 2014. Thus the reactor was commissioned on 31 Dec 2014 without clearing the final test. During 1186 days (between 1 Jan 14 and 31 Mar 17) the reactor was on full power on 281 days in 15 instalments. The maximum non-stop FP days attained so far is 48 days (19 Jul to 4 Sep 2016). Sadly enough, the commissioning was a political decision, stripped of legality, as admitted by the Supreme Court. After the bitter experience of KKNPP-1, the NPCIL decided to reduce the number of non- stop full power days from 100 to 30. The NPCIL informed the Southern Regional Power Committee (SRPC- the grid manager for South India) in December 2016 that “KK-2 would be on non-stop FP during January 2017 before declaring commercial operation in Feb 2017.

The reactor could not attain even the diluted decision of 30 days non-stop 100% FP so far. During 217 days since the grid connection and commercial commissioning, the reactor was on full power for 27 days in three instalments in January-February 2017. Days under forced shutdown, low power (990 MW) and full power (990 MW and above) was 30.4%, 57.1% and 12.4% respectively.

 Brief details of forced outages, also known as trips or SCRAM, which were the main events during the commissioning period are given below:

Trip No 1- 07 September 2016. On the day of synchronisation with the grid, the gross generation was 117 MWe (2.8 million units - MU). Its average output was 260 MWe during the first week. On 7 th September 2016, it dropped to 54 MWe and the reactor tripped on the same day. According to a dispatch from the Press Trust of India (PTI), published in the Financial Express, there were problems in the turbine and the specialists from Russia’s Rosatom and the NPCIL were engaged in its repair.

Trip No 2- 13 November 2016. After 38 days of outage, the unit was revived on 14 Oct’ 16. Average generation during the next 30 days was 390 MWe/day with a maximum of 443 MWe on 11 Nov 16. The reactor tripped again on 13 Nov 2016 and was off-grid for 10 days till 22 Nov 16. The reported reason for the trip is “Net Load Rejection Test’, which is one of the commissioning tests. During this test, the turbine-generator will be disconnected from the grid and reconnected within a few minutes. The reactor’s outage for 10 days is indicative of some serious problems.

Trip No 3-23 February 2017. During 22 Nov’ 16 to 20 Jan’ 17, the average and maximum generations were 647 MW and 894 MW respectively. On 21 Jan’ 17, the gross output crossed 900 MW and two days later it reached the Full Power (FP) of 990 MW. From 23 Jan 17 to 20 Feb 17, the average generation was 990 MWe/day; though on two days -8 Feb and 14 Feb 2017, the output was 916 MWe/d only. As per the NPCIL’s plan, the reactor was to be commissioned after 30 non-stop full power days. Unfortunately, on 23 Feb’ 17, the generation fell sharply to 660 MW and the reactor tripped for the third time due to ‘Steam Generation Level Low’.Trip No 4- 12 March 2017. The average generation during the 14 days since its revival on 26 Feb 20127 during the next 14 days was 697 MWe/day with the maximum of 920 MWe on 11 March 2017. On the next day, the output dropped to 460 MWe and the reactor tripped again. The reported reason for the trip was Dynamic Trip Test, a test that is not found in the AERB list of commissioning tests. Two days before the trip, NPCIL had informed the Southern Regional Power Committee (SRPC), Bengaluru that KK-2 will be shut down on 11th or 12th March 17 for 20-30 days and commercial commissioning is expected by 31st March 2017.

Trip No 5 and the First one after commissioning. The unit was revived on 29 March 2017. The gross generation on 30 March 2017, the day before the commissioning was 462 MW, which rose to 910 MW on 31 March and dropped again to 826 MW and 538 MW on 1st and 2nd April 2017. And then, 58 minutes after the midnight of 2 April 2017, the reactor tripped again. The reason for the outage, as reported by the SRLDC, is “to rectify the passing of steam dump valves to condenser in secondary side”. Two days after the trip, the Site Director of KKNPP “expected the unit to start generating power on April 7, 2017”. The reactor was under shutdown till 06:00 hours on 10 April 2017.

The first trip after the commissioning was due to defective condenser steam dump valve. Actually, the steam produced by the steam generators drives one high power turbine and three low power turbines and the spent steam is sent to the condenser for cooling and reusing as feedwater in the steam generators. If the turbine is not in a position to receive and use the steam, the steam dump valve (BRU-K) opens and the steam is directed to the condenser. The valve is analogous to a service road of an express highway. The steam bypass system is generally used during startrup and shutdown, steam turbine trip and steam turbine no-load or low-load operation.

After revival from the trip on 29 March, the gross generation is raised from 193 MW on 29th March to 910 MW on 31 March. Rather than moving up to its design potential of 1000 MW, the output started declining sharply to 538 MW on 02 April 2017. This means that on 2nd April, nearly half the steam was wasted via the steam dump valve. The failure of the valve forced the operator to shut down the reactor on 3 rd April 2017.

The plea of the site director of KKNPP was that, “due to some problem in the steam valve, the unit was shut down on Monday” and after its rectification, the unit will “start generating power on April 7.” They may be able to open the valve and set it right in a day or two, but the real problem lies in the turbine and its repair may require spares and expertise from Russia. Incidentally, on 3 September 2016, 5 days before the first outage due to the turbine defect, a 30 ton cargo plane landed at the Madurai airport with spares for Kudankulam.

KK-2 turbine was overhauled —disassembly, Servicing of internal components and assembly by a Hyderabad based contractor during 2013. Again in May-June 2015, the Bharat Heavy Electricals Ltd (BHEL) did a major repair-reassembly of the same turbine at a cost of Rs 19.8 million. The turbine generator appears to be the Achilles heel of KKNPP. Barely six weeks after the repairs of the second unit’s turbine, KKNPP-1 was also under forced outage for 72 days. The stated reason for the outage was “Routine Generator Inspection”. An inspection lasting for 72 days!. So far, there had been 12 events – trips, repairs and maintenance of KKNPP-1 turbine, which kept the reactor off-grid for 321 days.

The KNNPP-2 is a technological hoax, an abominable goof-up.The crucial question of energy security is subserviently surrendered to predatory interests abroad. When nuclear power is fast abandoned the world over, why nuclear lobby that has strong political connections is hell-bent on economically,environmantally and socially destructive ventures.

V T Padmanabhan <vtpadman@ gmail.com>,
Sankar Ray sankar.ray@gmail.com

Frontier
Vol. 49, No.46, May 21 - 27, 2017