R Ramesh, V Pugazhendi and VT Padmanabhan

Abstract

Introduction

A 1000 MW (e) pressurized water reactor is almost ready for commissioning at Kudankulam, Near Kanyakumari in Tamil Nadu, India.  Another reactor is nearing completion and is likely to be commissioned next year. The communities near the plant, fish workers unions and the environmentalists from all over the country have been opposing the project ever since it was mooted in 1980’s.  The campaign has grown stronger during the past one month. The Chief Minister of Tamil Nadu and several political parties have questioned the safety of the plant.  At the same time, the Department of Atomic Energy (DAE), the Nuclear Power Corporation of India Ltd (NPCIL) and the Government of India are engaging eminent scientists to ‘educate the people’.

In the wake of Fukushima disaster, the Prime Minister Dr Man Mohan Singh appointed four task forces to do an in depth study of Indian reactors.  The Committee headed by S Krishnamurthy looked into the Kudankulam Nuclear Power Plant (KKNPP)    The scientists reported that the reactor was safe.

Excerpts from the report:

“Review of the core cooling capability of the KKNPP during a postulated beyond design basis scenario of tsunami resulting in incapacitation of motive power and the designed water supply route was carried out. It is seen that KKNPP design has incorporated sufficient passive systems to ensure core cooling and radio activity confinement even in the case of an extended unavailability of electric power and the designed water supply route. (Emphasis added) … However, as a means to further enhance the level of safety and to build more defense in depth the committee recommends the implementation of the measures outlined to cope up with unanticipated and rare severe and multiple natural events having very low probability like the one that took place at Fukushima Nuclear Plants in Sendai prefecture of Japan. The engineering details of these additional measures are being worked out. The schedule (short term and long term) of implementation will be submitted along with engineering details by end August 2011[2].

Several stories have appeared in the national media showing that that KKNPP reactor is safe, quoting the Task Force Report and other government sources.  Excerpts from a report that appeared in Times of India: (Oct 19, 2011)

“In case of an accident or a natural disaster necessitating the activation of emergency measures, the cooling of the core is top priority and drawing lessons from the Fukushima scenario where gusts of radioactive steam escaped into the atmosphere for days, India’s plants are now supplied by alternate water sources that will not be vulnerable to disruption.” …“Not depending on on-site water sources alone, water pipelines from remote locations will supplement and provide fall-back apparatus.  …India has ramped up safeguards at its atomic power plants with three layers of power back ups, water pipes drawn from off-site locations, elevated water towers and options for injecting nitrogen to prevent explosions.” Rajeev Deshpande, Indian N-plants step up safety measures, Times of India TNN | Oct 19, 2011[3]

The only sources of water at KKNPP are four desalination plants with a combined capacity of 10,000 cub meters per day.  One of the plants will be on standby. The total reserve water in 11 tanks is 10,000 cubic meters, or equivalent to one and half days of production and two days of consumption.  In the EIA and the detailed project report, the source of water was the reservoir at Pechiparai, 65 km south west of the site.  In its clearance order issued in 1998, AERB had instructed NPCIL to make arrangements for a backup source from Upper Kodayar reservoir.  Among other recommendations were (a) policing the pipeline and (b) ensuring the structural integrity of the reservoirs.

The Government of India and NPCIL are bent upon commissioning the reactors without these basic safety features.  Commissioning of the reactors should be postponed till all the safety related issues are made public and approved by the people.  What at stake is the health and well being of over 300 million people and a million sq km of land in peninsular India, besides Rs 150 billion of public money.

Physics of Fission

There are two isotopes of uranium – 235Uranium (U235) and 238Uranium (238U).  Only U235 is fissioned by a thermal neutron.  When hit by a neutron, the 235U atoms undergoes fission.  This produces two atoms of different elements, known as fission products and 2-3 neutrons.  One of the neutrons hits another U235 and splits it.  This is known as chain reaction.  The other neutron that does not take part in the chain reaction enters the nucleus of the elements in the reactor environment.  If it enters the nucleus of aU238, it produces 239Plutonium (239Pu), which can also undergo fusion.  The process inside the nuclear core and the atom bomb are fundamentally the same.  The only difference is speed.  About a kilogram of 235U was fissioned in Hiroshima bomb instantaneously.  The same amount of 235U will be split in Kudankulam reactor during 8 hours.

The main raw materials used in a nuclear power plant are uranium and water.  Daily requirement for one 1000 MW (e) reactor at Kudankulam is listed below:

Uranium235                                                                 0.003 Tons

Fresh and pure water for cooling the core   –              3500 cubic meter

Sea Water for condenser cooling                              – 7.2 million cub meter

The Reactor Physics

The cylinder shaped core of the Water-Water-Energy-Reactor (VVER) 1000 megawatt (e) that has been set up in Kudankulam is about 20 meters in height and 5 meters in diameter.  In the middle of the core is the uranium fuel, weighing 100 tons, of which 4 tons will be uranium 235 and remainder 238U. 4 Tons of 235U will generate 3,100 MW of heat for 28,000 hours.  (You can also produce 800 Hiroshima type bombs with 4 tons of uranium.) The fuel is immersed in 290 cub meters of ultra-pure, de-mineralized and de-ionized water.  In one second 48 milligram of uranium will be fissioned. In that second, some 25 milligrams of 239Pu will also be produced, besides the fission products, radiation and heat.  The water in the core surrounding the fuel gets heated.  20 tons of water, temperature 321 C exits from the reactor, generates 408 kg of steam in the steam generator.  About 5% of the exited water is lost in evaporation.  The remainder is condensed and returns to reactor with the makeup for the evaporative loss.  The temperature at reentry is 291 C. The fine balance of volume and temperature water at exit and entry needs to be maintained for the health of the reactor.  If this fine balance is maintained, the reactors will generate about 900 MW of electricity without any interruption for about 18 months.

The fine balance is very important.   On this planet, every moment, 24 hours a day, 365 days a year, 450 highly skilled engineers glue their eyes to the computer screen to ensure that the water levels in the reactors under their control is optimum.  We owe a lot to these engineers.  We are alive and safe because of them.  Their contribution to our safety has not been recognized.  None of them received a Nobel Prize or Padmasree.

Water is the ultimate safety

If the water drains out of the reactor and the fuel rods are exposed, number of fissions per second will increase exponentially.  This will cause the temperature of the core to increase beyond 3000 C.  At this stage, the reactor becomes highly unstable.  The zirconium cladding of the fuel pellets and the uranium inside it starts melting.  The myriad of chemical and radiological reactions following this will lead to generation of hydrogen from water.  (The core has 32 tons of hydrogen locked inside the water molecules.) This hydrogen can ignite and rupture the reactor core made of steal and the containment building made of reinforced concrete.  A nuclear explosion is also possible, though rare. The time required for boiling off the coolant and reactor meltdown will be about four hours.  The spent fuel pool can experience a similar nightmare with in 12 to 96 hours depending upon the ‘age of the fuel’.

Both Chernobyl and Fukushima reactors exploded and dispersed the radioactive elements.  In Chernobyl, the hot gases and particles moved up in the air, 3000 meters high and drifted and rained in the whole of Northern Hemisphere.  Radioisotopes were released from Fukushima also and the release is still happening.  Much of the toxic load in Fukushima has been melted and is lying down under the reactor building.  This is known as melt down or China syndrome – meaning that a reactor that melts down in USA will pass through the centre of the Earth and exist somewhere in China.  That is an American imagination – the core does not go that further.  Most of it will get dispersed in the regional soil, water and air. Such accidents are classified as Level 7 which is the gravest radiological event.

Specific causes were different – but in all major radiological events so far – Three Mile Island, Chernobyl and Fukushima- the water balance of the core was disturbed.

The Spent Fuel

The radioactivity of the total fuel loaded in the reactor (100 Tons) will be about 2 trillion Bequrels (Bq).  Or every second, some two trillion uranium atoms will disintegrate and give off an alpha particle each.  Alpha radiation does not penetrate the dead outer layer of our skin.  It can be stopped by a piece of paper.  The radioactivity of the fuel after four years of working of the reactor will be a billion times more than what it was before the operation started.  More important, majority of the spent fuel isotopes are beta and gamma emitters.  They penetrate even steel and concrete.  Secondly the uranium in the fuel assembly is a big particle (macro particle).  Many of the new elements are either gases or nanometer (one billionth of a meter) – nanoparticles.  Nanoparticles can get into the plant leaves, paddy seeds and human bodies even when the skins are intact. People can breathe them also.

After every 12-18 months, the used fuel (about one-third of the total) will be removed and replaced by fresh fuel.  The spent fuel removed from the core will be hot.  About 30 tons of spent fuel will be removed during the refueling.  Its composition is given below:  All of these are very potent poisons, the most dangerous of them being the fission products, weighing about 900 kg.  Total radioactivity from the fission products will be 3E+19, or 3 followed by 19 zeros) disintegrations per second.  If all this is equally distributed in an area of 1 million sq km, there will ten million disintegrations per second from each sq meter area.  There are few hundred elements in fission products with different half lives ranging from a few seconds to millions of years.  Most important of them are tritium, cesium and carbon14.  These elements enter the food chain and colonize the entire biosphere within about a few months of the release.

235Uranium                  1%            300 kg

239 Plutonium  1%            300 kg

Fission products           3%            900 kg

Uranium238                95%        28500 kg

The spent fuel will be highly radioactive and also hot.  A person standing a meter away from it will die within 20 seconds.  Immediately at the shutdown of a reactor, the spent fuel will have 7% of the heat generated while the reactor was operating. Kudankulam reactor will generate 3100 MW of heat; on shut down it will still generate 217 MW of heat.  After 24 hours, the reactor will still generate 93 MW of heat. For next five years, this material will have to be cooled using ultra pure water – de-mineralized and de-ionized- of the same quality as that of the reactor coolant. Spent fuel removed from the core is kept in a spent fuel pool.  The Kudankulam pool is located inside the primary containment adjacent to reactor cavity. It can store 582 spent fuel assemblies or waste generated during 7 years. Water inventory inside the SFP is about 1500 cub meter.  After cooling for 6 years, the fuel will be taken out for separation of uranium and plutonium for reusing as reactor fuel. From a public health perspective, the spent fuel pool is even more dangerous than the reactor core.

Since the stock of spent fuel will double every 18 months, the water requirement of SPF will also increase as the reactor ages.  SPF will require about 5 to 10% of fresh water used in the reactor.  After about three decades, SPF will require more water than the reactor core.

History of Water Management by KKNPP

Considering its importance for the generation of electricity and the safety of the reactors, the workers and the general public, NPCIL had done its homework on water.  The reactor would need two types of water – ultra-pure, de-mineralized and de-ionized water to be circulated inside the core and other delicate structures and filtered sea water for use in not-so sensitive areas.

Each reactor and the accessories will require 3500 cubic meters of the ultra-pure water a day. For this fresh water was to be brought from Pechiparai reservoir, 65 km south-west of the reactor site.

One source not enough – AERB

In its clearance letter dated 10 November 1989, AERB said that depending on a single source of water is not sufficient from a safety point of view.

“Facility to store at site adequate quantities of water should be provided to meet the makeup requirements of uninterrupted cooling of core and other safety related systems on a long term basis.

Facilities engineered at site should meet the requirements even in the event of possible disruption of piped water supply from Pechiparai Dam.

Ground water sources in the site area should be surveyed and developed to serve as an additional back up source to meet the safety needs of the plant if water supply from Pechiparai dam is interrupted due to any contingency.

The safety of the 65 km long pipeline from Pechiparai dam should be ensured by appropriate security arrangement.

The intake well at the dam should be provided at lower elevation than the minimum draw down level of the reservoir.

The Board desires that the structural stability of the reservoir should be assessed taking into account the recent work of strengthening the dam.

In the unlikely event of the breach of the dam, alternative sources of water supply should be available for the site within a reasonable time. NPCIL should conceptualize schemes at the Detailed Project Report (DPR) stage for utilization of the water from Upper Kodayar reservoir for such an eventuality.”[4]

AERB is the highest authority on nuclear safety in India.  The Board was not satisfied with a single source of water.

Desalination

In 2004, five years receiving the consent of AERB, NPCIL abandoned the Pechiparai source and opted for desalination.  According to newspaper report “desalination plant established at Kudankulam Nuclear Power Project site at a cost of Rs.116 crore is all set to be commissioned shortly. The fresh water requirement of the KKNPP – both drinking and industrial purposes – would be met by the desalination plant, having a total capacity of 7,680 cubic meters per day. Supplied by IDE, Israel through Tata Projects Limited, the plant is based on mechanical vapour compression technology. The desalination plant has four units (three operating and one standby unit), each with the capacity of 2,560 cubic meter/day, which will meet the water requirements for commissioning and operation.” [5]

Two basic technologies are used in the desalination plants. They are either thermal based or membrane based. Membrane-based technologies include reverse osmosis (RO) and electro-dialysis (ED), while thermal-based technologies include multistage flash evaporation (MSE), multi-effect distillation (MED), multi-stage flash distillation (MSF), and mechanical  vapor compression (MVC). KKNPP plant is based on MVC.   According to BARC and the World Nuclear Association, nuclear establishment in India is a leader in desalination technology.  “Bhabha Atomic Research Centre (BARC) set up a 1.8 million-liters-a-day capacity desalination plant at Kalpakam in Tamil Nadu in 2008 and is set to commission a MSF-based plant there itself. BARC has set up several desalination plants in rural Rajasthan, Andhra Pradesh and Gujarat, producing 30,000 L a day. It has licensed its technology to as many as seven industries. IVRCL, IL&FS, Mahindra and Reliance are other companies that have set up desalination plants.

According to MP Ramaswamy, an expert on desalination at BARC, the cost of setting up a 10 million liters/day desalination plant is Rs 60 crores.  The cost of production was Rs 50 per cubic meter. The capital cost of desalination plants set up by the IDE of Israel was Rs 115 cores.  [6]

Production and Reserve of Water

There are 12 water tanks at KKNPP with a combined capacity of 11,445 cub meters.  This includes one overhead and three underground tanks storing 1425 cub meters for domestic purposes (located outside the ‘island’) and two tanks storing 2000 cub meters of water for fire-fighting.  Leaving aside the domestic and fire-fighting pools, the reserve at KKNPP is 8000 cub meters.  This is barely enough for meeting the production requirement for two days.

Since water is needed, even while the reactors are not running, KKNPP manager will have no option but to shut down the reactor in the event of any failure in the desalination plant.

Source:  S Krishnamurthy et al, Task Force Report (ref 1)

Desalination plants can fail for multiple reasons.  Corrosion of pipes is a major problem in all plants.  More important are the marine organisms, especially the smaller ones who get past the barriers and set up huge colonies inside the pipes and beyond.  These wonderful animals and plants belonging to thousands of known and unnamed species, called fowling agents by the industry, have been the biggest threat to the managers of Kalpakam nuclear power plant.  Not the terrorists, not the environmentalists.  Dozens of marine biologists have been making a living on these organisms for the past four decades.  The ‘fowling agents’ have been teaching them quite a few lessons on evolution besides clogging the pipes regularly and frequently.

If the desalination plants fail for a longer period, say more than a fortnight or so, there may not be water available for maintaining the core and the spent fuel pool.  Most of the desalination plants in India are based on Multi-stage flash (MSF) technology or reverse osmosis.  KKNPP plants use MVC technology in which  India does not have much expertise.  This means, in case of a serious problem, the experts will have to come from Israel.

MVC desalination uses 7 to 12 KWh of electricity per cub meter of water.[7] The consumption at   KKNPP will be 70 MW(e).  This is only less than 5% of the generation by two reactors.  If the reactors are not functioning and if there is a station black out, this might be a problem.

In the detailed project report and environmental impact assessment reports of four KKNPP reactors, Pechiparai reservoir was the source of water.  AERB was not satisfied with one single source of water.  The Board had asked NPCIL to have a backup source from another reservoir.  Today, all what we have is an ocean full of saline water and a complicated machine that is supposed to filter the life forms and suspended and dissolved solids, heavily dependent on electricity.

The nuclear scientists the world over have been living in cloistered techno-centric world. Accidents at Three Mile Island, Chernobyl and Fukushima are slowly but steadily changing this mindset.  The following paragraph from an IAEA document, published a week ago (19 Oct 11) shows that things are changing for the better. “Events in recent years have raised the spectre of new threats: that the greatest menace facing a plant’s operation lay outside its walls, not inside. Nuclear power generation does not occur in a vacuum, and with plants dotted around the globe exposed to the elements, the chance for interference by natural phenomena is ubiquitous. Exposure to the outside world can bring dangers such as hurricanes, earthquakes, fires, tsunamis and volcanoes.”[8]

The earlier the scientist-managers of NPCIL and technocrats of DAE acknowledge the elements outside their air-conditioned laboratories and beyond their tsunami-proof walls, the better for the country and the civilization.