'We deserve to know what tests were conducted and what the results were. AERB owes a detailed explanation to the people of India and the region,' PMANE said. 'Why did it accept an RPV with welds, when the agreement explicitly mandated a weld-free RPV?' PMANE asked.
In what may be a breach of the Indo-Russian agreement on the Koodankulam plant, NPCIL and AERB have accepted a lower-quality Reactor Pressure Vessel (RPV) with significant implications on radiation safety, according to two documents unearthed recently by PMANE's Expert Committee.
The contracted design envisioned an RPV without any welds in the area surrounding the reactor core. The RPV, which is a 19 metre high, 4.5 metre wide cylindrical structure made of 200 mm steel, is critical to radiation safety because it houses the reactor core (fuel assembly) and the coolant system. According to the two documents – one authored by NPCIL scientists in September 2005 and the other a 2008 AERB document -- the original contract specified that the RPV will be constructed without any welds in the area surrounding the reactor core. The AERB document additionally states that “the vessel now used has two welds in the core region.”
“Welds are the weak links. They can become brittle with neutron bombardment and cause the RPV to break. If that happens, you have an international radiological disaster on your hands,” PMANE said. The AERB document devotes only one sentence to the safety concerns arising out of the welds. “The effect of neutron fluence on these welds was evaluated and found to be acceptable,” AERB states.
“We deserve to know what tests were conducted and what the results were. AERB owes a detailed explanation to the people of India and the region,” PMANE said. “Why did it accept an RPV with welds, when the agreement explicitly mandated a weld-free RPV?” PMANE asked.
This revelation assumes increased significance in light of NPCIL's recent denial to publish the Safety Analysis Report despite an order by the Central Information Commission to reveal its contents. The report would throw light on what increased risks people are being asked to take on as a result of the substandard design. Czech Republic shared Temelin VVER 1000 reactor's details on RPV integrity and other safety aspects with the Austrian parliament as a routine aspect of safety evaluation. The Indian parliament too should have access to these details, PMANE and Chennai Solidarity Group said.
Because the RPV houses all radiological components, its integrity over the lifetime of the reactor is of paramount importance. “Tremendous care must be taken to ensure that the steel casing used for the RPV does not become brittle with time after it is bombarded by neutrons,” said PMANE expert committee member Dr. V.T. Padmanabhan. “The area of the RPV surrounding the core, where the fuel assembly is stored, is the most impacted by neutron bombardment. It is safest if steel casing of the RPV in the area surrounding the core is without welds,” he said. Metals such as nickel and manganese present in the welds can increase their vulnerability to neutron bombardment.
The International Atomic Energy Agency and the European Union insist that welds in the core area, if any, should be subjected to tests that assess their strength under pressure and rapid temperature fluctuations. Such tests cannot be conducted after the insertion of fuel rods. Because the safety reports are not being shared with public, it is not known if the required tests have been conducted. PMANE, Chennai Solidarity Group and PMANE's expert members said that the Government's hurry to insert fuel rods is to avoid public scrutiny of the integrity of the welds.
PMANE's request for information relating to the Indo-Russian liability arrangement too has been denied on grounds that its revelation would affect bilateral relations. In this instance, there is clear evidence that the supplier has violated the contract and supplied a substandard RPV. However, it is generally known that the liability arrangement protects the Russian supplier in the event of any disaster.
“The Bhopal disaster was a result of substandard technology, cost-cutting and a devil-may-care attitude towards safety. The State and Central Governments are doing a replay of the Bhopal disaster,” PMANE and Chennai Solidarity Group for Koodankulam Struggle said.