Safeguards Inspectors in Action: Behind the Scenes at Dukovany Nuclear Power Plant

Date Published: 15 March 2013

Nuclear technology has the potential to save lives, make food and medical supplies safer and produce energy. But it is also the basis for the development of nuclear weapons. One of the IAEA's core functions is to confirm that countries are abiding by their obligations not to use nuclear materials or equipment to produce nuclear explosive devices. To verify that nuclear materials are used solely for peaceful purposes, the IAEA has developed a safeguards system based on legal Safeguards Agreements. 178 States have entered into Safeguards Agreements with the IAEA, submitting nuclear materials, facilities and activities to the regular scrutiny of the IAEA's inspectors. Inspectors visit a wide range of nuclear facilities that are related to the nuclear fuel cycle. These include power plants, research reactors, fuel fabrication plants, uranium enrichment and reprocessing facilities. In November 2012, the IAEA conducted a 'Physical Inventory Verification (PIV)' at the Dukovany Nuclear Power Plant, in the Czech Republic, which is situated 170 km south east of Prague. This kind of inspection takes places after fresh fuel is loaded into a reactor core and the displaced irradiated fuel has been removed and transferred to the spent fuel pond. As the nuclear materials in both fresh fuel and spent fuel, namely plutonium and uranium could be used to manufacture nuclear weapons after further enrichment or reprocessing, it is essential the IAEA verifies that they are not diverted from peaceful use.
Inside the power plant's control room, the operators monitor the operational conditions of fuel in the reactor core. The reactors are fuelled by uranium dioxide UO<sub>2</sub>. The core is composed of 312 fuel assemblies. Each assembly consists of 126 fuel rods that contain the fuel pellets. Dukovany is one of two nuclear power plants in the Czech Republic. It has two main production units, each of them contains two pressurized water reactors. The plant supplies around 20 percent of the total consumption of electricity in the country. During an inspection, the IAEA inspectors are accompanied by the state inspectors and the operators of the plant. Inspections in European Union countries are carried out in cooperation with inspectors from EURATOM, the European Atomic Energy Community. Inspection activities include attachment and detachment of seals, installing and servicing of surveillance systems and verifying inventories, receipts and shipments at the facilities. Inspectors from the IAEA and Euratom look into the spent fuel pond. This fuel has been used in one of Dukovany's reactors. It has been removed since it no longer contains enough of the uranium isotope necessary to sustain nuclear fission - known as 'splitting the atom'. This splitting releases energy that is used to heat water and produce high pressure steam. The steam turns a turbine connected to a generator which generates electricity. The inspector uses a special night vision device (ICVD) to inspect the spent fuel pond. This enables him to observe the blue 'Cherenkov Glow' which is a unique characteristic of irradiated fuel.  The process allows inspectors to confirm that the fuel assemblies in the pond match those removed from the core, confirming that no fuel assemblies are missing. The spent fuel assemblies removed from the reactor are very hot and highly radioactive. They are stored under water which provides both cooling and radiation shielding. The spent fuel is stored this way for several years before being transferred to intermediate storage where it will spend around 50 years. The IAEA inspector verifies that the seals on the reactor core have not been tampered with. The seal used is an electronic seal, known as a VACOSS. The verification of the VACOSS seal is done on-site, using a seal reader which is a palm-top with dedicated software.  With this device the inspector can check the dates when the seal was opened and closed. The inspectors seal the spent fuel pond, which is situated next to the reactor. Metal seals are commonly used by IAEA and Euratom inspectors in the countries belonging to the European Union. They attach and detach seals on spent fuel ponds, reactor cores and surveillance cameras. The purpose is to verify that there has been no unauthorized access to the nuclear material under the seal. Detached common seals are taken back to Euratom and IAEA headquarters and examined to check whether they have been tampered with. IAEA inspectors need to check the surveillance cameras at the nuclear facilities. Some video systems operate 24 hours a day, while others are installed only for specific activities such as the loading and unloading of fuel from the reactor core.  These surveillance cameras in Dukovany have been monitoring the operational activities at the reactor core and the spent fuel pond. The inspector services the surveillance system and takes the memory card back to IAEA headquarters for analysis. Once detaching the seal from the camera to remove the memory card, the inspector closes it again and attaches a new seal. The inspectors also conduct verification activities on the fresh nuclear fuel. These include item counting and control of serial numbers. Using the inventories provided by the operators, the inspectors can detect if any of the fuel is missing. With the assistance of detectors, they can also measure whether the uranium in the fuel is enriched uranium. IAEA inspectors have a range of high-tech instruments. One of these instruments is a 'Cadmium Tellurium Detector'. This enables the inspector to confirm the presence of enriched uranium. This is important because whereas low enriched uranium used as nuclear fuel for power reactors cannot be used for making nuclear explosives, if diverted and enriched further it could be used for such purposes. The fresh fuel used at the Dukovany plant spends around three years in the reactor core. About once a year around a quarter of the core is unloaded, moved to the spent fuel pond and replaced with fresh fuel. The IAEA currently has around 250 inspectors. In 2012 they performed over 2000 inspections.