{"id":52333,"date":"2026-05-05T07:38:45","date_gmt":"2026-05-05T05:38:45","guid":{"rendered":"https:\/\/blog.wika.com\/en\/?p=52333"},"modified":"2026-05-05T13:00:44","modified_gmt":"2026-05-05T11:00:44","slug":"level-measurement-in-nuclear-power-plants-reliability-during-accidents","status":"publish","type":"post","link":"https:\/\/blog.wika.com\/en\/anwendungen\/level-measurement-in-nuclear-power-plants-reliability-during-accidents\/","title":{"rendered":"Level measurement in nuclear power plants: Reliability during accidents"},"content":{"rendered":"

The N-ALM level sensor from WIKA is a specialised instrument for level measurement in nuclear power plants. It operates reliably under LOCA and BDBA conditions, even in the event of a total loss of power supply. Containing neither active electronics nor organic materials such as plastics or seals, the sensor withstands nuclear operating conditions. The instrument remains functional for up to one year, while almost everything else has long since failed.<\/strong><\/p>\n

11 March 2011, Fukushima Daiichi. A magnitude 9.0 earthquake followed shortly afterwards by a tsunami suddenly faces operators with a question to which no digital system can provide an answer: How much cooling water is still in the reactor? Is the level rising or falling? Such moments define the highest demands of nuclear technology and what experts refer to as a beyond design basis accident (BDBA) \u2013 namely scenarios that lie outside any planning basis.<\/p>\n

What counts when almost everything fails<\/h2>\n

Nuclear power plants go through various states during operation: from normal full-power operation and planned maintenance periods to design basis accidents (DBA), i.e. events for which a plant is structurally prepared. For scenarios beyond these limits, i.e. BDBA, measurement technology is needed that works when everything else fails. In severe accident management it is not millimetre-accurate values that are required, but trends, threshold values and plausibility. That is also how it is defined in the international standard IEEE 497.<\/p>\n

At the same time, the measurement technology must withstand temperatures up to 250\u00a0\u00b0C, pressures up to 10\u00a0bar, air humidity of 100\u00a0% and intense radiation \u2013 for months, without external power supply. Any attempt to solve this using programmable electronics is bound to be unsuccessful. Such components already fail at around 50\u00a0kGy. In a BDBA scenario, radiation doses a hundred times higher, up to 5.05\u00a0MGy, are to be expected. In addition, according to the IAEA and NEA, accident measurement technology must always be designed specifically for the plant.<\/p>\n

Level measurement in nuclear power plants: Three critical areas<\/h2>\n

For this task, WIKA has developed a specialised level sensor: the N-ALM level sensor with reed-chain technology for use in open tanks and pools as well as for applications with pressure vessels. The basic principle is simple. The sensor operates without active electronics and without organic materials such as plastics or seals, which can quickly lose their function under radiation, heat and moisture. This explicitly qualifies it for use under nuclear accident conditions. Depending on the reactor type (PWR or BWR) and the design of the containment, it is used in up to three areas, each with its own risk profile:<\/p>\n