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The importance of sealing electrical cabling across nuclear industries

09 March 2011

“Protecting electrical equipment requires powerful solutions,” says Graham O’Hare, UK Managing Director of Swedish owned international safety seal manufacturer Roxtec. Here Graham explains why seals are so important in the nuclear sector.

The importance of sealing electrical cabling cannot be understated across industries. Failure to seal electrical cables could result in vital equipment malfunctioning or shutting down. This scenario could lead to huge disruption, massive costs and, in the worst cases, major accidents endangering lives and assets.

One industry which is acutely aware of the need to protect cables is the nuclear sector. Safety is being brought into sharp focus as the UK embarks on its multi billion pound decommissioning and new build nuclear programmes. These programmes must meet stringent safety standards and design and electrical engineers are right at the sharp end of this process.

Properly sealing power cables and utility systems in new and decommissioned buildings is a major area of expertise. Seals need to be extremely tough. They need to be right at the cutting edge of technology and able to withstand a wide range of hazards which could affect a nuclear site. This including fire, explosion, flooding, vibration, electromagnetic interference, dust and vermin.

One story which graphically explains the importance of deploying the latest safety sealing technology to protect electrical cabling is the Brown’s Ferry nuclear power plant emergency in the United States.
The Brown’s Ferry emergency of March 1975 was one of America’s worst nuclear incidents and nearly resulted in a nuclear disaster. It is highly relevant today as the UK nuclear industry embarks on a programme to build 12 new reactors around the UK.

So what happened at the Alabama based nuclear site? Both Units one and two at the plant were operating at full power, delivering 2200 megawatts of electricity to the Tennessee Valley Authority. Just below the plant's control room, two electricians were trying to seal air leaks in the cable spreading room, where the electrical cables that control the two reactors are separated and routed through different tunnels to the reactor buildings. They were using strips of spongy foam rubber to seal the leaks. They were also using candles to determine whether or not the leaks had been successfully plugged by observing how the flame was affected by escaping air. The electrical engineer put the candle too close to the foam rubber, and it burst into flame.

The fire disabled several safety systems, including the emergency core cooling system and the reactor core isolation cooling system. The emergency, which almost resulted in a major incident closed the plant for one year.

However, using a safety seal – instead of foam – can prevent an incident like this from happening. A seal needs at the very least to be tested and certified to withstand fire for over three hours.

It is worth stating just how rigorous the process is to certify a seal in the nuclear sector. Firms need to be able to show considerable depth in their technology and commitment to research. Roxtec for example had to meet 25 different criteria including quality, sustainable development, nuclear safety, values, R&D and competitiveness to win work with nuclear giant Areva and its Olkiluoto 3 (OL3) project in Finland.

Outside the UK the nuclear sector is also seeing considerable growth and increased demand for innovative safety products. One such market is China. For example working with China National Power Engineering Co, Roxtec has secured contracts to supply the Taishan Nuclear Power Stations 1 & 2 in Guangdong. In Unit 2 seals are being used in the main structure of the reactor island, forming part of a compartmentalised fire protection system.

Here seals are vital in the containment of electrical fires and can also protect against flood and air releases.

As the nuclear industry continues to grow and dominate power production across the globe the need to find new and innovative forms of safety will remain a constant challenge.

Research and development and the ability of electrical and mechanical engineers to work closely with manufacturers will play a huge role in developing the next generation of safety equipment.

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