The challenge
The accident at the Fukushima Dai-ichi Nuclear Power Plant in Japan in March 2011 is one of only a few serious nuclear accidents in the history of the global nuclear industry. The focus of nuclear operators worldwide, and at EDF Energy, continues to be on safety as the nuclear industry emerged from this tragedy with an even stronger commitment to nuclear safety. The Japanese Earthquake Response (JER) programme, set up after the latest nuclear accident in Japan, has a unique safety focus at a level not explored before; to enhance the safety margins of EDF Energy’s entire fleet to protect against those unpredictable, extreme, ‘beyond design basis’ events.
Beyond design basis (BDB) events are those catastrophic and severe events that exceed the normal design basis requirements of a plant. They are rare initiating events. Fukushima has brought into the scope of worldwide nuclear safety that additional protection is required against these events to prevent a large uncontrolled release of radioactivity.
Calder were tasked with the design and build of lightweight, high pressure auxiliary cooling water pump packages capable of being deployed on demand throughout the UK. The packages were to be able to operate within a range of flows and pressures to suit the specific requirements of the power stations. Package 1 (10 units) to provide high pressure emergency cooling through the existing cooling system. Package 2 (2 units) to be dual use. In addition to high pressure cooling, the units are to be capable of flooding the reactor containment vessel.
The solution
With reliability paramount, Calder selected Hammelmann high pressure plunger pumps coupled with diesel engines and transmissions and mounted them on a robust baseframe. The units are installed in weather enclosures designed to ensure easy access to components. Powered hose reels (high pressure) and lay-flat hoses (flooding) are stored within the enclosure making the packages self-contained.
Various weight-saving measures were incorporated into the unit. The largest of these savings was through the design and manufacturing process of the baseframe and a detailed stress analysis was carried out on the whole frame to minimise material use. The base frame was leak tested and then stress analysed using FEA (Finite Element Analysis) techniques.
Other design considerations were that the structure had to be designed to accommodate 45 degree pitch when hook loading onto the Unimog. The structure was designed to accommodate 38 degree roll superimposed when off-road in the form of load shocks when loaded onto the Unimog. And due to the lightweight structure, the loads exerted by the lifting of the unit via a lifting beam and crane and when transporting by forklift also had to be considered.
Each unit was required to have a hose reel mounted inside to enable all parts to be transported as one. Research showed there were no hose reels on the market that could be procured to enable the type and length of hose to be stored and reeled in and out. Calder, therefore, designed its own hose reel in order for it to be as light as possible and still function as required. The hose reel is electrically driven via the skid-mounted on-board batteries.
The result
Utilizing the latest 3D software and FEM analysis, and drawing on their extensive experience of producing bespoke pump packages for operation in some of the harshest environments worldwide,
Calder designed and built 12 units which exceeded the customer’s expectations. The project was a success. The jetter package design was proven to be technically compliant by the use of detailed engineering analyses and thoroughly tested during the Factory Acceptance Test phase.
Calder hosted the unit/vehicle interface trials, provided operation and maintenance training, and offers full product support. The customer also tested the equipment in practice emergency scenarios should the need for the units to be used arise.
The customer now has numerous high pressure pump units that are lightweight, portable, capable of being deployed by off-road vehicle, and feature on-board powered hose reels for ease of use during high pressure pumping operations.
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