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Ensuring complete and safe containment at a nuclear power plant

3 September 2020

When a contractor at a nuclear power plant in the Southeastern United States needed to test the effectiveness of an accumulator, a nuclear reactor’s failsafe device in the case of a loss of coolant accident (LOCA), Atlas Copco Specialty Rental delivered the tools and know-how needed to ensure worker and community safety.

Nuclear Power Plant Project - Rental
Following a short-duration integrated leakage rate test (ILRT) at the plant, the contractor needed help testing the accumulator on one of the plant’s reactors, with both tests being vital to plant safety. The first test is meant to ensure that no radioactive materials are released into the environment in the case of a reactor accident or outage. The latter is meant to confirm that the reactor’s final safeguard against environmental leakage, the accumulator, is structurally sound and functioning properly. To test the accumulator, which is a large storage tank connected to the reactor’s cooling system, the vessel must be filled to 70% to 80% capacity with water, then topped off with a gas. Typically, nitrogen or oil-free air are pushed into the tank until it achieves a desired pressure and maintains that pressure for several hours. While the process is often performed by injecting nitrogen from the plant’s on-site supply or by buying the needed nitrogen in bulk, no nitrogen was currently available at the plant. Further, buying bulk nitrogen is very expensive, and determining just how much to purchase can be quite a challenge, especially for leak testing when the exact volume needed is an unknown until the process is underway. For these reasons, it was determined that the most efficient way to perform this test would be by using oil-free air or nitrogen, both of which are Atlas Copco specialties.

Leveraging an expert in air supply

Knowing that we could quickly deliver the sustainable complete solution needed to conduct the testing, in addition to implementing it with expert operators, the contractor called upon us to help with the job. Further, the testing would need to be done during the night shift, and thanks to our 24/7 service availability, we were available to provide immediate accommodation.

The accumulator being tested at the plant had a storage capacity of 800 cubic feet and would need to be slowly pressurized. In this case, a precise 8 psi/minute was required to protect sensitive equipment associated with the accumulator from damage. From a starting pressure of 200 psi, the internal pressure was gradually raised to 650 psi, the required level to successfully complete the test. Highly sensitive testing equipment was installed to monitor containment during the test. The accumulator was first filled with water to a capacity between 75% and 80%, then monitored for leaks and flow past check valves as oil-free air was introduced to raise the pressure.

A steady and strategic success

Our operators were able to closely monitor and precisely control the rate of pressurization in the accumulator by installing a D Booster compressor and equipping it with an HP ball valve featuring a pair of outlets, enabling precision pressure control as needed.

Using a handheld device, the controller inside the plant stayed in constant communication with the operator at the ball valve on the outlet of the D Booster, and the controller was able to guide the operator to exactly when and how much to open the ball valve to vent off pressure as needed. As requested by the project coordinators, our operators increased the pressure on the booster in increments of 100 psi and, through this careful process, were able to maintain a steady 8 psi/minute pressure increase up to the desired 650 psi.

In the end, the accumulator passed its inspection, and the customer was quite pleased with the use of oil-free air for the testing procedure and the economic benefits of replacing bulk nitrogen. In fact, they plan to use the same air-powered pressurization process for testing the plant’s remaining accumulators.

When the nuclear power plant needed to ensure that its last line of defense could effectively contain any radioactive materials, keep plant workers and the community safe in the case of a nuclear incident, we provided the technology, solution, and expertise needed to confirm safe operations.

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At Atlas Copco, we have been turning industrial ideas into business-critical benefits since 1873. By listening to our customers and knowing their needs, we deliver value and innovate with the future in mind. Great ideas reinforce sustainable development. At Atlas Copco Specialty Rental, we team up with our customers to set up state-of-the-art temporary air, flow, steam and nitrogen solutions. Our passionate experts have extensive application and equipment knowledge. We understand our customers' needs and can provide a total solution for any industry, no matter if it is for emergencies or planned projects. We are a division of the Power Technique business area, headquartered in Boom, Belgium and offer specialty rental solutions under several brands around the globe.