Todays consumers have a boundless appetite for electricity, which power plants could never meet if it werent for a steady diet of lubricants. In this three-part series, LubesnGreases looks at some of the technologies, people and lubricants that help create the buzz.

October: Hydro

November: Wind

This month: Nuclear

It could be said that nuclear power plants are not so different from other types of power plants; its just that people treat them differently.

The same could also be said for the lubricants used in these facilities. Those used in nuclear plants are largely the same as those used in plants powered by coal or petroleum. But substantially more scrutiny is given to the lubricants that go into nuclear plants – as seems to be the case with everything. Whether undergoing testing that seems superfluous or being checked and rechecked, lubes used in nuclear plants spend a good deal of time under the magnifying glass. As LubesnGreases learned during a visit to a Virginia facility, its all part of the overriding effort to avoid nuclear accidents.

LubesnGreases took its tour at Dominion Energys North Anna Power Station, located near the small rural town of Mineral, Va. A subsidiary of Richmond, Va.-based Dominion Resources Inc., Dominion Energy is one of the nations largest suppliers of nuclear energy. The company also operates a number of conventional power plants from North Carolina to Illinois, but its nuclear facilities generate nearly 45 percent of the electricity used in Connecticut and more than 30 percent of that used in Virginia.

Splitting Atoms at the Lake

The North Anna station began operating in 1978 and sits on a man-made lake built to support it. The facility actually consists of two plants, each with capacity to generate 921 megawatts of power.

Like other nuclear power plants in the United States, only the front end of North Anna is nuclear. The process begins in the stations two nuclear reactors – shells of 8-inch steel that are 42 feet tall and 16 feet in diameter. The reactors, in turn, are inside 190-foot containment silos made of concrete that is up to four-and-a-half feet thick.

Inside the reactors, half-inch ceramic pellets containing low-grade uranium are used to fuel nuclear fission. Pellets are packed in the metal alloy rods, which are bundled into fuel assemblies. North Anna uses three assemblies at a time in each reactor, although individual rods can be withdrawn to control the rate of reaction.

Water flowing through the reactor – referred to as the primary water system – is heated to 600 degrees F, but is subjected to very high pressure to keep it from boiling. The primary water flows from a reactor to a steam generator, where it passes through a heat exchanger – metal tubes the thickness of a finger that transfer the heat to the secondary water system. Keeping the secondary system separate on the outside of the heat exchanger tubes prevents radiation in the primary system from proceeding beyond the steam generator.

The secondary water system turns to steam, which is piped to a separate building to turn a turbine generator, thereby creating electricity. The steam then cools and condenses by exchanging heat with a third stream of water, this one drawn continuously from Lake Anna and returned to the lake after it has cooled. Meanwhile, the secondary water loops back to the steam generator to await reheating.

Lubes and Radiation

There are few extraordinary lubrication requirements in nuclear power plants. First of all, there is very little lubricant in the radioactive area of the plant. There is relatively little mechanical movement and nothing to generate deposits like those that come from burners that run on fossil fuels.

Moreover, as unhealthy as it is for humans, high radiation levels do not affect lube oils, according to Steven Whetzel, head of North Annas engineering department. The station does use a certified lubricant for its Safety Injection Equipment. Exxon Terrestic 46 has been tested for its performance under the effects of radiation, Whetzel pointed out. The initial testing of a product to qualify is expensive to the vender and user, he added, but necessary to meet the high standard of integrity and reliability of the plants safety related equipment.

When youre talking about equipment that helps bring the plant to a shutdown in an emergency, you want to make sure that equipment is in top shape, he said. He added that this safety equipment has only ever been used in tests that Dominion performs each month.

The fluids and greases used elsewhere in facility are no different than those found at any other type of power plant. What is different is the level of precaution that North Anna takes with its lubes – care that is representative of the emphasis that the entire nuclear energy industry places on safety.

Safety is the top priority throughout Dominions nuclear program, spokesman Richard Zuercker said.

Obsessing Over Safety

Safety measures are layered like an onion, seemingly touching every aspect of facilities and operations at North Anna. The stations design includes a long series of systems aimed at preventing an accident with the reactor or leak of radioactivity. For example, it is important that the station never be without power, since the reactors need electricity to shut down safely. So Dominion wired the transformer outside the plant back to the plant, allowing it to supply its own electricity if the power grid blacks out.

In the event the transformer became disabled, the plant has four backup diesel generators, each strong enough to power a ship. The station would need two of the 12-piston generators to keep both plants operating. It has four. None has ever been used, except during periodic tests conducted to ensure their readiness.

Finally, the walls of the building housing each generator are designed to withstand the force of an airborne tree, just in case a tornado strikes at the same time the power is out and simultaneous to a transformer failure.

Many [of the stations] safety features are designed to protect the public under emergency conditions and are unlikely to ever be used during the plants entire lifetime, Zuercker said. Nonetheless, they are there if they are needed.

That preoccupation with safety goes beyond the physical aspects of the plant. Dominion says it takes an equally rigorous approach to preventing sabotage or accidents caused by human error. The parking lot in front of the plant office is open access. Approaching the plant, however, means getting through a gate manned by several guards, who search all vehicles. Once inside the facility, employees and visitors must gain clearance from another armed guard before being allowed through a security entrance.

A limited number of plant employees are permitted unescorted access to restricted areas. Those who are must first undergo background security investigations and psychological screening. Once approved, they are subject to ongoing requirements designed to ensure fitness for duty. These include random alcohol and drug testing, periodic evaluations and continual behavioral observation by trained supervisors.

Picky About Lubes

Given the overall attention to safety, its no surprise that plant maintenance personnel are meticulous about lubes. The plant has approximately 1,700 pieces of rotating equipment and uses 1,500 gallons of various lubricants in a year. Dwarfing that volume, however, is the turbine oil for the stations twin 921-megawatt generators-another 10,000 gallons every 18 months. Turbine oil (Chevron GST 32) is delivered in bulk and stored in 16,000-gallon tanks. Most of the 18 types of oil and 19 types of greases used at the station are delivered in drums and kept in vats in a small storage building.

Dominion takes samples of all products upon delivery and tests them to check that they meet specification. In the vats, they are filtered to three milicrons, in order to prevent potential contamination caused by the condition of containers.

Before installing lubes in any equipment, staff is required to document the procedure in logs kept in the storage building. Each vat has its own book and, attached to the book, its own key.

Its just another layer of safety to protect against human error, Whetzel said.

North Anna follows a condition monitoring program that includes oil analysis. Maintenance personnel take samples from every piece of lubricated equipment every month, and send them to an outside, independent lab that tests for wear metals, additive content, acid levels – anything that might signal degradation of equipment or the lubricant.

Its done more frequently if we ever see a trend that we need to monitor, Whetzel noted, and the thresholds for that are very low.

Just as the stations expectations for safe operations are very, very high, that may mean taking redundant precautions throughout the facility, including with its lubricants. But if thats what it takes to ensure against a nuclear accident, Whetzel said he and his coworkers dont mind a bit.