THE VIRGINIAN-PILOT
Copyright (c) 1995, Landmark Communications, Inc.
DATE: Monday, April 3, 1995 TAG: 9504030048
SECTION: LOCAL PAGE: B1 EDITION: FINAL
SOURCE: BY SCOTT HARPER, STAFF WRITER
LENGTH: Long : 106 lines
Not long ago, engineers at the Surry nuclear power plant made a disturbing discovery: Not enough cooling water was reaching some of the most sensitive equipment at the facility, including the reactors.
A team of investigators was dispatched quickly to try to determine what was blocking the flow. What they found was not pretty.
Long, stringy mats of what resembled spinach casserole gone bad were growing almost everywhere. These green blobs were clogging an intake system that each day is supposed to deliver millions of gallons of water from the James River.
The Nuclear Regulatory Commission soon got edgy. The federal agency put the Virginia Power-owned plant on notice that something - anything - had to be done to combat what has become known as ``the hydroids problem.''
Virginia Power is not alone. Hydroids - aquatic animals akin to jellyfish and coral - have played the role of unwanted house guest for years in the Chesapeake Bay watershed.
Looking remarkably like common seaweed, the animals have invited themselves into power plants, fishing nets, crab pots, boat engines and even Navy warships.
Indeed, the Navy currently is battling its own hydroids problem at the Norfolk Naval Shipyard in Portsmouth, where several ships have had their cooling systems invaded, officials said.
Since Virginia Power first discovered these barnaclelike animals in coolant pipes in 1990, the utility has spent about $400,000 a year to clear hydroids from pipe walls and heat exchangers, said David A. Christian, the plant manager at Surry.
The utility also hired Bob Diaz, a marine biologist at the Virginia Institute of Marine Science, affiliated with the College of William and Mary, to study and help devise a long-term strategy for fighting hydroids.
Diaz describes the experience as ``quite bizarre.''
``They took us into the plant itself (where the nuclear reactors are contained), and we were walking around in these huge pipes,'' Diaz recalled. ``You could see these things literally growing in the plant. It was like a scene out of a movie.''
The plan eventually drafted was a five-year, $6 million maintenance program that relies more on engineering and street-smarts than toxic chemicals, Diaz and Christian said.
And so far, it seems to be working, according to the NRC, which gave Virginia Power high marks for coping with its biological intruder on a report card issued in March.
``It remains an operational nuisance, but they seem to have nicely avoided what could have become a safety problem,'' said Morris Branch, NRC's resident inspector at Surry.
But Branch quickly added: ``They still have a long way to go. This seems to be one of those things that isn't going to go away.''
There are about 60 types of hydroids in the Bay watershed. Most thrive in the saltier waters of the Bay, while only a few live in rivers and creeks that have less-salty water, Diaz said.
Like other marine creatures, their ability to proliferate varies according to weather and water conditions. They seem especially to enjoy dry, warm weather, such as summer, Diaz said.
``There's more of them in the Bay than around Surry,'' he said. ``The trick is - and the reason you don't hear more about them - is there's no power plants for them to get into in the middle of the Bay.''
Officials stress that hydroids never put Surry in danger. But the animals are blamed for the plant failing a key water-flow test, which the NRC requires as an assurance that sufficient water is available to cool reactors, Branch said.
Hydroids also caused the plant to curtail its electricity output at certain times, usually in the summer, because insufficient water was available to operate at full throttle, Christian said.
``They've been a real pain, I'll say that about them,'' Christian said.
One crack in the plant's defense was inadequate screening on intake pipes that extend into the James River. Hydroids, along with eels and small grasses, slipped through screens that were too big and corroded.
As part of the $6 million maintenance program, Christian said, new steel screens with a tighter mesh-grid are being installed.
Also, instead of pouring strong chemicals down intake pipes to kill existing hydroids, technicians are sealing sections of the cooling system to starve hydroids of two things essential for their survival: oxygen and water.
Crews then are sent into the pipes where they pull dead hydroids from walls and floors. Christian said crews fill 10 to 12 large trash bags a day with dead hydroids.
Hydroids depend on the flow of water over them for food and oxygen, Diaz explained. As they attach to solid objects with a sticky substance released from their rootlike tentacles, they draw oxygen from water and sting tiny plankton that float by. The plankton are then ingested through a small mouth.
By closing down sections of coolant pipes, the plant loses some of its backup capacity. So Surry is experimenting with mild chemicals as a shielding agent against hydroids to avoid disrupting operations.
``We're still searching,'' Christian said. ``It's a constant effort to keep up with these things.'' ILLUSTRATION: VIRGINIA POWER color photo
A Virginia Power engineer at the Surry nuclear power plant inspects
a pipe coated with hydroids, animals that look like seaweed. The
utility spends about $400,000 a year to rid the pipes of the
animals.
Virginia Institue of Marine Science color photo
A colony of hydroids...\
KEYWORDS: SURRY NUCLEAR POWER STATION by CNB