Newspaper: The Patriot
Date: April 4, 1979
Title: Cold Shutdown Next Objective
Author: Richard Roberts, Staff Writer
A hazardous gas bubble that was considered a main stumbling block in cooling down the Unit 2 reactor vessel at Three Mile Island Nuclear Generation Station has been eliminated “for all practical purpose,” a federal Nuclear Regulatory Commission official said Tuesday.
Harold Denton, director of the NRC’s Office of Reactor Regulation, at a news conference in Middletown Borough Hall also said that the possibility of a hydrogen explosion in the reactor vessel or reactor containment building no longer is considered a “significant problem.”
But he did not rule out a possible evacuation of area residents, depending upon the method selected for cooling the reactor down.
In another development, Gov. Dick Thornburgh announced that the U.S. Food and Drug Administration and the State Department of Environmental Resources had discovered small amounts of radioactive iodine in some milk produced within an 18-mile radius of the plant.
The iodine 131 levels are not considered to constitute a health hazard.
“I think the danger point is considerably down from where it was a few days ago because of the concerns about the bubble and hydrogen explosion,” Denton said. “We can fall back on the traditional options for ringing the reactor core to a cold condition.
“The main obstacle to doing so is to pick one which doesn’t do further fuel damage and which doesn’t result in the release of highly radioactive water inside the containment to the environment.”
A potential danger remains that a loss of pressurized coolant in the reactor could cause the core to overheat and release highly radioactive products of fission from the fuel rod assemblies, which were extensively damaged during the initial accident March 28, he said.
“I think that the concern we had with the bubble was it interfered with the normal proven ways of cooling,” he said. “The hydrogen brought with it a chance for complete disruption of the coolant system due to an explosion.
“With those potentials out of the way, I expect there to continue to be frustrating problems, that the equipment may fail. But with each day that goes by, the core gets cooler.”
He attributed the decrease in size of the bubble to “a little bit of luck and a little bit of forethought.”
Denton said he hoped that “from here on out we can move rapidly” towards allowing the return of pregnant women and pre-school children to their homes within a five-mile radius of the plant. Thornburgh on Friday afternoon requested their evacuation and ordered schools with the radius closed.
Denton reiterated his stand that the governor must make any decision concerning an evacuation. He advised the governor Monday night that “routine, low-level” radiation is being released from the plant and that he is “very optimistic” about progress in proceeding toward cold shutdown.
But he said he was “not yet ready to give a prediction” when the reactor would be brought to cold shutdown. “The staff is looking at it,” he said. “But I’m hopeful we can now move forward as we’ve eliminated these (bubble and hydrogen explosion) problems.”
Before cold shutdown can be reached, the coolant that circulates inside the reactor vessel must be depressurized, the temperature must fall below the boiling point and a cooling system known as a residual heat removal system must be tested for leaks, he said.
The residual heat removal system will transport primary coolant outside the main containment building into the auxiliary building.
“Since the RHR brings contaminated water from the containment out and cools it and returns it, it’s very critical that we don’t turn it on until we have all the leaks or potential leaks in that system isolated and be sure the system would perform adequately for the type of conditions we’ve got,” he said.
The reactor is stable, he said. Temperature of the core is 281 degrees and the core pressure is 1,100 pounds per square inch. A few fuel rod assemblies remain above 400 degrees.
Special converters called “recombiners” have been put into operation to remove hydrogen gas from the containment building and combine it with air to form water, he said.
Thornburgh said milk from 22 dairy farms showed iodine 131 levels of from 11 to 46 picocuries per liter in samples were taken Saturday and Sunday.
Iodine 131 is a radioisotope that accumulates on grass, is ingested by cows and contaminates their milk. Radioactive iodine, when ingested by humans, collects in the thyroid gland.
The radioactive content of the milk is less than a proposed federal maximum recommended allowed level of 12,000 picocuries and less than the maximum of 300 picocuries found in locally produced milk in the wake of fallout from a 1976 Chinese nuclear weapons test.
“Based on these figures and advice from appropriate federal, state and medical authorities, I can say there is no present danger to consumers from milk produced in this state,” Thornburgh said.
Denton said the FDA had “refined their numbers,” and that the maximum amount of iodine 131 found in milk was 31 picocuries and averaged 10-20 picocuries per liter.
“If you were to consume milk like that for a month, the radiation level would be approximately the same as would be permitted under our limits for routine operations,” he said. “I don’t consider these radiation levels of 10-20 picocuries per liter any cause for alarm with regard to milk.”
The total amount of iodine released since the initial nuclear accident at Three Mile Island is about one curie, he said.
Radioactive iodine and cobalt have been found in wastewater dumped from Three Mile Island into the Susquehanna River, Denton said. The NRC and DER on Monday night asked Metropolitan Edison Co. of Reading, operator of the plant, to cease dumping the contaminated wastewater, he said.
He said he doubted that any radioactivity has been detected in the water supplies of cities downstream. “The plant has essentially been releasing radioactivity at or near, slightly above or slightly below our normal limits for releases,” he said.
The NRC will make “some further analyses” of the water, and Denton said he anticipated that MetEd eventually will be allowed to resume dumping the radioactive wastewater into the river.
Some radioactive gases have escaped from waste gas storage tanks during attempts to sample the gases, he said. “It’s difficult to take a sample without having a leak somewhere within the sampling point and back to the tank. The total amounts of radioactivity getting out aren’t changing the off-site dosage significantly,” he said.
In the wake of an instrument failure in the containment building, an NRC task force has been assigned to investigate the effects of high-level radiation on instruments, Denton said. A radiation level of 30,000 rems- 30 million millirems-has been measured at the top the inside of the structure.
The average annual radiation dosage for area residents is 100-200 millirems.
“Most of the instrumentation at the plant is redundant, and we have a means to get the information we are seeking,” he said. “But we do have a task force looking ahead and making contingency plans if we don’t lose vital instrumentation.”
A state Commerce Department spokesman said Tuesday that about 100,000 bottles of potassium iodide had been sent to Middletown as a precautionary measure by the FDA and that more is on the way.
Steven Fink, state Department of Commerce press secretary, said potassium iodide is a drug used to counteract overdoses of radiation. “It’s being housed in a storage facility in Middletown but I don’t know where,” he said. “It was not ordered by anyone in the state.”
He said the each bottle has about four dosages.