Power Surge At Savannah River Reactor Remains Unexplained, Panel Told
WASHINGTON (AP) _ An unreviewed calculation flawed four different ways led to the failed restart of a nuclear weapons production reactor, an Energy Department advisory panel was told Thursday.
But no one knows why the same reactor at the Savannah River Plant near Aiken, S.C., underwent a power surge a few days later, after a successful restart, the panel was told.
It was discovery of a flawed calculation decades ago that led the department earlier this year to order its remaining weapons reactors limited to half power. A runaway power surge with safety systems disconnected caused the 1986 Chernobyl reactor explosion in the Soviet Union.
Department officials have said their concern was not so much the two abnormal restart events in themselves, but delays in being told about them by the operating contractor, the Du Pont Co.
Du Pont reported the Aug. 10 power surge only in the next day’s routine operations report despite assuring the department on Aug. 9 it would be quicker to report unusual events.
The series of events at Savannah River’s P-Reactor was described in a report to the department’s new Advisory Committee on Nuclear Facility Safety by a subcommittee headed by Elmer Schwartz, associate dean of engineering at the University of South Carolina.
Richard Starostecki, deputy assistant secretary for environment, safety and health, told reporters that new communications agreements had been reached between Du Pont and the department, but the reactor in question was shut down Aug. 17 and would remain closed until investigators discover why power surged by 2 percent without explanation.
When the power surge occured, the reactor was 90 percent of the way to its planned half-power operating level.
″You aren’t supposed to have any power surges,″ Starostecki said.
The committee also was given an analysis of the events of Aug. 8-Aug. 17 done for Schwartz by Dana A. Powers of the Sandia National Laboratory in New Mexico.
Powers’ report said the surge was ″miniscule″ and though rare had happened before. It was quickly corrected by the operators. Schwartz said it was well within the trigger point that would have led to an automatic shutdown.
The three reactors at Savannah River produce no electricity. Neutrons produced in the nuclear reactions of uranium make either plutonium or tritium, a radioactive form of hydrogen, for nuclear weapons.
All three reactors were shut for various reasons when the department decided to finish a tritium production run in the P-Reactor after a 119-day shutdown. This was the longest idle period the reactor had ever undergone with a fuel core in place.
The flawed calculation of the expected strength of the nuclear reactions on startup was used to position the neutron-absorbing control rods, according to Powers’ report. The reactor becamed self-sustaining only when the rods where withdrawn far more than the calculation said they should have been, and self- sustaining operation could not be maintained.
The department admitted earlier that the calculation had ignored the buildup of helium in the reactor from decay of tritium during the long shutdown. Helium tends to ″poison″ or suppress the nuclear reaction.
Powers pinpointed three other flaws in the calculation he said no one reviewed.
-The actual history of the fuel was not used in the calculation. The analyst in question used the out-of-date planned use of the fuel. ″Oversight or not, this is a less readily excused error″ than neglecting helium.
-The presence in the fuel of samarium, a metallic element in the rare- earths group, was not sufficiently accounted for.
-Three control rods that couldn’t be raised were left out of the calculation.
″There appears to be no Department of energy standards on the nature of operational readiness reviews,″ Powers said.
Since the shutdown had been the longest ever, ″It is surprising then that no Department of Energy personnel were present for this restart. What kind of oversight is it that does not follow unusual events during this period of enhanced scrutiny of the production reactors?″ he said.
Powers said he found no evidence that ″desire for production at the expense of safety″ prompted the restart and in fact a fresh fuel charge would have optimized production after the long shutdown.