Report Of The President's Commission On
The Accident At Three Mile Island           > TMI-2 > Kemeny

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The Accident


Commission Findings:


1.  In a number of important cases, General Public Utilities Corporation (GPU), Met Ed, and B&W failed to acquire enough information about safety problems, failed to analyze adequately what information they did acquire, or failed to act on that information. Thus, there was a serious lack of communication about several critical safety matters within and among the companies involved in the building and operation of the TMI-2 plant. A similar problem existed in the NRC. (See finding G.)

a.  The September 1977 incident at Davis-Besse, another plant with a B&W reactor, foreshadowed several aspects of the TMI-2 accident. A serious warning by a senior engineer at B&W that more precise instructions be given to operators "fell between the cracks." This warning, issued 13 months before the TMI-2 accident, if heeded, could have prevented the accident. (See also finding A.7.a.)

b.  Nine times before the TMI accident, PORVs stuck open at B&W plants. B&W did not inform its customers of these failures, nor did it highlight them in its own training program so that operators would be aware that such a failure causes a small-break LOCA.

c.  A report by an engineer at TVA questioning how operators might respond to rising pressurizer level and falling pressure was sent to B&W in April 1978. B&W took 9 months to respond and never advised its utility customers of the concern expressed in the report. The concern was similar to the one which B&W itself had identified from the Davis-Besse incident.

d.  TMI-2 had repeated problems with the condensate polishers. During the 18-month period before the accident, no effective steps were taken to correct these problems. These polishers probably initiated the March 28 sequence of events.

e.  The TMI-2 operators had never had specific training about the dangers of saturation conditions in the core, although they were generally familiar with the concept. Although Met Ed believed saturation had occurred in an incident a year before the accident that could have led to core uncovery, its hazards were not emphasized to the operators. When saturation occurred again on March 28, operators did not recognize the significance of that fact and take corrective action promptly.

f.  After an incident at TMI-2 a year earlier during which the PORV stuck open, an indicator light was installed in the control room. That light showed only that a signal had been sent to close the valve -- it did not show whether the valve was actually closed -- and this contributed to the confusion during the accident. (See finding A.3.) Timely attention to all of these factors probably would have prevented the accident.

2.  The GPU Service Corporation (GPUSC) had final responsibility for design of the plant. However, by its own account, it lacked the staff or expertise in certain areas to discharge that responsibility. Once construction was complete, GPUSC turned the plant over to Met Ed to run, but Met Ed did not have sufficient knowledge, expertise, and personnel to operate the plant or maintain it adequately.

3. Responsibility for management decisions was divided among the TMI site, Met Ed, and GPU. GPU recognized in early 1977 that integration of operating responsibility into one organization was desirable. A management audit by Booz, Alien, and Hamilton completed in the spring of 1977 recommended clarifying and reevaluating the roles of GPUSC and Met Ed in the design and construction of new facilities; strengthening communications between GPUSC and Met Ed; and establishing minimum standards for the safe operation of GPU's nuclear plants. However, integration of management did not occur until after the accident.

4.  The Met Ed management systems, procedures, and practices did not provide Met Ed a firm understanding of TMI's operations, nor were effective systems of checks and balances in use.

a.  Met Ed had a plan for a quality assurance program that met NRC requirements. The NEC requirements, however, were inadequate because they did not require quality assurance programs to be applied to the plant as a whole, but rather only to systems classified as "safety-related." Neither the PORV nor the condensate polishers were classified as "safety-related." In addition, the NRC did not require the level of independent review (i.e., outside of line management) normally found in the quality assurance programs of safety-critical industries.

b.  There was no requirement for an independent (i.e., outside of line management) safety assessment of operating procedures. Independent audit of the performance of surveillance procedures was required only every 2 years.

c.  Met Ed's implementation of its own quality assurance plan was found to contain significant deficiencies by the Commission staff and in an NRC post-accident audit of TMI-2. For example:

(i)    There were not enough inspectors to do the inspections required under the Met Ed plan.

(ii)   The NRC audit reported deficiencies in maintaining "as built" drawings and in the purchasing of "safety-related" equipment without . quality controls.

(iii)   Although all plant procedures were required to be reviewed every 2 years, there was no plan for such a review and no review had in fact been made of those TMI-2 procedures that were more than 2 years old.

(iv)   Although such inspections were required, Met Ed had not scheduled or conducted any inspections of materials, components, or equipment in storage.

(v)    There were deficiencies in the reporting, analysis, and resolution of problems in "safety-related" equipment and other events required to be reported to the NRC.

(vi)   Independent assessment of general plant operations was minimal.

d.  Met Ed did not go beyond NRC requirements in such areas as:

(i)    Requiring reporting, resolution, and trending of problems in plant equipment and procedures which were not "safety-related."

(ii)   Applying its quality assurance program to the operation of non-"safety-related" equipment and systems vital to plant operation, consistent with the importance of those systems to safety. For example, no quality assurance review was given to radiation monitoring equipment, control rod drive mechanisms, hydrogen recombiners, the PORV, or condensate polishers. In addition, Met Ed's quality assurance program was not applied to the maintenance or the procedures associated with such non-"safety-related" equipment.

As a result of these deficiencies, the safe operation of the TMI-2 plant was impaired.

5.  Utility management did not require attention to detail as a way of life at Three Mile Island. For example:

 a.  Management permitted operation of the plant with a number of poor control room practices:

(i)    A shift supervisor testified that there had never been less than 52 alarms lit in the control room.

(ii)   TMI Commission staff and NRC inspections noted a large number of control room instruments out of calibration and tags hanging on the instrument panel indicating equipment out of service. Operators testified that one of these tags obscured one of the emergency feedwater block control valve indicator lights.

(iii)   When shifts changed in the control room, there was no systematic check on the status of the plant and the line-up of valves.

b.  There were deficiencies in the review, approval, and implementation of TMI-2 plant procedures.

(i)  Although Met Ed procedures required closing the PORV block valve when temperatures in the tailpipe exceeded 130F, the block valve had not been closed at the time of the accident even though temperatures had been well above 130F in the tailpipe for weeks.

(ii)  Operators were not given adequate information about temperatures to be expected in the PORV tailpipe after the PORV opened.

(iii) A 1978 B&W analysis of a certain kind of small-break LOCA was misinterpreted by Met Ed. That misinterpretation was incorporated by Met Ed into the LOCA emergency procedure available at the time of the accident.

(iv) Operating and emergency procedures that had been approved by Met Ed and were in use at the time of the accident contained many minor substantive errors, typographical errors, and imprecise or sloppy terminology. Some were inadequate. (See finding A.6.)

(v) A 1978 revision in the TMI-2 surveillance procedure for the emergency feedwater block valves violated TMI-2's technical specifications, but no one realized it at the time. The approval of the revision in the surveillance procedure was not done according to Met Ed's own administrative procedures.

(vi) Performance of surveillance tests was not adequately verified to be sure that the procedures were followed correctly. On the day of the accident, emergency feedwater block valves which should have been open were closed. They may have been left closed during a surveillance test 2 days earlier.

c.  There were deficiencies in maintenance:

(i) After the accident, valves in the TMI-1 containment building exhibited long-term lack of maintenance. Boron stalactites more than a foot long hung from the valves and stalagmites had built up from the floor.

(ii) Review of equipment history for the 6 months prior to the accident showed that a number of equipment items that figured in the accident had had a poor maintenance history without adequate corrective action. These included the pressurizer level transmitter, the hydrogen recombiner, pressurizer heaters, make-up pump switches, and the condensate polishers.

(iii) Despite a history of problems with the condensate polishers, procedures were not changed to ensure that operators would bypass the polishers during maintenance operations to protect the plant from a possible malfunction of the polisher.

d.  After the accident, radiological control practices were observed to be deficient. Contaminated and potentially contaminated equipment was found in uncontrolled areas of the auxiliary building.

e.  Training of operators and supervisors did not give sufficient emphasis to a fundamental understanding of the reactor. There was no comprehensive evaluation of operator performance on the job to meet the requalification requirements of 10 CFR 55. (See finding F.)

f.  Reports of operating experience at other plants were screened by technical analysts who did not have nuclear backgrounds. They were given no instruction in how to screen such operating reports, according to Station Manager Gary Miller. The technical analysts routed experience summaries to designated people at TMI. The routing sometimes took several months. The person in the training department who was assigned to review these summaries often did not get to them for several months after he received them because of the press of other work. The training department held only one 2-hour class per year on operating experience at other plants.

g.  There was no group with special responsibility for receiving and acting upon potential safety concerns raised by employees.

h.  Management did not assure adequate identification of piping and valves throughout the plant. The Commission staff noted that pipe and valve identification practices were significantly below standard industrial practices. Eight hours into the accident, Met Ed personnel spent 10 minutes trying unsuccessfully to locate three decay heat valves in a high radiation field in the auxiliary building.

i.  Management did not assure that Licensee Event Reports (LER) met basic NEC requirements. A review of TMI-2's LERs disclosed repeated omissions, inadequate failure analyses, and inadequate corrective actions.

j.  Met Ed did not correct deficiencies in radiation monitoring equipment, although the deficiencies were pointed out by an NRC audit months before the accident.

k.  On November 3, 1978, a mechanic caused a complete shutdown of the plant, including exercising of emergency systems, when he tripped a switch on the polisher electrical panel, thinking he was turning on a light. The only corrective action was to put a guard on the switch.

l.  Sensitive areas of the plant were accessible to large numbers of people. On the day before the accident, as many as 750 people had access to the auxiliary building.

m.  The manual control station of the polisher bypass valve was nearly inaccessible and took great effort, in a physically awkward position, to operate.

n.  Iodine filters were left in continuous use rather than being preserved to filter air in the event of radioactive contamination. As a result, they did not have full capacity on the day of the accident. (See finding A.11.).