Bulletin 79-05: Nuclear Incident at Three Mile Island
NUCLEAR REGULATORY COMMISSION
OFFICE OF INSPECTION AND ENFORCEMENT
WASHINGTON, D.C. 20555
April 1, 1979
IE Bulletin No. 79-05
NUCLEAR INCIDENT AT THREE MILE ISLAND
Description of Circumstances:
On March 28, 1979 the Three Mile Island Nuclear Power Plant, Unit 2
experienced core damage which resulted from a series of events which were
initiated by a loss of feedwater transient. Several aspects of the incident
may have general applicability in addition to apparent generic applicability
at operating Babcock and Wilcox reactors. This bulletin is provided to
inform you of the nuclear incident and to request certain actions.
Actions To Be Taken By Licensees
(Although the specific causes have not been determined for individual
sequences in the Three Mile Island event, some of the following may have
For all Babcock and Wilcox pressurized water reactor facilities with an
1. Review the description (Enclosure 1) of the initiating events and
subsequent course of the incident. Also review the evaluation by the
NRC staff of a postulated severe feedwater transient related to Babcock
and Wilcox PWRs as described in Enclosure 2.
These reviews should be directed at assessing the adequacy of your
reactor systems to safely sustain cooldown transients such as these.
2. Review any transients of a similar nature which have occurred at your
facility and determine whether any significant deviations from expected
performance occurred. If any significant deviations are found, provide
the details and an analysis of the significance and any corrective
actions taken. This material may be identified by reference if
previously submitted to the NRC.
3. Review the actions required by your operating procedures for coping
with transients. The items that should be addressed include:
IE Bulletin No. 79-05 April 1, 1979
Page 2 of 3
a. Recognition of the possibility of forming voids in the primary
coolant system large enough to compromise the core cooling
b. Operator action required to prevent the formation of such voids.
c. Operator action required to ensure continued core cooling in the
event that such voids are formed.
4. Review the actions requested by the operating procedures and the
training instruction to assure that operators do not override automatic
actions of engineered safety feature without sufficient cause for doing
5. Review all safety related valve positions and positioning requirements
to assure that engineered safety feature and related equipment such as
the auxiliary feedwater system, can perform their intended functions.
Also review related procedures, such as those for maintenance and
testing, to assure that such valves ar e returned to their correct
positions following necessary manipulations.
6. Review your operating modes and procedures for all systems designed to
transfer potentially radioactive gases and liquid out of the
containment to assure that undesired pumping of radioactive liquids and
gases will not occur inadvertently.
In particular assure that such an occurrence would not be caused by the
resetting of engineered safety features instrumentation. List all such
systems and indicate:
a. Whether interlocks exist to prevent transfer when high radiation
indication exists and,
b. Whether such systems are isolated by the containment isolation
7. Review your prompt reporting procedures for NRC notification to assure
very early notification of serious events.
The detailed results of these reviews shall be submitted within ten (10)
days of the receipt of this Bulletin.
IE Bulletin No. 79-05 April 1, 1979
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Reports should be submitted to the Director of the appropriate NRC Regional
Office and a copy should be forwarded to the NRC Office of Inspection and
ENforcement, Division of Reactor Construction Inspection, Washington, D.C.
For all other operating reactor or reactor under construction, this Bulletin
is for information purposes and no report is requested.
Approved by GAO. B180225 (R0072); clearance expires 7-31-80. Approval was
given under a blanket clearance specifically for identified generic
1. Preliminary Notifications
Three Mile Island -
PNO-67 and 67A, B, C, D,
E, F, G
2. Evaluation of Feedwater
3. List of IE Bulletins issued
in last 12 months
Page Last Reviewed/Updated Friday, May 22, 2015