[Federal Register Volume 60, Number 227 (Monday, November 27, 1995)]
[Notices]
[Pages 58387-58390]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 95-28835]
=======================================================================
-----------------------------------------------------------------------
NUCLEAR REGULATORY COMMISSION
Report to Congress on Abnormal Occurrences April-June, 1995;
Dissemination of Information
Section 208 of the Energy Reorganization Act of 1974, as amended,
requires NRC to disseminate information on abnormal occurrences (AOs)
(i.e., unscheduled incidents or events that the Commission determines
are significant from the standpoint of public health and safety).
During the second quarter of CY 1995, the following incidents at NRC
licensed facilities were determined to be AOs and are described below,
together with the remedial actions taken. Each event is also being
included in NUREG-0090, Vol. 18, No. 2, (``Report to Congress on
Abnormal Occurrences: April-June 1995''). This report will be available
at NRC's Public Document Room, 2120 L Street NW. (Lower Level),
Washington, DC, about three weeks after the publication date of this
Federal Register Notice.
Nuclear Power Plants
95-2 Reactor Coolant System Blowdown at Wolf Creek Nuclear Generating
Station
One of the AO reporting guidelines notes that major deficiencies in
design, construction, use of, or management controls for licensed
facilities or material can be considered an AO.
Date and Place--September 17, 1994; Wolf Creek Nuclear Generating
Station, a Westinghouse-designed pressurized water reactor nuclear
power plant, operated by Wolf Creek Nuclear Operating Corporation and
located about 5.63 kilometers (3.5 miles) northeast of Burlington,
Kansas.
Nature and Probable Consequences--An inadvertent blowdown of
approximately 34,868 liters (9200 gallons) of reactor coolant through
the residual heat removal (RHR) system to the refueling water storage
tank (RWST) occurred because of incompatible, concurrent RHR valve
manipulations. At the time of the event, the reactor had been shutdown
for 28 hours and was on RHR cooling (2413 kPa gauge and 149 C [350 psi
gauge and 300 F]). The event was successfully terminated in 1 minute by
operator intervention. There was only minimal interruption to heat
removal processes, and no core damage or fission product release
occurred. However, if the blowdown continued, the licensee estimated
that RHR cooling could have failed in about 3.5 minutes, the RWST
header could have filled with steam in about 6 minutes, and uncovering
of the core could have begun in about 30 minutes.
All of the emergency core cooling system (ECCS) pumps take their
suction from the RWST header line. If the ECCS pumps were started to
mitigate the blowdown after the RWST header filled with steam, a
common-mode failure of all ECCS pumps could have occurred as a result
of steam binding. The ECCS pumps could also have failed as a result of
pressure pulses caused by cold RWST
[[Page 58388]]
water collapsing the steam in the RWST and RWST header. If they failed,
successful mitigation of such an event would depend on the control room
operators' cognitive abilities to establish core heat removal via the
steam generators.
If core damage did occur, then a possibility for a significant
offsite release existed because the blowdown path in place at the time
bypassed the reactor containment.
Cause or Causes--This event was attributed to the following three
causes:
(1) Unrecognized design vulnerability--An RHR-RWST connecting line
was designed to provide operational convenience for refilling the RWST
after a refueling outage, but not for safety purposes. The
inappropriate use of this line while on RHR cooling could result in a
rapid blowdown event and a subsequent common-mode failure of all ECCS
pumps.
(2) Inappropriate use of the RHR-RWST connecting line--The licensee
inappropriately used the RHR-RWST connecting line to increase the boron
concentration of the RHR train. (Other boration paths existed that
would not have resulted in an inadvertent blowdown.)
(3) Inadequate work control--The licensee was deficient in the
control of maintenance and operational evolutions by allowing
incompatible activities to occur simultaneously. The control room crew
had ample warning of the potential adverse effects of these activities
just prior to the event, but failed to limit the concurrent
manipulation of selected RHR valves.
The licensee also had previous warnings of blowdown events from its
experience at Wolf Creek and from the following NRC Information
Notices: 90-55, ``Recent Operating Experience on Loss of Reactor
Coolant Inventory While in a Shutdown Condition''; and 91-42, ``Plant
Outage Events Involving Poor Coordination Between Operations and
Maintenance Personnel During Valve Testing and Manipulations.'' The
licensee's response to these warnings was that its administrative
controls adequately addressed the concerns.
Actions Taken to Prevent Recurrence
Licensee--The licensee implemented the following actions: (1) Chain
locked the isolation valve in the RHR-RWST connecting line, and made
the plant manager and operations manager solely responsible for access
to this valve; (2) removed the use of the RHR-RWST connecting line from
the RHR boration procedures; and (3) approached the Westinghouse Owners
Group to address the issue generically.
NRC--NRC issued Information Notice No. 95-03, ``Loss of Reactor
Coolant Inventory and Potential Loss of Emergency Mitigation Functions
While in a Shutdown Condition,'' to inform all reactor licensees of the
circumstances and potential consequences associated with the Wolf Creek
event.
95-3 Previously Unidentified Path for the Potential Release of
Radioactivity at Millstone Nuclear Power Station Unit 2
One of the AO reporting guidelines notes that a loss of plant
capability to perform essential safety functions, such that a potential
release of radioactivity in excess of 10 CFR Part 100 guidelines could
result from a postulated transient or accident (e.g., loss of emergency
core cooling system, loss of control rod system), can be considered an
AO.
Date and Place--December 6, 1994; Millstone Nuclear Power Station
Unit 2, a Combustion Engineering-designed pressurized water reactor
nuclear power plant, operated by Northeast Nuclear Energy Company and
located about 5.15 kilometers (3.2 miles) west-southwest of New London
County, Connecticut.
Nature and Probable Consequences--While the plant was in a
refueling outage, a systems engineer employed by the licensee
identified a condition that established a potential unfiltered release
path to the atmosphere that could have resulted in offsite doses in
excess of 10 CFR Part 100 guidelines in the event of a postulated loss-
of-coolant accident (LOCA). The licensee immediately declared the
enclosure building inoperable and promptly reported the condition to
NRC.
The Millstone Unit 2 design includes an Enclosure Building around
the reactor Containment Building to collect all leakage out of the
containment during a postulated LOCA. The Enclosure Building
Ventilation System contains a charcoal bed filtration unit to remove
radioactive iodine prior to discharging the Enclosure Building air out
of the 114.4-meter (375-foot) high Unit-1 stack. The condition
identified on December 6, 1994, was that the ventilation system
associated with the Hydrogen Analyzer cabinet and waste gas sample hood
fan, located within the East Electrical Penetration Room of the
Enclosure Building, would not isolate in the event of a LOCA. During a
postulated accident, this ventilation system, which does not contain a
charcoal filter unit, would draw Enclosure Building air (contaminated
with any containment leakage) from the East Penetration Room and
discharge it through the 45.8-meter (150-foot) high Unit 2 vent. The
lack of a charcoal filter and the lower release point would
significantly increase the potential of a thyroid dose in excess of the
10 CFR Part 100 guideline at the exclusion area boundary.
The Technical Specifications for Millstone Unit 2 require that the
Enclosure Building integrity be maintained to ensure that the Enclosure
Building Ventilation System limits the site boundary doses to within 10
CFR Part 100 guidelines following a postulated design basis accident.
NRC performed a design basis dose calculation which took into account
the lack of charcoal filtration and the lower elevation release path
which would result from the noted design deficiency. This calculation
indicated that an exclusion area boundary dose to the thyroid greater
than the 10 CFR Part 100 guideline of 3000 millisievert (mSv) (300 rem)
would occur. It also indicated that the whole body dose would not
exceed the 250 mSv (25 rem) 10 CFR Part 100 guideline. The NRC
calculation was very conservative in that it assumed that all of the
designed allowable containment leakage, following the design basis
accident, would be through the penetrations in the East Electrical
Penetration Room and released from the Enclosure Building through the
Hydrogen Analyzer Ventilation system.
Cause or Causes--The cause of this condition was an original design
deficiency of the hydrogen analyzer cabinet exhaust system.
Actions Taken to Prevent Recurrence
Licensee--The licensee modified the design to route the exhaust
path from the hydrogen analyzer cabinet into the enclosure building
ventilation system, thereby going through the appropriate filtration,
in order to reduce any post-LOCA radioactive release to below 10 CFR
Part 100 guidelines. The waste gas sample sink was relocated from the
enclosure building to the auxiliary building. This design modification
was implemented prior to the start up of Millstone Unit 2.
NRC--On February 16, 1995, NRC exercised enforcement discretion and
did not issue a violation. In accordance with the ``General Statement
of Policy and Procedure for NRC Enforcement Actions,'' (Enforcement
Policy) then set out at 10 CFR Part 2, Appendix C, this design
deficiency would normally be categorized as a Severity Level III
violation and enforcement action would normally be considered because
it involved a violation of the Technical Specifications and could have
resulted in 10 CFR Part 100 guidelines being exceeded in the event of a
LOCA. However, the exercise of discretion for the apparent Severity
Level III violation
[[Page 58389]]
was determined to be warranted in this instance because: (1) The
condition was identified by the licensee's staff as a result of a
questioning attitude by a system engineer and was promptly reported to
the NRC; (2) the condition, which existed since initial startup, was
difficult to discover and such identification was not likely by routine
inspection, surveillance and quality assurance activities; (3)
comprehensive corrective actions were taken within a reasonable time
period that involved an adequate root cause determination and a review
for failures caused by similar root causes; and (4) the condition was
caused by an old performance failure that is not reasonably linked to
present performance.
This event was determined to be plant specific due to the unique
design of the ventilation system.
Other NRC Licensees (Industrial Radiographers, Medical Institutions,
Industrial Users, etc.)
95-4 Medical Brachytherapy Misadministration at the University of
Virginia, in Charlottesville, Virginia
One of the AO reporting guidelines notes that a therapeutic
exposure to any part of the body not scheduled to receive radiation can
be considered an AO.
Date and Place--March 14, 1995; University of Virginia Medical
Center; Charlottesville, Virginia.
Nature and Probable Consequences--A patient was prescribed a manual
brachytherapy procedure using cesium-137 (Cs-137) sources loaded in an
applicator, for a total gynecological treatment dose of 3000 centigray
(cGy) (3000 rad).
During insertion of the applicator into the patient, one of the
sources fell onto the patient's bed and was unnoticed by the licensee
staff involved in performing the procedure. A nurse found the source in
the bed on March 15 and removed it. The source was reloaded into the
applicator and the physician revised the prescribed dose to 2500 cGy
(2500 rad). The licensee estimated that the source remained at
approximately 10 centimeters (4 inches) from the patient's foot for 18
hours and delivered a dose of about 13 cGy (13 rad) to the foot.
The licensee notified the referring physician and the patient of
the misadministration. An NRC medical consultant was obtained who
concluded that the patient was receiving appropriate follow-up care. In
addition, the licensee and the medical consultant concluded that the
patient will not experience any adverse health effects as a result of
the misadministration.
Cause or Causes--The licensee's staff involved in the brachytherapy
procedure were not familiar with handling of the applicator that
contained the Cs-137 sources. Also, because of anatomic characteristics
of the patient, the physician had difficulty inserting the source
carrier into the applicator. The design of the afterloading device
allows the source to slide out of the carrier if any unusual
manipulation of source carrier is required. The difficulty experienced
by the physician in inserting the source in the applicator and the
design of the source carrier resulted in the source falling out of the
carrier during the insertion process.
Actions Taken to Prevent Recurrence
Licensee--The licensee provided training for its staff, involved in
brachytherapy procedures, concerning the precautions which must be
taken when handling an applicator such as the one used in the subject
procedure. Also, emphasis was placed on the need to be more attentive
during the source insertion process in order to account for all
prescribed sources.
NRC--NRC conducted a special inspection on March 23-24, 1995, to
review the circumstances surrounding the misadministration. The
inspection report was issued on May 2, 1995. Enforcement action will be
taken as appropriate.
95-5 Medical Therapeutic Radiopharmaceutical Misadministration of
Iodine-131 at Massachusetts General Hospital in Boston, Massachusetts
One of the AO reporting guidelines notes that administering a
therapeutic dose of a radiopharmaceutical differing from the prescribed
dose by more than 10 percent and the actual dose is greater than 1.5
times the prescribed dose can be considered an AO.
Date and Place--May 9, 1995; Massachusetts General Hospital;
Boston, Massachusetts.
Nature and Probable Consequences--A patient was prescribed a 296
megabecquerel (MBq) (8 millicurie [mCi]) dosage of iodine-131 (I-131)
for hyperthyroidism; however, a dosage of 1106.3 MBq (29.9 mCi) was
administered.
Representatives of the hospital informed the referring physician
and the patient of the misadministration. An NRC medical consultant was
obtained to evaluate the event and stated that the higher dosage given
to the patient will result in a more likely achievement of the intended
therapeutic goal to eliminate the patient's hyperthyroidism.
Additionally, the consultant determined that it is unlikely that the
patient is at significant risk of experiencing long-term consequences
from receiving the higher dosage beyond the risk associated with the
prescribed dosage. Therefore, the impact on the patient's health is
expected to be negligible with no expected long-term disability. (The
intent of the prescribed dose was to ablate the portion of the thyroid
remaining after surgery and then support the patient with thyroid
supplement the rest of her life. This did not change with the
administered dose.)
Cause or Causes--The licensee stated that this event occurred
because of a human error. The technologist involved in this procedure
inadvertently switched the labeled lids on the vial shields containing
the I-131 dosages prescribed for different patients. Additionally, the
technician failed to check for the correct dosage on the vial label,
and the wrong dose was administered to the intended patient.
Actions Taken to Prevent Recurrence
Licensee--The licensee instituted a procedure for checking the vial
label before giving a dose. In addition, the licensee is obtaining a
second dose calibrator which will be used in the out-patient dosing
room of the Thyroid Clinic. Each dose will be re-assayed immediately
before the I-131 is administered to the patient, rather than relying on
the assay which was performed in the Thyroid Lab before the dose was
transported to the out-patient dosing room.
NRC--NRC performed an inspection on May 12, 1995, to learn about
the event and determined that it constituted a misadministration as
defined in 10 CFR 35.2. NRC determined that this was an isolated
violation of the licensee's Quality Management Program and issued a
Notice of Violation at the Severity Level IV on June 26, 1995.
95-6 Multiple Medical Brachytherapy Misadministrations at Madigan Army
Medical Center in Fort Lewis, Washington
One of the AO reporting guidelines notes that administering a
therapeutic dose from a sealed source such that the treatment dose
differs from the prescribed dose by more than 10 percent and the event
(regardless of health effects) affects two or more patients at the same
facility can be considered an AO.
Date and Place--February 1994 through May 1995; Madigan Army
Medical Center (MAMC); Fort Lewis, Washington.
[[Page 58390]]
Nature and Probable Consequences--Four patients were prescribed
brachytherapy procedures, using iridium-192 seeds of different source
strengths, and received doses other than those prescribed because of
the same computer input error. (The same computer input error could
cause either underdoses or overdoses because the algorithm used was
dose dependent.) Details of the misadministrations are as follows:
Patient A: The patient was prescribed a dose of 2800 centigray
(cGy) (2800 rad) for a gynecological brachytherapy treatment, but
received a dose of about 1680 cGy (1680 rad) instead.
Patient B: Event 1--The patient was prescribed a dose of 1600 cGy
(1600 rad) for lung treatment, but received a dose of about 2128 cGy
(2128 rad) instead.
Event 2--On another day, the same patient was prescribed a dose of
1500 cGy (1500 rad) for lung treatment, but received a dose of about
2350 cGy (2350 rad) instead.
Patient C: The patient was prescribed a dose of 3000 cGy (3000 rad)
for gynecological treatment, but received a dose of about 5142 cGy
(5142 rad) instead.
Patient D: The patient was prescribed a dose of 1500 cGy (1500 rad)
for a biliary tract treatment, but received a dose of about 2050 cGy
(2050 rad) instead.
The licensee does not expect the patients to experience any adverse
health effects as a result of the misadministrations.
Cause or Causes--Based upon NRC's initial review of the
misadministrations, it appears that the probable causes of the
treatment errors were failures to: (1) independently review or check
the data input to the computerized treatment planning system, and (2)
perform an independent check of dose rate calculations generated by the
treatment planning system.
Actions Taken to Prevent Recurrence
Licensee--The physics staff at MAMC promptly corrected the data
entered into the computer treatment planning computer, recalculated the
doses received by the patients, and took steps to ensure that
appropriate data will be used for future treatment plans.
NRC--NRC initiated an inspection on June 6, 1995, to review the
circumstances associated with the misadministrations and to review the
licensee's corrective actions. (As of the date of this report, the
inspection is ongoing.) An NRC medical consultant will review each case
in order to provide an independent assessment of the potential
consequences of the overdoses.
Dated at Rockville, MD this 20th day of November, 1995.
For the Nuclear Regulatory Commission.
John C. Hoyle,
Secretary of the Commission.
[FR Doc. 95-28835 Filed 11-24-95; 8:45 am]
BILLING CODE 7590-01-P
