ML20116E296
| ML20116E296 | |
| Person / Time | |
|---|---|
| Site: | Fort Calhoun  |
| Issue date: | 07/30/1996 |
| From: | Andrews T NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV) |
| To: | |
| Shared Package | |
| ML20116E298 | List: |
| References | |
| 50-285-96-06, 50-285-96-6, NUDOCS 9608050197 | |
| Download: ML20116E296 (9) | |
See also: IR 05000285/1996006
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ENCLOSURE
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U.S. NUCLEAR REGULATORY COMMISSION
REGION IV
Docket No.:
50-285
License No.:
Report No.:
50-285/96-06
Licensee:
Omaha Public Power District
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Facility:
Fort Calhoun Station
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Location:
Fort Calhoun Station FC-2-4 Adm.
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P.O. Box 399. Hwy. 75 - North of Fort Calhoun
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Fort Calhoun. Nebraska
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Dates:
June 18-20. 1996
Inspector:
Thomas H. Andrews. Radiation Specialist
Approved By:
Blaine Murray. Chief. Plant Support Branch
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ATTACHMENT:
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Attachment
Partial List of Persons Contacted
Inspection Procedures Used
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9608050197 960730
ADOCK 05000285
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EXECUTIVE SUMMARY
Fort Calhoun Station
NRC Inspection Report 50-285/96-06
This reactive inspection was performed to assess the radiological problems
resulting from leaking fuel.
The focus was primarily on the radiation
protection organization's response to the radiological problems.
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Plant Suncort
The radiation protection organization responded well to the leaking fuel
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problems and aggressively addressed radiological issues.
The calculated exposure to a critical organ of a person in the
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unrestricted area offsite was over 50% of the design guidance in
10 CFR Part 50. Appendix I.
Additional measures were implemented to
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reduce releases to the environment.
Leaking fuel impacted plant operations and will likely jeopardize the
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licensee's goals for personnel exposure, radwaste volume, and operating
capacity factor.
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Reoort Details
Summary of Plant Status
The )lant was shut down throughout the inspection period.
This condition did
not lave an adverse impact upon the results of the inspection.
IV.
Plant Sucoort
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Hiscellaneous Radiological Controls & Chemistry Issues
a. Insoection Scooe
The inspector reviewed licensee documentation and conducted interviews
to determine the history of fuel failures during the current o?erating
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cycle using the guidance in NRC Inspection Procedure 83750. T1e
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inspector reviewed licensee assessments and conducted interviews with
licensee personnel to determine the impact leaking fuel was having on:
projected offsite doses, personnel exposures, plant operations, and
radioactive waste production.
b. Observations and Findings
b.1 Backaround
During the 1995 refueling outage, the licensee inspected fuel assemblies
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removed from the reactor core to identify leaking fuel rods.
Based upon
reactor coolant system chemistry results, the licensee anticipated
finding 3 leaking fuel rods.
However, thirteen leaking fuel and three
potentially leaking rods were identified. All sixteen rods were removed
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and encapsulated in the spent fuel pool.
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The licensee and the fuel vendor initiated an investigation into the
failure mechanism.
They determined that the failures were the result of
vibration induced fretting caused by forces induced from the flow of
coolant by the core baffle plates coupled with the frequency of the
reactor internals.
Using a specially designed test facility, the fuel
vendor was able to duplicate the types of failures observed.
According to the licensee, changes will be incorporated in the fuel that
is to be inserted during the next refueling outage.
Because the fuel
for the next cycle will be inserted in the center region of the core,
fuel with the existing design will be placed on the periphery of the
core.
Because problems have been identified with the existing fuel
design on the periphery of the core. leaking fuel can happen again in
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the next cycle.
The plant was operated within license limits, however, leaking fuel has
nad an impact on the operation of the facility. As early as
October 1995. the licensee observed indications in the reactor coolant
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chemistry that fuel failures had occurred.
Conditions worsened to the
point where the licensee initiated fuel integrity monitoring action
plans.
These action plans were based upon pre-established reactor
coolant activity levels and contained general guidance to assess,
document, and help the licensee develop a plan of action as needed.
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Coolant activity was used to project that 10 average power rods were
leaking.
Using the data from the previous cycle where the fuel failures
were on the periphery, lower power rods than average were assumed.
The
licensee estimated that there were currently between 10 and 25 leaking
fuel rods.
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b.2 Imoact on Proiected Offsite Doses
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According to Technical Specification 5.16.1 limitations on annual and
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quarterly doses from liquid and gaseous effluent to unrestricted areas
are to conform with Appendix I to 10 CFR Part 50.
A)pendix I contains
design guidance on maintaining doses to members of t1e public ALARA (as
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low as is reasonably achievable).
The licensee trended these results and determined that the Appendix I
design guidance associated with annual dose to critical organ from
gaseous effluent could be exceeded during 1996.
As shown in the table
below, at the time of this inspection, the calculated exposure to the
thyroid of an individual in the unrestricted area was 8.7 millirem.
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design guidance for dose to critical organ from gaseous effluent stated
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in 10 CFR 50 Appendix I limit is 15 millirem.
The licensee has set an administrative limit of 12 millirem (80 percent
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of the 15 millirem).
Once this point is reached, the licensee will
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evaluate the steps needed to continue operation.
Ap)endix I
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Jesign
Calhoun
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Exposure
Guidance
1996 Doses
Effluent Pathway
Type
Category
(millirem)
(millirem)
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Total Body Gamma
10
0.42
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Noble Gas
Total Body Beta
20
1.34
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Gaseous
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Total Body Dose
15
0.01
1-131
Critical Organ
15
8.70
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Total Body Dose
3
0.18
Liquid
Critical Organ
10
0.25
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Because of the concern regarding offsite environmental dose to critical
organ, the licensee was aggressively monitoring the plant for sources of
The monitoring program consisted of area radiation surveying
and air sampling.
Data was used to characterize areas and to identify
trends.
When elevated radiation levels were detected, the room was
isolated and leaks were reduced as much as possible.
Charcoal
adsorption /HEPA (high-efficiency particulate air) units were placed in
the room and the air recirculated to reduce iodine levels.
To minimize the amount of iodine released to the environment, the
licensee was installing charcoal adsorption units in the auxiliary
building vent.
This was intended to capture and hold iodine for decay.
When questioned by the inspector regarding potential consequences of a
fire in a charcoal adsorption unit, licensee staff stated that they had
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evaluated the fire loading associated with the charcoal.
The
ventilation system contained devices that would isolate the plant vent
if a fire were detected.
In addition, the licensee determined that the
quantity of charcoal (approximately 300 pounds) did not pose a
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significant risk of fire.
The licensee stated that there were areas that may be overly
conservative in the offsite dose calculation manual calculations. They
were considering reevaluating the offsite dose calculation manual
calculations to remove this excessive conservatism.
This may help scale
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the projected offsite results downward.
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3 Imoact on Personnel E.xoosures
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Doses to onsite workers have increased as a result of leaking fuel.
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dose increase was primarily from exposure to xenon gas.
The issue
regarding radiation exposure was complicated by a discovery made by the
licensee following the processing of the thermoluminecent dosimetry at
the end of the first quarter 1996.
Beginning in January 1996, the licensee stopped processing their own
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thermoluminecent dosimetry and obtained this service from a contract
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source. The contractor used a different methodology from that
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previously used by the licensee to assess the dose measured by the
thermoluminecent dosimeters.
The contractor methodology implemented the
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revised ANSI N13.11-1993 guidance.
The electronic dosimeters were used on a regular basis to " track" a
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worker's dose, and the official dose of record was from the
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thermoluminecent dosimeter.
Historically, the electronic dosimeters
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provided conservative estimates of worker doses.
When the dosimetry
results for the first quarter 1996 were reviewed, there was a
significant, nonconservative deviation between the electronic dosimeter
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results and thermoluminecent dosimeter results.
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In March 1996, during an outage. the licensee experienced very high
concentrations of xenon gas in containment.
Review of access records
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rcc. ..J there was a significant difference in dosimetry results for
people who entered containment during the March 1996, outage where there
was a high concentration of xenon gas.
People who did not enter
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containment had close agreement between the electronic dosimeter results
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and thermoluminecent dosimeter results.
Because xenon emits a low energy photon, this was originally not
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considered to be significant.
However. with substantially increased
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levels of noble gases, this was no longer the case.
Furthermore,
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according to the licensee's subsequent review of the algorithm used by
the thermoluminecent dosimetry processing contractor (ANSI N13.11-1993).
this low energy photon contributed to deep dose measurements.
The
licensee stated that the previous methodology would have considered this
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as a shallow dose, therefore, not as limiting as deep dose.
The licensee initiated an evaluation of electronic dosimeters.
thermoluminecent dosimetry pocket ion chambers, and survey
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instrumentation used by the licensee.
This evaluation was performed
using several low energy photon spectra Cesium-137. ano mixtures of
these sources.
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Preliminary results of this investigation revealed that:
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Electronic dosimeters greatly under respond to the low energy
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photon spectra while the thermoluminecent dosimeters over-
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responded to the same sources.
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The pocket ion chamber and survey instrument were found to be
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reasonably accurate when exposed to low energy photon spectra.
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Based on these results, the licensee was developing correction factors
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to adjust exposures observed by the electronic dosimeters to accurately
reflect the actual dose received by the worker.
This )ermitted better
comparison between the electronic dosimeters and the tiermoluminecent
dosimeters.
The cumulative exposure for 1996 was above the exposure goal for the
nonoutage portion of the year.
The licensee also anticipated that it
would be very difficult to meet the outage collective goal of 140
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person-rem.
The ALARA group was preparing to re-evaluate this goal.
The licensee anticipated the use of additional respirators for certain
jobs during the outage.
Because of the reduction in the use of
respirators following the implementation of the revised 10 CFR Part 20.
the licensee reduced the number of people who maintained current
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respirator qualifications.
However, training and medical evaluation
resources were readily available if needed.
Planning was in progress to
ensure personnel were trained and qualified as needed to support the use
of respirators,
b.4
Imoact on Plant Ooerations
Transient conditions have caused reactor coolant system activity to
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exceed the iodine dose equivalent technical specification limit of 1
microcurie / milliliter. When this occurred, additional monitoring
requirements were initiated as recuired. This happened on two
occasions; once in March 1996, anc once in June 1996.
The licensee em)loyed techniques to minimize the amount of iodine
released from t1e reactor coolant.
The most notable was the use of
higher lithium concentrations during midcycle outages to keep iodine
entrained in the coolant.
Two charging pumps were being operated to increase the reactor coolant
system cleanu).
The licensee evaluated the impact of the increased run
time on the clarging pumps and determined that the extra maintenance
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costs were offset by the reduction in doses.
The licensee was evaluating the use of a power ramp down at the end of
cycle.
This would be followed by a long cleanup period for the
beginning of the refueling outage.
Depending on the reactor coolant
activity, the cleanup Jeriod could last as long as 6-8 days instead of
10-12 hours. A slow slut down would reduce the amount of iodine
produced. The long cleanup would provide for the removal of more
radioactive material from the reactor coolant system, as well as permit
time for iodine decay.
b.5 Imoact on Radioactive Waste Production
The production of radioactive waste has significantly int eased compared
to previous years.
The licensee-increased the frequency of changing out
resin to improve the removal of activated products from the reactor
coolant system. According to information provided by the licensee. 2
resin liners have been filled in 1996.
This was especially notable when
compared to the period from 1987 to 1995 when 6 resin liners were
filled.
The licensee was preparing to perform additional analyses to evaluate
the isotopic mixture for various waste streams.
Because of increased
activity in the reactor coolant, the ratios of isotopes were likely to
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have changed.
These ratios were used to characterize certain types of
waste where measurements were not easily made and various isotopes were
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difficult to detect.
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The size of contaminated areas was not significantly impacted.
However,
contamination levels have increased.
This information was based upon
the activity of dry active waste streams.
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c. Conclusions
The radiation protection organization responed well to the leaking fuel
problems and aggressively addressed radiological issues.
The calculated exposure to a critical organ of a person in the
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unrestricted area offsite was over 50% of the design guidance in
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Additional measures were implemented to
reduce releases to the environment.
Leaking fuel impacted plant operations and will likely jeopardize the
licensee's goals for personnel exposure, radwaste volume, and operating
capacity factor.
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V. Manaaement Meetinos
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Exit Meeting Summary
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The inspector presented the inspection results to members of licensee
management at the conclusion of the inspection on June 20, 1996.
The licensee
acknowledged the findings listed.
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The inspector asked the licensee whether materials examined during the
inspection should be considered proprietary.
No proprietary information was
identi fied.
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ATTACHMENT
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PARTIAL LIST OF PERSONS CONTACTED
Licensee
R. Andrews, Division Manager. Nuclear Services
G. Cavanaugh, Licensing Specialist
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R. Conner. Manager, Training
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G. Cook. Su)ervisor. Licensing
S. Gebers. .ianager, Radiation Protection
R. Haug, Corporate Health Physicist
J. Herman. Manager, Outage Management
R. Jaworski, Manager. Design Engineering
T. Patterson, Division Manager, Nuclear Operations
D. Spires, Manager, Chemistry
NRC
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W. Walker, Senior Resident Inspector
INSPECTION PROCEDURES USED
83750
Occupational Radiation Exposure
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