ML20133Q284
| ML20133Q284 | |
| Person / Time | |
|---|---|
| Site: | McGuire, Mcguire  |
| Issue date: | 08/02/1985 |
| From: | Hosey C, Weddington R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| To: | |
| Shared Package | |
| ML20133Q202 | List: |
| References | |
| 50-369-85-22, 50-370-85-23, NUDOCS 8508150089 | |
| Download: ML20133Q284 (9) | |
See also: IR 05000369/1985022
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UNITED STATES
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NUCLEAR REGULATORY COMMISSION
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101 MARIETTA STREET,N.W.
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ATLANTA. GEORGI A 30323
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Report Nos.:
50-369/85-22 and 50-370/85-23
Licensee: ~ Duke Power Company
422 South Church Street
Charlotte, NC 28242
Docket Nos. : 50-369 and 50-370
License Nos.: NPF-9 and NPF-17
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Facility Name: McGuire 1 and 2
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Inspection Conducted: June 10 - 14, 1985 and Enforcement Conference July 12, 1985
Inspec"or: hNi
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R. E. Weddington
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Date Signed
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Accompanying Personnel:, T. G. Lee
Approved by:
cPA
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C. M. Hos'ey? Sectioi Chief
Date Signed
Division of Radiation Safety and Safeguards
SUMMARY
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Scope: This special, unannounced inspection involved 34 inspector-hours on-site
responding to a report of an apparent exposure to the skin of the whole body of a
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licensee employee in excess of the limits of 10 CFR 20.101(a).
Results: Two violations were identified:
(1) exposure to 1 cm2 of the skin of
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the whole body of a licensee employee in excess of the limits of 10 CFR 20.101(a)
and (2) failure to post a radiation area.
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REPORT DETAILS
1.
Persons Contacted
Licensee Employees
- T. L. McConnell, Plant Manager
- J. W. Foster, Station Health Physicist
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- N. McCraw, Compliance Staff
- W. F. Byrum, Health Physics Staff
- B. Hamilton, Superintendent of Technical Services
- B. Travis, Scheduling
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- D. J. Rains, Superintendent of Maintenance
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- P. B. Nardoci, General Office Licensing Staff
T. Keane, Corporate Health Physicist
Other licensee employees contacted included two foremen, six technicians, a
mechanic, a nuclear equiprcent operator and two office personnel.
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NRC Resident Inspectors
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- W. Orders, Senior Resident Inspector
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R. Pierson, Resident Inspector
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- Attended exit interview
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2.
Exit Interview
The inspection scope and findings were summarized on June 17, 1985, with
those persons indicated in paragraph 1 above.
The following issues were
discussed in detail:
(1) an apparent violation for exposure to the skin of
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the whole body of a licensee employee in excess of the limits of
10 CFR 20.101(a) (paragraph 3) and (2) an apparent violation for failure to
post a radiation area (paragraph 4).
The licensee acknowledged the
inspection findings and took no exceptions.
The licensee did not identify
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as proprietary any of the materials provided to or reviewed by the inspector
during this inspection.
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3.
Overexposure Investigation (92700)
On June 7,1985, the licensee notified Region II that a licensee employee
had apparently received an exposure to the skin of his whole body of
10.6 Rems, which is in excess of the quarterly skin exposure limit of
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7.5 Rems given in 10 CFR 20.101(a).
The exposure was caused by a single
cobalt-60 (Co-60) particle that was discovered on the worker's skin when he
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exited the Unit 1 containment.
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Through discussions with licensee representatives, the inspector determined
that the individual in question was a contractor employee supporting the
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Unit I steam generator tube plugging.
At approximately 2200 hours0.0255 days <br />0.611 hours <br />0.00364 weeks <br />8.371e-4 months <br /> on
June 5,1985, the individual exited the Unit I lower containment access
after having assisted another contractor employee who was plugging tubes
inside the 1-D steam generator.
The individual had primarily worked from
the steam generator platform with video cameras.
The licensee had
positioned an Eberline PCM-1 portal monitor in the vicinity of the contain-
ment exit to perform a prt:liminary contamination check prior to personnel
going to the whole body frisking station in the vicinity of the change rooni.
After removing his protective clothing at the containment exit, the worker
stepped into the portal monitor and set off the alarm.
Heal th physics
personnel determined that the worker was contaminated in the vicinity of his
left arm pit by using a RM-14 portable frisker with hand-held probe,
however, the amount of contamination could not be quantified due to it
exceeding the maximum scale of the instrument (50,000 counts per minute). A
survey was then performed using an Eberline R0-2 beta-gamma survey meter
which indicated that the contamination was reading 0.5 millirem per hour
gamma and 58 millirem per hour betc.
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The worker was decontaminated by wiping the contaminated area with a wet
paper towel.
The decontamination material was retained and was determined
by analysis on a GeLi dectector to be a single 1.2 microcurie particle of
It appeared that the Co-60 particle had remained on the inside of the
protective clothing worn by the worker after they were laundered and was
subsequently transferred to the worker's skin after he put them on.
The
individual had worn a plastic suit over the top of his protective clothing
inside the containment and there was no evidence that the plastic suit had
been torn or damaged.
Personnel from the licensee's corporate health physics staff performed
calculations to determine the amount of exposure the individual had incurred
due to this contamination event.
It was assumed that the exposure was
received over an approximately two hour period from the time the protective
clothing was put on in the dressing room until the contamination was
successfully removed.
The resulting exposure estimate was 10.6 Rem to the
skin of the whole body distributed over a one square centimeter area, which
when added to the previous skin of the whole body exposure during the
current calendar quarter of 580 millirem, gave the individual a total dose
for the calendar quarter of 11.18 Rem to the skin of his whole body.
The licensee believed that the high activity Co-60 particles were produced
by neutron activation of elemental cobalt found in stellite.
During
previous outages valves composed of stellite had been lapped in place inside
the containment.
Studies performed by the licensee indicated that as much
as 40 percent of the debris produced by this process remained on the valve
seat even after cleaning. This material was transported through the reactor
core by the primary coolant and subsequently plated out on the interior of
the primary piping.
Smears performed by the licensee inside containment
during the current outage were determined to contain high activity Co-60
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particles mixed with other contaminants.
Licensee surveys of the facility
revealed the only place that these high activity Co-60 particle were
discovered disassociated from other contaminants was in the contaminated
laundry area.
On June 7, 1985, a 0.5 microcurie Co-60 particle was found
on the floor of the laundry area while performing a massolin mopping of the
area.
A licensee representative stated that a high activity Co-60 particle
had also been discovered inside one of the clothing dryers.
Since the
laundry area was the only place that these high activity Co-60 particles had
been identified disassociated from other contaminants, the licensee
determined that the likely source of the personnel contamination was the
laundered protected clothing.
The circumstances surrounding the event of
June 5,1985, and other previous contamination events also support the
conclusion that high activity Co-60 particles remained on the protective
clothing after laundering and was the source of the personnel contamination.
The licensee had documented seven other contamination events that they
believed were similar and that occurred prior to the one that had caused the
apparent overexposure.
These events occurred during the period April 12
through May 31, 1985.
Five of the seven events involved personnel
contaminations discovered after individuals had worked in protective
clothing. The contamination levels associated with these events ranged from
6000 counts per minute to a single particle reading 490 millirem per hour
beta.
The exposure estimates to the skin of the whole body of the
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contaminated individuals ranged from 15 to 5510 millirem.
As these contamination events occurred the licensee initiated a number of
actions to identify and eliminate the source of the contamination.
The
laundry operation was identified as a likely source of the problem early on
in the licensee's investigation.
Independent of the personnel contamination
problem,'the licensee had started using an off-site contractor to laundry
used protective clothing.
The licensee was using the off-site contractor
laundry service when the second and third contamination events occurred on
May 2 and 3, 1985 occurred.
The licensee terminated the service contract
and began laundering used protective clothing on-site again to preclude any
possibility that the licensee's protective clothing was being cross con-
taminated at the contractor laundry by washing with contaminated clothing
from other facilities.
The permissible level of contamination the licensee permitted on laundered
protective clothing was one millirem per hour.
The survey on laundered
protective clothing had consisted of a frisk with a portable beta-gamma
survey _ meter with hand held probe paying close attention to the knees,
elbows, arms and ' seat with the rest of the clothing receiving a less
detailed scan. When the licensee began laundering protective clothing again
on-site in mid May 1985, they began a detailed survey of the outside of each
item of clothing after it came from the dryer.
They also, for a period of
time, surveyed the protective clothing in the dressing room innediately
prior to the individual putting it on.
After the apparent overexposure
event on June 5, 1985, they began to perform detailed frisks of the inside
and outside of each item of protective clothing after it was laundered.
After several days, the surveys were relaxed to just the outside of each
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item.
On June 13, 1985, the licensee informed the inspector that they were
going back to frisking both the inside and outside of the laundered garments
based on a corporate health physics staff evaluation of the question.
As a
long term solution to the problem, the licensee stated that they are
pursuing obtaining an automated clothing scanner.
The licensee had required that personnel working in the laundry wear a
labcoat and rubber gloves, which was changed to a full set of protective
clothing in mid May 1985. A frisker was also installed at the exit from the
laundry and all personnel leaving the area were required to perform a whole
body frisk.
The licensee also changed several of their limits within the laundry area.
The licensee had permitted protective clothing contaminated up to
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50 millirem per hour to be laundered.
The licensee decreased the limit to
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25 millirem per hour, however, a licensee representative stated that they
would further decrease the limit to 10 millirem per hour by July 1,1985.
The licensee also surveyed the washer and dryer for contamination after each
load was removed.
Massolin moppings of the laundry area floor every shift
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was implemented.
The licensee implemented a color coding and segregation procedure for
protective clothing.
White protective clothing was worn next to the
worker's skin and was worn as the outer garment in areas of low contamina-
tion potential.
Yellow protective clothing was used as the outer suit when
double layers of protective clothing were required.
A yellow plastic suit
was also required over the double layer of protective clothing in areas of
high levels of contamination, such as inside the steam generator.
The
yellow and white protective garments were segregated after use and laundered
separately.
The licensee also replaced all of their old protective clothing
with new protective clothing on June 10, 1985.
The licensee had placed a portal monitor at the entrance to the radio-
logically controlled area to determine if personnel were being contaminated
by these high activity Co-60 particles from some unidentified source outside
of the controlled area.
No problem of this nature was detected and the use
of the entrance portal monitor was discontinued.
The licensee conducted an inventory of all their sealed sources,
particularly those used in radiography, and determined that none were
missing.
Leak checks also revealed that all of the Co-60 sources were
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intact.
During the inspection, the inspector examined the source storage
area and accountability log and determined that proper source control was
being maintained and that there were no records of missing sources.
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The licensee had conducted a special grid survey of the facility to deter-
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mine if there was some previously unidentified soum ' of the contamination.
No such source was identified.
The licensee aP,o
splemented periodic
massolin moppings of the uncontrolled areas t
thr iuxiliary building,
laundry, changeroom, and the pathway from th' ,' sad . om to the containment
accesses.
On June 7,1985, a 0.5 microcuries Co-60 particle was discovered
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in the protective clothing laundry area.
This was the only area that pure
Co-60 contamination was discovered during these surveys.
Contamination was
discovered on three other occasions during the period June 8 - 11, 1985 in
uncontrolled areas of the auxiliary building by these mop surveys.
The
contamination was isolated spots up to 6000 counts per minute and contained
a number of other radionuclides in addition to Co-60.
These three instances
were not significant considering the number of surveys that had been
performed and their relatively small activity and was not indicative of any
programmatic weaknesses in the licensee's contamination control program.
The inspector interviewed six of the eight personnel who had received skin
exposures as a result of the previously discussed contamination events,
including the worker who had received an apparent overexposure on June 5,
1985.
The worker's account of the events were consistent with the
licensee's investigation reports.
It appeared that the laundered protective
clothing was the likely source of most of the contamination events.
During tours of the facility, the inspector observed activities in progress
in the protective clothing laundry area, at the Unit 1 containment accesses,
the hot machine shop and in the change rooms.
Work was performed in
conformance with posted radiation work permits.
Housekeeping appeared very
good, particularly since the unit was in an outage.
Acceptable contamina-
tion controls were observed while removing material from contaminated areas.
Health physics personnel were observed closely following work in
contaminated areas.
Personnel were also observed performing thorough whole
body frisks upon exiting contaminated areas.
The surveys of laundered
protective clothing were being performed by health physics personnel.
Only
a small number of garments were being discarded because of excessive
residual contamination.
The inspector reviewed the licensee's reports of personnel skin contamina-
tions for the period January through May 1985.
A total of 268 events were
documented during this period.
Thirty-four of these events resulted in the
licensee assigning skin of the whole body doses to the employees concerned.
The majority of the dose assignments were less than 100 millirem.
Only 8
of these 34 events, as discussed previously, involved high activity isolated
Co-60 particles and potentially contaminated laundered protective clothing
as a likely source of the contamination.
No other pattern or evidence of a
programmatic type problem was observable in the description of these events.
Based on the above, it was determined that seven workers had received
exposures from skin contamination due to high activity isolated Co-60
particles being transferred from the interior of laundered protective
clothing.
One of these events, the one of June 5,1985, had resulted in an
exposure to the skin of an employee's whole body of 10.6 Rem, which when
added to his previous skin exposure for the calendar quarter of 580 milli-
rem, resulted in his receiving a dose of 11.18 Rems to the skin of his whole
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body.
10 CFR 20.101(a) requires that no licensee shall posses, use, or
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transfer licensed material in such a manner as to cause any individual in a
restricted area to receive in any period of one calendar quarter from
radioactive material and other sources of radiation a total occupational
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dose in excess of 7.5 Rems to the skin of the whole body.
The exposure
event of June 5,1985, which resulted in a licensee employee receiving a
total exposure of 11.18 Rems to the skin of his whole body, was identified
as an apparent violation of 10 CFR 20.101(a)(50-369/85-22-01 and
50-370/85-23-01).
On July 5,
1985, the licensee submitted a Licensee Event Report (LER)
describing the circumstances of the exposure event and giving the employee's
total quarterly exposure to the skin of the whole body as 11.18 Rems.
4.
Control of Radiation Areas (83724)
10 CFR 20.203(b) requires that each radiation area shall be conspicuously
posted with a sign or signs bearing the radiation caution symbol and the
words:
" Caution-Radiation Area."
During the inspection, the inspector performed surveys in the auxiliary and
service buildings, in the radioactive waste area and in areas around the
plant site outside of the buildings.
On June 13, 1985, the inspector discovered an area along the soutn wall of
Room 637 on the 716' elevation of the auxiliary building that had dose rates
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of 72 millirem per hour at near contact with the interface area of the wall
and floor and 6 millirem per hour at 18 inches and at approximately waist
height in the vicinity of the source.
The survey was performed with XETEX
305B, portable beta gamma survey meter, serial number 3685, calibration due
March 20,1986.
The area was not posted as a radiation area.
The licensee
verified the radiation levels with their own survey instruments and posted
the area.
A licensee representative stated that the likely source of the
radiation area was a pipe trench that ran under the floor that connected the
Units 1 and 2 valve galleries.
The pipe trench contained piping that had
required shielding in the past.
Failure to post the radiation area was an
apparent
violation
of
10 CFR 20.203(b)
(50-369/85-22-02
and
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50-370/85-23-02).
5.
Enforcement Conference
An Enforcement Conference was held at NRC Region II on July 12, 1985, to
discuss the exposure of a licensee employee apparently in excess of the skin
of the whole body quarterly exposure-limits given in 10 CFR 20.101(a).
The
following persons were in attendance:
a.
Duke Power Company
H. B. Tucker, Vice President, Nuclear Production
W. A. Haller, Manager, Nuclear Technical Services
T. L. McConnell, Station Manager
J. Foster, Station Health Physicist
N. McCraw, Station Compliance Engineer
R. Gill, McGuire Licensing, General Office
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b.
Nuclear Regulatory Commission
J. Nelson Grace, Regional Administrator
J. P. Stohr, Director, Division of Radiation Safety and Safeguards
R. D. Walker, Director, Division of Reactor Projects
G. R. Jenkins, Director, Enforcement and Investigation Coordination
B. W. Jones, Regional Counsel
D. M. Collins Chief, Emergency Preparedness and Radiological
Protection Branch
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C. M. Hosey, Chief, Facilities Radiation Protection Section
H. C. Dance, Chief, Reactor Projects Section 2A
R. E. Weddington, Radiation Specialist
C. W. Burger, Project Engineer
T. G. Lee, Radiation Specialist
L. Trocine, Enforcement Specialist
During the meeting, licensee personnel presented discussions of the sequence
of events leading up to the personnel exposure in question and detailed the
corrective steps taken and planned to preclude recurrence of such exposures.
Licensee representatives stated that their skin exposure calculations were
based on several very conservative assumptions and that there are now more
technically sound methods of determining skin dose than those used as the
basis of the regulations.
The licensee maintained that it was unlikely that
an overexposure had occurred and that the employee's exposure was not safety
significant.
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NRC personnel expressed concern that the licensee's surveys of laundered
protective clothing had not been adequate to discover residual contamination
in the clothing that could cause significant personnel exposures.
It was
further stated that the NRC technical staff would carefully review and
evaluate what had been presented by the licensee.
6.
Staff Evaluation of Licensee Position Taken in the Enforcement
Conference
The licensee discussed in the Enforcemenc Conference on July 12, 1985, six
alternatives to the possibly conservative means of determining the licensee
employee's skin exposure used as the basis for submitting their LER of
July 5, 1985.
Three of the alternatives proposed discussed the technical basis for the
regulations in regard to at what tissue depth does the skin contain tissues
at risk for cancer inducement (i.e. , 7 mg/cm2 in the regulations as opposed
to 40 mg/cm2 or 125 mg/cm2 suggested by recent animal studies) and the
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appropriate exposure limit to the skin of the whole body (7.5 Rems / quarter
over any one square centimeter of the skin as opposed to 50 Rems / year
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averaged over ten ' square centimeters in the proposed revision to 10 CFR 20).
For regulatory purposes, the NRC continues to view skin exposure as that
dose which penetrates through a tissue equivalent layer of 7 mg/cm2 over any
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one square centimeter with a corresponding quarterly exposure limit of
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7.5 Rems.
However, the staff does consider the positions presented by the
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licensee useful in viewing the safety significance of the event and agrees
that the exposure likely would produce no adverse health effects in the
individual.
The other three proposals presented by the licensee varied the assumptions
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regarding the circumstances of the exposure event.
The licensee assumed
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that the Co-60 particle was transferred to the employee's skin as soon as he
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donned the protective clothing and did not move over more than a one square
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centimeter area of the skin during the two hour duration of- the exposure.
If the radioactive particle was not transferred immediately onto the
employee, a shorter exposure time (one hour for the statistical mean or
0.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> based on work he had performed) would result in a calculated skin
exposure below the regulatory limit.
Similarly, if the particle would have
moved during the two hour period over greater than a one square centimeter
area, no overexposure would have occurred.
It is the NRC position that in
the absence of any objective evidence to the contrary, that~ conservative
assumptions are appropriate.
However, the NRC agrees that the exposure
would not likely produce any adverse health effects,
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