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radiographer "overexposure"
Please review the attached, NRC event report, based on an Agreement
State report. Although the radiographers' actions seem reasonable
(lesson learned - Secure the control cable to the lift.), I have 2
concerns: (1) the film badge processor reported a dose of "1,423,000
mrem". For an acute exposure of that magnitude, mrem is not a valid
unit. The dose should have been reported in mrads gamma. (2) Although,
based on a lack of symptoms, the reported dose is not valid, it seems
that the investigators wrote off the overexposure too easily. They
should have determined whether the processor has a serious QA problem.
Have they looked at the film? My guess is that, if they did, they'd see
that there's a pinhole light leak. In any event, the processor's QA
program should be reviewed.
The opinions expressed are strictly mine.
It's not about dose, it's about trust.
Curies forever.
Bill Lipton
liptonw@dteenergy.com
EVENT TEXT
+------------------------------------------------------------------------------+
| WA AGREEMENT STATE REPORT ON POSSIBLE OVEREXPOSURE
INCIDENT |
|
|
|
|
| "Licensee: PM TESTING
LABORATORY |
| "Licensee number:
WN-11R047-1 |
| "Type of licensee: Industrial
Radiography |
|
|
| "Date of event: March 5,
2003 |
| "Location of event: Port of Tacoma, WA. German cargo ship 'Big
Lift' |
|
|
| "ABSTRACT: (as reported by licensee's representative) A radiographer
and |
| Assistant Radiographer were performing radiography at the Port of
Tacoma, on |
| a German cargo ship 'Big Lift' on March 5, 2003, at approximately 10
PM |
| [PST]. The work required the radiographers to use a cherry-picker
type |
| lifting vehicle to access the work area since the area was about 100
feet |
| above deck level. The Radiographer and Assistant were both in the
lift |
| bucket, 2 feet apart, at the time of the incident. The
industrial |
| radiographic device (Amersham Corporation Model 660B,
containing |
| approximately 70 curies of iridium 192) with connected guide
tube, |
| collimator and control cables had been lifted into position and
secured in |
| the area of the intended exposure. The exposure device had been made
ready |
| for the exposure. The operation required the Radiographer and
Assistant to |
| move the lift as far from the exposure area as possible while
extending the |
| control
cable. |
|
|
| "As the lift was being positioned away from the work area it swayed,
this |
| startled the radiographer who dropped the control cable. The sway
also |
| caused the lift's engine to stall. The action of dropping the control
cable |
| to the extent of its length and resulting sudden stop at the end of
the drop |
| caused the source to become unshielded. Their survey meter immediately
went |
| off scale on the highest scale and their alarm-rate meters were
alarming. |
|
|
| "It took the radiographers, by their estimate, about 30 seconds to
restart |
| the [lift] vehicle, move the bucket so they could recapture the
control |
| cable and secure the source. When they were able to check their
pocket |
| ion-chambers, they found them off scale. Work was stopped for the day
and |
| both film badges were sent for
processing. |
|
|
| "Results from film badge processing and analysis indicated the
Radiographer |
| received a whole body exposure of 1600 millirem. This coincided with
the |
| calculations made by the Radiographer after the incident. The film
badge for |
| the Assistant indicated an exposure of 1,423,000 millirem. When the
badge |
| processor was contacted and asked to reanalyze the film they stated
they got |
| the same
exposure. |
|
|
| "Since both radiographers were within 2 feet of each other in the
lift |
| basket and calculations confirmed that the Radiographer's exposure was
1600 |
| milliRem, it appears the exposure to the Assistant was
incorrectly |
| determined. In addition, the Assistant is not exhibiting any signs of
an |
| excessive exposure. The company is submitting a report of the
incident. The |
| Division is performing an investigation. Media, at present, are
not |
|
involved.
|
|
|
| "What is the notification or reporting criteria involved? WAC
246-221-260, |
| Reports of overexposures and excessive levels and
concentrations. |
|
|
| "Activity and Isotope(s) involved? 70 curies of Iridium
192. |
|
|
| "Overexposure? Until the investigation indicates otherwise, the
process |
| report of the Assistant's film badge indicates a whole body exposure
of |
| about 1,423,000 milliRem. The over exposure is apparently not real
since |
| calculations using exposure time, distance and source activity and a
second |
| film badge, worn by another individual closely associated with the
first all |
| indicate exposure is unusual but much lower. Staff will
investigate." |
|
|
| * * * UPDATE 1326 EDT on 7/25/03 FROM A. SCROGGS VIA EMAIL TO THE OPS
CENTER |
| * *
*
|
|
|
| The following is a portion of an email received from the Dept. of
Health, |
| Rad Materials
Section: |
|
|
| "The initial report indicated that an Assistant Radiographer appeared
to |
| have received an overexposure. The Department's investigation
determined |
| this not to be
true. |
|
|
| "As a result of the department's investigation of the event and review
of |
| the radiography company's assumptions and calculations, the
Assistant's |
| exposure was determined to be 1600 millirem. Although this is a
significant |
| and unusual exposure, given the circumstances of the event, the
department |
| considers that any health effects would be
minimal. |
|
|
| "The event is considered to be
closed." |
|
|
| Notified R4DO (Pruett) and NMSS
(Greeves). |
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