[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
[Fwd: Re: Cs-137 event]
The following is posted with the permission of the author.
-------- Original Message --------
From: Linda Psyk-Gersey <LMP1@nrc.gov>
Subject: Re: Cs-137 event
To: liptonw@DTEENERGY.COM
Bill,
NRC asked the same question and is waiting for follow-up from the State
of CA. Unfortunately, event reports do not always accurately reflect
what really occurred. Updates for this event will be available on the
NRC website as an updated Preliminary Notification.
Linda M.Gersey
Health Physicist
US Nuclear Regulatory Commission
Div. of Industrial and Medical Nuclear Safety
(301) 415-0215
LMP1@nrc.gov
>>> William V Lipton <liptonw@DTEENERGY.COM> 01/20/04 08:34AM >>>
I noticed this event description in the NRC daily events report. It
involved a rigger inadvertently handling a 1.3 Ci Cs-137 source for 10
sec. From my HP-101 course:
specific gamma ray constant = 0.33 R-m2/Ci-h (from Cember, 3rd
edition, page 187)
assumptions: extremity dose (fingertips) at 1 cm
whole body dose at 1 ft
source encapsulation completely attenuates betas
The resulting calculations show an extremity dose of ~ 12 R and a whole
body dose of 13 mR for the 10 second exposure, ignoring the approach and
withdrawal doses.
I can't figure out how the licensee reported an extremity dose of 20
mR. I also don't understand why they used a whole body distance of 2.5
feet. The distance from the fingertips (with fingers curled to hold the
source) to just above the elbow is approximately 1 foot; definitely less
than 2.5 feet.
I'd be grateful if someone with first hand knowledge of the event could
explain this.
The opinions expressed are strictly mine.
It's not about dose, it's about trust.
Curies forever.
Bill Lipton
liptonw@dteenergy.com
General Information or Other Event Number: 40445
Rep Org: CALIFORNIA RADIATION CONTROL PRGM
Licensee: SCHLUMBERGER TECHNOLOGY CORP
Region: 4
City: OILDALE State: CA
County:
License #: 0144-15
Agreement: Y
Docket:
NRC Notified By: ROBERT GREGER
HQ OPS Officer: JEFF ROTTON Notification Date: 01/13/2004
Notification Time: 23:10 [ET]
Event Date: 01/10/2004
Event Time: 18:00 [PST]
Last Update Date: 01/13/2004
Emergency Class: NON EMERGENCY
10 CFR Section:
AGREEMENT STATE
Person (Organization):
Jeffrey Clark (R4)
PATRICIA HOLAHAN (NMSS)
Event Text
AGREEMENT STATE REPORT INVOLVING PERSONNEL RADIATION EXPOSURE
On 01/12/04, the State of California received a report from Schlumberger
Technology of an incident that occurred about 1800 PST on 01/10/04. A
1.3 curie Cs-137 source fell off of its tool. A rig hand picked up the
source with his fingertips thinking it was the base of a lightbulb. A
Schlumberger crew member told the worker to leave it on the deck. The
source was recovered with the source handling tool, and returned it to
the shielded container.
Touching exposure was estimated to be 20 mrem with calculations based on
maximum touching time of 10 seconds. Whole body exposure was estimated
to be 2.9 mrem with calculation exposure based on beginning at 6 feet
from the source and closest distance at 2.5 feet for maximum of 2
minutes. The source has exposure characteristics of 2 mrem/hr at 200
inches (min) from shielded (dovetail) end, and 2 mrem/hr at 680 inches
(max) from the non-shielded end.
************************************************************************
You are currently subscribed to the Radsafe mailing list. To
unsubscribe, send an e-mail to Majordomo@list.vanderbilt.edu Put the
text "unsubscribe radsafe" (no quote marks) in the body of the e-mail,
with no subject line. You can view the Radsafe archives at
http://www.vanderbilt.edu/radsafe/
************************************************************************
You are currently subscribed to the Radsafe mailing list. To
unsubscribe, send an e-mail to Majordomo@list.vanderbilt.edu Put the
text "unsubscribe radsafe" (no quote marks) in the body of the e-mail,
with no subject line. You can view the Radsafe archives at
http://www.vanderbilt.edu/radsafe/