UNITED STATES

NUCLEAR REGULATORY COMMISSION

OFFICE OF NUCLEAR MATERIAL SAFETY AND SAFEGUARDS

WASHINGTON, D.C. 20555

February 24, 2004

NRC INFORMATION NOTICE 2004-003: RADIATION EXPOSURES TO MEMBERS OF THE

PUBLIC IN EXCESS OF REGULATORY LIMITS

CAUSED BY FAILURES TO PERFORM

APPROPRIATE RADIATION SURVEYS DURING

WELL-LOGGING OPERATIONS

Addressees:

All well-logging licensees.

Purpose:

The U.S. Nuclear Regulatory Commission (NRC) is issuing this Information Notice (IN) to alert

addressees to several events, some of which resulted in oilfield workers receiving radiation

doses in excess of 1.0 millisievert (mSv) [100 millirem (mrem)] per year, NRC’s dose limit for

members of the public. It is expected that recipients will review the information for applicability

to their facilities and consider actions, as appropriate, to avoid similar problems. However,

suggestions contained in this IN are not new NRC requirements; therefore, no specific action nor

written response is required.

Description of Circumstances:

During May 2002, NRC conducted a reactive inspection to review an event involving the loss of

control of a cesium-137 (Cs-137) well-logging source and the unintended radiation exposure to

several members of the public (rig workers). During the course of the inspection, NRC

performed interviews with several individuals from various well logging licensees and equipment

manufacturers. Based on these interviews and by observation of source-handling techniques

employed by multiple well-logging licensees, the inspection team determined that well-logging

sources do, periodically, fall off the handling tools during source transfers. However, compared

to the overall number of well-logging operations, these incidents are infrequent and when they

do occur, the logging crews usually identify the fact that the source has become detached, and

recovery of the source is accomplished quickly and safely. 

Although the number of incidents where loss of control occurs may be small in comparison to the

total number of successful source transfers accomplished each day by well-logging licensees,

the potential for unnecessary exposures, and of exposures exceeding NRC’s dose limit to

members of the public, is high whenever such an event occurs. The inspection disclosed that

the licensee had experienced several additional instances similar to the May 2002 event, in

which logging personnel failed to identify when sources were improperly transferred to their 

ML040500336
IN 2004-03 

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shielded containers and loss of control occurred. In at least two of the instances, oil/gas rig

workers were inadvertently exposed to radiation. In each instance a contributing cause

regarding the loss of control and exposure events was the failure of licensee personnel to

perform an adequate survey of source shields (transport containers) and/or the source transfer

area, before leaving the site.

Examples of events the licensee experienced during the past 15 years in NRC and Agreement

State jurisdictions are described below. A contributing cause in each of these events was the

failure of the logging crew to perform a radiation survey of the source container or well area

before leaving the site.

 The May 2002 event involved the loss of control of a nominal 48-gigabecquerel (GBq)

[1.3-curie (-Ci)] Cs-137, source which was left unshielded on the rig floor. This incident

resulted in 31 members of the public (drilling-rig workers) receiving unnecessary radiation

exposures, 13 of whom received doses in excess of 1.0 mSv (100 mrem). The licensee’s

review of the incident determined that the logging engineer accidently pulled the source

back out of the shield at the conclusion of the source-transfer procedure.

 In 2001, an event occurred involving the loss of control of a nominal 63 GBq (1.7 Ci)

Cs-137 source which was left unshielded on the rig floor. This incident resulted in 16

members of the public (drilling-rig workers) receiving unnecessary radiation exposures,

seven of whom received doses in excess of 1.0 mSv (100 mrem). The licensee’s review

of the incident determined that the logging engineer accidently pulled the source back out

of the shield at the conclusion of the source-transfer procedure.

 In 1987, control of a nominal 592 GBq (16 Ci) americium-241 neutron source was lost

when, after removing the source from the logging tool, the engineer placed the handling

tool, with the source still attached, on the catwalk section of the drill rig and left the site. 

The source remained on the job site, unshielded, for approximately 1 day.

Discussion:

Although 10 CFR Part 39, “Licenses and Radiation Safety Requirements for Well Logging,” does

not specifically require that a licensee perform a radiation survey of source containers before

leaving a temporary job site, 10 CFR 39.63 (c) does require licensees to develop and follow

written operating procedures involving methods and occasions for conducting radiation surveys. 

Section 20.1302 of 10 CFR Part 20, “Standards for Protection Against Radiation,” requires that a

licensee perform adequate surveys to ensure compliance with the radiation dose limits for

individual members of the public. In this regard, the inspection team noted that each welllogging licensee interviewed during the inspection did in fact have standard operating

procedures in place requiring logging personnel to perform some type of confirmatory radiation

survey, before leaving the well site, to confirm the proper transfer of sealed sources to their

shielded containers. The inspection team also concluded that, for each of the events described 
IN 2004-03 

Page 3 of 4 

above, if a radiation survey had been properly conducted, the logging crews would have been

alerted to the fact that the sources were not properly shielded, thereby avoiding unnecessary

exposures to members of the public (rig workers).

The regulations in 10 CFR 20.1802 require that licensees “... control and maintain constant

surveillance of licensed material that is in a controlled or unrestricted area and not in storage.” 

NRC considers a licensee’s failure to secure or constantly maintain surveillance of licensed

material a significant safety issue. Implementation of adequate oversight and control practices

is intended, in part, to prevent: (1) inadvertent exposure of workers and members of the public to

radioactive material; and (2) the loss or theft of licensed material. Because of NRC’s concern

over licensee failure to maintain control and constant surveillance of licensed material, such

violations have normally been categorized in accordance with the “General Statement of Policy

and Procedure for Enforcement Actions“ (Enforcement Policy), NUREG-1600, at Severity Level

III. Issuance of escalated enforcement for such actions may also subject licensees to a civil

penalty and increased inspection effort.

Direct, Contributing, and Root Causes

In summary, the direct, contributing, and root causes for the May 2002 event are:

 The direct cause of the event was the failure of a logging engineer to properly transfer

the Cs-137 source to its storage container immediately after removal of the source from

the logging tool. This led directly to the loss of control event, without any additional

intervening actions.

 Contributing causes of the event included: (1) the failure to perform appropriate radiation

surveys; (2) a false indication by the source shield plug assembly; and (3) the failure to

include a design specification for the cable attachment for the plug assembly.

 It appears that the investigation of the similar events did not focus sufficient attention on

why improper source transfers continue to happen, and why logging engineers failed to

conduct proper radiation surveys.

 The root cause of the event was the licensee’s failure to investigate precursor events

adequately, focusing primarily on the direct cause of events and not on factors that 

made recurrent events more probable. Consequently, the licensee’s limited review of

precursor events failed to prevent similar incidents from happening.

Although individual licensees are not required to take any specific action, they should consider

reviewing the contents of this IN with those responsible for well-logging source transfers, to

reinforce the need and importance of confirming the proper transfer of sources from logging

tools to their respective shielded transport containers, before leaving the well site.
IN 2004-03 

Page 4 of 4 

This IN requires no specific action nor written response. If you have any questions about the

information in this notice, please contact the technical contact listed below, or the appropriate

regional office.

/RA/

 Charles L. Miller, Director

 Division of Industrial and

 Medical Nuclear Safety

 Office of Nuclear Material Safety 

 and Safeguards

Technical contacts: Mark R. Shaffer, Region IV J. Bruce Carrico, NMSS

(817) 860-8287 (301) 415-7826

E-mail: mrs@nrc.gov E-mail: jbc@nrc.gov

Attachments:

1. List of Recently Issued NRC Information Notices

2. List of Recently Issued NMSS Information Notices 
____________________________________________________________________________________

OL = Operating License

CP = Construction Permit

Attachment 1

IN 2004-03

Page 1 of 1

LIST OF RECENTLY ISSUED

NRC INFORMATION NOTICES

____________________________________________________________________________________

Information Date of 

Notice No. Subject Issuance Issued to

____________________________________________________________________________________

2004-02 Strontium-90 Eye Applicators

New Calibration Values and

Use

02/05/2004 All U.S. Nuclear Regulatory

Commission (NRC) medical-use

licensees and NRC master

materials license medical-use

Permittees.

2004-01 Auxiliary Feedwater Pump

Recirculation Line Orifice

Fouling - Potential Common

Cause Failure

01/21/2004 All holders of operating licenses

or construction permits for

nuclear power reactors, except

those that have permanently

ceased operations and have

certified that fuel has been

permanently removed from the

reactor.

2002-26, Sup 2 Additional Failure of Steam

Dryer After A Recent Power

Uprate

01/09/2004 All holders of an operating license

or a construction permit for

nuclear power reactors, except

those that have permanently

ceased operations and have

certified that fuel has been

permanently removed from the

reactor.

2003-11, Sup 1 Leakage Found on BottomMounted Instrumentation

Nozzles

01/08/2004 All holders of operating licenses

or construction permits for

nuclear power reactors, except

those that have permanently

ceased operations and have

certified that fuel has been

permanently removed from the

reactor.

Note: NRC generic communications may be received in electronic format shortly after they are

issued by subscribing to the NRC listserver as follows:

To subscribe send an e-mail to <listproc@nrc.gov >, no subject, and the following

command in the message portion:

subscribe gc-nrr firstname lastname
____________________________________________________________________________________

OL = Operating License

CP = Construction Permit

Attachment 2

IN 2004-03

Page 1 of 1

LIST OF RECENTLY ISSUED

NMSS INFORMATION NOTICES

____________________________________________________________________________________

Information Date of 

Notice No. Subject Issuance Issued to

____________________________________________________________________________________

2004-02 Strontium-90 Eye Applicators

New Calibration Values and

Use

02/05/2004 All U.S. Nuclear Regulatory

Commission (NRC) medical-use

licensees and NRC master

materials license medical-use

permittees.

2003-22 Heightened Awareness for

Patients Containing Detectable

Amounts of Radiation from

Medical Administrations

12/09/2003 All medical licensees and NRC

Master Materials License medical

use permittees.

2003-21 High-Dose-Rate-RemoteAfterloader Equipment Failure11/24/2003 All medical licensees.

2003-20 Derating Whiting Cranes

Purchased Before 1980

10/22/2003 All holders of operating licenses

for nuclear power reactors,

except those who have

permanently ceased operations

and have certified that fuel has

been permanently removed from

the reactor vessel; applicable

decommissioning reactors, fuel

facilities, and independent spent

fuel storage installations.

2003-16 Icing Conditions Between

Bottom of Dry Storage System

and Storage Pad

10/06/2003 All 10 CFR Part 72 licensees and

certificate holders.

2003-12 Problems Involved in

Monitoring Dose to the Hands

Resulting from the Handling of

Radiopharmaceuticals

08/22/2003 All holders of 10 CFR Parts 32,

33, and 35 licenses.

Note: NRC generic communications may be received in electronic format shortly after they are issued by

subscribing to the NRC listserver as follows:

To subscribe send an e-mail to <listproc@nrc.gov >, no subject, and the following command in the

message portion:

subscribe gc-nrr firstname lastname