Information Notice 2004-18, Recent Safety Related Event at Panaromic Wet-Source-Storage Irradiator
| ML042950687 | |
| Person / Time | |
|---|---|
| Issue date: | 10/26/2004 |
| From: | Chris Miller NRC/NMSS/IMNS |
| To: | |
| Modes K, Decker T, Ullrich, B. | |
| References | |
| IN-04-018 | |
| Download: ML042950687 (7) | |
UNITED STATES
NUCLEAR REGULATORY COMMISSION
OFFICE OF NUCLEAR MATERIAL SAFETY AND SAFEGUARDS
WASHINGTON, DC 20555 October 26, 2004 NRC INFORMATION NOTICE 2004-18: RECENT SAFETY-RELATED EVENT AT
PANORAMIC WET-SOURCE-STORAGE
IRRADIATOR
Addressees
All licensees authorized to possess and use sealed sources in panoramic wet-source-storage
irradiators, and irradiator vendors.
Purpose
The U.S. Nuclear Regulatory Commission (NRC) is issuing this information notice (IN) to inform
addressees of a recent safety-related incident at a panoramic wet-source-storage irradiator. It
is expected that recipients will review this notice for applicability to their facilities and consider
actions, if 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
On April 21, 2004, an event occurred at an NRC-licensed panoramic wet-source-storage pool
irradiator used for sterilization of medical supplies. The irradiator contains two source racks
that operate simultaneously, each containing approximately 74 petabecquerel (2 million curies)
of cobalt-60, for a total of 148 petabecquerel (4 million curies). The irradiator operator was
experiencing problems with the source rack upper-limit switch (up-switch) and attempted to
repair it. The up-switchs function is to signal when the source racks are in the raised, exposed
position. Faults occurred after repeated attempts to fix the switch when the sources were
raised to test the repair, causing the safety interlocks to prevent access to the irradiation room.
The alternate radiation safety officer (ARSO) authorized the irradiator operator to defeat the
safety interlocks; enter the irradiator via the product exit barrier door; walk through the
irradiation room (e.g., room where source racks and pool are located); and open the locked
personnel access maze door from inside the room. Defeating safety interlocks to enter the
irradiator had been a practice at this facility for a number of years. The repair required the use
of a ladder, which was placed over the source pool (adjacent to the rack hoist mechanism).
After multiple repair attempts failed during a 6-hour period, the operator forgot to remove the
ladder, and with the supervision of the ARSO, raised and lowered the source racks to test the
repairs that had been made. However, unknown to the operator or ARSO, the ladder jammed
against one of the source racks, preventing it from lowering into the pool and into the safe, shielded position. The operator and ARSO incorrectly assumed that the control panel indication
of an exposed source rack was a continuation of the source rack switch problem. They believed
it was yet another false indication. Based on this incorrect understanding, the ARSO again
authorized the irradiator operator to defeat safety interlocks and enter the irradiator via the
product exit barrier door.
The operator enlisted the assistance of a materials handler and they entered the irradiator. The
materials handler was not wearing required dosimetry for this entry. On entering the irradiator, with only one wall of concrete separating them from direct exposure to the stuck source rack, the operator noticed an unexpectedly high reading on the survey meter and told the material
handler to leave immediately. After leaving the irradiator, the operator informed the ARSO of
the unexpected radiation levels. The two workers received doses of 44 and 28 millisievert (4.4 and 2.8 rem), respectively, in a matter of seconds.
NRC conducted a special inspection to respond to this event and, upon learning of the potential
for occupational exposure significantly in excess of regulatory limits, dispatched an Augmented
Inspection Team (AIT) to the site. The team was charged with reviewing the circumstances of
the event and determining root causes. Documentation of these inspections can be found in
NRC Inspection Reports 03019882/2004002 [Agencywide Documents Access and
Management System (ADAMS) Accession No. ML041820011] and 03019882/2004003
[ADAMS Accession No. ML0420300490].
The NRC AIT identified the following:
The licensee did not implement its emergency procedures under conditions that
required them to be implemented.
The licensee did not perform surveys that were adequate to ensure that sources were in
a safe storage condition before defeating safety interlocks and entering the irradiator, although the emergency procedures required this. The irradiator operator did perform a
survey, but did not identify elevated radiation levels before entering the product exit
barrier door. Elevated levels were detected inside the interim area, with only a concrete
wall separating the operator and assistant from the room with the stuck source rack.
Even without implementing the emergency procedure, good radiation safety practices
would have required appropriate radiation surveys before entering the room.
Defeating safety interlocks and entering the irradiation room via the product exit barrier
door and into the interim area of the irradiator had become common practice at this
facility.
Persistent maintenance problems may have existed with the switch systems; however, problems were repaired individually and the licensee did not identify trends nor
determine if underlying causes existed for the problems, nor if preventive maintenance
would have reduced the number of problems.
Licensee personnel did not have a complete understanding of the operation and use of
the irradiation rooms radiation monitor. For instance, when the source rack is in the
exposed position, the operator could have depressed the monitor test switch on the
control console to verify if the source racks were exposed or shielded. During this
event, the licensee did not use this feature, which could have prevented personnel from
entering the interim area and receiving an unnecessary dose. There was no clear guidance in the licensees operating procedures as to when to
engage the emergency procedures, except during start-up.
Annual safety training did not always include performance of a drill. When a drill was
done, the same exit maze scenario was used each time. Therefore, the operators were
not drilled on any of the other nine emergency conditions, such as a stuck source
rack event.
Discussion:
At irradiators, adherence to requirements is critical, because the sources of radiation involved
are capable of delivering life-threatening exposures. If the two employees had continued on
their intended path instead of turning around when they identified elevated radiation levels, each individual could have received a dose of at least 4.5 gray (450 rad), a potentially lethal
exposure. To be properly protective of health and safety, it is important that licensee
management strongly emphasize safety as the highest priority, accompanied by training, adherence to procedures, attention to detail, critical self-assessment, and a questioning attitude
toward safety.
Events regarding exposure of personnel and source rack jams, like the ones just described, are
preventable. NRC expects licensees to train their personnel to recognize an emergency, when
to engage their emergency procedures, and how to prevent a stuck source rack from occurring.
NRC also expects that licensees will not defeat safety interlocks. Safety interlocks are designed
to ensure the safety of personnel from the intense radiation fields at irradiators. If the access
door(s) are locked, it is important to engage your emergency procedures to verify the location of
the source racks and associated irradiation room dose rates. For this type of irradiator, this
could have been done by: (a) checking the position of the source hoist cables from inside the
penthouse area; (b) verifying known hot spots around the irradiator with an operable survey
meter; and/or (c) depressing the monitor test switch on the control console to check for
elevated radiation levels inside the cell.
If appropriate actions, such as the above, indicate that the source racks are in their safe
shielded position, but the interlocks still continue to prevent access, licensees should contact
the irradiator manufacturer to: (1) determine the cause of the interlock activation and (2) to
discuss proper actions to pursue maintenance and repair. The irradiator manufacturer may
provide detailed instructions for entering the irradiator if safety interlocks must be defeated.
However, this manner of entry is only to be used when absolutely necessary and is not an
accepted routine. As noted above, entry into the irradiator in this case delivered unintended
doses to two individuals because the above steps were not completed, and could have resulted
in lethal doses.
Although individual licensees are not required to take specific action, they should consider
reviewing the contents of this IN with those responsible for irradiator operations, to reinforce the
need and importance of a fully functional radiation safety program that ensures the safety of
its employees. This IN requires no specific action nor written response. If you have any questions about the
information in this notice, please contact one of the technical contacts 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: Kathy Modes, RI Betsy Ullrich, RI
(610) 337-5251 (610) 337-5040
E-mail: kad@nrc.gov E-mail: exu@nrc.gov
Tom Decker, RI - Atlanta Office
(404) 562-4721 E-mail: trd@nrc.gov
Attachments:
1. List of Recently Issued NRC Information Notices
2. List of Recently Issued NMSS Information Notices This IN requires no specific action nor written response. If you have any questions about the
information in this notice, please contact one of the technical contacts 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: Kathy Modes, RI Betsy Ullrich, RI
(610) 337-5251 (610) 337-5040
E-mail: kad@nrc.gov E-mail: exu@nrc.gov
Tom Decker, RI - Atlanta Office
(404) 562-4721 E-mail: trd@nrc.gov
Attachments:
1. List of Recently Issued NRC Information Notices
2. List of Recently Issued NMSS Information Notices
DISTRIBUTION:
IMNS r/f
DOCUMENT NAME:E:\Filenet\ML042950687.wpd
- see previous concurrence
OFC RI RI RI RI RI RI
NAME KModes* EUllrich* TDecker* JDiaz* SSherbini* FCostello*
DATE 9/2 /04 9/15/04 9/15/04 9/15/04 9/15/04 9/15/04 OFC RI MSIB Tech Ed. MSIB MSIB MSIB IMNS
NAME GPangburn* ICabrera* EKraus* SWastler* TEssig* PHolahan CMiller*
DATE 9/15/04 9/29/04 9/29/04 9/30/04 10/5/ 04 / / 04 10/12 / 04 OFFICIAL RECORD COPY
Attachment 1 LIST OF RECENTLY ISSUED
NRC INFORMATION NOTICES
_____________________________________________________________________________________
Information Date of
Notice No. Subject Issuance Issued to
_____________________________________________________________________________________
2004-17 Loose Part Detection and 08/25/2004 All holders of operating licenses
Computerized Eddy Current for pressurized-water reactors
Data Analysis in Steam (PWRs), except those who have
Generators permanently ceased operations
and have certified that fuel has
been permanently removed from
the reactor.
2004-16 Tube Leakage Due to a 08/03/2004 All holders of operating licenses
Fabrication Flaw in a for pressurized-water reactors
Replacement Steam Generator (PWRs), except those who have
permanently ceased operations
and have certified that fuel has
been permanently removed from
the reactor.
2004-15 Dual-Unit Scram at Peach 07/22/2004 All holders of operating licenses
Bottom Units 2 and 3 for nuclear power reactors except
those who have permanently
ceased operation and have
certified that fuel has been
permanently removed from the
reactor vessel.
2004-14 Use of less than Optimal 07/19/2004 All licensees authorized to
Bounding Assumptions in possess a critical mass of special
Criticality Safety Analysis at nuclear material.
Fuel Cycle Facilities
2004-13 Registration, Use, and Quality 06/30/2004 All materials and
Assurance Requirements for decommissioning reactor
NRC-Certified Transportation licensees.
Packages
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 LIST OF RECENTLY ISSUED
NMSS INFORMATION NOTICES
_____________________________________________________________________________________
Information Date of
Notice No. Subject Issuance Issued to
_____________________________________________________________________________________
2004-14 Use of less than Optimal 07/19/2004 All licensees authorized to
Bounding Assumptions in possess a critical mass of special
Criticality Safety Analysis at nuclear material.
Fuel Cycle Facilities
2004-13 Registration, Use, and Quality 06/30/2004 All materials and
Assurance Requirements for decommissioning reactor
NRC-Certified Transportation licensees.
Packages
2004-03 Radiation Exposures to 02/24/2004 All well-logging licensees.
Members of the Public in
Excess of Regulatory Limits
Caused by Failures to Perform
Appropriate Radiation Surveys
During Well-logging
Operations
2004-02 Strontium-90 Eye Applicators 02/05/2004 All U.S. Nuclear Regulatory
New Calibration Values and Commission (NRC) medical-use
Use licensees and NRC master
materials license medical-use
permittees.
2003-22 Heightened Awareness for 12/09/2003 All medical licensees and NRC
Patients Containing Detectable Master Materials License medical
Amounts of Radiation from use permittees.
Medical Administrations
2003-21 High-Dose-Rate-Remote- 11/24/2003 All medical licensees.
Afterloader Equipment Failure
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