Information Notice 1996-35, Failure of Safety Systems on Self-Shielded Irradiators Because of Inadequate Maintenance and Training: Difference between revisions

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{{#Wiki_filter:UNITED STATES NUCLEAR REGULATORY
{{#Wiki_filter:UNITED STATES


COMMISSION
NUCLEAR REGULATORY COMMISSION


===OFFICE OF NUCLEAR MATERIAL SAFETY AND SAFEGUARDS===
OFFICE OF NUCLEAR MATERIAL SAFETY AND SAFEGUARDS
WASHINGTON, D.C. 20555 June 11, 1996 NRC INFORMATION


NOTICE 96-35: FAILURE OF SAFETY SYSTEMS ON SELF-SHIELDED
WASHINGTON, D.C. 20555 June 11, 1996 NRC INFORMATION NOTICE 96-35:   FAILURE OF SAFETY SYSTEMS ON SELF-SHIELDED


IRRADIATORS
IRRADIATORS BECAUSE OF INADEQUATE MAINTENANCE
 
BECAUSE OF INADEQUATE
 
MAINTENANCE


AND TRAINING
AND TRAINING


==Addressees==
==Addressees==
All U.S. Nuclear Regulatory
All U.S. Nuclear Regulatory Commission irradiator licensees and vendors.
 
Commission
 
irradiator
 
licensees
 
and vendors.


==Purpose==
==Purpose==
The U.S. Nuclear Regulatory
The U.S. Nuclear Regulatory Commission (NRC) is issuing this information
 
Commission (NRC) is issuing this information
 
notice (IN) to alert addressees
 
to two incidents
 
where safety interlocks
 
on self-shielded
 
irradiators (Category
 
I) failed to prevent inadvertent
 
exposure.The causes of these exposures
 
stemmed from a lack of appropriate
 
maintenance
 
and/or worker training.
 
The incidents
 
include a broken spring -- possibly causing malfunction
 
of the safety interlock
 
-- and a worker who intentionally
 
bypassed a safety interlock.
 
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 information
 
notice are not NRC requirements;
therefore, no specific action nor written response is required.Description
 
of Circumstances
 
The first incident occurred when an operator may have been able to open the shielded door of an irradiator
 
with the sources in the exposed position.After irradiation
 
of several pocket dosimeters, the operator opened the shielded door of the irradiator
 
to retrieve the dosimeters, but did not perform a radiation
 
survey, as required by the facility's
 
internal procedures, before opening the door. Twice, the operator placed one hand inside the irradiator
 
to retrieve the dosimeters.
 
Subsequently, the operator observed that the unit timer continued
 
to count, indicating
 
that the sources remained in the exposed position.
 
The operator checked his personal pocket dosimeter, but did not note an unusual reading. However, the operator did not report the incident until questioned
 
by the radiation
 
safety officer, who had noted an unusually
 
high dosimetry
 
report of 3.55 millisievert
 
(355 mrem) deep dose equivalent
 
for the worker. The dose to the right hand was calculated
 
to be a maximum of 12.5 millisievert
 
(1.25 rem).The design of the irradiator
 
includes two interconnected
 
interlock
 
systems, intended to prevent unshielded
 
exposure of the sources. These include a door interlock
 
system -- designed to allow opening of the shielded door only after the sources are placed in the fully shielded position -- and a source exposure-.
 
interlock
 
system -- designed to secure the sources in the fully shielded tDR FE E NO r/C9 03 ?C 0t, II
 
k k JI IN 96-35 June 11, 1996 position whenever the shielded door is open or unlocked.
 
The manufacturer
 
of the irradiator
 
indicated
 
that under normal operations, either system individually


wouldiprevent
notice (IN)to alert addressees to two incidents where safety interlocks on


inadvertent
self-shielded irradiators (Category I) failed to prevent inadvertent exposure.


access to the unshielded
The causes of these exposures stemmed from a lack of appropriate maintenance


sources.Following
and/or worker training. The incidents include a broken spring -- possibly


the incident, the manufacturer
causing malfunction of the safety interlock -- and a worker who intentionally


of the irradiator
bypassed a safety interlock. It is expected that recipients will review the


was requested
information for applicability to their facilities and consider actions, as


to perform an onsite inspection
appropriate, to avoid similar problems. However, suggestions contained in


of the irradiator
this information notice are not NRC requirements; therefore, no specific


and facilities.
action nor written response is required.


During the inspection, the manufacturer
==Description of Circumstances==
The first incident occurred when an operator may have been able to open the


noted: (1) the irradiator
shielded door of an irradiator with the sources in the exposed position.


was located in an area that was not climate-controlled;
After irradiation of several pocket dosimeters, the operator opened the
(2) internal components


of the irradiator
shielded door of the irradiator to retrieve the dosimeters, but did not


were in a degraded state;(3) maintenance
perform a radiation survey, as required by the facility's internal procedures, before opening the door. Twice, the operator placed one hand inside the


of the irradiator
irradiator to retrieve the dosimeters. Subsequently, the operator observed


had last been performed
that the unit timer continued to count, indicating that the sources remained


approximately
in the exposed position. The operator checked his personal pocket dosimeter, but did not note an unusual reading. However, the operator did not report the


10 years ago; and (4) a return spring, integral to the source exposure safety interlock system, was broken. The manufacturer
incident until questioned by the radiation safety officer, who had noted an


indicated
unusually high dosimetry report of 3.55 millisievert (355 mrem) deep dose


that the lack of environmental
equivalent for the worker. The dose to the right hand was calculated to be a


control may have accelerated
maximum of 12.5 millisievert (1.25 rem).


the degradation
The design of the irradiator includes two interconnected interlock systems, intended to prevent unshielded exposure of the sources. These include a door


of the internal components
interlock system -- designed to allow opening of the shielded door only after


of the irradiator, and that the lack of periodic maintenance
the sources are placed in the fully shielded position -- and a source exposure-.


of the irradiator
interlock system -- designed to secure the sources in the fully shielded


may have contributed
tDR FEE NOr/C9                  03        ?C 0t,                              II


to the failure of the return spring.The broken return spring may have caused the source securing mechanism
k                              k JI


of the source exposure interlock
IN 96-35 June 11, 1996 position whenever the shielded door is open or unlocked. The manufacturer of


system to malfunction, possibly allowing exposure of the sources after the shielded door was unlocked and opened. However, during the post-incident
the irradiator indicated that under normal operations, either system


investigation, neither the manufacturer
individually wouldiprevent inadvertent access to the unshielded sources.


nor the licensee were able to identify a failed component
Following the incident, the manufacturer of the irradiator was requested to


of either interlock
perform an onsite inspection of the irradiator and facilities. During the


system that could have allowed the shielded door to be opened with the sources in the exposed position.
inspection, the manufacturer noted:
    (1)    the irradiator was located in an area that was not climate- controlled;
    (2)    internal components of the irradiator were in a degraded state;
    (3)    maintenance of the irradiator had last been performed approximately


The manufacturer
10 years ago; and


indicated
(4)    a return spring, integral to the source exposure safety interlock


that the design of the source exposure mechanism
system, was broken. The manufacturer indicated that the lack of


-- the operator must manually move the sources from the shielded to the exposed position with a lever -- would have provided the operator with a positive indication
environmental control may have accelerated the degradation of the


of source position even if the interlock
internal components of the irradiator, and that the lack of periodic


systems failed.Source position would have been further provided by a series of green and red source position lights on the irradiator.
maintenance of the irradiator may have contributed to the failure of


The operator's
the return spring.


actions indicate either a lack of training on the proper functioning
The broken return spring may have caused the source securing mechanism of the


and use of the irradiator, a lack of understanding
source exposure interlock system to malfunction, possibly allowing exposure of


of the training provided, and/or a disregard
the sources after the shielded door was unlocked and opened. However, during


for following
the post-incident investigation, neither the manufacturer nor the licensee


the established
were able to identify a failed component of either interlock system that could


operating
have allowed the shielded door to be opened with the sources in the exposed


and safety procedures.
position. The manufacturer indicated that the design of the source exposure


The operator indicated
mechanism -- the operator must manually move the sources from the shielded to


that the timer continued
the exposed position with a lever -- would have provided the operator with a


to count when the shielded door was opened. However, the manufacturer
positive indication of source position even if the interlock systems failed.


reported that the timer automatically
Source position would have been further provided by a series of green and red


activates
source position lights on the irradiator.


whenever the source lever is manually moved to one of the two source exposed positions
The operator's actions indicate either a lack of training on the proper


and the lever is fully engaged in the source slot, and stops counting as soon as the lever is moved from the fully engaged position.
functioning and use of the irradiator, a lack of understanding of the training


The fact that the timer continued
provided, and/or a disregard for following the established operating and


to count indicates that the operator had not moved the sources from the fully exposed and engaged position.
safety procedures. The operator indicated that the timer continued to count


The licensee reported that the operator had been trained in the operation
when the shielded door was opened. However, the manufacturer reported that


of the irradiator
the timer automatically activates whenever the source lever is manually moved


and was listed as an authorized
to one of the two source exposed positions and the lever is fully engaged in


user, but that the irradiator
the source slot, and stops counting as soon as the lever is moved from the


was used infrequently
fully engaged position. The fact that the timer continued to count indicates


and that this was only the operator's
that the operator had not moved the sources from the fully exposed and engaged


second use of the irradiator
position. The licensee reported that the operator had been trained in the


since being trained.The second incident occurred when a maintenance
operation of the irradiator and was listed as an authorized user, but that the


worker preparing
irradiator was used infrequently and that this was only the operator's second


to perform maintenance
use of the irradiator since being trained.


on an irradiator
The second incident occurred when a maintenance worker preparing to perform


bypassed the irradiator
maintenance on an irradiator bypassed the irradiator door interlock system to


door interlock
observe movement of the inner irradiation chamber. The maintenance was being


system to observe movement of the inner irradiation
K>
                                                            IN 96-35 June 11, 1996 performed to correct previous maintenance that resulted in the irradiator not


chamber. The maintenance
functioning properly. The maintenance worker was unaware that, although the


was being
sources remained shielded during movement of the irradiation chamber from the


K>IN 96-35 June 11, 1996 performed
load to irradiate position, high levels of radiation scatter would be present.


to correct previous maintenance
The maintenance worker, upon hearing the in-room monitor alarm, immediately


that resulted in the irradiator
returned the radiation chamber to the 'load' position (maximum shielding).


not functioning
Although the maintenance worker was familiar with the operation of the


properly.
irradiator and had been responsible for its maintenance for nearly 15 years, the worker apparently had not been given formal training on radiation safety


The maintenance
or the operation and maintenance of the irradiator. The maintenance worker


worker was unaware that, although the sources remained shielded during movement of the irradiation
was not aware of the scatter radiation and assumed that since the sources were


chamber from the load to irradiate
not directly exposed, radiation from the sources would be contained within the


position, high levels of radiation
device.


scatter would be present.The maintenance
During this incident, another worker, hired to perform contract maintenance on


worker, upon hearing the in-room monitor alarm, immediately
the irradiator, was also in the room near the irradiator. Neither worker wore


returned the radiation
dosimetry nor had any documented training in radiation safety. Therefore, their doses could only be calculated based on their recollection and were


chamber to the 'load' position (maximum shielding).
estimated to both be approximately 4 microsievert (0.4 mrem) whole body.


Although the maintenance
Discussion


worker was familiar with the operation
Although neither incident resulted in doses in excess of regulatory limits, the doses received in both incidents were unnecessary and possibly could have


of the irradiator
been avoided with proper training and routine equipment maintenance. A


and had been responsible
similar incident in 1984, where a door interlock failed, resulted in the


for its maintenance
operator being exposed to 222 terabequerel (6000 curies) of cesium-137.


for nearly 15 years, the worker apparently
The first incident clearly demonstrates the need to perform appropriate


had not been given formal training on radiation
maintenance on these types of units. Even though these units are designed


safety or the operation
with interlocks and safety features intended to prevent inadvertent exposures, the components of these systems depend on adequate maintenance to function


and maintenance
properly. Failure to properly maintain these systems and provide appropriate


of the irradiator.
training could result in unnecessary exposures. Manufacturers of these types


The maintenance
of irradiators frequently provide initial and periodic training on the


worker was not aware of the scatter radiation
operation of their units and, in some cases, training on other manufacturers'
units, as well. Initial training is typically a condition of the license and, therefore, must be provided to all irradiator users and maintenance personnel.


and assumed that since the sources were not directly exposed, radiation
Periodic refresher training is also beneficial as a reminder for working


from the sources would be contained
safely around the irradiator and provides for a means to receive or


within the device.During this incident, another worker, hired to perform contract maintenance
disseminate additional or updated information.


on the irradiator, was also in the room near the irradiator.
In addition, most manufacturers have a recommended schedule of maintenance


Neither worker wore dosimetry
and/or recommended preventative/periodic maintenance that should be performed.


nor had any documented
Users of these types of irradiators should evaluate their usage to determine


training in radiation
the applicability of the recommended maintenance to their situation and usage.


safety. Therefore, their doses could only be calculated
Users who operate their unit more than usual or who use their units under


based on their recollection
harsh conditions should consider the need for stepped-up maintenance or


and were estimated
'->                                                            IN 96-35 June 11, 1996 shortened maintenance intervals. In addition, each manufacturer's recommended


to both be approximately
maintenance may vary according to the specific unit or type of use.


4 microsievert
Therefore, personis performing maintenance on their unit may require specific


(0.4 mrem) whole body.Discussion
maintenance training for their unit.


Although neither incident resulted in doses in excess of regulatory
Users who are not aware of the required training for their unit, or who wish


limits, the doses received in both incidents
to receive information concerning training in general, should consult their


were unnecessary
license, licensing authority, or the manufacturer of the unit. Regulatory


and possibly could have been avoided with proper training and routine equipment
Guide 10.9, provides additional guidance in this area and may assist persons


maintenance.
who wish to develop a training and maintenance program. Users who wish to


A similar incident in 1984, where a door interlock
receive additional information concerning recommended maintenance for their


failed, resulted in the operator being exposed to 222 terabequerel
unit should contact the manufacturer of the unit. In addition, third-party


(6000 curies) of cesium-137.
service companies may also be available for training and maintenance services


The first incident clearly demonstrates
for these types of irradiators.


the need to perform appropriate
This information notice requires no specific action nor written response. If


maintenance
you have any questions about the information in this notice, please contact


on these types of units. Even though these units are designed with interlocks
one of the technical contacts listed below or the appropriate regional office.


and safety features intended to prevent inadvertent
I3W¶flstn    8 by9WWstIA


exposures, the components
Donald A. Cool, Director


of these systems depend on adequate maintenance
Division of Industrial and


to function properly.
Medical Nuclear Safety


Failure to properly maintain these systems and provide appropriate
Office of Nuclear Material Safety


training could result in unnecessary
and Safeguards


exposures.
Technical contacts:                  Douglas Broaddus, NMSS


Manufacturers
(301) 415-5847 Internet:dab~nrc.gov


of these types of irradiators
Anthony Kirkwood, NMSS


frequently
(301) 415-6140
 
                                                      Internet:ask~nrc.gov
provide initial and periodic training on the operation
 
of their units and, in some cases, training on other manufacturers'
units, as well. Initial training is typically
 
a condition
 
of the license and, therefore, must be provided to all irradiator
 
users and maintenance
 
personnel.
 
Periodic refresher
 
training is also beneficial
 
as a reminder for working safely around the irradiator
 
and provides for a means to receive or disseminate
 
additional
 
or updated information.
 
In addition, most manufacturers
 
have a recommended
 
schedule of maintenance
 
and/or recommended
 
preventative/periodic
 
maintenance
 
that should be performed.
 
Users of these types of irradiators
 
should evaluate their usage to determine the applicability
 
of the recommended
 
maintenance
 
to their situation
 
and usage.Users who operate their unit more than usual or who use their units under harsh conditions
 
should consider the need for stepped-up
 
maintenance
 
or
 
'-> IN 96-35 June 11, 1996 shortened
 
maintenance
 
intervals.
 
In addition, each manufacturer's
 
recommended
 
maintenance
 
may vary according
 
to the specific unit or type of use.Therefore, personis performing
 
maintenance
 
on their unit may require specific maintenance
 
training for their unit.Users who are not aware of the required training for their unit, or who wish to receive information
 
concerning
 
training in general, should consult their license, licensing
 
authority, or the manufacturer
 
of the unit. Regulatory
 
Guide 10.9, provides additional
 
guidance in this area and may assist persons who wish to develop a training and maintenance
 
program. Users who wish to receive additional
 
information
 
concerning
 
recommended
 
maintenance
 
for their unit should contact the manufacturer
 
of the unit. In addition, third-party
 
service companies
 
may also be available
 
for training and maintenance
 
services for these types of irradiators.
 
This information
 
notice 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.I3W¶flstn 8 by9WWstIA Donald A. Cool, Director Division of Industrial
 
and Medical Nuclear Safety Office of Nuclear Material Safety and Safeguards
 
Technical
 
contacts:
Douglas Broaddus, NMSS (301) 415-5847 Internet:dab~nrc.gov
 
Anthony Kirkwood, NMSS (301) 415-6140 Internet:ask~nrc.gov


Attachments:
Attachments:
1. List of Recently issued NMSS Information
              1.         List of Recently issued NMSS Information Notices
 
Notices 2. List of Recently issued NRC Information
 
Notices DOCUMENT NAME: 96-35.IN To receive a copy of this document, Indicate In the box: C' = Copy without attachment/enclosure


*E' -Copy with attachmentjendosure
2.          List of Recently issued NRC Information Notices


N
DOCUMENT NAME:              96-35.IN


* No copy* See previous concurrence
To receive a copy of this document, Indicate In the box: C' = Copy without attachment/enclosure *E' - Copy with attachmentjendosure  N


OFFICE IIMAB* [ClIMAB* [C Tech Editor* l IMOB* [C IMNS* I C, NAME IDBroaddus*
* No copy
LCamper lEKraus _KRamsey jDCof'DATE 14/17/96 5/28/96 4/01/96 5/31/96 6/4 96 11 OFFICIAL RECORD COPY


j;IN 96-XX May XX, 1996 Users who are not aware of the required training for their unit, or who wish to receive information
*  See previous concurrence


concerning
OFFICE IIMAB*                              [ClIMAB*                  [C Tech Editor* l                IMOB*                [C IMNS*            I C,
  NAME          IDBroaddus*                        LCamper                  lEKraus                _KRamsey                        jDCof'
  DATE          14/17/96                            5/28/96                  4/01/96                    5/31/96                    6/4 96            11 OFFICIAL RECORD COPY


training in general, should consult their license, licensing
j;
                                                                                                                          IN 96-XX


authority, or the manufacturer
May XX, 1996 Users who are not aware of the required training for their unit, or who wish


of the unit. Regulatory
to receive information concerning training in general, should consult their


Guide 10.9, provides additional
license, licensing authority, or the manufacturer of the unit. Regulatory


guidance in this area and may assist persons who wish to develop a training and maintenance
Guide 10.9, provides additional guidance in this area and may assist persons


program. Users who wish to receive additional
who wish to develop a training and maintenance program. Users who wish to


information
receive additional information concerning recommended maintenance for their


concerning
unit should contact the manufacturer of the unit. In addition, third-party


recommended
service companies may also be available for training and maintenance services


maintenance
for these types of irradiators.


for their unit should contact the manufacturer
This information notice requires no specific action nor written response. If


of the unit. In addition, third-party
you have any questions about the information in this notice, please contact


service companies
one of the technical contacts listed below or the appropriate regional office.


may also be available
Donald A. Cool, Director


for training and maintenance
Division of Industrial and


services for these types of irradiators.
Medical Nuclear Safety


This information
Office of Nuclear Material Safety


notice requires no specific action nor written response.
and Safeguards


If you have any questions
Technical contacts: Douglas Broaddus, NMSS


about the information
(301) 415-5847 Anthony Kirkwood, NMSS


in this notice, please contact one of the technical
(301) 415-6140
              Attachments:
              1.          List of Recently issued NMSS Information Notices


contacts listed below or the appropriate
2.          List of Recently issued NRC Information Notices


regional office.Donald A. Cool, Director Division of Industrial
DOCUMENT NAME:              A:\IRADIATR.FIN


and Medical Nuclear Safety Office of Nuclear Material Safety and Safeguards
To receive a copy of this docunent, Indicate hI the box: 'C Copy without attachmentlenclosure WE-= Copy with attachmentlenclosure    ONE copY


Technical
*  See previous concurrence                                                                                                        a


contacts:
OFFICE          IMAB                      I      INAB    15    /HTech          Editor    I      IMOB                        IMN h
Douglas Broaddus, NMSS (301) 415-5847 Anthony Kirkwood, NMSS (301) 415-6140 Attachments:
1. List of Recently issued NMSS Information


Notices 2. List of Recently issued NRC Information
NAME          DBroaddus*                        LCam er'              1EKraus*                    KRamse Kmfl                  Co


Notices DOCUMENT NAME: A:\IRADIATR.FIN
DATE          4/17/96                            L/46/96              14/01/96                    5-13j /96                    /
                                                              OFFICIAL RECORD COPY


To receive a copy of this docunent, Indicate hI the box: 'C Copy without attachmentlenclosure
IN 96-XX


WE- = Copy with attachmentlenclosure
May XX, 1996 Users who are not aware of the required training for their unit, or who wish


ONE copY* See previous concurrence
to receive information concerning training in general, should consult their


a OFFICE IMAB I INAB 15 /HTech Editor I IMOB IMN h NAME DBroaddus*
license, licensing authority, or the manufacturer of the unit. Regulatory
LCam er' 1EKraus* KRamse Kmfl Co DATE 4/17/96 L/46/96 14/01/96 5-13j /96 /OFFICIAL RECORD COPY


IN 96-XX May XX, 1996 Users who are not aware of the required training for their unit, or who wish to receive information
Guide 10.9, provides additional guidance in this area and may assist persons


concerning
who wish to develop a training and maintenance program. Users who wish to


training in general, should consult their license, licensing
receive additional information concerning recommended maintenance for their


authority, or the manufacturer
unit should contact the manufacturer of the unit. In addition, third-party


of the unit. Regulatory
service companies may also be available for training and maintenance services


Guide 10.9, provides additional
for these types of irradiators.


guidance in this area and may assist persons who wish to develop a training and maintenance
This information notice requires no specific action nor written response. If


program. Users who wish to receive additional
you have any questions about the information in this notice, please contact


information
one of the technical contacts listed below or the appropriate regional office.


concerning
Donald A. Cool, Director
 
recommended
 
maintenance
 
for their unit should contact the manufacturer
 
of the unit. In addition, third-party
 
service companies
 
may also be available
 
for training and maintenance
 
services for these types of irradiators.
 
This information
 
notice 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.Donald A. Cool, Director Division of Industrial
 
and Medical Nuclear Safety Office of Nuclear Material Safety and Safeguards
 
Technical
 
contacts:
Douglas Broaddus, NMSS 301-415-5847 Anthony Kirkwood, RI 610-337-5050
Attachments:
1. List of Recently issued NMSS Information


Notices 2. List of Recently issued NRC Information
Division of Industrial and


Notices DOCUMENT NAME: A:\IRADIATR.FIN
Medical Nuclear Safety


To receiv a copy of this document, Indicate In the box: C' = Copy without attachmentlenclosure
Office of Nuclear Material Safety


'E' = Copy with aftachment/enclosure
and Safeguards


*'N -No copy lOFFICE IMAB [ IMAB LJTech Editor LAL IMOB LJIMNS INAME DBroaddus
Technical contacts: Douglas Broaddus, NMSS


LCamper EKraus wa KRamsey DCool DMTE 4//f/96 4/ /96 4/W /96 4/ /96 4/ /96 OFFICIAL RECORD COPY
301-415-5847 Anthony Kirkwood, RI


KUJ KU Attachment
610-337-5050
              Attachments:
              1.          List of Recently issued NMSS Information Notices


1 IN 96-35 June 11, 1996 LIST OF RECENTLY ISSUED NMSS INFORMATION
2.          List of Recently issued NRC Information Notices


NOTICES Information
DOCUMENT NAME:              A:\IRADIATR.FIN


' Date of Notice No. Subject Issuance Issued to 96-33 Erroneous
To receiv a copy of this document, Indicate In the box: C' = Copy without attachmentlenclosure 'E' = Copy with aftachment/enclosure  *'N - No copy


Data from Defec-tive Thermocouple
lOFFICE        IMAB                      [      IMAB              LJTech Editor                LAL IMOB                    LJIMNS


Results in a Fire 05/224/96 All material and fuel cycle licensees
INAME          DBroaddus                          LCamper                  EKraus wa                  KRamsey                    DCool


that monitor tem-perature with thermocouples
DMTE          4//f/96                            4/ /96                    4/W /96                    4/ /96                      4/ /96 OFFICIAL RECORD COPY


96-28 96-21 96-20 96-18 Suggested
KUJ                            KU


Guidance Relat-ing to Development
Attachment 1 IN 96-35 June 11,  1996 LIST OF RECENTLY ISSUED


and Implementation
NMSS INFORMATION NOTICES


of Correc-tive Action Safety Concerns Related to the Design of the Door Interlock
Information                      '        Date of


Circuit on Nucletron
Notice No.            Subject              Issuance    Issued to


High-Dose
96-33      Erroneous Data from Defec-    05/224/96    All material and fuel cycle


Rate and Pulsed Dose Rate Remote Afterloading
tive Thermocouple Results                  licensees that monitor tem- in a Fire                                  perature with thermocouples


Brachy-therapy Devices Demonstration
96-28      Suggested Guidance Relat-      05/01/96    All material and fuel cycle


of Associ-ated Equipment
ing to Development and                      licensees


Compliance
Implementation of Correc- tive Action


with 10 CFR 34.20 Compliance
96-21      Safety Concerns Related        04/10/96    All NRC Medical Licensees


With 10 CFR Part 20 for Airborne Thorium Incident Reporting Requirements
to the Design of the Door                  authorized to use brachy- Interlock Circuit on                        therapy sources in high- Nucletron High-Dose Rate                    and pulsed-dose-rate remote


for Radiography
and Pulsed Dose Rate


Licensees 10 CFR 34.20; Final Effective
Remote Afterloading Brachy- therapy Devices


===Date Handling Uncontained===
96-20      Demonstration of Associ-      04/04/96    All industrial radiography
Yellowcake


Outside of a Facility Processing
ated Equipment Compliance                  licensees and radiography


Circuit Recent Incidents
with 10 CFR 34.20                          equipment manufacturers


Involving Potential
96-18      Compliance With 10 CFR        03/25/96    All material licensees


Loss of Control of Licensed Material 05/01/96 04/10/96 04/04/96 03/25/96 01/10/96 12/18/95 12/6/95 10/27/95 All material and fuel cycle licensees All NRC Medical Licensees authorized
Part 20 for Airborne                        authorized to possess and


to use brachy-therapy sources in high-and pulsed-dose-rate
Thorium                                    use thorium in unsealed form


remote All industrial
96-04      Incident Reporting            01/10/96    All Radiography Licensees


radiography
Requirements for                            and Manufacturers of


licensees
Radiography Licensees                      Radiography Equipment


and radiography
95-58      10 CFR 34.20; Final            12/18/95    Industrial Radiography


equipment
Effective Date                            Licensees.


manufacturers
95-55      Handling Uncontained          12/6/95    All Uranium Recovery


All material licensees authorized
Yellowcake Outside of a                    Licensees.


to possess and use thorium in unsealed form All Radiography
Facility Processing Circuit


Licensees and Manufacturers
95-51      Recent Incidents Involving    10/27/95    All material and fuel cycle


of Radiography
Potential Loss of Control                  licensees.


Equipment Industrial
of Licensed Material


Radiography
K>-                            iKJ


Licensees.
Attachment 2 IN 96-35 June 11, 1996 LIST OF RECENTLY ISSUED


All Uranium Recovery Licensees.
NRC INFORMATION NOTICES


All material and fuel cycle licensees.
Information                                  Date of


96-04 95-58 95-55 95-51 K> -iKJ Attachment
Notice No.            Subject                Issuance        Issued to


2 IN 96-35 June 11, 1996 LIST OF RECENTLY ISSUED NRC INFORMATION
96-34          Hydrogen Gas Ignition          05/31/96      All holders of OLs or CPs


NOTICES Information
during Closure Welding                        for nuclear power reactors


Date of Notice No. Subject Issuance Issued to 96-34 96-33 96-32 96-31 96-30 Hydrogen Gas Ignition during Closure Welding of a VSC-24 Multi-Assembly
of a VSC-24 Multi-Assembly


Sealed Basket Erroneous
Sealed Basket


Data From Defective
96-33          Erroneous Data From           05/24/96        All material and fuel cycle


===Thermocouple===
Defective Thermocouple                         licensees that monitor tem- Results in a Fire                             perature with thermocouples
Results in a Fire Implementation


of 10 CFR 50.55a(g)(6)(ii)(A),"Augmented
96-32          Implementation of 10 CFR       06/05/96      All holders of OLs or CPs


Examination
50.55a(g)(6)(ii)(A),                          for nuclear power reactors


of Reactor Vessel" Cross-Tied
"Augmented Examination


Safety Injec-tion Accumulators
of Reactor Vessel"
96-31          Cross-Tied Safety Injec-       05/22/96        All holders of OLs or CPs


Inaccuracy
tion Accumulators                              for pressurized water


of Diagnostic
reactors


Equipment
96-30          Inaccuracy of Diagnostic      05/21/96      All holders of OLs or CPs


for Motor-Operated Butterfly
Equipment for Motor-                           for nuclear power reactors


Valves Requirements
Operated Butterfly Valves


in 10 CFR Part 21 for Reporting
96-29          Requirements in 10 CFR         05/20/96      All holders of OLs or CPs


and Evaluating
Part 21 for Reporting and                     for nuclear power reactors


Software Errors Suggested
Evaluating Software Errors


Guidance Relating to Development
96-28          Suggested Guidance Relating   05/01/96      All material and fuel cycle


and Imple-mentation
to Development and Imple-                     licensees


of Corrective
mentation of Corrective


Action Potential
Action


Clogging of High Pressure Safety Injection Throttle Valves During Recirculation
96-27          Potential Clogging of High     05/01/96      All holders of OLs or CPs


Recent Problems with Over-head Cranes Transversing
Pressure Safety Injection                    for pressurized water


In-Core Probe Overwithdrawn
Throttle Valves During                        reactors


at LaSalle County Station, Unit 1 05/31/96 05/24/96 06/05/96 05/22/96 05/21/96 05/20/96 05/01/96 05/01/96 04/30/96 04/30/96 All holders of OLs or CPs for nuclear power reactors All material and fuel cycle licensees
Recirculation


that monitor tem-perature with thermocouples
96-26          Recent Problems with Over-    04/30/96      All holders of OLs or CPs


All holders of OLs or CPs for nuclear power reactors All holders of OLs or CPs for pressurized
head Cranes                                  for nuclear power reactors


water reactors All holders of OLs or CPs for nuclear power reactors All holders of OLs or CPs for nuclear power reactors All material and fuel cycle licensees All holders of OLs or CPs for pressurized
96-25          Transversing In-Core Probe    04/30/96      All holders of OLs or CPs


water reactors All holders of OLs or CPs for nuclear power reactors All holders of OLs or CPs for nuclear power reactors 96-29 96-28 96-27 96-26 96-25 OL -Operating
Overwithdrawn at LaSalle                      for nuclear power reactors


License CP -Construction
County Station, Unit 1 OL - Operating License


Permit}}
CP - Construction Permit}}


{{Information notice-Nav}}
{{Information notice-Nav}}

Latest revision as of 04:38, 24 November 2019

Failure of Safety Systems on Self-Shielded Irradiators Because of Inadequate Maintenance and Training
ML031060046
Person / Time
Site: Beaver Valley, Millstone, Hatch, Monticello, Calvert Cliffs, Dresden, Davis Besse, Peach Bottom, Browns Ferry, Salem, Oconee, Mcguire, Nine Mile Point, Palisades, Palo Verde, Perry, Indian Point, Fermi, Kewaunee, Catawba, Harris, Wolf Creek, Saint Lucie, Point Beach, Oyster Creek, Watts Bar, Hope Creek, Grand Gulf, Cooper, Sequoyah, Byron, Pilgrim, Arkansas Nuclear, Three Mile Island, Braidwood, Susquehanna, Summer, Prairie Island, Columbia, Seabrook, Brunswick, Surry, Limerick, North Anna, Turkey Point, River Bend, Vermont Yankee, Crystal River, Haddam Neck, Ginna, Diablo Canyon, Callaway, Vogtle, Waterford, Duane Arnold, Farley, Robinson, Clinton, South Texas, San Onofre, Cook, Comanche Peak, Yankee Rowe, Maine Yankee, Quad Cities, Humboldt Bay, La Crosse, Big Rock Point, Rancho Seco, Zion, Midland, Bellefonte, Fort Calhoun, FitzPatrick, McGuire, LaSalle, 05000442, Fort Saint Vrain, Shoreham, Satsop, Trojan, Atlantic Nuclear Power Plant  Entergy icon.png
Issue date: 06/11/1996
From: Cool D
NRC/NMSS/IMNS
To:
References
IN-96-035, NUDOCS 9606060078
Download: ML031060046 (8)
v • d • e


UNITED STATES

NUCLEAR REGULATORY COMMISSION

OFFICE OF NUCLEAR MATERIAL SAFETY AND SAFEGUARDS

WASHINGTON, D.C. 20555 June 11, 1996 NRC INFORMATION NOTICE 96-35: FAILURE OF SAFETY SYSTEMS ON SELF-SHIELDED

IRRADIATORS BECAUSE OF INADEQUATE MAINTENANCE

AND TRAINING

Addressees

All U.S. Nuclear Regulatory Commission irradiator licensees and vendors.

Purpose

The U.S. Nuclear Regulatory Commission (NRC) is issuing this information

notice (IN)to alert addressees to two incidents where safety interlocks on

self-shielded irradiators (Category I) failed to prevent inadvertent exposure.

The causes of these exposures stemmed from a lack of appropriate maintenance

and/or worker training. The incidents include a broken spring -- possibly

causing malfunction of the safety interlock -- and a worker who intentionally

bypassed a safety interlock. 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 information notice are not NRC requirements; therefore, no specific

action nor written response is required.

Description of Circumstances

The first incident occurred when an operator may have been able to open the

shielded door of an irradiator with the sources in the exposed position.

After irradiation of several pocket dosimeters, the operator opened the

shielded door of the irradiator to retrieve the dosimeters, but did not

perform a radiation survey, as required by the facility's internal procedures, before opening the door. Twice, the operator placed one hand inside the

irradiator to retrieve the dosimeters. Subsequently, the operator observed

that the unit timer continued to count, indicating that the sources remained

in the exposed position. The operator checked his personal pocket dosimeter, but did not note an unusual reading. However, the operator did not report the

incident until questioned by the radiation safety officer, who had noted an

unusually high dosimetry report of 3.55 millisievert (355 mrem) deep dose

equivalent for the worker. The dose to the right hand was calculated to be a

maximum of 12.5 millisievert (1.25 rem).

The design of the irradiator includes two interconnected interlock systems, intended to prevent unshielded exposure of the sources. These include a door

interlock system -- designed to allow opening of the shielded door only after

the sources are placed in the fully shielded position -- and a source exposure-.

interlock system -- designed to secure the sources in the fully shielded

tDR FEE NOr/C9 03 ?C 0t, II

k k JI

IN 96-35 June 11, 1996 position whenever the shielded door is open or unlocked. The manufacturer of

the irradiator indicated that under normal operations, either system

individually wouldiprevent inadvertent access to the unshielded sources.

Following the incident, the manufacturer of the irradiator was requested to

perform an onsite inspection of the irradiator and facilities. During the

inspection, the manufacturer noted:

(1) the irradiator was located in an area that was not climate- controlled;

(2) internal components of the irradiator were in a degraded state;

(3) maintenance of the irradiator had last been performed approximately

10 years ago; and

(4) a return spring, integral to the source exposure safety interlock

system, was broken. The manufacturer indicated that the lack of

environmental control may have accelerated the degradation of the

internal components of the irradiator, and that the lack of periodic

maintenance of the irradiator may have contributed to the failure of

the return spring.

The broken return spring may have caused the source securing mechanism of the

source exposure interlock system to malfunction, possibly allowing exposure of

the sources after the shielded door was unlocked and opened. However, during

the post-incident investigation, neither the manufacturer nor the licensee

were able to identify a failed component of either interlock system that could

have allowed the shielded door to be opened with the sources in the exposed

position. The manufacturer indicated that the design of the source exposure

mechanism -- the operator must manually move the sources from the shielded to

the exposed position with a lever -- would have provided the operator with a

positive indication of source position even if the interlock systems failed.

Source position would have been further provided by a series of green and red

source position lights on the irradiator.

The operator's actions indicate either a lack of training on the proper

functioning and use of the irradiator, a lack of understanding of the training

provided, and/or a disregard for following the established operating and

safety procedures. The operator indicated that the timer continued to count

when the shielded door was opened. However, the manufacturer reported that

the timer automatically activates whenever the source lever is manually moved

to one of the two source exposed positions and the lever is fully engaged in

the source slot, and stops counting as soon as the lever is moved from the

fully engaged position. The fact that the timer continued to count indicates

that the operator had not moved the sources from the fully exposed and engaged

position. The licensee reported that the operator had been trained in the

operation of the irradiator and was listed as an authorized user, but that the

irradiator was used infrequently and that this was only the operator's second

use of the irradiator since being trained.

The second incident occurred when a maintenance worker preparing to perform

maintenance on an irradiator bypassed the irradiator door interlock system to

observe movement of the inner irradiation chamber. The maintenance was being

K>

IN 96-35 June 11, 1996 performed to correct previous maintenance that resulted in the irradiator not

functioning properly. The maintenance worker was unaware that, although the

sources remained shielded during movement of the irradiation chamber from the

load to irradiate position, high levels of radiation scatter would be present.

The maintenance worker, upon hearing the in-room monitor alarm, immediately

returned the radiation chamber to the 'load' position (maximum shielding).

Although the maintenance worker was familiar with the operation of the

irradiator and had been responsible for its maintenance for nearly 15 years, the worker apparently had not been given formal training on radiation safety

or the operation and maintenance of the irradiator. The maintenance worker

was not aware of the scatter radiation and assumed that since the sources were

not directly exposed, radiation from the sources would be contained within the

device.

During this incident, another worker, hired to perform contract maintenance on

the irradiator, was also in the room near the irradiator. Neither worker wore

dosimetry nor had any documented training in radiation safety. Therefore, their doses could only be calculated based on their recollection and were

estimated to both be approximately 4 microsievert (0.4 mrem) whole body.

Discussion

Although neither incident resulted in doses in excess of regulatory limits, the doses received in both incidents were unnecessary and possibly could have

been avoided with proper training and routine equipment maintenance. A

similar incident in 1984, where a door interlock failed, resulted in the

operator being exposed to 222 terabequerel (6000 curies) of cesium-137.

The first incident clearly demonstrates the need to perform appropriate

maintenance on these types of units. Even though these units are designed

with interlocks and safety features intended to prevent inadvertent exposures, the components of these systems depend on adequate maintenance to function

properly. Failure to properly maintain these systems and provide appropriate

training could result in unnecessary exposures. Manufacturers of these types

of irradiators frequently provide initial and periodic training on the

operation of their units and, in some cases, training on other manufacturers'

units, as well. Initial training is typically a condition of the license and, therefore, must be provided to all irradiator users and maintenance personnel.

Periodic refresher training is also beneficial as a reminder for working

safely around the irradiator and provides for a means to receive or

disseminate additional or updated information.

In addition, most manufacturers have a recommended schedule of maintenance

and/or recommended preventative/periodic maintenance that should be performed.

Users of these types of irradiators should evaluate their usage to determine

the applicability of the recommended maintenance to their situation and usage.

Users who operate their unit more than usual or who use their units under

harsh conditions should consider the need for stepped-up maintenance or

'-> IN 96-35 June 11, 1996 shortened maintenance intervals. In addition, each manufacturer's recommended

maintenance may vary according to the specific unit or type of use.

Therefore, personis performing maintenance on their unit may require specific

maintenance training for their unit.

Users who are not aware of the required training for their unit, or who wish

to receive information concerning training in general, should consult their

license, licensing authority, or the manufacturer of the unit. Regulatory

Guide 10.9, provides additional guidance in this area and may assist persons

who wish to develop a training and maintenance program. Users who wish to

receive additional information concerning recommended maintenance for their

unit should contact the manufacturer of the unit. In addition, third-party

service companies may also be available for training and maintenance services

for these types of irradiators.

This information notice 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.

I3W¶flstn 8 by9WWstIA

Donald A. Cool, Director

Division of Industrial and

Medical Nuclear Safety

Office of Nuclear Material Safety

and Safeguards

Technical contacts: Douglas Broaddus, NMSS

(301) 415-5847 Internet:dab~nrc.gov

Anthony Kirkwood, NMSS

(301) 415-6140

Internet:ask~nrc.gov

Attachments:

1. List of Recently issued NMSS Information Notices

2. List of Recently issued NRC Information Notices

DOCUMENT NAME: 96-35.IN

To receive a copy of this document, Indicate In the box: C' = Copy without attachment/enclosure *E' - Copy with attachmentjendosure N

  • No copy
  • See previous concurrence

OFFICE IIMAB* [ClIMAB* [C Tech Editor* l IMOB* [C IMNS* I C,

NAME IDBroaddus* LCamper lEKraus _KRamsey jDCof'

DATE 14/17/96 5/28/96 4/01/96 5/31/96 6/4 96 11 OFFICIAL RECORD COPY

j;

IN 96-XX

May XX, 1996 Users who are not aware of the required training for their unit, or who wish

to receive information concerning training in general, should consult their

license, licensing authority, or the manufacturer of the unit. Regulatory

Guide 10.9, provides additional guidance in this area and may assist persons

who wish to develop a training and maintenance program. Users who wish to

receive additional information concerning recommended maintenance for their

unit should contact the manufacturer of the unit. In addition, third-party

service companies may also be available for training and maintenance services

for these types of irradiators.

This information notice 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.

Donald A. Cool, Director

Division of Industrial and

Medical Nuclear Safety

Office of Nuclear Material Safety

and Safeguards

Technical contacts: Douglas Broaddus, NMSS

(301) 415-5847 Anthony Kirkwood, NMSS

(301) 415-6140

Attachments:

1. List of Recently issued NMSS Information Notices

2. List of Recently issued NRC Information Notices

DOCUMENT NAME: A:\IRADIATR.FIN

To receive a copy of this docunent, Indicate hI the box: 'C Copy without attachmentlenclosure WE-= Copy with attachmentlenclosure ONE copY

  • See previous concurrence a

OFFICE IMAB I INAB 15 /HTech Editor I IMOB IMN h

NAME DBroaddus* LCam er' 1EKraus* KRamse Kmfl Co

DATE 4/17/96 L/46/96 14/01/96 5-13j /96 /

OFFICIAL RECORD COPY

IN 96-XX

May XX, 1996 Users who are not aware of the required training for their unit, or who wish

to receive information concerning training in general, should consult their

license, licensing authority, or the manufacturer of the unit. Regulatory

Guide 10.9, provides additional guidance in this area and may assist persons

who wish to develop a training and maintenance program. Users who wish to

receive additional information concerning recommended maintenance for their

unit should contact the manufacturer of the unit. In addition, third-party

service companies may also be available for training and maintenance services

for these types of irradiators.

This information notice 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.

Donald A. Cool, Director

Division of Industrial and

Medical Nuclear Safety

Office of Nuclear Material Safety

and Safeguards

Technical contacts: Douglas Broaddus, NMSS

301-415-5847 Anthony Kirkwood, RI

610-337-5050

Attachments:

1. List of Recently issued NMSS Information Notices

2. List of Recently issued NRC Information Notices

DOCUMENT NAME: A:\IRADIATR.FIN

To receiv a copy of this document, Indicate In the box: C' = Copy without attachmentlenclosure 'E' = Copy with aftachment/enclosure *'N - No copy

lOFFICE IMAB [ IMAB LJTech Editor LAL IMOB LJIMNS

INAME DBroaddus LCamper EKraus wa KRamsey DCool

DMTE 4//f/96 4/ /96 4/W /96 4/ /96 4/ /96 OFFICIAL RECORD COPY

KUJ KU

Attachment 1 IN 96-35 June 11, 1996 LIST OF RECENTLY ISSUED

NMSS INFORMATION NOTICES

Information ' Date of

Notice No. Subject Issuance Issued to

96-33 Erroneous Data from Defec- 05/224/96 All material and fuel cycle

tive Thermocouple Results licensees that monitor tem- in a Fire perature with thermocouples

96-28 Suggested Guidance Relat- 05/01/96 All material and fuel cycle

ing to Development and licensees

Implementation of Correc- tive Action

96-21 Safety Concerns Related 04/10/96 All NRC Medical Licensees

to the Design of the Door authorized to use brachy- Interlock Circuit on therapy sources in high- Nucletron High-Dose Rate and pulsed-dose-rate remote

and Pulsed Dose Rate

Remote Afterloading Brachy- therapy Devices

96-20 Demonstration of Associ- 04/04/96 All industrial radiography

ated Equipment Compliance licensees and radiography

with 10 CFR 34.20 equipment manufacturers

96-18 Compliance With 10 CFR 03/25/96 All material licensees

Part 20 for Airborne authorized to possess and

Thorium use thorium in unsealed form

96-04 Incident Reporting 01/10/96 All Radiography Licensees

Requirements for and Manufacturers of

Radiography Licensees Radiography Equipment

95-58 10 CFR 34.20; Final 12/18/95 Industrial Radiography

Effective Date Licensees.

95-55 Handling Uncontained 12/6/95 All Uranium Recovery

Yellowcake Outside of a Licensees.

Facility Processing Circuit

95-51 Recent Incidents Involving 10/27/95 All material and fuel cycle

Potential Loss of Control licensees.

of Licensed Material

K>- iKJ

Attachment 2 IN 96-35 June 11, 1996 LIST OF RECENTLY ISSUED

NRC INFORMATION NOTICES

Information Date of

Notice No. Subject Issuance Issued to

96-34 Hydrogen Gas Ignition 05/31/96 All holders of OLs or CPs

during Closure Welding for nuclear power reactors

of a VSC-24 Multi-Assembly

Sealed Basket

96-33 Erroneous Data From 05/24/96 All material and fuel cycle

Defective Thermocouple licensees that monitor tem- Results in a Fire perature with thermocouples

96-32 Implementation of 10 CFR 06/05/96 All holders of OLs or CPs

50.55a(g)(6)(ii)(A), for nuclear power reactors

"Augmented Examination

of Reactor Vessel"

96-31 Cross-Tied Safety Injec- 05/22/96 All holders of OLs or CPs

tion Accumulators for pressurized water

reactors

96-30 Inaccuracy of Diagnostic 05/21/96 All holders of OLs or CPs

Equipment for Motor- for nuclear power reactors

Operated Butterfly Valves

96-29 Requirements in 10 CFR 05/20/96 All holders of OLs or CPs

Part 21 for Reporting and for nuclear power reactors

Evaluating Software Errors

96-28 Suggested Guidance Relating 05/01/96 All material and fuel cycle

to Development and Imple- licensees

mentation of Corrective

Action

96-27 Potential Clogging of High 05/01/96 All holders of OLs or CPs

Pressure Safety Injection for pressurized water

Throttle Valves During reactors

Recirculation

96-26 Recent Problems with Over- 04/30/96 All holders of OLs or CPs

head Cranes for nuclear power reactors

96-25 Transversing In-Core Probe 04/30/96 All holders of OLs or CPs

Overwithdrawn at LaSalle for nuclear power reactors

County Station, Unit 1 OL - Operating License

CP - Construction Permit


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