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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| issue date = 06/11/1996
| issue date = 06/11/1996
| title = Failure of Safety Systems on Self-Shielded Irradiators Because of Inadequate Maintenance and Training
| title = Failure of Safety Systems on Self-Shielded Irradiators Because of Inadequate Maintenance and Training
| author name = Cool D A
| author name = Cool D
| author affiliation = NRC/NMSS/IMNS
| author affiliation = NRC/NMSS/IMNS
| addressee name =  
| addressee name =  
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| page count = 8
| page count = 8
}}
}}
{{#Wiki_filter:UNITED STATESNUCLEAR REGULATORY COMMISSIONOFFICE OF NUCLEAR MATERIAL SAFETY AND SAFEGUARDSWASHINGTON, D.C. 20555June 11, 1996NRC INFORMATION NOTICE 96-35: FAILURE OF SAFETY SYSTEMS ON SELF-SHIELDEDIRRADIATORS BECAUSE OF INADEQUATE MAINTENANCEAND TRAINING
{{#Wiki_filter: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==
==Addressees==
Line 20: Line 30:


==Purpose==
==Purpose==
The U.S. Nuclear Regulatory Commission (NRC) is issuing this informationnotice (IN) to alert addressees to two incidents where safety interlocks onself-shielded irradiators (Category I) failed to prevent inadvertent exposure.The causes of these exposures stemmed from a lack of appropriate maintenanceand/or worker training. The incidents include a broken spring -- possiblycausing malfunction of the safety interlock -- and a worker who intentionallybypassed a safety interlock. It is expected that recipients will review theinformation for applicability to their facilities and consider actions, asappropriate, to avoid similar problems. However, suggestions contained inthis information notice are not NRC requirements; therefore, no specificaction nor written response is required.
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==
==Description of Circumstances==
The first incident occurred when an operator may have been able to open theshielded door of an irradiator with the sources in the exposed position.After irradiation of several pocket dosimeters, the operator opened theshielded door of the irradiator to retrieve the dosimeters, but did notperform a radiation survey, as required by the facility's internal procedures,before opening the door. Twice, the operator placed one hand inside theirradiator to retrieve the dosimeters. Subsequently, the operator observedthat the unit timer continued to count, indicating that the sources remainedin the exposed position. The operator checked his personal pocket dosimeter,but did not note an unusual reading. However, the operator did not report theincident until questioned by the radiation safety officer, who had noted anunusually high dosimetry report of 3.55 millisievert (355 mrem) deep doseequivalent for the worker. The dose to the right hand was calculated to be amaximum 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 doorinterlock system -- designed to allow opening of the shielded door only afterthe sources are placed in the fully shielded position -- and a source exposure-.interlock system -- designed to secure the sources in the fully shieldedtDR FE E NO r/C9 03 ?C 0t, II kk JIIN 96-35June 11, 1996 position whenever the shielded door is open or unlocked. The manufacturer ofthe irradiator indicated that under normal operations, either systemindividually wouldiprevent inadvertent access to the unshielded sources.Following the incident, the manufacturer of the irradiator was requested toperform an onsite inspection of the irradiator and facilities. During theinspection, 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 approximately10 years ago; and(4) a return spring, integral to the source exposure safety interlocksystem, was broken. The manufacturer indicated that the lack ofenvironmental control may have accelerated the degradation of theinternal components of the irradiator, and that the lack of periodicmaintenance of the irradiator may have contributed to the failure ofthe return spring.The broken return spring may have caused the source securing mechanism of thesource exposure interlock system to malfunction, possibly allowing exposure ofthe sources after the shielded door was unlocked and opened. However, duringthe post-incident investigation, neither the manufacturer nor the licenseewere able to identify a failed component of either interlock system that couldhave allowed the shielded door to be opened with the sources in the exposedposition. The manufacturer indicated that the design of the source exposuremechanism -- the operator must manually move the sources from the shielded tothe exposed position with a lever -- would have provided the operator with apositive indication of source position even if the interlock systems failed.Source position would have been further provided by a series of green and redsource position lights on the irradiator.The operator's actions indicate either a lack of training on the properfunctioning and use of the irradiator, a lack of understanding of the trainingprovided, and/or a disregard for following the established operating andsafety procedures. The operator indicated that the timer continued to countwhen the shielded door was opened. However, the manufacturer reported thatthe timer automatically activates whenever the source lever is manually movedto one of the two source exposed positions and the lever is fully engaged inthe source slot, and stops counting as soon as the lever is moved from thefully engaged position. The fact that the timer continued to count indicatesthat the operator had not moved the sources from the fully exposed and engagedposition. The licensee reported that the operator had been trained in theoperation of the irradiator and was listed as an authorized user, but that theirradiator was used infrequently and that this was only the operator's seconduse of the irradiator since being trained.The second incident occurred when a maintenance worker preparing to performmaintenance on an irradiator bypassed the irradiator door interlock system toobserve movement of the inner irradiation chamber. The maintenance was being K>IN 96-35June 11, 1996 performed to correct previous maintenance that resulted in the irradiator notfunctioning properly. The maintenance worker was unaware that, although thesources remained shielded during movement of the irradiation chamber from theload to irradiate position, high levels of radiation scatter would be present.The maintenance worker, upon hearing the in-room monitor alarm, immediatelyreturned the radiation chamber to the 'load' position (maximum shielding).Although the maintenance worker was familiar with the operation of theirradiator and had been responsible for its maintenance for nearly 15 years,the worker apparently had not been given formal training on radiation safetyor the operation and maintenance of the irradiator. The maintenance workerwas not aware of the scatter radiation and assumed that since the sources werenot directly exposed, radiation from the sources would be contained within thedevice.During this incident, another worker, hired to perform contract maintenance onthe irradiator, was also in the room near the irradiator. Neither worker woredosimetry nor had any documented training in radiation safety. Therefore,their doses could only be calculated based on their recollection and wereestimated to both be approximately 4 microsievert (0.4 mrem) whole body.DiscussionAlthough neither incident resulted in doses in excess of regulatory limits,the doses received in both incidents were unnecessary and possibly could havebeen avoided with proper training and routine equipment maintenance. Asimilar incident in 1984, where a door interlock failed, resulted in theoperator being exposed to 222 terabequerel (6000 curies) of cesium-137.The first incident clearly demonstrates the need to perform appropriatemaintenance on these types of units. Even though these units are designedwith interlocks and safety features intended to prevent inadvertent exposures,the components of these systems depend on adequate maintenance to functionproperly. Failure to properly maintain these systems and provide appropriatetraining could result in unnecessary exposures. Manufacturers of these typesof irradiators frequently provide initial and periodic training on theoperation 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 workingsafely around the irradiator and provides for a means to receive ordisseminate additional or updated information.In addition, most manufacturers have a recommended schedule of maintenanceand/or recommended preventative/periodic maintenance that should be performed.Users of these types of irradiators should evaluate their usage to determinethe applicability of the recommended maintenance to their situation and usage.Users who operate their unit more than usual or who use their units underharsh conditions should consider the need for stepped-up maintenance or
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


'-> IN 96-35June 11, 1996 shortened maintenance intervals. In addition, each manufacturer's recommendedmaintenance may vary according to the specific unit or type of use.Therefore, personis performing maintenance on their unit may require specificmaintenance training for their unit.Users who are not aware of the required training for their unit, or who wishto receive information concerning training in general, should consult theirlicense, licensing authority, or the manufacturer of the unit. RegulatoryGuide 10.9, provides additional guidance in this area and may assist personswho wish to develop a training and maintenance program. Users who wish toreceive additional information concerning recommended maintenance for theirunit should contact the manufacturer of the unit. In addition, third-partyservice companies may also be available for training and maintenance servicesfor these types of irradiators.This information notice requires no specific action nor written response. Ifyou have any questions about the information in this notice, please contactone of the technical contacts listed below or the appropriate regional office.I3W¶flstn8by9WWstIADonald A. Cool, DirectorDivision of Industrial andMedical Nuclear SafetyOffice of Nuclear Material Safetyand SafeguardsTechnical contacts: Douglas Broaddus, NMSS(301) 415-5847Internet:dab~nrc.govAnthony Kirkwood, NMSS(301) 415-6140Internet:ask~nrc.gov
head Cranes                                  for nuclear power reactors


===Attachments:===
96-25          Transversing In-Core Probe    04/30/96      All holders of OLs or CPs
1. List of Recently issued NMSS Information Notices2. List of Recently issued NRC Information NoticesDOCUMENT NAME: 96-35.INTo receive a copy of this document, Indicate In the box: C' = Copy without attachment/enclosure *E' -Copy with attachmentjendosure N


* No copy* See previous concurrenceOFFICE 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 11OFFICIAL RECORD COPY j;IN 96-XXMay XX, 1996 Users who are not aware of the required training for their unit, or who wishto receive information concerning training in general, should consult theirlicense, licensing authority, or the manufacturer of the unit. RegulatoryGuide 10.9, provides additional guidance in this area and may assist personswho wish to develop a training and maintenance program. Users who wish toreceive additional information concerning recommended maintenance for theirunit should contact the manufacturer of the unit. In addition, third-partyservice companies may also be available for training and maintenance servicesfor these types of irradiators.This information notice requires no specific action nor written response. Ifyou have any questions about the information in this notice, please contactone of the technical contacts listed below or the appropriate regional office.Donald A. Cool, DirectorDivision of Industrial andMedical Nuclear SafetyOffice of Nuclear Material Safetyand SafeguardsTechnical contacts: Douglas Broaddus, NMSS(301) 415-5847Anthony Kirkwood, NMSS(301) 415-6140
Overwithdrawn at LaSalle                      for nuclear power reactors


===Attachments:===
County Station, Unit 1 OL - Operating License
1. List of Recently issued NMSS Information Notices2. List of Recently issued NRC Information NoticesDOCUMENT NAME: A:\IRADIATR.FINTo receive a copy of this docunent, Indicate hI the box: 'C Copy without attachmentlenclosure WE- = Copy with attachmentlenclosure ONE copY* See previous concurrence aOFFICE IMAB I INAB 15 /HTech Editor I IMOB IMN hNAME DBroaddus* LCam er' 1EKraus* KRamse Kmfl CoDATE 4/17/96 L/46/96 14/01/96 5-13j /96 /OFFICIAL RECORD COPY IN 96-XXMay XX, 1996 Users who are not aware of the required training for their unit, or who wishto receive information concerning training in general, should consult theirlicense, licensing authority, or the manufacturer of the unit. RegulatoryGuide 10.9, provides additional guidance in this area and may assist personswho wish to develop a training and maintenance program. Users who wish toreceive additional information concerning recommended maintenance for theirunit should contact the manufacturer of the unit. In addition, third-partyservice companies may also be available for training and maintenance servicesfor these types of irradiators.This information notice requires no specific action nor written response. Ifyou have any questions about the information in this notice, please contactone of the technical contacts listed below or the appropriate regional office.Donald A. Cool, DirectorDivision of Industrial andMedical Nuclear SafetyOffice of Nuclear Material Safetyand SafeguardsTechnical contacts: Douglas Broaddus, NMSS301-415-5847Anthony Kirkwood, RI610-337-5050


===Attachments:===
CP - Construction Permit}}
1. List of Recently issued NMSS Information Notices2. List of Recently issued NRC Information NoticesDOCUMENT NAME: A:\IRADIATR.FINTo receiv a copy of this document, Indicate In the box: C' = Copy without attachmentlenclosure 'E' = Copy with aftachment/enclosure *'N -No copylOFFICE IMAB [ IMAB LJTech Editor LAL IMOB LJIMNSINAME DBroaddus LCamper EKraus wa KRamsey DCoolDMTE 4//f/96 4/ /96 4/W /96 4/ /96 4/ /96OFFICIAL RECORD COPY KUJ KUAttachment 1IN 96-35June 11, 1996 LIST OF RECENTLY ISSUEDNMSS INFORMATION NOTICESInformation ' Date ofNotice No. Subject Issuance Issued to96-33Erroneous Data from Defec-tive Thermocouple Resultsin a Fire05/224/96All material and fuel cyclelicensees that monitor tem-perature with thermocouples96-2896-2196-2096-18Suggested Guidance Relat-ing to Development andImplementation of Correc-tive ActionSafety Concerns Relatedto the Design of the DoorInterlock Circuit onNucletron High-Dose Rateand Pulsed Dose RateRemote Afterloading Brachy-therapy DevicesDemonstration of Associ-ated Equipment Compliancewith 10 CFR 34.20Compliance With 10 CFRPart 20 for AirborneThoriumIncident ReportingRequirements forRadiography Licensees10 CFR 34.20; FinalEffective DateHandling UncontainedYellowcake Outside of aFacility Processing CircuitRecent Incidents InvolvingPotential Loss of Controlof Licensed Material05/01/9604/10/9604/04/9603/25/9601/10/9612/18/9512/6/9510/27/95All material and fuel cyclelicenseesAll NRC Medical Licenseesauthorized to use brachy-therapy sources in high-and pulsed-dose-rate remoteAll industrial radiographylicensees and radiographyequipment manufacturersAll material licenseesauthorized to possess anduse thorium in unsealed formAll Radiography Licenseesand Manufacturers ofRadiography EquipmentIndustrial RadiographyLicensees.All Uranium RecoveryLicensees.All material and fuel cyclelicensees.96-0495-5895-5595-51 K> -iKJAttachment 2IN 96-35June 11, 1996 LIST OF RECENTLY ISSUEDNRC INFORMATION NOTICESInformation Date ofNotice No. Subject Issuance Issued to96-3496-3396-3296-3196-30Hydrogen Gas Ignitionduring Closure Weldingof a VSC-24 Multi-AssemblySealed BasketErroneous Data FromDefective ThermocoupleResults in a FireImplementation of 10 CFR50.55a(g)(6)(ii)(A),"Augmented Examinationof Reactor Vessel"Cross-Tied Safety Injec-tion AccumulatorsInaccuracy of DiagnosticEquipment for Motor-Operated Butterfly ValvesRequirements in 10 CFRPart 21 for Reporting andEvaluating Software ErrorsSuggested Guidance Relatingto Development and Imple-mentation of CorrectiveActionPotential Clogging of HighPressure Safety InjectionThrottle Valves DuringRecirculationRecent Problems with Over-head CranesTransversing In-Core ProbeOverwithdrawn at LaSalleCounty Station, Unit 105/31/9605/24/9606/05/9605/22/9605/21/9605/20/9605/01/9605/01/9604/30/9604/30/96All holders of OLs or CPsfor nuclear power reactorsAll material and fuel cyclelicensees that monitor tem-perature with thermocouplesAll holders of OLs or CPsfor nuclear power reactorsAll holders of OLs or CPsfor pressurized waterreactorsAll holders of OLs or CPsfor nuclear power reactorsAll holders of OLs or CPsfor nuclear power reactorsAll material and fuel cyclelicenseesAll holders of OLs or CPsfor pressurized waterreactorsAll holders of OLs or CPsfor nuclear power reactorsAll holders of OLs or CPsfor nuclear power reactors96-2996-2896-2796-2696-25OL -Operating LicenseCP -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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