Information Notice 1994-89, Equipment Failures at Irradiator Facilities: Difference between revisions
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| issue date = 12/28/1994 | | issue date = 12/28/1994 | ||
| title = Equipment Failures at Irradiator Facilities | | title = Equipment Failures at Irradiator Facilities | ||
| author name = Paperiello C | | author name = Paperiello C | ||
| author affiliation = NRC/NMSS/IMNS | | author affiliation = NRC/NMSS/IMNS | ||
| addressee name = | | addressee name = |
Revision as of 05:40, 14 July 2019
-/UNITED STATES NUCLEAR REGULATORY
COMMISSION
OFFICE OF NUCLEAR MATERIAL SAFETY AND SAFEGUARDS
WASHINGTON, D.C. 20555 December 28, 1994 NRC INFORMATION
NOTICE 94-89: EQUIPMENT
FAILURES AT IRRADIATOR
FACILITIES
Addressees
All U.S. Nuclear Regulatory
Commission
irradiator
licensees.
PurRose The U.S. Nuclear Regulatory
Commission (NRC) is issuing this information
notice to alert addressees
to several equipment
failures -- some of which have generic implications
-- that involve wet source storage irradiators.
It is expected that all recipients (including
dry source storage irradiator
licensees)
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 new NRC requirements;
therefore, no specific action or written response is required.Descrition
of Circumstances
The first equipment
failure involved the time delay system required in 10 CFR 36.23(f).
The second equipment
failure involved two incidents
where the control console provided false indications
of irradiator
condition.
The final equipment
failure involved a source rack that failed to return to its shielded position after the comnand was initiated
at the control console.1. Fault in the Operational
Time Delay Reset Power Supply.In this incident, a fault in the control console circuitry
occurred at a licensee's
facility when an external electrical
power surge caused a fuse to blow in the operational
time delay reset power supply. This circuit had been recently installed
to meet the requirements
of 10 CFR Part 36. The operational
time delay circuit prevents the control console from activating
for a preset time after being initiated
by the operator in the irradiation
room, thereby preventing
source rack movement per 10 CFR 36.23(f).
In addition, the operational
time delay circuit of this irradiator
must be operational
for the audible and visual warning circuit and the door interlock circuit to function properly.
The audible and visual warning systems are designed to activate whenever the irradiator
door is opened and source movement is initiated.
Nevertheless, the audible and visual warning systems did not activate when the operator left the irradiation
room, until the control console was turned 0ON6 with the console key. The planned irradiation
was performed, however, since the audible warning system did activate before irradiation, per the requirement
In 10 CFR 36.31(a).9412210186 PDR ZV > cL(~ (l4eX am t31195 IN 94-89 December 28, 1994 The operational
time delay circuit was also designed to reset after an irradiation
to prevent the control console from being re-energized
and allowing additional
source movement.
The control console should not re-energize until the circuit is again initiated
by the operator In the irradiation
room. However, in this incident, the control console was able to be re-energized
before the time delay circuit was initiated.
The blown fuse in the reset power supply prevented
the time delay circuit from resetting
as designed.To prevent reoccurrence, a surge protector
was installed
to protect the entire system from external power surges, and the time delay circuit was redesigned
to disable the control console, audio and visual safety circuits, and the source positioning
system, in case the fuse blows again. This alerts the operator to a fault and prevents source movement until the fuse is replaced.2. False Indications
of Source Rack Position.A false indication
of source rack position (rack not in the fully down position)
was received at the control console of a wet source storage licensee when the wire that carries the source position signal shorted because of worn insulation.
Vibration
in the system caused the wire to rub against nearby metal and wore away the insulation.
The short-circuit
also caused an initial intermittent
false indication
of a collision
between the source rack and the carrier. The licensee verified that the sources were in the shielded position and traced the fault to the damaged wire. The wire was replaced and rerouted through a flexible conduit to reduce the possibility
of additional
wear.A second false indication
of source rack position occurred at the same facility when the plunger of a source rack down-position
switch failed to extend and thereby did not properly indicate the true position of the source rack. The plunger failed to extend because of corrosion
between the plunger and sleeve causing increased
friction.
The irradiator
licensee received conflicting
signals when the lower position switch indicated
that the source rack was not fully down, but the upper position switch Indicated
that the source rack was fully down. The installed
radiation
monitors and subsequent
surveys performed
outside of the cell indicated
that the source rack was shielded.
Further visual analysis confirmed
that the source racks were in the fully shielded position.The licensee concluded
that the lower source rack position switch was malfunctioning
and replaced the switch. On further analysis of the switch, it was determined
that green corrosion
deposits on the brass sleeve and steel plunger of the switch caused the plunger to stick in the retracted
position, preventing
it from springing
back to the extended position.
With the plunger in the retracted
position, the switch indicates
the source rack is not in the fully down position.
The Irradiator
vendor, Nordion International, Inc.(NII), was notified and has issued Service Bulletin IND-93-2, which is included as Attachment
1 to this information
notice. Service Bulletin IND-93-2 advises all users of NIl pool type irradiators
containing
these plunger-type
position indicators
to check the switches for evidence of corrosion, clean the switches if corrosion
is found, and replace the switches as soon as possible.
IN 94-89 December 28, 1994 In addition, NII has provided replacement
switches constructed
of corrosion- resistant
materials (porcelain
sleeve and stainless
steel plunger) to all users whose irradiators
contain the non-corrosion-resistant
switches, and has provided instructions
for installation
and initial testing of the new switches.3. Failure of Source Rack to Return to the Shielded Position.In this incident, a source rack at a licensee's
facility failed to return to the shielded position.
This occurred when an air solenoid valve failed to fully return to the exhaust position and stuck in an intermediate
position that blocked any air passage through the valve, thereby trapping air pressure in the line between the valve and source rack hoist. During a typical irradiation, the licensee noted an irregular
reading on the control console (not related to source rack position)
and pressed the emergency
stop button.The source rack position indication
on the control console indicated
that one of the two irradiator
source racks failed to return to the fully down/shielded
position.
The installed
radiation
monitors, the position of the source rack cable on the roof of the irradiator
builcing, and subsequent
radiation
surveys performed
outside the Irradiation
cell confirmed
that one source rack had remained in the up/unshielded
position.
Further investigation
revealed that pressure remained in the air line to the source rack hoist, keeping the rack in the exposed position, when this pressure should have been released.
The licensee cut the air line to release the pressure, and the source rack returned to the fully down/shielded
position.
The licensee determined
that one or both of the air solenoid valves in the supply line failed to move to the exhaust position when the source down command was initiated, thereby not lowering the source rack. Both valves were replaced and the source hoist system operated normally.The irradiator
vendor, NII, was notified and both solenoid valves were returned to NII for further investigation.
NII determined
that the solenoid valves that were indicated
to be four-way, two-position (exhaust/pressurize), five-port
valves could in certain circumstances, operate as four-way, three-position (exhaust/pressurize/neutral), five-port
valves. A two-position
valve would exhaust pressure in the air line to the source rack hoist upon loss of supply air pressure, regardless
of valve position.
The neutral position of a three-position
valve would maintain pressure In the air line to the source rack hoist regardless
of supply air pressure.
Therefore, a three-position
valve would not allow for a fail-safe
operation.
The circumstance
that allowed the valve to operate as a three-position
valve was attributed
to the deterioration
and hardening
of the seals in the valve spool, causing the valve spool to stick in the neutral position.
Nil's investigation
showed that it is unlikely that the ingress of contaminants
caused the valve spool to stick in the 'neutral position.
However, NII did not rule that out as a contributing
factor. According
to NII, harding of the seals is thought to be caused by oxidation
over time of the seal material.
One of the spools, in use for over 5 years, showed considerable
hardening
of the seal material, whereas the seals of the other spool, in use for only 14 months, had become hardened, but not as hard as the first valve's seals.
...j IN 94-89 December 28, 1994 As a result of this incident, NII issued Service Bulletin IND-94-1, which is included as Attachment
2 to this information
notice. To preclude future failures of this nature, NlI recommends
that Norgren part 54237-56 valve spools no longer be used in Norgren Nugget 200 Series Source Hoist Valves, part K71EAOO KSI AECKGI, and that Norgren part 54237-58 spools be used as replacement
spools in existing and all new valves of this type used in NII pool type irradiators.
The 54237-58 spools allow for the exhaust of air in all positions, thus eliminating
the possibility
of pressure remaining
in the air line to the source rack hoist on removal of supply air pressure.
In addition, NII recommended
in their report to the licensee, that the spools be replaced periodically
to reduce the possibility
of additional
failures because of seal hardening.
NII's investigation
revealed that detectable
hardening
of the seal material has occurred, in at least one case, within 14 months of use.However, the valve in that case continued
to operate without failure.In addition, NII reports that licensees
who have ordered replacement
valves for the original installed
valves (part K71EAOO KSI AECKGI), may have received replacement
valves labeled with Norgren's
off-the-shelfl
part numbers.Therefore, Norgren Nugget 200 Series Source Hoist Valves with part numbers K71EAOO KS6 KQI, K71EAOO KS6 AECKGI, and any other variants of the K71EAOO valves used for these operations
should have their valve spools replaced also.NII asserts that the construction
and operation
of these valves are identical to the K71EAOO KSI AECKGI valves.Discussion:
The failures of the audible and visual warning systems and operational
time delay to initiate properly were caused by a blown fuse in the operational
time delay reset power supply, failing to cause the timer to reset. This allowed the control console to be energized
and source movement to occur before the operational
time delay being re-initiated, contrary to Part 36 requirements.
The redesigned
circuit prevents this situation
from occurring
by not allowing the control console to re-energize
if this fuse blows again. The control console is designed such that source movement cannot occur unless the control console is energized.
Irradiator
users should evaluate all possible failure modes of source positioning
control circuitry
and interlocks, or circuitry that supports these systems, upon installation
and whenever modifications
are made.The worn insulation
that caused the short in the source rack position indication
circuit did not cause a situation
in which the source racks were in the exposed position unintentionally.
However, the licensee was required to bypass safety interlocks (using appropriate
safety measures)
to verify the true position of the source rack. Users should be aware of and take precautions
against conditions (e.g., wear caused by vibration, excessive heat, embrittlement
caused by high radiation, etc.) which could cause the failure of essential
electrical
components
and indicators.
IN 94-89 December 28, 1994 Users of NII pool-type
irradiators
containing
source down-position
indication
switches constructed
of non-corrosion-resistant
materials
should be aware that if the recommendations
contained
in NII Service Bulletin IND-93-2 are not followed, the potential
for false or conflicting
source rack position signals exists. If a false signal is received, the operator may be required to bypass safety interlocks (using appropriate
safety measures)
to verify the true position of the source rack.The most likely cause of the corrosion
was the close proximity
of the switch to the water line and high humidity in the irradiation
room. To date, NII is not aware of any indications
of corrosion
developing
in the upper source position switch, which is constructed
using materials
similar to the original bottom source down-position
switches.
The upper switch is located away from the water line and is exposed to higher temperatures
and lower humidity when the source rack is in the raised/exposed
position.
However, if conditions
exist in the area around the upper switch that are favorable
to corrosion (e.g., high humidity or a caustic atmosphere), this switch could corrode also.Users of NII pool-type
irradiators
containing
Norgren part 54237-56 valve spools used in Norgren Nugget 200 Series Source Hoist Valves, part K71EAOO, should be aware that if they do not follow the NII recommendation
to replace the 54237-56 spools with 54237-58 spools, the source racks may become stuck in the exposed position.
Licensees
may have to cut the air line to the source rack hoist to return the source rack to the shielded position.
In addition, the licensees
should consider NII's recommendation
that the spools be replaced on a periodic basis to reduce the possibility
of failure, according
to their specific operation.
If not replaced, the replacement
valve spools could fail because of seal material hardening, although such failure would not cause pressure to remain trapped in the air line.This information
notice requires no specific action or written response.
If you have any questions
about the information
in this notice, please contact the technical
contact listed below or the appropriate
regional office.Carl J. perie o, Director Division of Industrial
and Medical Nuclear Safety Office of Nuclear Materials
Safety and Safeguards
Technical
contact: Douglas Broaddus, NKSS (301) 415-5847 Attachments:
1. Nordion International
Inc., Service Bulletin IND-93-2 2. Nordion International
Inc., Service Bulletin IND-94-1 3. List of Recently issued NMSS Information
Notices 4. List of Recently issued NRC Information
Notices
<_4 _ 94-89 December 28, 1994 Users of NII pool-type
irradiators
containing
source down-position
indication
switches constructed
of non-corrosion-resistant
materials
should be aware that if the recommendations
contained
in NII Service Bulletin IND-93-2 are not followed, the potential
for false or conflicting
source rack position signals exists. If a false signal is received, the operator may be required to bypass safety interlocks (using appropriate
safety measures)
to verify the true position of the source rack.The most likely cause of the corrosion
was the close proximity
of the switch to the water line and high humidity in the irradiation
room. To date, NII is not aware of any indications
of corrosion
developing
in the upper source position switch, which is constructed
using materials
similar to the original bottom source down-position
switches.
The upper switch is located away from the water line and is exposed to higher temperatures
and lower humidity when the source rack is in the raised/exposed
position.However, if conditions
exist in the area around the upper switch that are favorable
to corrosion (e.g., high humidity or a caustic atmosphere), this switch could corrode also.Users of NII pool-type
irradiators
containing
Norgren part 54237-56 valve spools used in Norgren Nugget 200 Series Source Hoist Valves, part K71EA00, should be aware that if they do not follow the NII recommendation
to replace the 54237-56 spools with 54237-58 spools, the source racks may become stuck in the exposed position.
Licensees
may have to cut the air line to the source rack hoist to return the source rack to the shielded position.
In addition, the licensees
should consider Nil's recommendation
that the spools be replaced on a periodic basis to reduce the possibility
of failure, according to their specific operation.
If not replaced, the replacement
valve spools could fail because of seal material hardening, although such failure would not cause pressure to remain trapped in the air line.This information
notice requires no specific action or written response.
If you have any questions
about the information
in this notice, please contact the technical
contact listed below or the appropriate
regional office.Carl J. Paperiello, Director Division of Industrial
and Medical Nuclear Safety Office of Nuclear Materials
Safety and Safeguards
Technical
contact: Douglas Broaddus, NMSS (301) 415-5847 Attachments:
1. Nordion International
Inc., Service Bulletin IND-93-2 2. Nordion International
Inc., Service Bulletin IND-94-1 3. List of Recently issued NMSS Information
Notices 4. List of Recently issued NRC Information
Notices DOCUMENT MANE: 94-89.IN Technical
Editor*EKraus 11/16/94 *See previous concurrence
cop without at L. 6* WM attachs t L. BE- a Co p1* ous 'on c OFC IMOB* IMOB* SCDB* lKE INS I KANE KRamsey/l
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FCombs RBaer MFederline
EBrach CPa p 110 DATE 11/15/94 11/29/94 11/30/94 12/09/94 12/09/94 Not In 124l1V9= _ _ _ _ _ _ FLRoffice
j
~'IN 94-~ December , 1994 Users of NII pool-type
irradiators
containing
source down-position
indication
Ailtdas. constructed
of non-corrosion-resistant
materials
should be aware that if the recommendations
contained
In NII Service Bulletin IND-93-2 are not followed, the potmntial
for false or conflicting
source rack position signals exists.- IfMa false signal Is received, the operator may be required to bypass safety interlocks (using appropriate
safety measures)
to verify the true position of the source racuk The most likely cause of the corrosion
was the close proximity
of the switch to the water line and high humidity In the irradiation
room. To date, NII is not aware of any Indicattons
of.corrosion
developing
in the upper source position switch, which Is constructed
using Oateri as similar to the original bottom source down-position
switches.
The upper switch is located away from the water line and Is exposed to higher toWperatures
and lower humidity when the source rack Is in the raised/exposed
position.
However, if conditions
exist in the area around the upper switch that are favorable
to corrosion (e.g., high humidity or a caustic atmosphere), this switch could corrode also.Users of NII pool-type
irradiators
containing
Norgren part 54237-56 valve spools used In Norgren Nugget 200 Series Source Hoist Valves, part K71EA00, should be aware that if they do not follow the NII recommendation
to replace the 54237-56 spools with 54237-58 spools, the source racks may become stuck in the exposed position.
Licensees
may have to cut the air line to the source rack hoist to return the source rack to the shielded position.
In addition, the licensees
should consider NII s recommendation
that the spools be replaced on a periodic basis to reduce the possibility
of failure, according
to their specific operation.
If not replaced, the replacement
valve spools could fail because of seal material hardening, although such failure would not cause pressure to remain trapped In the air line.This information
notice requires no specific action or written response.
If you have any questions
about the information
in this notice please contact the technical
contact listed below or the appropriate
reglonal office.Carl J. Paperiello, Director Division of Industrial
and Medical Nuclear Safety Office of Nuclear Materials
Safety and Safeguards
Contact: Douglas Broaddus, NMSS (301) 415-5847 Attachments:
1. Nordion International
Inc., Service Bulletin IND-93-2 2. Nordion International
Inc., Service Bulletin IND-94-1 3. List of Recently issued NMSS Information
Notices 4. List of Recently issued NRC Information
Notices DOCUMENT NAME: G:IM-IRRAD.KNR
Technical
Editor*EKraus 11/16/94 *See previous concurrence
without t GP With, tt tu. upt
- U _ ___OFC J IMOB* SCW .M lM"+)KANE KRamsey/ll
GPangburn
FCombs RBaer NFederline
c C'peuello DATE 11/15/94 11/29/94 11/30/94 129/94 1209/94V 9 4 94^ -OFFI:'CIAL
RECOR COP
IN 94-November , 1994 aware of any Is4kcations
of corrosion
developing
in the upper source position switch, whicd is coestructed
using materials
similar to the original bottom source do"w#mpositls
switches.
The upper switch Is located away from the water line and Is exposed to higher taperatures
and lower humidity when the source rack is In the ralse/Uxposed
position.
However, if conditions
exist In the area around the upper switch that are vorable to corrosion (e.g., high humidity or a caustic atmosphere), this switc could corrode also.Users of KIU pool-type
irradiato
containing
Norgren part # 54237-56 valve spools used I. Korgren Nugget 200 rios Source Hoist Valves, part # K71EAOO, should be aware that If they do not fllow the NII recommendation
to replace the 54237-S6 spools with 5423748 spo4ls, the source racks may become stuck In the exposed position.
Licensees
may hav to cut the air line to the source rack hoist to return the source rack to shielded position.
In addition, the licensees
should consider NII's recoe ation that the spools be replaced on a periodic basis to reduce the possibility
of failure, according
to their specific operation.
If not replaced, the replace nt valve spools could fail because of seal material hardening, although such fa ure would not cause pressure to remain trapped In the air line.This information
notice requires no specifi action or written response.
If you have any questions
about the information
n this notice, please contact the technical
contact listed below or the appro Wate regional office.Carl J. periello, Director Division f Industrial
and* Medical uclear Safety Office of uclear Materials
Safety and Safegua Contact: Douglas Broaddus, NKSS (301) 415-5847 Attachments:
1. Nordion International
Inc., Service Bulleti IND-93-2 2. Nordion International
Inc., Service Bulletin IND-94-1 3. List of Recently issued NISS Information
Hoti es 4. List of Recently issued NRC Information
Notic s DISTRIBUTION:\
INOB r/f SCOB r/f iNKS r/f DOCIMENT NAME: G:IN-RRAD.KN\
Technical
Editor*EKraus 11/16/94 , mc'. Caov ulthout attedaclMmtc. -V a Caw wifth mttclumVc.qCuu
_U_______-!g OFC IM I IO M0BEI l -_ I I S INNS I INANE IKRUSseYIll
6Pnbr cobS , K\ E~aCh Pe110-ngur k t _ -.drC~peiel DAE 11/15/94 11/29/94 I~D AT E I 9 li994 1 1 194 -/q/ 1 I 1 I I OFFICM R ECOD COP
K>IN 94-November , 1994 aware of any indications
of corrosion
developing
in the upper source pos iton switch, which is constructed
using materials
similar to the original ottom source down-position
switches.
The upper switch is located away from e water line and is exposed to higher temperatures
and lower humidity when e source rack is In the raised/exposed
position.
However, if conditions
exis in the area around the upper switch that are favorable
to corrosion (e.g., h humidity or a caustic atmosphere), this switch could corrode also.Users of NII pool-type
irradiators
containing
Norgren par t 54237-56 valve spools used In Norgren Nugget 200 Series Source Hoist Va es, part t K71EA00, should be aware that if they do not follow the NII rec ation to replace the 54237-56 spools with 54237-58 spools, the source racksay become stuck in the exposed position.
Licensees
may have to cut the ai line to the source rack hoist to return the source rack to the shielded p ition. In addition, the licensees
should consider NII's recommendation
tha the spools be replaced on a periodic basis to reduce the possibility
of failure, in their specific application.
If not replaced, the replacement
alve spools could fail because of seal material hardening, although such fa ure would not cause pressure to remain trapped in the air line.This information
notice requires no sped c action or written response.
If you have any questions
about the informati
in this notice, please contact the technical
contact listed below or the ipproprate
regional office.Carl J. Paperiello, Director Division of Industrial
and Medical Nuclear Safety Office of Nuclear Materials
Safety and Safeguards
Contact: Douglas Broaddu , NMSS (301) 415-5847 Attachments:
1. Nordion Intern lonal Inc., Service Bulletin IND-93-2 2. Nordion Inte ational Inc., Service Bulletin IND-94-1 3. List of Rec tly Issued NHSS Information
Notices 4. List of Re ntly issued NRC Information
Notices DISTRIBMTON:/
INOB r/f SCDB r IHNS r/f DOCUKENT NARE: 6: IRRAD.KKR Technical
Edito EKraus/ /IC/94%'On CpY WitMou sttaduasnwInc.
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- NNS INN KANE KRams trn VQS RBaer iin Etrach CPaperiello
DATE J L f -j ff \ F -I _