Information Notice 1998-14, Undocumented Changes to Non-Power Reactor Safety System Wiring
UNITED STATES
NUCLEAR REGULATORY COMMISSION
OFFICE OF NUCLEAR REACTOR REGULATION
WASHINGTON, D.C. 20555-0001
April 20, 1998
NRC INFORMATION NOTICE 98-14: UNDOCUMENTED CHANGES TO NON-POWER
REACTOR SAFETY SYSTEM WIRING
Addressees
All holders of operating licenses or construction permits for test and research reactors.
Purpose
The U.S. Nuclear Regulatory Commission (NRC) is issuing this information notice to inform
addressees of undocumented modifications that have occurred in the scram system wiring of
two research reactors. In the first case, the modification in conjunction with a switch failure
resulted in the reactor being operated for a short time without any technical specification (TS)
required scrams. In the second case, because of a modification, a switch failure could have
resulted in a TS required scram being disabled. It is expected that recipients will review the
information for applicability to their facilities and consider action, as appropriate, to avoid similar
problems. However, suggestions contained in this information notice are not NRC
requirements; therefore, no specific action or written response is required.
Description of Circumstances
Oregon State Universty
On the morning of February 17, 1998, the TRIGA non-power reactor at Oregon State University
(OSU) had completed a routine 14-minute run at 15 watts of power to perform core excess
reactivity measurements. An attempt was made to manually scram the reactor at the end of the
run using the scram button. When the manual scram button did not work, the operators next
step was to turn off power to the scram circuit using the reactor's three-position key switch.
This switch-1s OFF, OPERATE, and RESET positions with a spring return between the
RESET and OPERATE positions. As the operator touched the switch, the switch moved from a
position between OPERATE and RESET to the OPERATE position. The operator then tried the
manual scram button again and this time it worked.
The licensee determined that a buildup of dirt prevented the three-position switch from returning
to the OPERATE position. When the switch is in the RESET position, the scram bus is
disabled. This switch dates to 1967 when the original console was installed. The switch
operated properly during preoperational testing before startup.
Upon further investigation, the licensee discovered that the wiring of the scram circuit was
different from the wiring shown in the Instrument Maintenance Manual provided by the reactor
vndr. Fgure I shows part of the circuitry as designed. If the key switch is in the OPERATE
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IN 98-14 April 20, 1998 position, ac power is supplied from terminal block one, terminal number four (TBI -4) through
TBI-9, to TB2-3, the A3 and Al contacts of the three-position switch, and then the console
power switch. This allows transformer four (T4) to power the rod magnets. When the key is
turned to RESET, this circuit is opened and the magnet current is cut off. This prevents rod
withdrawal if the rods are down, or causes the rods to drop if they are up. This design feature
prevents a single failure of the three-position switch from disabling the scram circuits. In the
RESET position, power is supplied to the scram reset relays (K19, K20, and K24), which reset
the scram relays (only one scram relay, K12, is shown). If the key switch sticks in the RESET
position, the scram relay will continued to be energized by the reset relay even if a scram signal
occurs. This is not a problem because the power would already be cut off to the magnets.
Figure 2 shows the wiring as found in the OSU console. The wiring that was between TB1-9 and TB2-3 in the "as designed" circuit was between TBI-9 and TBIO-10 in the OSU console.
As a result, there is power to the magnets when the switch is in the RESET or OPERATE
position.
The licensee concluded that the location of the jumper was probably modified during initial
installation of the reactor console in 1967. This modification was probably done to provide
power to the *B deck3 on the three-position switch to power REACTOR ON lights.
The licensee took a number of corrective actions. The three-position switch was removed, cleaned, relubricated, and reinstalled in the console. The reactor console wiring was restored
to its as-designed condition. The wiring in the scram circuitry and in other non-scram-related
circuits was checked physically and electronically to demonstrate that the wiring in the console
is as designed. The reactor startup procedure was rewritten to test that the magnet power is
cut off when the three-position switch is placed in the RESET position. The reactor console
was subject to routine startup checks and the semiannual console check procedure. The
reactor vendor was contacted to obtain checkout procedures to confirm that all suggested
surveillances are done before reactor operation.
Texas A&M Universiy
OSU quickly placed information about the failure to scram on the Organization of Test, Researth and Training Reactors (TRTR) list server. As a result, the staff at the Texas A&M
University N&clear Science Center checked the logic diagrams for its TRIGA research reactor
and determined that its reactor could not fail to scram. The Texas A&M console differs from the
one at OSU in that there is no master reset equivalence to the three-position switch. Three of
the scrams have push-button spring-returned switches that clear the locked-in alarm on the
console and allow the scram relay coil to be reenergized if the signal is clear.
The licensee also tested the circuit and determined that each of the three scrams associated
with these switches could be defeated by holding its switch down in the RESET position (this
simulated a switch failure). In this case, the failure of a single switch could prevent an individual
scram signal but would have not disabled all scrams. The licensee then checked the wiring
diagrams for the console and discovered that the wiring of the console matched the wiring
diagrams. The RESET switches were wired in parallel with the normally closed scram contacts.
This wiring maintained power to the magnets through one parallel path if the switch was
IN 9S*14 April 20, 1998 depressed, even if a scram contact opened in the other parallel path. The switches should
have been wired in series. The licensee cannot determine when the console was wired this
way, but notes that the console underwent a major upgrade in 1968. The logic diagram, drawn
in 1976, which differs from the wiring diagram and the as-wired console, appears to have been
based on system knowledge of how it should be configured rather than on the actual
configuration.
To correct this situation, the licensee changed the wiring to put the RESET switch in series with
the protective action contacts, physically verified console wiring for scram circuits, identified
various failure modes, and tested the console for proper operation.
Discussion
The circumstances described above demonstrate the importance of controlling modifications, ensuring that all of the consequences of a modification are carefully considered, and ensuring
that design features in the scram circuitry perform as designed. Careful reviews of
modifications through the safety review process can be an effective method to help to ensure
that unintended deleterious effects from modifications do not occur. The identification of safety
system design features could lead to surveillances or tests that could prevent the occurrence of
similar problems. The staff noted that many licensees contacted the NRC to discuss the results
of testing performed on consoles because of the information placed on the TRTR listed server
by OSU.
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.
Jack Roe, Acting Director
Division of Reactor Program Management
Office of Nuclear Reactor Regulation
Technical contact: Alexander Adams, Jr., NRR
301-415-1127
.E-mail: axa@nrc.gov
Attachments:
1. Figure 1, *Reactor Operate Circuit, As-Designed"
2. Figure 2, Reactor Operate Circuit - As Found"
3. List of Recently Issued NRC Information Notices-L
vD C Em
DOCUMENT NAME: G:WVERN\\OSUSCRAM.INF Tech Editor concurred on 3126/98 To receive a copy of this document, indicate in the box C=Copy wlo attachmentlenclosure E=Copy with attachmentfenclosure N = NIcopy
OFFICE
PDND
(A)D:PDND
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(A)D:DRPIV\\S
A
NAME
AAdams*
MMendonca*
JStolz*
JRoe*
[DATE
03/30198
03/30/98
04/06/98
04/13/98
5'
OFFICIAL RECORD COPY
P6-3 5 P22-1 0 TB10
Switched AC (H)
T
P2 f6
2 T
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4 T4
50
Operate Permissive Jumper
1
3 A
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Part of Console Key Switch
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Attachment 3
April20, 1998 LIST OF RECENTLY ISSUED
NRC INFORMATION NOTICES
Information
Date of
Notice No.
Subject
Issuance
Issued to
98-13 Post-Refueling Outage Reactor
4120/98
All holders of operating licenses
Pressure Vessel Leak Testing
Before Core Criticality
for nuclear power reactors except
those that have permanently
ceased operations and have
certified that fuel has been
permanently removed from the
reactor vessel
98-12
9&-1 1 Licensees' Responsibilities
Regarding Reporting and Follow-up
Requirements for Nuclear-Powered
Pacemakers
Cracking of Reactor Vessel
Internal Baffle Former Bolts
in Foreign Plants
4/3/98
3/25/98
All U.S. Nuclear Regulatory
Commission nuclear pacemaker
licensees
All holders of operating licensing
for pressurized-water reactors
(PWRs) except those who have
ceased operation and have
certified that fuel has been
permanently removed from the
reactor vessel.
95-52, Supp. 1
Fire Endurance Test Results
for Electrical Raceway Fire
Barrier Systems Constructed
From 3M Company Interam
-ire Barrier Materials
3/17/98
All holders of operating
licenses for nuclear power
reactors except those who
have permanently ceased
operation and have certified that
fuel has been permanently
removed from the reactor vessel.
98-10
98-09
Probable Misadministrations
Occurring During Intravascular
Brachytherapy With The
Novoste Beta-Cath System
Collapse Of An Isocam II
Dual-Headed Nuclear
Medicine Gamma Camera
3/9/98
3/5/98
All Medical Licensees
All Medical Licensees
OL = Operating License
CP = Construction Permit
KIN
?-14 April 20, 1998 depressed, even if a scram contact opened in the other parallel path. The switches should
have been wired in series. The licensee cannot determine when the console was wired this
way, but notes that the console underwent a major upgrade in 1968. The logic diagram, drawn
in 1976, which differs from the wiring diagram and the as-wired console, appears to have been
based on system knowledge of how it should be configured rather than on the actual
configuration.
To correct this situation, the licensee changed the wiring to put the RESET switch in series with
the protective action contacts, physically verified console wiring for scram circuits, identified
various failure modes, and tested the console for proper operation.
Discussion
The circumstances described above demonstrate the importance of controlling modifications, ensuring that all of the consequences of a modification are carefully considered, and ensuring
that design features in the scram circuitry perform as designed. Careful reviews of
modifications through the safety review process can be an effective method to help to ensure
that unintended deleterious effects from modifications do not occur. The identification of safety
system design features could lead to surveillances or tests that could prevent the occurrence of
similar problems. The staff noted that many licensees contacted the NRC to discuss the results
of testing performed on consoles because of the information placed on the TRTR listed server
by OSU.
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.
orig /sfd by D. B. Matthews
FOR
Jack Roe, Acting Director
Division of Reactor Program Management
Office of Nuclear Reactor Regulation
Technical contact: Alexander Adams, Jr., NRR
301-415-1127 E-mail: axa~nrc.gov
Attachments:
1. Figure 1, OReactor Operate Circuit, As-Designed'
2. Figure 2, uReactor Operate Circuit - As Found"
3. List of Recently Issued NRC Information Notices
DOCUMENT NAME: G:WVERN\\OSUSCRAM.INF Tech Editor concurred on 3/26198 To receive a copy of this document indicate In the box C=Copy wlo attachmentenclosure E=Copy with attachmentlenclosure N = No copy
OFFICE
PDND
(A)D:PDND
I
C:PECB
Il
(A)D:DRPM
I
l NAME
AAdams*
MMendonca*
JStolz*
JRoe*
lDATE _
03/30/98
03/30/98
04106198 j 04/13/98
OFFICIAL RECORD COPY
--
INbe14 April 20, 1998 depressed, even if a scram contact opened in the other parallel path. The switches should
have been wired in series. The licensee cannot determine when the console was wired this
way, but notes that the console underwent a major upgrade in 1968. The logic diagram, drawn
in 1976, which differs from the wiring diagram and the as-wired console, appears to have been
based on system knowledge of how it should be configured rather than on the actual
configuration.
To correct this situation, the licensee changed the wiring to put the RESET switch in series with
the protective action contacts, physically verified console wiring for scram circuits,.identified
various failure modes, and tested the console for proper operation.
Discussion
The circumstances described above demonstrate the importance of controlling modifications, ensuring that all of the consequences of a modification are carefully considered, and ensuring
that design features in the scram circuitry perform as designed. Careful reviews of
modifications through the safety review process can be an effective method to help to ensure
that unintended deleterious effects from modifications do not occur. The identification of safety
system design features could lead to surveillances or tests that could prevent the occurrence of
similar problems. The staff noted that many licensees contacted the NRC to discuss the results
of testing performed on consoles because of the information placed on the TRTR listed server
byOSU.
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.
Jack Roe, Acting Director
Division of Reactor Program Management
Office of Nuclear Reactor Regulation
Technical contact: Alexander Adams, Jr., NRR
301-415-1127 E-mail: axa@nrc.gov
Attachments:
1. Figure 1, uReactor Operate Circuit, As-Designed"
2. Figure 2, "Reactor Operate Circuit - As Found"
3. List of Recently Issued NRC Information Notices
DOCUMENT NAME: G:WVERNOSUSCRAM.INF Tech Editor concurred on 3/26198 To receive a copy of this document, indicate in the box C=Copy wlo attachmentlenclosure E=Copy with attachmentenclosure N = Nlcopy
I
OFFICE
PDND
I
(A)D:PDND
l
C:PECB
I
(A)D:DRP
NAME
AAdams*
MMendonca*
JStoz*
JRoe*
l DATE
03/30/98
03/30/98
04/06/98
04/13/98
OFFICIAL RECORD COPY
IN'
XX
.
K
ApexL
1998 (this simulated a switch failure). In this case, the failure of a single switch could preve
an
individual scram signal but would have not disabled all scrams. The licensee then
ecked the
wiring diagrams for the console and discovered that the wiring of the console moed the
wiring diagrams. The RESET switches were wired in parallel with the normall y-losed scram
contacts. This wiring maintained power to the magnets through one paralle
ath if the switch
was depressed, even if a scram contact opened in the other parallel pathThe switches should
have been wired in series. The licensee cannot determine when the
sole was wired this
way, but notes that the console underwent a major upgrade in 1968.
e logic diagram, drawn
in 1976, which differs from the wiring diagram and the as-wired co sole, appears to have been
based on system knowledge of how i should be configured rat
r than on the actual
configuration.
To correct this situation, the licensee changed the wiring
put the RESET switch in series with
the protective action contacts, physically verified conso wiring for scram circuits, identified
various failure modes, and tested the console for probr operation.
Discussion
The circumstances described above demon
ate the importance of controlling modifications, ensuring that all of the consequences of a odification are carefully considered, and ensuring
that design features in the scram circuit perform as designed. Careful reviews of
modifications through the safety revie process can be an effective method to help to ensure
that unintended deleterious effects f m modifications do not occur. The Identification of safety
system design features could lead o surveillances or tests that could prevent the occurrence of
similar problems. The staff note that many licensees contacted the NRC to discuss the results
of testing performed on consols because of the information placed on the TRTR listed server
by OSU.
This information notice r
uires no specific action or written response. If you have any
questions about the inf
ation in this notice, please contact the technical contact listed below.
Jack Roe, Acting Director
Division of Reactor Program Management
Office of Nuclear Reactor Regulation
Technical c
ctac: Alexander Adams, Jr., NRR
301-415-1127 E-mail: axaenrc.gov
Attac
ent: List of Recently Issued NRC Information Notices
DT e MENT NAME: G:WVERN\\OSUSCRAM.INF
To receive a copy f this document. indicate In the box C=Copy w/o attachmeE=Copy with
co
OFFICE
PDND
I
_ (A)D:PDND
l
C:PE'CB
(A)D:DR hl1 I
NAME
AAdams*
MMendonca*
iQStolz
JRoe
Jk
DATE
03/30198
03/30/98 g 4
/j3198 OFFICIAL RECORD COPY a-)
.
IN'- XX
_
ApiV..x, 1998 switch failure). The licensee then checked the wiring diagrams for the console and discovered
that the wiring of the console matched the wiring diagrams. In this case, the failure of a single
switch could prevent an individual scram signal but would have not disabled all scrams. The
RESET switches were wired in parallel with the normally closed scram contacts. This wiring
maintained power to the magnets through one parallel path if the switch was depressed, even if
a scram contact opened in the other parallel path. The switches should have been wired in
series. The licensee cannot determine when the console was wired this way, but notes that the
console underwent a major upgrade in 1968. The logic diagram, drawn in 1976, which differs
from the wiring diagram and the as-wired console, appears to have been based on system
knowledge of how it should be configured rather than on the actual configuration.
To correct this situation, the licensee changed the wiring to put the RESET switch in series with
the protective action contacts, physically verified console wiring for scram circuits, identified
various failure modes, and tested the console for proper operation.
Discussion
The circumstances described above demonstrate the Importance of controlling modifications, ensuring that all of the consequences of a modification are carefully considered, and ensuring
that design features in the scram circuitry perform as designed. Careful reviews of
modifications through the safety review process can be an effective method to help to ensure
that unintended deleterious effects from modifications do not occur. The identification of safety
system design features could lead to surveillances or tests that could prevent the occurrence of
similar problems.
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.
Jack Roe, Acting Director
Division of Reactor Program Management
Office of Nuclear Reactor Regulation
Technical contact: Alexander Adams, Jr., NRR
301-415-1127 E-mail: axa@nrc.gov
Attachment: List of Recently Issued NRC Information Notices
DOCUMENT NAME: G:WVERN\\OSUSCRAM.INF
To receive a copy of this document, indicate in the box C=Copy wlo attachment/endosure E=Copy with attachment/enclosure N = No copy
OFFICE
PDND
I
l (A)D:PDND
l
l C:PECB
(A)D:DRPM
Il
NAME
AAdams OA
l MMendonca
L4/) T
JStolz
JRoe
DATE
1 031/)/98 l 0313)198
1 03/
/98
7
03/ /98 OFFICIAL RECORD COPY