Information Notice 1990-02, Potential Degradation of Secondary Containment
I
ft
I
i-
UNITED STATES
NUCLEAR REGULATORY COMMISSION
OFFICE OF NUCLEAR REACTOR REGULATION
WASHINGTON, D.C.
20555
January 22, 1990
NRC INFORMATION NOTICE NO. 90-02: POTENTIAL DEGRADATION OF SECONDARY
CONTAINMENT
Addressees
All holders of operating licenses or construction permits for boiling water
reactors (BWRs).
Purpose
This information notice is intended to alert addressees to potential problems
involving degradation of secondary containment as a result of unforeseen inter- actions with various normal plant ventilation systems and inadequate surveillance
testing of secondary containment integrity.
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 do not constitute NRC requirements; therefore, no specific
action or written response is required.
Detcription of Circumstances:
Duane Arnold Energy Center
During a reactor building exhaust ventilation inspection, an Iowa Electric
system engineer discovered a large hole in the duct work (see Figure 1).
This hole allowed the main plant ventilation system to communicate directly
with the reactor building ventilation system, thus bypassing the standby gas
treatment system (SGTS) and providing a direct path for an untreated release
of radioactive effluents to the environment. This pathway would have existed
even with an automatic Engineered Safety Feature (ESF) isolation of the reactor
building ventilation system and an autostart of the SGTS. The licensee dis- covered that .its normal secondary containment integrity surveillance test
(which requires a measurement of 0.25 inch water vacuum with one train of
SGTS operating) was still apparently satisfied with the main plant ventilation
fans running. This has been the test configuration used at the plant since
initial startup in 1974. However, upon conducting the test with the SGTS
operating as designed and the main plant ventilation secured, the 0.25-inch
vacuum could not be achieved because of numerous secondary containment leaks.
A 10 CFR 50.72 4-hour notification was made to the NRC upon this discovery.
The licensee determined that during the performance of the secondary contain- ment integrity surveillance as it was previously conducted, the main plant
9001160420 Zjl_ _v
c
6,6CA_
IN 90-02 January 22, 1990 ventilation, turbine building ventilation, and the radwaste building ventila- tion exhaust fans had aided the SGTS in drawing the required vacuum.
Because
surveillance tests performed since initial unit startup usually indicated that
the required negative pressure had been obtained, numerous secondary contain- ment integrity deficiencies went undetected and uncorrected. The maintenance
to correct this overall degradation of the secondary containment required more
than 3 weeks of effort to locate and repair numerous door seals, electrical
penetrations, steam tunnel boot seals, dampers, building seals, and duct systems.
These repairs resulted in an improvement in the measured secondary containment
vacuum from less than 0.08 inch of water to greater than 0.25 inch of water, as
determined by retesting with a new surveillance test procedure.
This test now
requires all major plant exhaust ventilation fans that potentially communicate
with secondary containment to be secured.
Continued testing after repairs has shown that one main plant exhaust ventilation
fan can still draw an approximate 500 to 1000 standard cubic feet-per-minute (SCFM)
volume' from the reactor building ventilation system (the secondary containment
boundary) when the ESF-required isolation is in effect.
As this circumstance
could result in an untreated ground-level release under certain accident scenarios, the licensee developed alarm response procedures designed to secure the main
plant ventilation fans when secondary containment isolation is initiated and
main plant exhaust ventilation radiation monitors reach specified values.
Electric is also considering long-term corrective action involving hardware
modifications that would prevent main plant ventilation from drawing air out
of the reactor building under accident conditions.
Monticello
As a result of the secondary containment deficiencies identified at Duane Arnold, the NRC resident inspector contacted the licensee for the Monticello plant con- cerning the procedures and practices for testing the secondary containment system.
The licensee had normally tested the secondary containment integrity with the
main plant exhaust fans running and isolated both supply and exhaust fans in
the reactor building. However, on October 14, 1989, the licensee conducted
the secondary containment integrity test with the main plant exhaust fans
secured and was not able to maintain the 0.25-inch water vacuum required by
the technical specifications. The vacuum reached in the reactor building was
only 0.1 inch of water. Preliminary investigation revealed that failure of
the test was due to leaks in the reactor building supply and exhaust system
dampers and various other secondary containment leaks.
The licensee also
believes that the operation of the main plant exhaust fans assisted the SGTS
in drawing the required vacuum on the secondary containment, thus establishing
a path that bypassed the SGTS. A 10 CFR 50.72 notification was made to the NRC.
Discussion of Safety Significance:
Plant heating, ventilation, and air conditioning (HVAC) systems are diverse
among boiling water reactors. Interactions between these systems and the
standby gas treatment system could mask degradation of the secondary contain- ment boundary during surveillance testing and could exacerbate such degradatiof+t'
by diverting flow from the SGTS following an accident.
-
K>
IN 90-02 January 22, 1990 For those plants discussed above, a portion of the secondary containment
boundary is formed by the ductwork and isolation dampers of the reactor build- ing ventilation system. This system exhausts to a common plenum area within
the reactor building, but outside secondary containment, where ventilation
flows from other plant HVAC systems are also directed. The high-capacity main
plant ventilation exhaust fans take suction from the plenum area and discharge
the flow through the reactor building roof stacks.
Because of the high capa- city of the main plant exhaust fans and their proximity to the reactor building
ventilation system components that form part of the secondary containment
boundary, the potential exists for air flow to bypass the SGTS even when the
secondary containment is isolated. Further, if the main plant ventilation fans
are operated during surveillance testing, degradation of secondary containment
could go undetected as the main plant fans and the SGTS fans could collectively
draw the required vacuum.
In view of the possibility of the main plant ventilation systems masking
deficiencies in SGTS and/or secondary containment integrity and of creating
possible untreated release paths under accident conditions, licensees for other
BWR plants may wish to review the design and operation of major plant ventila- tion systems and to review their secondary containment integrity surveillance
procedures.
This information notice requires no specific action or 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 NRR project manager.
Charles E. Rossi, Director
Division of Operational Events Assessment
Office of Nuclear Reactor Regulation
Technical Contacts: William L. Axelson, Region III
(708) 790-5574
John A. Kudrick, NRR
(301) 492-0871
James R. Hall, NRR
(301) 492-1391 Attachments:
1. Figure 1 - Reactor Building Ventilation
2. List of Recently Issued NRC Information Notices
Attachment 1
January 22, 1990 Failed DucUng
Isolatlon Dampers
Reactor Buiding
VentShaft
Fgure 1
Reactor Building Ventilation
Iw/I1-89 A1087
K>
Attachment 2
January 22, 1990 ti e
.
-
.
.11 -
1
.
.,
-1-LIST
OF RECENTLY ISSUED
NRC INFORMATION NOTICES
Information
Date of
Notice No.
Subject
Issuance
Issued to
90-01
89-90
89-89
89-88
89-87
89-45, Supp. 2
89-86
89-85
89-84
Importance of Proper
Response to Self-Identified
Violations by Licensees
Pressurizer Safety Valve
Lift Setpoint Shift
Event Notification
Worksheets
Recent NRC-Sponsored
Testing of Motor-Operated
Valves
Disabling of Emergency
Diesel Generators by
Their Neutral Ground-Fault
Protection Circuitry
Metalclad, Low-Voltage
Power Circuit Breakers
Refurbished with
Substandard Parts
Type HK Circuit Breakers
Missing Close Latch Anti- Shock Springs.
EPA's Interim Final Rule
on Medical Waste Tracking
and Management
Failure of Ingersoll Rand
Air Start Motors as a Result
of Pinion Gear Assembly
Fitting Problems
1/12/90
12/28/89
12/26/89
12/26/89
12/19/89
12/15/89
12/15/89
12/15/89
12/12/89
All holders of NRC
materials licenses.
All holders of OLs
All holders of OLs
or CPs for nuclear
power reactors.
All holders of OLs
or CPs for nuclear
power reactors.
All holders of OLs
or CPs for nuclear
power reactors.
All holders of OLs
or CPs for nuclear
power reactors.
All holders of OLs
or CPs for nuclear
power reactors.
All medical, academic, industrial, waste
broker, and waste
disposal site licensees.
All holders of OLs
or CPs for nuclear
power reactors.
OL = Operating License
CP = Construction Permit
IN 90-02 January 22, 1990 For those plants discussed above, a portion of the secondary containment
boundary is formed by the ductwork and isolation dampers of the reactor build- ing ventilation system. This system exhausts to a common plenum area within
the reactor building, but outside secondary containment, where ventilation
flows from other plant HVAC systems are also directed. The high-capacity main
plant ventilation exhaust fans take suction from the plenum area and discharge
the flow through the reactor building roof stacks.
Because of the high capa- city of the main plant exhaust fans and their proximity to the reactor building
ventilation system components that form part of the secondary containment
boundary, the potential exists for air flow to bypass the SGTS even when the
secondary containment is Isolated.
Further, if the main plant ventilation fans
are operated during surveillance testing, degradation of secondary containment
could go undetected as the main plant fans and the SGTS fans could collectively
draw the required vacuum.
In view of the possibility of the main plant ventilation systems masking
deficiencies in SGTS and/or secondary containment integrity and of creating
possible untreated release paths under accident conditions, licensees for other
BWR plants may wish to review the design and operation of major plant ventila- tion systems and to review their secondary containment integrity surveillance
procedures.
This information notice requires no specific action or 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 NRR project manager.
Charles E. Rossi, Director
Division of Operational Events Assessment
Office of Nuclear Reactor Regulation
Technical Contacts: William L. Axelson, Region III
(708) 790-5574
John A. Kudrick, NRR
(301) 492-0871
James R. Hall, NRR
(301) 492-1391 Attachments:
1. Figure 1 - Reactor Building Ventilation
2.
List of Recently Issued NRC Information Notices
Document Name:
INFO NOTICE - JACKIW, KIESSEL
- SEE PREVIOUS CONCURRENCES
D
- C/OGCB:DOEA:NRR *RPB:ARM
- D/DST:NRR
E
CHBerlinger
TechEd
AThadani
01//190
01/10/90
12/21/89
12/18/89
- OGCB:DOEA:NRR*RIII
- PD33:DRSP:NRR
- SPLB:DST:NRR*C/SPLB:DST:NRR
RJKiessel
EGGreenman
JRHall
JKudrick
CEMcCracken
11/16/89
11/21/89
11/16/89
12/12/89
12/12/89
IN 90-XX
January xx, 1990 For those plants discussed above, a portion of the secondary containment
boundary is formed by the ductwork and isolation dampers of the reactor build- ing ventilation system.
This system exhausts to a common plenum area within
the reactor building, but outside secondary containment, where ventilation
flows from other plant HVAC systems are also directed. The high-capacity main
plant ventilation exhaust fans take suction from the plenum area and discharge
the flow through the reactor building roof stacks.
Because of the high capa- city of the main plant exhaust fans and their proximity to the reactor building
ventilation system components that form part of the secondary containment
boundary, the potential exists for air flow to bypass the SGTS even when the
secondary containment is isolated.
Further, if the main plant ventilation fans
are operated during surveillance testing, degradation of secondary containment
could go undetected as the main plant fans and the SGTS fans could collectively
draw the required vacuum.
In view of the possibility of the main plant ventilation systems' masking
deficiencies in SGTS and/or secondary containment integrity and of creating
possible untreated release paths under accident conditions, licensees for other
BWR plants may wish to review the design and operation of major plant ventila- tion systems and to review their secondary containment integrity surveillance
procedures.
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 contacts listed below or the appropriate NRR project manager.
Charles E. Rossi, Director
Division of Operational Events Assessment
Office of Nuclear Reactor Regulation
Technical Contacts: William L. Axelson, Region III
(708) 790-5574
John A. Kudrick, NRR
(301) 492-0871
James R. Hall, NRR
(301) 492-1391 Attachments:
1. Figure 1 - Reactor Building Ventilation
2. Figure 2 - Exhaust Fan Room
3. List of Recently Issued NRC Information Notices
Document Name:
INFO NOTICE - JACKIW, KIESSEL
- SEE PREVIOUS CONCURRENCES
D/DOEA:NRR
C/OGCB:D
C
Byt;*RPB:ARM
- D/DST:NRR
CERossi
CHBerline j) TechEd
AThadani
01/ /90
01/Y,/90-
' 12/21/89
12/18/89
- OGCB:DOEA:NRR*RIII
- PD33:DRSP:NRR
- SPLB:DST:NRR*C/SPLB:DST:NRR
RJKiessel
EGGreenman
JRHall - lf
JKudrick
CEMcCracken
11
11/21
11/16/8w
12/12/89
12/12/89
441/44s~4
IN 89-XX
%2
~November xx, 1989 standby gas treatment system could mask degradation of the secondary contain- ment boundary during surveillance testing and could exacerbate such degradation
by diverting flow from the SGTS following an accident.
For those plants discussed above, a portion of the secondary containment
boundary is formed by the ductwork and isolation dampers of the reactor build- ing ventilation system. This system exhausts to a common plenum area within
the reactor building, but outside secondary containment, where ventilation
flows from other plant HVAC systems are also directed. The high capacity main
plant ventilation exhaust fans take suction from the plenum area and discharge
the flow out through the reactor building roof stacks.
Due to the high capa- city of the main plant exhaust fans and their proximity to the reactor building
ventilation system components that form part of the secondary containment
boundary, the potential exists for air flow to bypass the SGTS even when the
secondary containment is isolated.
Further, if the main plant ventilation fans
are operated during surveillance testing, degradation of secondary containment
could go undetected as the main plant fans and SGTS fans could collectively
draw the required vacuum.
In view of the possibility of main plant ventilation systems masking deficien- cies in SGTS and/or secondary containment integrity and of creating possible
untreated release paths under accident conditions, other BWR plants may wish to
review the design and operation of major plant ventilation systems and to
review their secondary containment integrity surveillance procedures.
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 contacts listed below or the appropriate NRR project manager.
Charles E. Rossi, Director
Division of Operational Events Assessment
Office of Nuclear Reactor Regulation
Technical Contacts:
William L. Axelson, Region III
(708) 790-5574
John A. Kudrick, NRR
(301) 492-0871
James R. Hall, NRR
(301) 492-1391 Attachments:
1. Figure 1 - Reactor Building Ventilation
2. Figure 2 - Exhaust Fan Room
3. List of Recently Issued NRC Information Notices
Document Name:
INFO NOTICE - JACKIW, KIESSEL
- SEE PREVIOUS CONCURRENCES
sit
D/DOEA:NRR
C/OGCB:DOEA:NRR RPB:ARO'
CERossi
CHBerlinger
TechEd
11/ /89
11/ /89 ftH/.Zf/
- OGCB:DOEA:NRR*RIII
- PD33:DRSP:NRR
SPLB:
R
RJKiessel
EGGreenman
JRHall
- udri
11/16/89
11/21/89
11/16/89 WMI
Al'
D/DST:NRR
ni
MAK /89 C/SPLB:DST: WG9 CEMcCracken,_ --
/d 89