Information Notice 1989-79, Degraded Coatings and Corrosion of Steel Containment Vessels
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I
UNITED STATES
NUCLEAR REGULATORY COMMISSION
OFFICE OF NUCLEAR REACTOR REGULATION
WASHINGTON, D.C. 20555
December 1, 1989
NRC INFORMATION NOTICE NO. 89-79: DEGRADED COATINGS AND CORROSION OF
STEEL CONTAINMENT VESSELS
Addressees
All holders of operating licenses or construction permits for light-water
reactors.
Purpose
This information notice is intended to alert addressees to the discovery of
severely degraded coatings and the corrosion of steel ice condenser contain- ment vessels that are caused by boric acid and collected condensation in the
annular space between the steel shell and the surrounding concrete shield
building. 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.
Description of Circumstances
On August 24, 1989, Duke Power Company reported significant coating damage and
base metal corrosion on the outer surface of the steel shell of the McGuire
Unit 2 containment which was discovered during a pre-integrated leak rate test
inspection (as required by Appendix J to 10 CFR Part 50). Subsequently, Duke
Power identified similar degradation of the McGuire Unit 1 containment, which
is essentially identical to the Unit 2 structure.
Both units have ice condenser-type containments consisting of a freestanding
steel shell surrounded by a concrete shield building. Between the shell and
the shield building is a 6-foot-wide annular space. The steel shells have a -
nominal thickness near the annulus floor of 1 inch.
The degraded area on the
shells of both units is limited to 30-foot circumferential sections no higher
than 1i inches above the annulus floors. The average depth of the corrosion
is 0.1 inch with pits of up to 0.125 inch. Corrosion that is up to 0.03 inch
deep was also found in areas below the level of-the annulus floor on the Unit 2 shell, where concrete was removed to expose the shell surface. This below-floor
corrosion is due to a lack of sealant at the interface between the shell and the
annulus floor.
8911270001
IN 89-79 December 1, 1989 The probable cause of the degradation is attack by condensed boric acid coolant
leaking from instrument line compression fittings. Drains are provided in the
annulus floor, but they are widely separated and the floor is not sufficiently
graded to prevent pooling of the condensate between the drain locations.
The
current average thickness of the corroded areas of the containment shells of
0.9 inch is expected to be reduced to no less than 0.85 inch for Unit 1 and
0.88 inch for Unit 2 by the time they are repaired during the next planned
outages for these units.
These estimates were made assuming the worst cor- rosion rates that could reasonably be expected and are greater than the
minimum thickness allowed by the applicable ASME Code.
On September 21, 1989, Duke Power Company discovered coating damage and base
metal corrosion during inspections of the steel shells of its two Catawba con- tainments. These containments are also of the ice condenser type and are very
similar to the McGuire containments; the nominal floor level shell thickness
is 1 inch.
Here also, the degradation was located on the outer surfaces of
the shells at the intersection of the shell and the concrete annulus floor.
At Catawba the damage was less extensive and was limited to a circumference
of 15 feet, a height of 1 inch above the annulus floor, and an average depth
of 0.03 inch.
The cause is also believed to be attack by boric acid coolant, which had leaked from instrument line compression fittings, condensed, and
collected on the annulus floor.
Duke Power Company plans to repair the steel shells of all four units during
their next respective refueling outages.
This will include weld repair and
recoating of the corroded areas.
Discussion:
The degradation of the containment shells at the McGuire and Catawba plants
is considered significant for several reasons.
The fact that the corrosion
affects four different units indicates that other steel containments with
similar configurations may be susceptible to the same problem.
Furthermore, the observed rate of corrosion far exceeds the allowance made for corrosion
in the containment design. This condition leads to the concern that such
corrosion could result in undetected wall thinning to less than the minimum
design thickness, accompanied by a loss of leaktightness or structural inte- grity. This problem can be prevented by a containment inservice inspection
program that is adequate to ensure early detection and the maintenance of
design margins through proper corrosion control.
The NRC regulations (Appendix J to 10 CFR Part 50) require that a general
visual inspection of the accessible surfaces in the containment be performed
before each integrated leak rate test.
The purpose of this inspection is to
identify any evidence of structural deterioration or other problems that may
affect containment integrity or leaktightness. As a result of these and other
inspections, several instances of containment wall thinning due to corrosion
have been discovered during the past 3 years at operating power reactors.
However, the visual inspections done in connection with the integrated leak
IN 89-79 December 1, 1989 rate tests are only required to be performed three times in each 10-year period.
In addition, because of the physical arrangement of plant systems, the steel
surfaces in the annular spaces of some containments may not be easily accessible
to the visual inspections associated with leak tests. Considering the frequency
and severity of recent instances of containment degradation due to corrosion, additional efforts to inspect steel containment surfaces potentially susceptible
to corrosion may be prudent.
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.
/'6
7A0
Charles E. Rossi, Director
Division of Operational Events Assessment
Office of Nuclear Reactor Regulation
Technical Contacts: Chen P. Tan, NRR
(301) 492-0829
Keith R. Wichman, NRR
(301) 492-0908 Attachment: -List of Recently Issued NRC Information Notices
Attachment
IN 89-79 D*cUmb4t I
1959 Page I of I
LIST OF RECENTLY
ISSUED
lRC INFODIATIOII
NOTICES
-. ,ant- Mate
U
T
itcei
No.
Subject
ilssunce
89-SI.
Questionable Certification
11/22/S9 Supp. I
of material Supplied to
the Defense Department
by Nuclear Supplirs
8t-78 Fel lure of Packing NutU
11/22t89 n One-Inch Uranium
lexefluoride Cylinder
Valves
89-77 Debris In Contaienwnt
11/21/t89
Esergency Sumps end
Incorrect Sreenn
Configuretions
t9-7i
S1ifouling Agent, Zebra
11/21/t9
89.7S
Felsification of Holder
11/20/89
Quealifications for
Coetrector Expleoys
t-74 Clerification of Traes- ll7/8 portsti1e Rqrbments
Applicable to Return of
Spent Radiopharraq Dosages
trom Users to Suppliers
It-73 Potential Owverenesrization II/1/St
of Low Pressure SyStaft
lusued to
All holders of Ots
or CPa for nuclear
power reactors.
All ItC 11icnsees
authorized to possess
and use source metarial
end/or special nuclear
material for the heating.
ewptying, filling or
shipping of uranium
hexafluoride In 30.
and 48-inch diareter
Cylinders.
All holden of OLs
or CPs tor PaRs.
All holders of OLs
or CPS for nuclear
power reactors.
All holders of OLs
or CPa tor nuclear
power reactors.
All munufecturern
and distributors of
radisphormecewticals
for sedical une
nuclear phareacen.
and medical licensees.
All holders of OLs
or Cfa for nuclear
pOer reactors.
All holders of OLs
or CPs for nuclear
power reactors.
89-72
Failure of Licensed Senier
Operntors to Classify
Emargeacy Events Properly
10/24/8t
- Opereting License
- Constrctioe Permit
UNITED STATES
NUCLEAR REGULATORY COMMISSION
WASHINGTON, D.C. 20555
OFFICIAL BUSINESS
PENALTY FOR PRIVATE USE, *300
FIRST CLASS MAIL
POSTA0IS FEES PAID
PERIr No.Ale
4-
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IN 89-79 December 1, 1989 rate tests are only required to be performed three times in each 10-year period.
In addition, because of the physical arrangement of plant systems, the steel
surfaces in the annular spaces of some containments may not be easily accessible
to the visual inspections associated with leak tests.
Considering the frequency
and severity of recent instances of containment degradation due to corrosion, additional efforts to inspect steel containment surfaces potentially susceptible
to corrosion may be prudent.
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:
Chen P. Tan, NRR
(301) 492-0829
Keith R. Wichman, NRR
(301) 492-0908 Attachment:
List of Recently Issued NRC Information Notices
Document Name:
- SEE PREVIOUS CONCURRENCES
- EMTB:DET:NRR
CYCheng
11/22/89
- OGCB:DOEA:NRR
DCKirkpatrick
11/15/89
- EMlTB:DET:NRR
KWichman
11/22/89 D/DOEA:NRR%
CERossi A
11/2W89
- ESGB:DET:NRR
CPTan
11/21/89
- C/OGCB:DOEA:NRR
CHBerlinger
11/22/89
- C/ESGB:DET:NRR
GBagchi
11/21/89
- RPB:ARM
TechEd
11/17/89
- D/DET: NRR
JRichardson
11/22/89
IN 89-XX
November xx, 1989 accessible to the visual Inspections associated with leak tests. Considering
the frequency and severity of recent instances of containment degradation due
to corrosion, additional efforts to inspect steel containment surfaces poten- tially susceptible to corrosion may be prudent.
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:
Chen P. Tan
(301) 492-0829
Keith R. Wichman, NRR
(301) 492-0908 Attachment:
List of Recently Issued NRC Information Notices
Document Name: IN CONl
- SEE PREYIQV CONCURRENCES
T/, :.
0Pz
- OGCB: J0BA 4LRR
i
DCKirkpatrck KW
man
11/15/89
11/12!89 rAINMENT CORROSION
D/DOEA:NRR
CERossi
11/
/89
- ESGB:DET:NRR *(
CPTan
11/21/89 C/OGCB:DOEA:NRR
CHBerlinger
11A918 C/ESGB:DET:NRR
Bagchi
L1/21/89
- RPB:ARM
TechEd
11/17/89 D/DET: NRR
V
JRichardsW
11/Z;U89 M
IN 89-XX
November xx, 1989
the frequency and severity of recent instances of containment degradation due
to corrosion, additional efforts to inspect steel containment surfaces at some
plants may be prudent.
This information notice requires
you have any questions about the
of the technical contacts listed
no specific action or written response. If
information In this notice, please contact one
below or the appropriate NRR project manager.
Charles E. Rossi, Director
Division of Operational Events Assessment
Office of Nuclear Reactor Regulation
Technical Contacts:
Chen P. Tan
(301) 492-0829
Keith R. Wichman, NRR
(301) 492-0908 Attachment:
List of Recently Issued NRC Information Notices
Document Name:
IN CONTAINMENT CORROSION
- SEE PREVIOUS CONCURRENCES
- OGCB:DOEA:NRR EMTB:DET:NRR
DCKirkpatrick KWichman
11/15/89
11/ /89 D/DOEA:NRR
CERossi
11/
/89 ESGB:DET:NRR
CPTan Aret
11/al /89 C/OGCB:DOEA:NRR
CHBerlinger
11/ /89 C/ESGJ -j~ hR
GBag hi
V
11/n /89
- RPB:ARM
TechEd
11/17/89 D/DET: NRR
JRichardson
11/ /89
-
vi
instances of containment wall thinning due to corrosion have been discovered
during the past three-years at operating power reactors. However, the visual
inspections done in connection with the integrated leak rate tests are only
required to be performed three times in each a
year period.
In addition, because of the physical arrangement of plant systems, the steel surfaces in the
annular spaces of some containments may fall outside o the usual scope of the
lektt-i
LLret ted visual inspectionv' Considering the frequency and severity
of recent instances of containment degradation due to corrosion, additional
efforts to inspect steel containment surfaces at some plants may be prudent.
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: Chen P. Tan
(301) 492-0829
Keith R. Wichman, NRR
(301) 492-0908 Attachment:
List of Recently Issued NRC Information Notices
Document Name:
IN CONTAINMENT CORROSION
D/DOEA:NRR
C/OGCB:DOEA:NRR
CERossi
CHBerlinger
11/
/89
11/
/89 OGCB:DOEA:NRR EMTB:DET:NRR
ESGB:DET:NRR
C/ESGB:DET:NRR
RPB:ARM
DCKirkpatrick KWichman
CPTan
GBagchi
TechEdM
X
1114AWDe 11/
/89
11/
/89
11/
/89
11//9 /89