Information Notice 2004-09, Corrosion of Steel Containment and Containment Liner
| ML041170030 | |
| Person / Time | |
|---|---|
| Issue date: | 04/27/2004 |
| From: | Beckner W NRC/NRR/DIPM/IROB |
| To: | |
| Hodge, CV, NRR/DIPM/IROB, 415-1861 | |
| References | |
| IN-04-009, IN-97-010 | |
| Download: ML041170030 (8) | |
UNITED STATES
NUCLEAR REGULATORY COMMISSION
OFFICE OF NUCLEAR REACTOR REGULATION
WASHINGTON, D.C. 20555-0001 April 27, 2004 NRC INFORMATION NOTICE 2004-09: CORROSION OF STEEL CONTAINMENT AND
CONTAINMENT LINER
Addressees
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.
Purpose
The U.S. Nuclear Regulatory Commission (NRC) is issuing this information notice to alert
addressees to recent occurrences of corrosion in freestanding metallic containments and in
liner plates of reinforced and pre-stressed concrete containments. It is expected that recipients
will review this information for applicability to their facilities and consider actions, as appropriate.
However, the suggestions in this information notice are not NRC requirements; therefore, no
specific action or written response is required.
Background:
As discussed in Information Notice 97-10, Liner Plate Corrosion in Concrete Containments, the containment liners have safety factors well above the theoretically calculated strains. Any
corrosion (metal thinning) of the liner plate or freestanding metallic containment could change
the failure threshold of the containment under a challenging environmental or accident
condition. Thinning changes the geometry of the containment shell or liner plate, which may
reduce the design margin of safety against postulated accident and environmental loads.
Recent experience has shown that the integrity of the moisture barrier seal at the floor-to-liner
or floor-to-containment junction is important in avoiding conditions favorable to corrosion and
thinning of the containment liner plate material.
Description of Circumstances
Inspections of containment at the floor level, as well as at higher elevations, have identified
various degrees of corrosion and containment plate thinning. This is a partial listing of such
occurrences.
Corrosion of freestanding metallic containment
C In July of 2002, at the Davis-Besse Nuclear Power Station, the NRC identified corrosion
where the containment meets the floor. The licensee subsequently performed ultrasonic
examinations to confirm that the freestanding metal containment had not been corroded
below the minimum design thickness. The licensee subsequently installed a moisture
barrier at the containment-to-floor junction to prevent moisture intrusion (NRC Inspection
Report 50-346/02-09, ADAMS Accession No. ML022560237).
C In May of 2002, at the Sequoyah Nuclear Plant, Unit 2, the NRC identified areas of the
steel containment vessel (SCV) with degraded coatings and rust (NRC Inspection
Report 50-328/02-02, ADAMS Accession No. ML022070149). One of the floor drains
was clogged in the annulus area (1.5 m [5 feet] wide) between the SCV and the
reinforced concrete shield building. Localized water ponding at the clogged drain had
come in contact with a section of the SCV, causing deterioration of the SCV coatings
and rusting of the SCV. This SCV is restricted for access due to the close proximity
between the SCV and the emergency gas treatment system (EGTS) duct work. After
reviewing NRC Information Notice 89-79, the licensee had identified the problem in
1990, but the corrective action was inadequate. Since the identification in 2002, additional corrective actions have been implemented by the licensee. These actions
consist of the removal of the EGTS duct work on both Unit 1 and Unit 2 to allow the SCV
area behind the EGTS duct work to be cleaned and recoated. Also the licensee has
identified this SCV area behind the EGTS duct work for periodic visual examination.
C In November of 2001, at the Dresden Unit 2 Nuclear Power Station, the licensee
identified an area of missing coating and primer encircling the drywell shell adjacent to
the basement floor. The area was 5-10 cm (2-4 inches) wide. In this area, the base
metal of the drywell shell was found to be corroded. However, based on ultrasonic and
visual examinations, the degraded area was found to be within the corrosion allowance
for the drywell shell. The shell coating was repaired in this area to prevent further
degradation (Inservice Inspection Summary Report, Fall 2001 Inspection Period, ADAMS Accession No. ML020450608).
Corrosion of containment liner plate
C In March of 2001, at the D. C. Cook Nuclear Power Plant, the licensee discovered a
through-wall hole in the containment liner plate. Surface preparation for further
inspection of a weld repair of the liner plate dislodged the repair material, leaving a hole.
The hole was repaired. However, further examination of the repair area indicated
corrosion of the liner from the embedded side of the liner. The cause of this corrosion
was found to be a wire brush handle lodged in the concrete at the interface with the
liner. The licensee replaced an area about 30 cm (12 inches) square in the liner plate
and performed a local leak rate test as part of the corrective action (AEP:NRC:2612-01:
"Response to NRC Request for Additional Information Regarding License Amendment
Request for One-Time Extension of Containment Integrated Leakage Rate Test
Interval," November 11, 2002, ADAMS Accession No. ML023170524). * In February and March of 1998, at the D. C. Cook Nuclear Power Plant, the licensee
identified corrosion (pitting) of the containment liner at the moisture barrier seal areas of
both units. At Unit 1, the licensee identified more than 60 areas in which the thickness
(1 cm [3/8 inch] nominally) of the steel liner plate had been reduced below the minimum
design thickness value of (0.6 cm [0.25 inch]). The licensee subsequently installed a
new liner-to-floor moisture barrier seal (Licensee Event Report 50-315/98011-02, NUDOCS Accession No. 9809040123* and NRC Inspection Report 50-315/99026, ADAMS Accession No. ML003677533).
C In fall 2003, at the Surry Power Station, Unit 2, NRC inspectors found degraded
coatings and rust on the containment liner at the junction of the metal liner and interior
concrete floor. The inspectors also discovered that the moisture barrier at the junction
between the metal liner plate and interior concrete floor was degraded. Review of the
records of previous inspections performed by licensee personnel in 2000, 2002, and
2003 revealed that the licensee had not identified the degraded moisture barrier
(caulking), but had identified the degraded coatings. (NRC Inspection Report
50-281/2003-05, ADAMS Accession No. ML040280056).
C In October of 1999, at the Palisades Plant, the licensee discovered that a floor-to-liner
moisture barrier seal had never been installed and used a thin metal blade as a probe, confirming the presence of moisture in the crevice. Subsequently, the licensee used a
borescope to identify areas of liner corrosion. The licensee determined that the
corrosion had not yet appreciably degraded the liner in this area and installed a new
liner-to-floor moisture barrier seal.
C In May of 1999, at the Brunswick Steam Electric Plant, Unit 2, the licensee identified
three areas in the drywell liner where corrosion had penetrated the liner. These areas
were at the 5.5, 16, and 21 m (18, 52, and 70 feet) elevations. At the 16 m elevation, the wall had corroded from the outside to the inside surface. At the 21 m elevation, the
wall had corroded from the inside to the outside surface. At the 5.5 m elevation, the
direction of the through-wall corrosion could not be determined. The liner corrosion was
a result of foreign materials embedded in the concrete containment adjacent to the liner.
One hole in the liner was adjacent to a leather work glove found buried in the concrete, while the other two hole locations were adjacent to wood found buried in the concrete
(NRC Inspection Report 50-324/99-03, NUDOCS No. 9906170114*).
C In December, 1996, at the H.B. Robinson Steam Electric Plant, Unit 2, an NRC
inspector identified degraded caulking and insulation sheathing panels during a
containment walkdown. The vertical portion of the containment liner at Robinson is
protected by Vinylcel insulation, a polyvinyl chloride material, and a metal sheathing
material. The licensee determined that a portion of this insulation sheathing material
was loose and that some of the caulking between the sheathing panels was
_______________________
- These documents are available in the NRC Legacy Library. The legacy documents are
stored on microfiche in the NRC Public Documents Room. Copies may be made for a fee. deteriorated. After examination during subsequent refueling outages, the licensee
determined that the protective coating for the containment liner was degraded and that
while some corrosion of the containment liner had occurred, the liner met design
requirements. The licensee restored the coating and insulation panels (NRC Inspection
Reports 50-261/96-14, NUDOCS Accession No 9702110115* and 50-261/98-02, NUDOCS Accession No. 9805050171*).
Discussion:
An amendment to Section 50.55a of Title 10 of the Code of Federal Regulations (10 CFR
50.55a) (61 FR 41303) became effective September 9, 1996. This amendment requires the
use of Subsections IWE and IWL of Section XI of the ASME Boiler and Pressure Vessel Code
to perform inservice inspections of containment components. These subsections provide
detailed requirements for inservice inspection of Class MC pressure-retaining components and
their integral attachments and of metallic shells and penetration liners of Class CC pressure- retaining components and their integral attachments. Inspection of concrete containment shell
and steel liner plate in accordance with 10 CFR 50.55a involves consideration of potential
corrosion areas. Such inspection includes examination, evaluation, repair, and replacement of
corroded areas of the liner plate.
As a result of these required containment inservice inspections, licensees have found that over
time, the existing floor-to-containment seal can degrade, allowing moisture into the crevice
between the containment liner plate and floor. Small amounts of stagnant water behind the
floor seal area promote pitting corrosion. To identify corrosion in this area, licensees have had
to remove the original floor seal and either excavate the concrete or do a visual inspection
aided by fiber optics. Licensee corrective actions for this condition have typically included
inspections to determine the extent of corrosion, evaluations of containment integrity, and
installation of new floor-to-containment moisture seal barriers.
In some instances, corrosion has been found at higher elevations of the liner plates. Generally, the instances of such corrosion have been associated with foreign objects (wooden pieces, workers gloves, wire brush handles, etc.) lodged between the liner plate and the concrete. As
the corrosion is initiated in the areas not visible during visual examinations, such instances of
corrosion were found when corrosion had penetrated through the liner thickness. Some
licensees have performed ultrasonic examination of the suspect areas (areas of obvious
bulging, hollow sound, etc.) to detect such corroded areas.
_______________________
- These documents are available in the NRC Legacy Library. The legacy documents are
stored on microfiche in the NRC Public Documents Room. Copies may be made for a fee. Related Generic Communications:
NRC Information Notice 97-29, Containment Inspection Rule
NRC Information Notice 89-79, Degraded Coatings and Corrosion of Steel Containment
Vessels
This information notice requires no specific action or written response. If you have any
questions about information in this notice, please contact one of the technical contacts listed
below or the appropriate NRR project manager.
/RA/
William D. Beckner, Chief
Reactor Operations Branch
Division of Inspection Program Management
Office of Nuclear Reactor Regulation
Technical Contacts: Melvin Holmberg, RIII Dr. C. Vernon Hodge, NRR
(630) 829-9748 (301) 415-1861 E-mail: msh@nrc.gov E-mail: cvh@nrc.gov
Joseph Lenahan, RII Hans Ashar, NRR
(404) 562-4625 (301) 415-2851 E-mail: jjl3@nrc.gov E-mail: hga@nrc.gov
Attachment: List of Recently Issued NRC Information Notices
OFFICE DIPM:IROB:OES TECHEDITOR REGION3 REGION2 NAME CVHODGE PKLEENE MHOLMBERG JLENAHAN
DATE 04/22/2004 02/18/2004 03/11/2004 04/07/2004 OFFICE DE:EMEB DE:EMEB:C DIPM:IROB:OES:SC DIPM:IROB:BC
NAME HASHAR DT FOR EIMBRO CJACKSON WDBeckner
DATE 04/16/2004 04/16/2004 04/26/2004 04/27/2004
Attachment LIST OF RECENTLY ISSUED
NRC INFORMATION NOTICES
_____________________________________________________________________________________
Information Date of
Notice No. Subject Issuance Issued to
_____________________________________________________________________________________
2004-08 Reactor Coolant Pressure 04/22/2004 All holders of operating licensees
Boundary Leakage Attributable for nuclear power boiling-water
to Propagation of Cracking in reactors (BWRs), except those
Reactor Vessel Nozzle Welds who have permanently ceased
operations and have certified that
fuel has been permanently
removed from the reactor vessel.
2004-07 Plugging of Safety Injection 04/07/2004 All holders of operating licenses
Pump Lubrication Oil Coolers or construction permits for
with Lakeweed nuclear power reactors, except
those who have permanently
ceased operations and have
certified that fuel has been
permanently removed from the
reactor vessel.
2004-06 Loss of Feedwater Isokinetic 03/26/2004 All holders of operating licensees
Sampling Probes at Dresden for nuclear power reactors except
Units 2 and 3 those who have permanently
ceased operations and have
certified that fuel has been
permanently removed from the
reactor vessel.
2004-05 Spent Fuel Pool Leakage to 03/03/2004 All holders of operating licensees
Onsite Groundwater for nuclear power reactors (except
those who have permanently
ceased operations and have
certified that fuel has been
permanently removed from the
reactor vessel) and for research
and test reactors, and all holders
of fuel storage licenses and
construction permits.
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