Information Notice 1998-26, Settlement Monitoring and Inspection of Plant Structures Affected by Degradation of Porous Concrete Subfoundations
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UNITED STATES
NUCLEAR REGULATORY COMMISSION
OFFICE OF NUCLEAR REACTOR REGULATION
WASHINGTON, D.C. 20555-0001
July 24, 1998
NRC INFORMATION NOTICE 98-26: SETTLEMENT MONITORING AND INSPECTION OF
PLANT STRUCTURES AFFECTED BY
DEGRADATION OF POROUS CONCRETE
SUBFOUNDATIONS
Addressees
All holders of operating licenses for nuclear power reactors; all holders of or applicants for
licenses to operate Independent Spent Fuel Storage Installations; and designers and
fabricators of Independent Spent Fuel Storage Installations.
Purpose
The U.S. Nuclear Regulatory Commission (NRC) is issuing this information notice (IN) to inform
addressees who own and operate facilities with plant sites that include structures with porous
concrete subfoundations of the possibility of degradation of these subfoundations. Such
degradation could have deleterious effects on structures, systems, and components (SSCs).
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 are not NRC requirements; therefore, no specific action or written
response Is required.
Description of Circumstances
The containment structure at Millstone Nuclear Power Station, Unit 3 (MNPS-3), has a
3.05-meter (10-foot) thick reinforced-concrete basemat founded on rock. Between the
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foundation rock surface and the underside of the basemat are several layers of different
materials. These layers consist of (1) a 25.4-cm (1 -Inch) thick leveling layer of porous
concrete made of coarse aggregates and Portland cement, (2) a 0.16-cm (1/16th-inch) thick
butyl rubber waterproofing membrane, (3) a 5.08-cm (2-Inch) thick Portland cement mortar seal, IJ)
(4) a second layer of 22.86-cm (9-inch) thick porous concrete made of coarse aggregates and
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layer of the porous concrete. In the upper porous concrete layer, 15-cm (6-Inch) diameter
porous concrete pipes are Installed to collect and drain ground water, which may seep down
along the periphery of the containment wall. The collected water drains into two sumps inside
the engineered safety features (ESF) building.
The MNPS-3 licensee, Northeast Nuclear Energy Company, identified the Issue of cement
erosion from the porous concrete drainage system In 1987 upon examination of the
accumulated white residue In the two lower drain sumps In the ESF building. IN 97-11,
"Cement Erosion From Containment Subfoundations at Nuclear Power Plants," was Issued on
March 21, 1997, to alert addressees to the potential for erosion of cement from porous concrete
subfoundations.
The main concern raised by the cement erosion at MNPS-3 is the continued ability of the
degraded porous concrete subfoundations to transfer the loads of seismic Category I structures
to the underlying foundation medium without detrimental settlement. To address the question
of whether other nuclear power plant sites have this condition, the staff reviewed the updated
final safety analysis reports (UFSARs) of 24 plants selected on the basis of the unique practice
of the constructor or the architect/engineer (ANE) firm to use porous concrete subfoundations, and a sampling of other A/E firms. This limited-scope review revealed that at least 12 other
reactor units have porous concrete subfoundations (reference: IN 97-11). A survey of these
12 units indicated that the licensees of three units (i.e., Millstone 3, Nine Mile Point 2, and
Maine Yankee) have implemented surveillance programs to monitor for possible cement
erosion from the subfoundations beneath the containment basemats. In addition, the Perry
licensee has reported that dissolved calcium carbonate is being carried to the drainage pipes
and the sumps, where it is solidifying as a hard scale. The Perry licensee also discovered an
accumulation of mineral deposits that Is clogging the pores of the porous concrete pipes.
Although most of the surveyed licensees report that there is no evidence of cement erosion
from the porous concrete subfoundations, a review of their reports indicates that there is some
discharge of water (including some leachate) in several of the plants.
Discussion
Various types of porous concrete subfoundations may have been constructed at other plants.
The degradation of porous concrete leading to the creation of voids and local pockets of loose
concrete could eventually result In undesirable settlement of a structure. An effective way to
determine the presence of such effects is to Inspect and monitor seismic Category I structures
(that have porous concrete subfoundations) and the associated systems and components for
evidence of structural settlement
The settlement of a structure can give rise to a number of effects, some that are observable by
Inspection and some that are not so visible. If settlement Is uniform, that is, all parts of the
basemat settle an equal amount, the structure Itself may not show appreciable distress.
However, the alignments of the attached piping, electric cable lines, and Instrument lines would
be changed from their original, as-built configuration. If settlement is not uniform, the effects
could be visible on a concrete structure In the form of cracking near areas of stress
concentration, such as at discontinuities and large penetrations.
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\\JIN 98-26 July 24, 1998 The differential settlement could cause overstressing in a steel structure and could also affect
the alignment of, and stresses In, the attached piping, electric cable lines, and instrument lines.
Moreover, the differential settlement could cause misalignment of cranes and monorails. GDC 16 of Appendix A to 10 CFR Part 50 requires that "reactor containment and associated systems
shall be provided to establish an essentially leaktight barrier against the uncontrolled release of
radioactivity to the environment and to assure that the containment design conditions important
to safety are not exceeded for as long as postulated accident conditions require." GDC 55 (referring to reactor coolant pressure boundary penetrating containment) requires, In part, that
"other appropriate requirements to minimize the probability or consequences of an accidental
rupture of these lines or of lines connected to them shall be provided as necessary to assure
adequate safety." As explained In the preceding paragraphs, detrimental settlement as a result
of erosion of cement from the porous concrete subfoundation could result In overstressing of
the pipes (lines) penetrating the containment structure and Increase the probability of an
accidental rupture of these lines or of lines connected to them. Criterion XVI of Appendix B to
10 CFR Part 50 requires licensees to take appropriate corrective actions when conditions
adverse to quality and safety are detected. Detrimental settlement of a structure (for any
reason) can be characterized as a condition adverse to quality and safety.
Safety-related and certain non safety-related structures are required by the maintenance rule
(10 CFR 50.65) to be within the scope of the licensee's structural monitoring program.
NUMARC 93-011 provides guidelines to the industry for monitoring the effectiveness of
maintenance at nuclear power plants In accordance with the requirements of the maintenance
rule. NRC Regulatory Guide (RG) 1.160, Monitoring the Effectiveness of Maintenance at
Nuclear Power Plants," Revision 2, March 1997, endorses NUMARC 93-01, Revision 2.
Section C.1.5 of RG 1.160 describes the attributes of an acceptable structural monitoring
program for the purposes of complying with the maintenance rule and evaluating structural
degradation resulting from degraded conditions such as porous concrete erosion.
The NRC staff may Inspect licensees' subfoundation monitoring and preventive maintenance
programs as part of the NRC Inspection program as described In NRC Inspection Procedures
Related Generic Communications
IN 97-11, "Cement Erosion From Containment Subfoundations at Nuclear Power Plants, dated
March 21, 1997."
'NUMARC 93-01, "Industry Guideline for Monitoring the Effectiveness of Maintenance at
Nuclear Power Plants," Revision 2, April 1996.
IN 98-26 July24, 1998 This information notice requires no specific action or written response. However, recipients are
reminded that they are required to consider Industry-wide operating experience (including NRC
information notices) where practical, when setting goals and performing periodic evaluations
under 10 CFR 50.65, Requirements for Monitoring the Effectiveness of Maintenance at
Nuclear Power Plants." If you have any questions about the Information in this notice, please
contact one of the technical contacts listed below or the appropriate Office of Nuclear Reactor
Regulation (NRR) project manager.
Ja4e
. Roe, Acting Director
D
ion of Reactor Program Management
Office of Nuclear Reactor Regulation
Technical contacts:
R. Pichumani, NRR
H. Ashar, NRR
301-415-2734
301-415-2851 E-mail: rxp@nrc.gov
E-mail: hga~nrc.gov
W. Burton, NRR
301-415-2853 E-mail: wfb~nrc.gov
Attachment: List of Recently Issued NRC Information Notices
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Attachment
IN 98-26 -
July 24, 1998
Page 1 of I
LIST OF RECENTLY ISSUED
NRC INFORMATION NOTICES
Information
Date of
Notice No.
Subject
Issuance
Issued to
98-25 Loss of Inventory from Safety-
7/08198 Related, Closed-Loop Cooling
Water Systems
98-24
98-23
Stem Binding in Turbine
Govemor Valves In Reactor
Core Isolation Cooling (RCIC)
and Auxiliary Feedwater (AFW)
Systems
Crosby Relief Valve Setpoint
Drift Problems Caused by
Corrosion of the Guide Ring
Deficiencies Identified
During NRC Design
6/26/98
6/26/98
6123/98
All holders of OLs for nuclear
power reactors; except those
licensees who have permanently
ceased operations and have
certified that fuel has been
permanently removed from the
reactor vessel.
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
All holders of operating licenses
for pressurized water reactors
(PWRs), except those licensees
permanently ceased operations
and have certified that fuel has
been permanently removed from
the reactor vessel
All holders of operating licenses
for nuclear power reactors, except those licensees who have
permanently ceased operations
and have certified that fuel has
been permanently removed from
the reactor vessel
98-22 OL = Operating License
CP = Construction Permit
IN 98-26 July 24, 1998 This information notice requires no specific action or written response. However, recipients are
reminded that they are required to consider industry-wide operating experience (including NRC
information notices) where practical, when setting goals and performing periodic evaluations
under 10 CFR 50.65, "Requirements for Monitoring the Effectiveness of Maintenance at
Nuclear Power Plants." If you have any questions about the information in this notice, please
contact one of the technical contacts listed below or the appropriate Office of Nuclear Reactor
Regulation (NRR) project manager.
Jack W. Roe, Acting Director
Division of Reactor Program Management
Office of Nuclear Reactor Regulation
Technical contacts:
R. Pichumani, NRR
301-415-2734 E-mail: rxp~nrc.gov
H. Ashar, NRR
301-415-2851 E-mail: hgainrc.gov
W. Burton, NRR
301-415-2853 E-mail: wfb@nrc.gov
Attachment: List of Recently Issued NRC Information Notices
- See previous concurrence
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OFFICIAL RECORD COPY
IN 98-xx
July xx, 1998 This information notice requires no specific action or written response. However, recipients are
reminded that they are required to consider industry-wide operating experience (including NRC
information notices) where practical, when setting goals and performing periodic evaluations
under 10 CFR 50.65, "Requirements for Monitoring the Effectiveness of Maintenance at
Nuclear Power Plants." If you have any questions about the information in this notice, please
contact one of the technical contacts listed below or the appropriate Office of Nuclear Reactor
Regulation (NRR) project manager.
Jack W. Roe, Acting Director
Division of Reactor Program Management
Office of Nuclear Reactor Regulation
Technical contacts:
R. Pichumani, NRR
301-415-2734 E-mail: rxp@nrc.gov
H. Ashar, NRR
301-415-2851 E-mail: hga@nrc.gov
W. Burton, NRR
301-415-2853 E-mail: wfb@nrc.gov
Attachment: List of Recently Issued NRC Information Notices
- See previous concurrence
DOCUMENT NAME:
G:XWFB\\INSTRUC.WPD
PA #11J1
OFFICIAL RECORD COPY
To receive a copy of this document, indicate in the box C=Copy w/o attachment/enclosure E=Copy with attachmentlenclosure N = No copy
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IN 98-xx
July xx, 1998 This information notice requires no specific action or written response. However, recipients are
reminded that they are required to consider industry-wide operating experience (including NRC
information notices) where practical, when setting goals and performing periodic evaluations
under 10 CFR 50.65, Requirements for Monitoring the Effectiveness of Maintenance at
Nuclear Power Plants." If you have any questions about the information in this notice, please
contact one of the technical contacts listed below or the appropriate Office of Nuclear Reactor
Regulation (NRR) project manager.
Jack W. Roe, Acting Director
Division of Reactor Program Management
Office of Nuclear Reactor Regulation
Technical contacts:
R. Pichumani, NRR
301-415-2734 E-mail: rxp@nrc.gov
H. Ashar, NRR
301-415-2851 E-mail: hga@nrc.gov
W. Burton, NRR
301415-2853 E-mail: wfb@nrc.gov
Attachment: List of Recently Issued NRC Information Notices
- See previous concurrence
DOCUMENT NAME:
G:\\WFB\\INSTRUC.WPD
PA#11J1
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June xx, 1998 This information notice requires no specific action or written response. However, recipients are
reminded that they are required to consider industry-wide operating experience (including NRC
information notices) where practical, when setting goals and performing periodic evaluations
under 10 CFR 50.65, "Requirements for Monitoring the Effectiveness of Maintenance at
Nuclear Power Plants." If you have any questions about the information in this notice, please
contact one of the technical contacts listed below or the appropriate Office of Nuclear Reactor
Regulation (NRR) project manager.
Jack W. Roe, Acting Director
Division of Reactor Program Management
Office of Nuclear Reactor Regulation
Technical contacts:
R. Pichumani, NRR
H. Ashar, NRR
301-415-2734
301-415-2851 E-mail: rxp@nrc.gov
E-mail: hga@nrc.gov
W. Burton, NRR
301-415-2853 E-mail: wfb@nrc.gov
Attachment: List of Recently Issued NRC Information Notices
- See previous concurrence
DOCUMENT NAME:
G:\\WFB\\IN STRUC.WPD
PA#11JI
OFFICIAL RECORD COPY
To receive a copy of this document, Indicate in the box C=Copy wo attachmenVenclosure E=Copy with attachment/enclosure N = No copy
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performance or condition of all SSCs associated with storage, control, and maintenance of
spent fuel in a safe condition in a manner sufficient to provide reasonable assurance that such
SSCs are capable of fulfilling their intended functions.
Paragraph (a)(2) of 10 CFR 50.65 states that monitoring as specified in paragraph (a)(1) is not
required when it has been demonstrated that the performance or condition of an SSC is being
effectively controlled through the performance of appropriate preventive maintenance, such that
the SSC remains capable of performing its intended function. It is the staff's position that
monitoring for the subject condition and its associated effects as required by paragraph (a)(1)
or performance of appropriate preventive maintenance as required by paragraph (a)(2) is
appropriate and in keeping with NRC regulations. The NRC staff will inspect licensees'
subfoundation monitoring and preventive maintenance programs as part of its normal
maintenance rule inspection program.
Related Generic Communications
IN 97-11, 'Cement Erosion From Containment Subfoundations at Nuclear Power Plants, dated
March 21, 1997.'
This information notice requires no specific action or written response. However, recipients are
reminded that they are required to consider industry-wide operating experience (including NRC
information notices) where practical, when setting goals and performing periodic evaluations
under 10 CFR 50.65, Requirements for Monitoring the Effectiveness of Maintenance at
Nuclear Power Plants." If you have any questions about the information in this notice, please
contact one of the technical contacts listed below or the appropriate Office of Nuclear Reactor
Regulation (NRR) project manager.
Jack W. Roe, Acting Director
Division of Reactor Program Management
Office of Nuclear Reactor Regulation
Technical contacts:
R. Pichumani, NRR
H. Ashar, NRR
301-415-2734
301-415-2851 E-mail: rxp@nrc.gov
E-mail: hga@nrc.gov
W. Burton, NRR
301-415-2853 E-mail: wfb~nrc.gov
Attachment: List of Recently Issued NRC Information Notices
DOCUMENTNAME:
G:\\WFBUIN STRUC.WPD
PA#11JI
OFFICIAL RECORD COPY
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OFFICE
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June xx, 1998 It is the staff's position that monitoring for the subject condition and its associated effects as
required by Paragraph (a)(1 or performance of appropriate preventive maintenance as required
by Paragraph (a)(2) is appropriate and in keeping with NRC regulations. The NRC staff will
inspect licensees' subfoundathpn monitoring and preventive maintenance programs as part of
its normal Maintenance Rule ir~ pection program.
Related Generic Communicatioi
Information Notice (IN) 97-11,"Ce
nt Erosion from Containment Subfoundations at Nuclear
Power Plants"
This information notice requires no spec c action or written response. However, recipients are
reminded that they are required to consid
industry-wide operating experience (including NRC
information notices) where practical, when etting goals and performing periodic evaluations
under Section 50.65, "Requirements for Mon oring the Effectiveness of Maintenance at Nuclear
Power Plants," to Part 50 of Title 10 of the Co
of Federal Regulations. If you have any
questions about the information in this notice, plase contact any of the technical contacts listed
below or the appropriate Office of Nuclear React
Regulation (NRR) project manager.
Jack W.oe, Acting Director
Division o
eactor Program Management
Office of N lear Reactor Regulation
Technical Contacts:
R. Pichumani, NRR
H. Ash , NRR
301-415-2734
301-415 851 E-mail: rxp@nrc.gov
E-mail: hg @nrc.gov
W. Burton, NRR
301-415-2853 E-mail: wfbenrc.gov
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