Issue Date: 1/17/02
NRC Inspection Manual IIPB
INSPECTABLE AREA: | Permanent Plant Modifications |
CORNERSTONE: | Initiating Events (10%) Mitigating Systems (70%) Barrier Integrity (20%) |
INSPECTION BASIS: | Modifications to risk-significant structures, systems, and components (SSCs) can adversely affect their availability, reliability, or functional capability. Modifications to one system may also affect the design bases and functioning of interfacing systems. Similar modifications to several systems could introduce potential for common cause failures that affect plant risk. Modifications performed during increased risk configurations could place the plant in an unsafe condition. This inspectable area verifies aspects of the Initiating Events, Mitigating Systems, and Barrier Integrity cornerstones for which there are no indicators to measure performance. |
LEVEL OF EFFORT: | Biennial review of 5 to 10 permanent plant modifications. Annual review of 1 to 2 risk-significant permanent plant modifications performed on-line as they occur. |
01.01 | To verify that the design bases, licensing bases, and performance capability of risk significant SSCs have not been degraded through modifications. |
01.02 | To verify that modifications performed during increased risk-significant configurations do not place the plant in an unsafe condition. |
02.01 | Selection of Modifications. This
procedure is performed both as an annual
and a biennial review. Select
modifications to be reviewed, depending
on the type of review to be performed, as
outlined in the following table.
For the purpose of this inspection, permanent plant modifications include permanent plant changes, design changes, set point changes, procedure changes, equivalency evaluations, suitability analyses, calculations, and commercial grade dedications. |
Review Type | Frequency | Scope and Focus | Applicable Inspection Activities |
Biennial Review | Once every two years | Emphasis on
modifications which
affect SSCs with
high probabilistic
risk analysis (PRA)
rankings
Primarily modifications which affect mitigating systems At least one modification which affects barrier integrity |
Section 02.02a.
Design Review
Section 02.02c.Testing Review Section 02.02d. Updating Review Section 02.03 Ident. and Resolution of Problems |
Annual Review | Once every year | A minimum of one
modification with
one additional
modification
identified by Plant
Status reviews.
Modifications planned to be performed when the plant is either on-line or during increased shutdown risk configuration |
Section
02.02a.Design
Review
Section 02.02b.Implementation Review Section 02.02c.Testing Review |
02.02 | Inspection |
a.Design Review. During inspection preparation, identify which affected parameters listed in the following table are to be inspected. Emphasis should be placed on those parameters not verified by testing. Review the design adequacy of the modification by performing the inspection activities for the selected parameters. A pre-inspection visit by regional specialists for the biennial review should be included, if necessary, during inspection preparation to obtain necessary documentation to perform that review. |
Affected Parameter | Inspection Activity |
Energy Needs
• electricity |
Verify energy requirements can be
supplied by supporting systems when
required under accident/event
conditions.
Verify energy requirements of modified SSCs will not deprive other SSCs of required energy under accident/event conditions. |
Materials/Replacement Components
• material compatibility |
Verify materials/replacement
components are compatible with
physical interfaces.
Verify material/replacement component properties serve functional requirements under accident/event conditions. Verify materials/replacement components are environmentally qualified for application. Verify replacement components are seismically qualified for application. Verify Code and safety classification of replacement SSCs is consistent with design bases. Verify replacement schedule consistent with inservice/equipment qualification life. Verify that new SSCs added to the plant have been reviewed for inclusion in the maintenance rule scope. |
Timing
• Sequence |
Verify that any sequence changes are
bounded by accident analyses and
loading on support systems are
acceptable.
Verify SSC response time is sufficient to serve accident/event functional requirements assumed by design analyses. Verify modified SSC response time does not cause an unintended interaction with other SSCs. Verify equipment will be able to function for the duration required under accident/event conditions. |
Heat Removal | Verify that heat removal requirements can be addressed by support systems under accident/event conditions. |
Control Signals
• initiation |
Verify that control signals will be appropriate under accident/event conditions. |
Equipment Protection
• Fire |
Verify that equipment protection barriers and systems have not been compromised. |
Operations | Verify that affected operation
procedures and training have been
identified and necessary changes are in
process.
Verify that the plant simulator has been updated as required. |
Flowpaths | Verify that revised flowpaths serve functional requirements under accident/event conditions. |
Pressure Boundary | Verify pressure boundary integrity is not compromised. |
Ventilation Boundary | Verify that changes to ventilation
boundaries do not increase risk of
spreading contamination.
Verify that changes to ventilation boundaries do not adversely affect functionality of ventilation system under accident/event conditions. |
Structural | Verify modified SSCs structural
integrity acceptable for accident/event
conditions.
Verify modified SSCs structural effects upon attachment points acceptable. Verify modified SSCs effect on seismic evaluations acceptable. |
Process Medium
• Fluid Pressures |
Verify that affected process medium properties will be acceptable for both modified SSCs and unmodified SSCs under accident/event conditions. |
Licensing Basis
• 10 CFR 50.59 |
Verify that necessary Technical
Specification changes have been
identified and NRC approvals, if
required, were obtained prior to
modification implementation.
Verify acceptability of licensee's conclusions for those modifications where evaluations in accordance with 10 CFR 50.59 were not performed. |
Failure Modes | Verify those failure modes introduced by the modification are bounded by existing analyses. |
b. Implementation Review. Verify that modification preparation, staging, and implementation does not impair the following: | |
| |
(For biennial reviews, Section 02.02b.inspection activity is optional) | |
c. Testing Review. Verify that post-modification testing will maintain the plant in a safe configuration during testing. Verify that post-modification testing will establish operability by: | |
| |
NOTE: Licensees often use existing procedures, such as surveillance procedures, for post-modification testing. Although performance of existing procedures may have been reviewed by inspectors for other inspectable areas, inspectors still need to verify the appropriateness of using the existing procedures for validating the modification (as opposed to simply confirming continued operability). | |
d. Updating Review | |
| |
(For annual reviews, Section 02.02d inspection activity is optional.) | |
02.03 | Identification and Resolution of Problems. Verify that the licensee is identifying permanent plant modification issues at an appropriate threshold and entering them in the corrective action program. As it relates to permanent plant modifications, select a sample of problems documented by the licensee and verify appropriateness of the corrective actions. See Inspection Procedure 71152, "Identification and Resolution of Problems," for additional guidance. |
(For annual reviews, Section 02.03 inspection activity is optional.) |
Cornerstone | Inspection Objective | Risk Priority | Examples |
Initiating Events | Verify modifications have maintained system availability, reliability, and functional capability. | Modifications that increase the likelihood of initiating events | Modifications to
reactor coolant
pressure boundary
Modifications to switchyard or feedwater controls |
Mitigating Systems | Modifications
which affect
• protection against external events such as fire, weather, and flooding • risk-significant design features and assumptions • functionality of mitigating systems used during risk-significant accident sequences |
Modification of
reactor building
drain system
Replacement of a low pressure safety injection system injection valve with a valve of a different design | |
Barrier Integrity | Modifications which affect fuel cladding, reactor coolant system, or containment | Modification of personnel access hatch seal |
The inspection procedure is estimated to take 68 to 92 hours for the biennial review, and 14 to 18 hours a year for the annual review at a site regardless of the number of units at that site.
The biennial reviews should be performed by engineering specialists. Annual reviews may be performed by either a specialist or a resident inspector periodically during the year or at a scheduled time.
Inspection of the minimum sample size will constitute completion of this procedure in the RPS. That minimum sample size will consist of the review of one permanent plant modification on an annual basis for those intended to be performed when the plant is on-line or during an increased shutdown risk configuration, and five permanent plant modifications on a biennial basis to assess those that impact risk significant SSCs, mitigating systems, and risk significant barriers.
Inspection Procedure 71152, "Identification and Resolution of Problems"
END