IR 05000461/2016010
| ML16064A200 | |
| Person / Time | |
|---|---|
| Site: | Clinton  |
| Issue date: | 03/03/2016 |
| From: | Michael Kunowski NRC/RGN-III/DNMS/MCID |
| To: | Bryan Hanson Exelon Generation Co, Exelon Nuclear |
| Learn M | |
| References | |
| IR 2016001, IR 2016010 | |
| Download: ML16064A200 (16) | |
Text
UNITED STATES rch 3, 2016
SUBJECT:
NRC INSPECTION REPORT NOS. 05000461/2016010(DNMS);
07201046/2016001(DNMS) - CLINTON POWER STATION
Dear Mr. Hanson:
On February 11, 2016, the U.S. Nuclear Regulatory Commission (NRC) completed an inspection at your Clinton Power Station. The NRC inspectors discussed the results of this inspection with Mr. T. Stoner and other members of your staff. The inspectors documented the results of this inspection in the enclosed inspection report.
This inspection report documents a review of the control of heavy loads, specific to the fuel handling building crane and crane support structure, in preparation for independent spent fuel storage installation (ISFSI) loading activities. The inspection was conducted in accordance with Inspection Procedure (IP) 60856.1, Review of 10 CFR 72.212 Evaluations at Operating Plants.
The NRC inspectors documented one NRC-identified finding of very low safety significance (Green) in this report. This finding involved a violation of NRC requirements. The NRC is treating this violation as a Non-Cited Violation (NCV) consistent with Section 2.3.2.a of the Enforcement Policy.
If you contest the violation or the significance of the NCV, you should provide a response within 30 days of the date of this inspection report, with the basis for your denial, to the U.S. Nuclear Regulatory Commission, ATTN: Document Control Desk, Washington, DC 20555-0001, with copies to the Regional Administrator, Region III; the Director, Office of Enforcement, U.S.
Nuclear Regulatory Commission, Washington, DC 20555-0001; and the NRC Resident Inspector at the Clinton Power Station. If you disagree with the cross-cutting aspect assignment in this report, you should provide a response within 30 days of the date of this inspection report, with the basis for your disagreement, to the Regional Administrator, Region III, and the NRC Resident Inspector at the Clinton Power Station.
In accordance with Title 10 of the Code of Federal Regulations (10 CFR) 2.390, Public Inspections, Exemptions, Requests for Withholding, of the NRC's "Rules of Practice," a copy of this letter, its enclosure, and your response (if any) will be available electronically for public inspection in the NRCs Public Document Room or from the Publicly Available Records System (PARS) component of the NRC's Agencywide Documents Access and Management System (ADAMS). ADAMS is accessible from the NRC website at http://www.nrc.gov/reading-rm/adams.html (the Public Electronic Reading Room).
Sincerely,
/RA/
Michael Kunowski, Chief Materials Control, ISFSI, and Decommissioning Branch Division of Nuclear Materials Safety Docket Nos. 50-461; 72-1046 License No. NPF-62 Enclosure:
IR Nos. 05000461/2016010; 07201046/2016001 cc w/encl: Distribution via LISTSERV
SUMMARY OF FINDINGS
Inspection Report 05000461/2016010 and 07201046/2016001; 08/25/2014 - 2/11/2016;
Clinton Power Station, Unit 1; Review of 10 CFR 72.212 Evaluations at Operating Plants.
This inspection was performed by two region-based inspectors. One Green finding was identified by the inspectors. This finding and violation was considered a Non-Cited Violation (NCV) of U.S. Nuclear Regulatory Commission (NRC) regulations. The significance of inspection findings is indicated by their color (i.e., greater than Green, or Green, White, Yellow,
Red), and determined using Inspection Manual Chapter (IMC) 0609, Significance Determination Process, dated April 29, 2015. Cross-cutting aspects are determined using IMC 0310, Aspects Within Cross-Cutting Areas, dated December 4, 2014. All violations of NRC requirements are dispositioned in accordance with the NRCs Enforcement Policy dated February 4, 2015. The NRC's program for overseeing the safe operation of commercial nuclear power reactors is described in NUREG-1649, Reactor Oversight Process, Revision 5.
NRC-Identified
Violations
Cornerstone: Barrier Integrity
- Green.
A finding of very low safety significance (Green) and an associated NCV of 10 CFR Part 50, Appendix B, Criterion III, Design Control, was identified by the inspectors for the failure of the licensees design control measures to provide for the verifying or checking the adequacy of design of the fuel handling building crane and crane support structure elements. Specifically, calculations involving the crane trolley rails, crane rail clips, and crane rail clip bolts had not been verified or checked to ensure the design basis requirements of American Society of Mechanical Engineers (ASME)
NOG-1-2004; American Institute of Steel Construction (AISC), 7th Edition; and Updated Safety Analysis Report (USAR) Section 3.8.4.5 were included. The licensee documented these issues in its corrective action program and initiated actions to restore compliance.
The performance deficiency was determined to be more than minor because if left uncorrected the performance deficiency could lead to a more significant safety concern if independent spent fuel storage installation (ISFSI) loading was conducted. The inspectors determined the finding could be evaluated using the Significance Determination Process in accordance with Inspection Manual Chapter (IMC) 0609, The Significance Determination Process for Findings At-Power, Appendix A, Exhibit 3 -
Barrier Integrity Screening Questions (Section D). Based on answering No to all the questions in Exhibit 3, Section D, the inspectors determined the finding to be of very low safety significance (Green). The inspectors identified a Human Performance, Design Margin (H.6) cross-cutting aspect associated with this finding. Specifically, the licensee failed to ensure the crane trolley rails, crane rail clips, and crane rail clip bolts reflected the intended design margins of the design and licensing basis.
Licensee-Identified Violations
No violations were identified.
REPORT DETAILS
OTHER ACTIVITIES
Cornerstone: Barrier Integrity
4OA5 Other Activities
Review of 10 CFR 72.212 Evaluations at Operating Plants (Inspection Procedure (IP) 60856.1)
a. Inspection Scope
An inspection was performed of the licensees control of heavy loads program that supports the initial loading of an Independent Spent Fuel Storage Installation (ISFSI) at the Clinton Power Station. The inspection included in-office and on-site reviews of plant design calculations including structural evaluations of the Fuel Handling Building (FHB)crane and crane support structure. The inspectors reviewed structural evaluations associated with the seismic design of the trolley girders, crane bridge girders, trolley rail, crane rails, crane rail clips, crane rail clip bolts, and crane support structure.
Additionally, the inspectors reviewed inspection, testing, and maintenance documentation associated with the FHB crane, as well as, documentation supporting the upgrade of the FHB crane to Single Failure Proof in accordance with NUREG-0554, Single Failure Proof Cranes for Nuclear Power Plants, and American Society of Mechanical Engineers (ASME) NOG-1-2004, Rules for Construction of Overhead and Gantry Cranes (Top Running Bridge, Multiple Girder). The remaining balance of engineering inspection activities performed under IP 60856.1, Review of 10 CFR 72.212 Evaluations at Operating Plants, will continue into the next several quarters as the licensee nears its first loading campaign.
b. Findings
Failure to Perform Adequate Evaluation of Crane and Crane Support Structure Elements
Introduction:
A finding of very low safety significance (Green) and an associated NCV of 10 CFR Part 50, Appendix B, Criterion III, Design Control, was identified by the inspectors for the failure of the licensees design control measures to provide for the verifying or checking the adequacy of design of the fuel handling building crane and crane support structure elements. Specifically, calculations involving the crane trolley rails, crane rail clips, and crane rail clip bolts had not been verified or checked to ensure the design basis requirements of ASME NOG-1-2004; AISC, 7th Edition; and USAR Section 3.8.4.5 were included.
Description:
The process of safely moving spent nuclear fuel from the spent fuel pool to and ISFSI will place heavy loads on existing structures and components that must be evaluated to ensure structural integrity when subjected to the design loads. The FHB is a reinforced concrete structure that contains the spent fuel pool and an overhead crane that was designed to handle dry fuel storage casks. Table 3.2-1 of the USAR classified the FHB and FHB crane as Seismic Category I and subject to Appendix B of 10 CFR Part 50. The inspectors reviewed the licensees implementation of the control of heavy loads program for ISFSI operations. Per Engineering Change (EC) 392606, Upgrade Fuel Building Crane Specification K-10064, Revision 0, the upgraded crane was qualified to satisfy the requirements of ASME NOG-1-2004 and NUREG 0554. In addition, EC 39324, Structural Impacts Due to Upgrading FHB Crane, Revision 0, evaluated the FHB crane support structure for the applied loading from the FHB crane.
The inspectors reviewed design and licensing basis calculations for the FHB crane and crane support structure. The design and licensing basis requirements for the trolley rails were delineated in ASME NOG-1-2004. The design and licensing basis requirements for the FHB crane rails, rail clips, and rail clip bolts were defined in USAR Section 3.8.4.5, Structural Acceptance Criteria. This section states, in part, The stresses and strains in the structural steel are limited to those specified in the AISC Specifications, Part 1, when the loading combinations in Table 3.8-2, combinations 1, 2, and 4 through 8, are being designed for. The appropriate factors of safety against yield are discussed in the commentary to the AISC Specifications. The allowable steel stresses are increased to 1.6 times those specified above, subject to an upper bound of 0.95 fy (yield stress), when the loading combinations Table 3.8-2, conditions 9 through 18, are being designed. In this situation a minimum factor of safety of 1.05 against yield is assured. In either case, deformations of structural steel members are limited because the stresses are kept within the elastic range, and redistribution of loads due to plastic deformation is not permitted During review of Calculation No. US52-00085-09, Seismic Analysis Report, Revision 6; Calculation No. SDQ15-24-DG09, Mezzanine Floor - Design of Crane Girder, Revision 11 and Revision 11D; and licensee responses associated with the trolley rails, FHB crane rail clips, and rail clip bolts, the inspectors identified the following examples where the licensee failed to meet the requirements in 10 CFR Part 50, Appendix B, Criterion III, Design Control:
a) In Calculation No. US52-00085-09, Seismic Analysis Report, Revision 6, the calculation for the trolley rails did not take into account three directional applied loading to demonstrate compliance with ASME NOG-1-2004, Section 4154.3, Boundary Conditions at Trolley and Runway Rails. In addition, the calculations used an incorrect (and non-conservative) allowable stresses for the trolley rails based on 74 kips per square inch instead of 60 kips per square inch.
b) In Calculation No. SDQ15-24-DG09, Revision 11, the licensee used the plastic section modulus in lieu of the elastic section modulus for crane rail clips. USAR Section 3.8.4.5 prohibits the use of plastic deformation criteria.
In addition, the licensee used an allowable bolt stress based on yield and ultimate strength for rail clip bolts that did not conform to the American Institute of Steel Construction (AISC), 7th Edition, Sections 1.5.2.1 and 1.6.3.
In addition, the licensee did not consider the reduction in section modulus of the crane rail clips based on the rail clip bolted holes. Lastly, the licensee did not address prying action at the rail clip connection as delineated in accordance with AISC Section 1.5.2.1.
c) In Calculation No. SDQ15-24-DG09, Revision 11D, pages 50 to 53 and subsequent applicable responses (Operating Basis Earthquake (OBE) load case), the licensee did not address the most critical load combination and the most critical location for application of the wheel loads. Inspectors noted that the clips were located at 24 spacing while the wheels were spaced 50 apart. Based on this configuration, the inspectors determined that the wheel with the most critical loading being located at the center of clips would result in maximum impact and that most of the load would be resisted by a single pair of clips. Instead of considering individual wheel loading, the licensee calculation combined loading from all four wheels and then distributed the load over two pairs of clips. In addition, the licensee took credit for frictional force between the clip and the rail bottom flange in developing a frictional force resisting overturning moment as well as the applied lateral load. The inspectors reviewed the clip installation detail and concluded that existence of a clamping force at the rail/clip interface was uncertain as it would depend on the installation fit-up, clip material flexibility, etc.; and thus there was no basis for assuming that the force at the rail/clip interface would be the same as that at the bolt location. Further, the use of bolt preload as an allowable load for applied shear or tension was not in accordance with AISC Section 1.5.2.1.
The inspectors also noted that the 7th Edition of AISC stipulated a coefficient of friction (COF) = 0.35 for determination of installation requirements for pre-tensioned bolts while the evaluation was using COF = 0.7. The effect of the clamping force was already accounted for by using the bolt allowable for friction type connections in accordance with the AISC specification. The inspectors noted that the maximum lateral load at one wheel was 68 kips and if applied on two bolts on one clip, the maximum shear allowable load of 12.6 kips per bolt would be exceeded. Similarly, the calculated tension per bolt would also be adversely affected. In summary, the use of friction, bolt preload, and clamping force as a method to resist the applied tension and shear forces on the rail clip and rail clip bolts was not in accordance with the design and licensing basis described in the USAR and AISC.
d) In Calculation No. SDQ15-24-DG09, Revision 11D, Attachment M, the licensee performed a finite element analysis for the Safe Shutdown Earthquake (SSE) load case applying loads from two wheels on the rail. Each wheel loading included three loads, a longitudinal, a lateral, and a vertical load; thus, two pairs of loads were applied. Inspectors noted that the load pairs used in the analysis did not represent the most critical cases. For example, loads applied at one wheel consisted of 85 kips horizontal with 176 kips vertical, while the inspectors identified from the calculations a load pair consisting of 72 kips horizontal concurrent with 83 kips vertical. The inspectors determined that the later loading would be more critical for the overturning check due to smaller vertical (stabilizing) load. The licensee evaluation did not consider all loading combinations, including un-loaded hook, to determine the most critical combination for evaluation. In addition, the finite element model used in the evaluation defined contact elements at the rail/structural steel interface and at the rail/clip interface, using a COF value of 0.7. Such modeling would allow use of frictional forces based on bolt clamping force and the vertical downward gravity loads. As described above, the inspectors determined that use of friction based on clamping force was not adequate based on the discussion for the OBE load case. The inspectors also concluded use of frictional force based on gravity loads is not permitted by the industry standards, such as the Uniform Building Code and American Society of Civil Engineers (ASCE) Standard 7. The inspectors therefore concluded that the use of friction as resisting force was not in accordance with the design and licensing basis. In summary, the use of friction, bolt preload, and clamping force as a method to resist the applied tension and shear forces on the rail clips and rail clip bolts was not in accordance with the design and licensing basis described in the USAR and AISC.
Upon identification by the inspectors, the licensee documented these deficiencies in Action Request (AR) 2417450, NRC Inquiry from Fuel Building Crane Upgrade Inspection, dated October 30, 2014; AR 2422806, Engineering Judgment Improperly Documented in Calculations, dated December 9, 2014; AR 2439361, Incorrect Minimum Yield Strength in Trolley Rail Calculation, dated December 30, 2014; AR 2504614, Calculations for FB Crane Rail Unconservative, dated May 21, 2015; and AR 2624046, NRC Identified a Performance Deficiency During Inspection; February 10, 2016. The licensee initiated actions to restore compliance.
Analysis:
The inspectors determined that the failure of the calculations to include all of the design basis requirements was contrary to the design control requirements of 10 CFR Part 50 and was a performance deficiency. In accordance with Inspection Manual Chapter (IMC) 0612, Issue Screening, Appendix B, dated September 7, 2012, the inspectors determined the performance deficiency was associated with the Barrier Integrity cornerstone attribute of Design Control. The performance deficiency was determined to be more than minor because if left uncorrected the performance deficiency could lead to a more significant safety concern for plant equipment if ISFSI loading was conducted.
Specifically, compliance with ASME NOG-1-2004; AISC, 7th Edition; and USAR Section 3.8.4.5, and, for the FHB trolley rails, crane rail clips, and crane rail clip bolts was required to ensure structure integrity of structures, systems, and components described in the USAR, when subjected to design loads as part of safe load handling of heavy loads near the spent fuel pool, and to ensure integrity of the spent fuel cask.
The inspectors used IMC 0609, Attachment 4, Initial Characterization of Findings, and Appendix A, The Significance Determination Process for Findings at Power, dated June 19, 2012, to evaluate the performance deficiency. The finding was screened against the Barrier Integrity cornerstone and determined to be of very low safety significance (Green) because the inspectors answered no to the Exhibit 3 - Barrier Integrity Screening Questions applicable to the Spent Fuel Pool.
The inspectors identified a Human Performance, Design Margin (H.6) cross-cutting aspect associated with this finding. Specifically, the licensee failed to ensure the FHB crane trolley rails, crane rail clips, and rail clip bolts reflected the intended design margins established based on the design and licensing basis.
Enforcement:
10 CFR Part 50, Appendix B, Criterion III, Design Control, requires, in part, that measures be established to assure the applicable regulatory requirements and design basis are correctly translated into specifications, drawings, procedures, and instructions. It further requires, in part, that the design control measures provide for verifying or checking the adequacy of design, such as by the performance of design reviews, by the use of alternate or simplified calculation methods, or by the performance of a suitable testing program. For Clinton, the design basis for the crane is specified in ASME NOG-1-2004; AISC, 7th Edition; and USAR Section 3.8.4.5.
Contrary to the above, the licensee failed to ensure design control measures adequately provided for verifying or checking the adequacy of design for the fuel handling building crane. Specifically:
a) On December 9 and 30, 2014, in Calculation No. US52-00085-09, Seismic Analysis Report, Revision 6, the licensee failed to account for three directional applied loading to demonstrate compliance with ASME NOG-1-2004, Section 4154.3, Boundary Conditions at Trolley and Runway Rails. In addition, the licensee failed to use the design basis allowable stress for the crane trolley rails.
b) On October 30, 2014, May 21, 2015, and February 10, 2016, in Calculation No. SDQ15-24-DG09, Mezzanine Floor - Design of Crane Girder, Revision 11, the licensee failed to use the elastic section modulus for the crane rail clips in accordance with USAR Section 3.8.4.5. In addition, the licensee used an allowable bolt stress based on yield and ultimate strength for rail clip bolts that did not conform to AISC, 7th Edition, Sections 1.5.2.1 and 1.6.3. In addition, the licensee failed to consider the reduction in section modulus of the crane rail clips based on the rail clip bolted holes. Lastly, the licensee failed to address prying action at the rail clip connection as delineated in accordance with AISC, 7th Edition, Section 1.5.2.1.
c) On February 10, 2016, in Calculation No. SDQ15-24-DG09, Revision 11D, pages 50 to 53 and subsequent applicable responses, the licensee failed to address the most critical load combination and the most critical location for application of the wheel loads. In addition, the licensees use of COF = 0.7 on contact elements at the rail/structural steel interface and at the rail/clip interface was not in accordance with AISC, 7th Edition. Also, the licensees use of frictional forces based on bolt clamping force and the vertical downward gravity loads was based on unverified assumptions. And finally, the licensees use of bolt preload as an allowable load for applied shear or tension was not in accordance with AISC, 7th Edition.
d) On February 10, 2016, in Calculation No. SDQ15-24-DG09, Revision 11D, M, the licensee failed to use the most critical load pairs in the analysis. In addition, the licensees use of COF = 0.7 on contact elements at the rail/structural steel interface and at the rail/clip interface was not in accordance with AISC, 7th Edition. Also, the licensees use of frictional forces based on bolt clamping force and the vertical downward gravity loads was based on unverified assumptions.
This violation is being treated as an NCV, consistent with Section 2.3.2.a of the Enforcement Policy because it was of very low safety significance and was entered into the licensees corrective action program, as AR 2422806, 2417450, 2504614, 2439361, and 2624046 (NCV 05000461/2016010-01, Failure to Perform Adequate Evaluation of Crane and Crane Support Structure Elements).
4OA6 Management Meetings
.1 Exit Meeting
On February 11, 2016, the inspectors presented the inspection result to Mr. T. Stoner and other members of the licensee staff. The licensee acknowledged the issues presented. The inspectors confirmed that none of the potential report input discussed was considered proprietary.
ATTACHMENT:
SUPPLEMENTAL INFORMATION
KEY POINTS OF CONTACT
Licensee
- M. Newcomer, Site Vice-President (former)
- T. Stoner, Plant Manager (former) and Site Vice-President (current)
- J. Cunningham, Maintenance Director
- C. Dunn, Training Director
- M. Friedmann, Acting Regulatory Assurance Manager
- M. Heger, Plant Engineering Manager
- N. Hightower, Radiation Protection Manager
- C. Propst, Work Management Director
- D. Shelton, Operations Support Manager
- J. Ward, Nuclear Oversight Manager
- D. Avery, Regulatory Assurance
U.S. Nuclear Regulatory Commission
- J. Bozga, Reactor Engineer
- M. Learn, Reactor Engineer
LIST OF ITEMS OPENED, CLOSED, AND DISCUSSED
Opened
- 05000461/2016010-01 NCV Failure to Perform Adequate Evaluation of Crane and Crane Support Structure Elements (Section 4OA5.1)
Closed
- 05000461/2016010-01 NCV Failure to Perform Adequate Evaluation of Crane and Crane Support Structure Elements (Section 4OA5.1)
Discussed
None