LaSalle Inspection Report
It is imperative a licensee knows the conditions of the safety equipment and all documentation reflects the actual conditions. The torus has probably been inop since the plant has been in operation. This isn't the case.
When found, the torus should have been declared inop and emediately shutdown till the paperwork has been fixed. Plus an additional amount of time. It would help keep everyone else keep safe fearing the NRC would thrown down the hammer on them.
(Closed) Unresolved Item 05000373; 05000374/2016001–01: Adequacy of Changes to Pool Swell Analysis a. Inspection Scope During the 2016 first quarter integrated inspection period, the inspectors reviewed the operability evaluation associated with loss of coolant accident suppression pool analysis. The inspectors identified an unresolved item involving changes to the methodology and design assumptions of the suppression pool analysis and whether those aforementioned changes provide a reasonable expectation that the affected systems, structures and components were operable. During the follow-up inspection activities to the Unresolved Item (URI), the inspectors reviewed LaSalle County Station, Units 1 and 2—Issuance of Amendments Re: Request to Revise Suppression Pool Swell Design Analysis and the Facility Licensing Basis (CAC NOS. MF8702 AND MF8703); dated October 30, 2017. The inspectors also reviewed Operability Evaluation OE 12–003; Potential to Increase Pool Swell Loads; Revision 5 and supporting calculations of record. The inspectors determined the licensee’s operability evaluation provided a reasonable expectation of operability. Based on this review, the inspectors sufficiently resolved these concerns and consider URI 05000373; 05000374/2016001–01 closed with no performance deficiencies identified; however, during this review, the inspectors identified one additional issue described below. This operability inspection constituted one sample as defined in IP 71111.15–05. b. Findings Primary Containment Structure, Suppression Pool Columns, Downcomer Vent and Downcomer Vent Bracing Did Not Meet Seismic Category I Requirements 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 to ensure the adequacy of the design for the primary containment structure, suppression pool columns, downcomer vents and downcomer vent bracing. Specifically, the inspectors identified three representative examples where the licensee failed to perform adequate design calculations resulting in the design not being in conformance with Seismic Category I requirements as defined in UFSAR Sections 3.8.1.4.1, 3.8.1.5 and 3.8.6. Description. UFSAR Table 3.2–1 delineated the primary containment structure and downcomer vent as Seismic Category I and meeting the quality assurance requirements of 10 CFR Part 50 Appendix B. The suppression pool columns were part of the primary containment structure and support the drywell floor. The columns were designed to transfer design loading from the drywell floor to basemat.
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In UFSAR Section 3.8.1.1.1.1 described the primary containment as utilizing a Mark II over/under pressure-suppression configuration. The primary containment consisted of a steel pressure vessel enclosed by a concrete shield wall both supported by a concrete basemat. The primary containment was enclosed by the reactor building, a reinforced-concrete structure functioning as a secondary containment. The drywell was connected to the suppression chamber by downcomer pipes. Steam that could be released in the drywell during a postulated loss-of-coolant accident was channeled through these downcomer pipes into the suppression pool where it is condensed thus effecting pressure-suppression. This would result in a lower pressure and temperature. The downcomer vent pipes were braced at Elevation 697’-1” and Elevation 721’-0”. The downcomer vent bracing design function was to provide horizontal restraint for applied lateral loading on downcomer vent pipes due to the seismic and loss-of-coolant accident design event. The downcomer vent and downcomer vent bracing design requirements are delineated in Section 5.3.3.4 of LaSalle County Station, "Mark II-Design Assessment Report (LSCS-DAR)," Commonwealth Edison Company, Chicago, Illinois, September, 1982. The design assessment report was incorporated by reference in UFSAR Section 3.8.6. During a review of calculations for the primary containment structure, suppression pool columns, downcomer vents and downcomer vent bracing, the inspectors identified the following three representative examples in which the licensee failed to meet the design requirements: • Calculation No. 195B; Containment Assessment; Revision 0; and Calculation No. 161I; Suppression Pool Columns; Revision 0. UFSAR Section 3.8.1.4.1 stated, in part, “The design and analysis procedure is in full compliance with the requirements of Article CC–3000 of the ASME B&PV Code, Section III, Division 2…” The design yield strength of reinforcement shall not exceed 60,000 psi as described in Section CC–3422 of Article CC–3000. In addition, UFSAR Section 3.8.1.5 defined the allowable of Fy as the minimum guaranteed reinforcing steel yield strength. The licensee used certified material test reports or actual material yield strength for the reinforcing steel in the evaluation of the containment structure and suppression pool columns. The use of actual material yield strength did not meet American Society of Mechanical Engineers (ASME) Boiler & Pressure Vessel (B&PV) Code Section III, Division 2 and UFSAR requirements. The licensee documented these deficiencies in Issue Report No. 4070065; NRC Id: Clarification on Material Strength Values in Calcs; dated October 16, 2017. • Calculation No. L–002547; Assessment of Containment Wall, Basemat, Liner, Reactor Pedestal, Downcomer Bracing, Drywell Floor, and Suppression Pool Columns for 105 percent Power Uprate; Revision 0. As delineated in Section 5.3.3.4 of LaSalle County Station, "Mark II-Design Assessment Report, the stresses within the downcomer were considered acceptable if they satisfy the ASME B&PV Code, Section III, Subsection NE. As permitted by Subsection NE–1120 for Metallic Containment components the downcomers were analyzed using Subsection NB–3650 of Section III. The licensee did not use the ASME code acceptance limits. The licensee documented these deficiencies in Issue Report No. 4074674; NRC Id: Clarification of Design Basis Code of Downcomer Vent; dated November 14, 2017.
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• Calculation No. L–002547; Assessment of Containment Wall, Basemat, Liner, Reactor Pedestal, Downcomer Bracing, Drywell Floor, and Suppression Pool Columns for 105 percent Power Uprate; Revision 0. Section 5.3.3.4 of LaSalle County Station Mark II-Design Assessment Report described the allowable acceptance limits are based on the 1.6 times the American Institute of Steel Construction (AISC) allowables but no greater than 0.95 times Fy (minimum specified yield strength of section). The licensee increased the allowable stresses by 50 percent based on using plastic section modulus properties which exceeded the elastic acceptance limits set forth in Section 5.3.3.4 of LaSalle County Station Mark II-Design Assessment Report. The use of plastic section modulus properties would allow for permanent deformation of the material. Also, the downcomer bracing gusset plate uses plastic section modulus properties as well. Lastly, the licensee used a dynamic increase factor of 10 percent to increase the allowable acceptance limits. The dynamic increase factor was not contained in Section 5.3.3.4 of LaSalle County Station Mark II-Design Assessment Report. The licensee documented these deficiencies in Issue Report No. 4070067; NRC Id: Clarification on Acceptance Criteria in Calcs; dated October 16, 2017. The inspectors reviewed the operability evaluation in accordance with IMC 0326; Operability Determinations & Functionality Assessments for Conditions Adverse to Quality or Safety; dated November 20, 2017 to assess whether the nonconforming primary containment structure, suppression pool columns, downcomer vents and downcomer vent bracing were operable. The inspectors identified no performance deficiencies with the operability evaluation. In response to the inspector’s concern, the licensee initiated CAP documents as AR 4070067; NRC Id: Clarification on Acceptance Criteria in Calcs; dated October 16, 2017, AR 4070065; NRC Id: Clarification on Material Strength Values in Calcs; dated October 16, 2017 and AR 4074674; NRC Id: Clarification of Design Basis Code of Downcomer Vent; dated November 14, 2017. Analysis. The inspectors determined the licensee’s failure to perform adequate evaluations to demonstrate Seismic Category I compliance for the primary containment structure, suppression pool columns, downcomer vents and downcomer vent bracing was contrary to the design control measures per 10 CFR Part 50, Appendix B, requirements and was a performance deficiency. The performance deficiency was determined to be more than minor because the performance deficiency was associated with the Barrier Integrity Cornerstone attribute of design control and adversely affected the Cornerstone objective to provide reasonable assurance that physical design barriers (fuel cladding, reactor coolant system, and containment) protect the public from radionuclide releases caused by accidents or events. Specifically, compliance with Seismic Category I design basis requirements was to ensure the primary containment structure, suppression pool columns, downcomer vents and downcomer vent bracing would function as required during a Seismic Category I design basis event and not adversely affect the function of the containment barrier.
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