PNP 2023-021, Ventilated Storage Cask Inspection Summary Report
| ML23228A102 | |
| Person / Time | |
|---|---|
| Site: | Palisades, 07201007  |
| Issue date: | 08/16/2023 |
| From: | Noval W Holtec Decommissioning International |
| To: | Division of Fuel Management, Document Control Desk, Office of Nuclear Material Safety and Safeguards, Office of Nuclear Reactor Regulation |
| References | |
| HDI PNP 2023-021 | |
| Download: ML23228A102 (1) | |
Text
HDI PNP 2023-021 CoC 72-1007 Att. A, 1.3.3 August 16, 2023 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Director, Division of Fuel Management Office of Nuclear Material Safety and Safeguards Washington, DC 20555-0001 Palisades Nuclear Plant Docket Nos. 50-255 and 72-007 Renewed Facility Operating License No. DPR-20
Subject:
Ventilated Storage Cask Inspection Summary Report In accordance with the requirements of Energy Solutions Ventilated Storage Cask (VSC)
VSC-24 Renewed Certificate of Compliance 1007, Amendment 0, Attachment A, Conditions for Cask Use and Technical Specifications, Section 1.3.3, Interior VCC surface Inspection, Holtec Decommissioning International, LLC (HDI) on behalf of Holtec Palisades, LLC (Holtec Palisades) is submitting the summary report for the results of the five-year surveillance for the first VSC-24 cask placed in service.
Section 1.3.3 Surveillance requires that the ventilated concrete cask (VCC) interior surfaces and the multi-assembly sealed basket (MSB) exterior surfaces of the first VSC unit placed in service be inspected after every five years in service. The inspection is to identify potential air flow blockage and material degradation. A report summarizing the findings is required to be submitted within 30 days after the conclusion of the inspection. The first VSC, serial number, CVCC-24-01, was placed in service at the Palisades Nuclear Plant on May 12, 1993. The previous inspection was conducted in July 2018.
On July 25, 2023, a remote visual inspection of the VCC interior surfaces was completed.
Surfaces inspected included readily accessible areas of the ventilation flow path off the VCC air inlets and outlets for unacceptable blockage, readily accessible areas of inside surfaces of the VCC air inlets and outlets for unacceptable corrosion, readily accessible areas of the annulus-facing surfaces of the VCC cask liner bottom for unacceptable corrosion, readily accessible areas of the VCC cask liner shell for unacceptable corrosion, readily accessible areas of the VCC shield ring plates for unacceptable corrosion, and readily accessible areas of the MSB shell for unacceptable corrosion. The inspection concluded:
- 1. The VSC cooling paths were free of air flow blockage.
Krishna P. Singh Technology Campus, 1 Holtec Blvd., Camden, NJ 08104 Telephone (856) 797-0900 Fax (856) 797-0909 HOLTEC DECOMMISSION ING INTERNATIONAL
HDI PNP 2023-021 Page 2 of 2
- 2. The VCC interior surfaces and the MSB exterior surfaces were in satisfactory condition and considered to be normal for the VSC service environment and the specified materials of construction described in the Safety Analysis Report (SAR).
- 3. No additional degradation mechanisms affecting system performance were identified.
The inspection summary report is provided in the letter Enclosure.
This letter contains no new and no revised regulatory commitments.
Should you have any questions or require additional information, please contact Jim Miksa, Regulatory Assurance Engineer at (269) 764-2945.
Respectfully, William Noval Director, Regulatory Affairs Holtec Decommissioning, International, LLC
Enclosure:
Ventilated Storage Cask Inspection Summary Report cc:
NRC Region Ill Regional Administrator NRC Decommissioning Inspector - Palisades Nuclear Plant NRC NMSS Project Manager - Palisades Nuclear Plant William Noval Digitally signed by William Noval Date: 2023.08.16 10:16:37 -04'00' y
HDI PNP 2023-021 Enclosure Page 1 of 4 Enclosure to HDI PNP 2023-021 Palisades Nuclear Plant Ventilated Storage Cask Inspection Summary Report
HDI PNP 2023-021 Enclosure Page 2 of 4 VENTILATED STORAGE CASK INSPECTION
SUMMARY
REPORT 1.0 PURPOSE This report summarizes the results of the ventilated concrete cask (VCC) interior surface inspection conducted on ventilated storage cask (VSC) serial number CVCC-24-01, which is the first VSC-24 cask unit placed in service at the Palisades Nuclear Plant (PNP). The VCC interior surfaces and the multi-assembly sealed basket (MSB) exterior surfaces of the first VSC placed in service are required to be inspected after every five years in service, as specified in Section 1.3.3 Surveillance, of Attachment A, Technical Specifications, of the VSC-24 Renewed Certificate of Compliance, to identify potential air flow blockage and material degradation.
2.0 DISCUSSION The VSC air flow cooling path surfaces that were inspected are the VCC air inlet and air outlet assemblies, the VCC interior and the MSB exterior.
Inspection Equipment The inspection was performed using an Everest Mentor Visual iQ (MViQ) system with an 84100-quartz fiber probe with an internal light source to illuminate the surfaces for inspection. An Orange/Blue 6mm tip was utilized to photograph and video record general conditions. A monitor was used to view the surfaces and a Universal Serial Bus (USB) flash drive was used to provide a record of the inspection.
Inspection Methodology Access for the inspection of the VCC interior and the MSB exterior surfaces was achieved through the VCC air inlet and air outlet assemblies. The air inlet and air outlet protective screens were partially removed as needed to facilitate entry of the video probe. The interior surfaces of the air outlet assemblies, the VCC liner interior, and the MSB exterior surfaces (which form the air flow annulus) down to the top of the air inlet hole in the floor of the VCC were inspected via access through the air outlet assembly.
Inspection Results The results are summarized below for the VSC cooling path (inlet, annulus, outlet) surfaces inspected.
Air Inlet Assembly Interior Surfaces The air inlet assemblies, from the protective screens to the air inlet hole in the floor of the VCC, were found to be free of blockage. Minor debris were identified in the air inlet assembly. The VCC inlet steel surfaces exhibited some light to medium corrosion, as noted in the 1998, 2003, 2008, 2013, and 2018 inspections. There was no significant change in the condition of the VCC inlet liner steel.
HDI PNP 2023-021 Enclosure Page 3 of 4 VCC/MSB Annulus The VCC/MSB annulus from the air outlet assemblies to the air inlet hole in the floor of the VCC was free of significant blockage. Some minor blockage was noted in the inspection (inactive spider webs) that did not result in greater than 10% cross sectional area blockage.
- VCC Liner Interior Surface Minor areas of coating degradation were noted but did not result in exceeding any acceptance criteria. No unacceptable corrosion was observed during the inspection.
- MSB Exterior Surface General degradation of the paint coating was noted on the MSB Exterior. This coating degradation does not appear to be active and appears to be original to cask assembly.
Air Outlet Assembly Interior Surfaces The outlet vents had areas of considerable rust bleed-through in areas where proper surface preparation was difficult to attain. The areas where the coating has flaked are considered to have light to medium rust with minor pitting. The pitting was previously noted in the 1998, 2003, 2008, 2013, and 2018 reports. There appears to be no significant progression of the rust when comparing the previous inspection results. The function of the outlet vent steel is maintained with the existing condition. The noted vent rust does not result in blockage greater than 10% of the cross-sectional area of the flow path, this meets the surveillance acceptance criteria is met.
3.0
SUMMARY
EVALUATION Evaluation of the results from the VCC interior inspection on VSC serial number CVCC-24-01 after 30 years in service indicates the following:
- The internal air flow paths inside the VCC were found to be free of obstruction.
This is consistent with the daily thermal performance monitoring data. Thus, there is indication that the thermal performance of the cask has not degraded, and that the cask is operating properly.
- There were no new findings from the results summarized in previous inspections.
- Degradation on the MSB coating was observed but did not exceed the inspection acceptance criteria. Functionality of the MSB continues to be demonstrated by the daily surveillances, which assure that the air inlet/outlet screens are free from blockage, and verify satisfactory cask thermal performance.
- Surface rust was noted on the interior surfaces of the air inlet and air outlet assemblies. These assemblies serve only as a concrete form during fabrication and perform no structural or shielding function.
HDI PNP 2023-021 Enclosure Page 4 of 4
- Air Inlet Assemblies - Minor debris that has no impact on air flow pathway was observed.
- The inspection was performed using Nuclear Consultants International (NCI) inspection procedure HPP-10312-0003, Five Year Inspection of the First VSC Placed in Service at Palisades. The inspection concluded that all the acceptance criteria were met.
4.0 CONCLUSION
The VSC cooling paths were found to be free of air flow blockage. The VCC air inlet and air outlet assemblies, the VCC interior surfaces and the MSB exterior surfaces were found to be in good condition and are considered to be normal for the VSC service environment and the specified materials of construction described in the safety analysis report (SAR). The inspection did not identify any degradation mechanisms affecting system performance that were not identified in the SAR.
The VSC was found to be performing as described in the SAR, and no additional degradation mechanisms affecting system performance were identified.