05000206/LER-2018-001, Independent Spent Fuel Storage Installation, Spent Nuclear Fuel Canister Temporarily Wedged in Dry Cask Storage Container
| ML18317A060 | |
| Person / Time | |
|---|---|
| Site: | San Onofre, HI-STORM 100  |
| Issue date: | 11/08/2018 |
| From: | Bosch L Southern California Edison Co |
| To: | Document Control Desk, Office of Nuclear Material Safety and Safeguards |
| References | |
| LER 2018-001-00 | |
| Download: ML18317A060 (5) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 72.75(d)(1), ISFSI Safety System Functional Failure |
| 2062018001R00 - NRC Website | |
text
An EDISON 1NTERNATlONAL1il Compnny U.S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, D.C. 20555-0001 November 8, 2018
Subject:
Docket No. 72-41 1 "12--- J b c.f-D Lou Bosch Plant Manager 10 CFR 72.75(d)(1)
. 10 CFR 72. 75(g)
LER 2018-001-0, Spent Nuclear Fuel Canister Temporarily Wedged in Dry Cask Storage Container San Onofre Nuclear Generating Station (SONGS), Independent Spent Fuel Storage Installation
Dear Sir or Madam:
Attached is Licensee Event Report (LER) 2018-001-0, Spent Nuclear Fuel Canister Temporarily Wedged in Dry Cask Storage Container. The LER is being submitted in accordance with 10 CFR 72. 75(g) for the notification made in accordance with 1 O CFR 72.75(d)(1) for the SONGS Independent Spent Fuel Storage Installation on September 14, 2018.
This letter does not contain any regulatory commitments.
If you have any questions regarding the attached report, please call Mr. Al Bates at (949) 368-6945.
Sincerely, Attachment: LER 2018-001-0 cc:
K. Kennedy, Regional Administrator, NRC Region IV M. G. Vaaler, NRC Project Manager, San Onofre Units 1, 2 and 3 W.C. Allen, NRC Project Manager, SONGS ISFSI J:,Ftz.
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5NRC FORM U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY 0MB: NO. 3150-0104 EXPIRES: 03/31/2020 366 (04-2018)
, the NRC may not conduct or sponsor, and a
- 1t-*~it oerson is not required to respond to the information collection.
- 13. Page San Onofre Nuclear Generating Station ISFSI 07200041 1 OF4
- 4. Title Spent Nuclear Fuel Canister Temporarily Wedged in Dry Cask Storage Container
- 5. Event Date
- 6. LER Number
- 7. Report Date
- 8. Other Facilities Involved Sequential Rev Facility Name Docket Number Month Day Year Year Month Day Year Number No.
05000 08 03 2018 2018
- - 001 0
Facility Name Docket Number 05000
- 9. Operating Mode Abstract (Limit to 1400 spaces, i.e., approximately 14 single-spaced typewritten lines)
San Onofre Nuclear Generating Station (SONGS) is permanently defueled and is in the process of transferring spent nuclear fuel to dry cask storage in the Independent Spent Fuel Storage Installation (ISFSI). On Friday, August 3, 2018, at approximately 12:45 PDT, as vendor contract personnel were lowering a canister containing spent nuclear fuel into an underground dry storage vault, the canister became temporarily wedged between a shield ring within the vault's inner liner and the transfer cask; a condition that did not comply with the regulatory requirements for redundant drop protection features. The condition was corrected at approximately 13:41 PDT by lifting the canister off the shield ring. The canister was safely lowered into the dry cask storage vault at 14: 14 PDT.
This is a 10 CFR 72. 75(g) follow-up report to the event notification previously made under 10 CFR 72.75(d)(1 ), "An event in which important to safety equipment is disabled or failed to function as designed.... " The condition resulted from human performance issues. Corrective actions to address programmatic issues, including training, and equipment modifications, will be completed prior to resuming the spent fuel campaign. At no time during this event was there an impact on the health and safety of plant personnel, or the public.
NRG FORM 366 (02-2018)
A. Reportable Occurrence SEQUENTIAL NUMBER
- - 001 REV NO.
- - 0 On Friday,* August 3, 2018, at approximately 12:45 PDT, vendor personnel from Holtec International under contract to Southern California Edison (SCE), were lowering a Multi-Purpose Canister (MPC) into a dry storage vault within the Independent Spent Fuel Storage Installation (ISFSI). As it was lowered, the MPC came to rest on top of the shield ring and against the inner wall of the transfer cask. With the MPC supported by the shield ring, the crane [EIIS Code: CRN] and supporting rigging became unloaded, contrary to the requirements of the Technical Specifications contained in the Holtec Certificate of Compliance (CoC) 72-1040. The condition was corrected at approximately 13:41 PDT by lifting the MPC from the shield ring. The MPC was safely lowered into storage at 14:14 PDT, and radiation levels were normal in the area.
B. Initial Conditions Both units at San Onofre Nuclear Generating Station (SONGS) were permanently defueled (Unit 2 on July 24, 2013, Unit 3 on June 28, 2013). The MPC contains thirty-seven spent nuclear fuel assemblies that were being moved from storage in the Unit 2 spent fuel pool to dry cask storage in.the ISFSI.
C. Background Information
Holtec International (Holtec) was hired by SCE in 2014 to provide an expanded ISFSI and services for the storage of the spent nuclear fuel from SONGS Units 2 and 3. The ISFSI design employs the Holtec HI-STORM UMAX dry storage vault system. The HI-STORM system stores the spent nuclear fuel in an underground storage vault, protected from the environment, and utilizes passive, natural circulation cooling. Spent fuel assemblies are loaded into the stainless steel MPC in the fuel storage pool, located.
within the SONGS plant facility. The MPC cylinder is then removed from the pool, dried, filled with a helium cover gas, and all confinement boundary locations are seal welded. A HI-TRAC transfer cask provides shielding and support for the MPC during transit to the ISFSI. A mobile Vertical Cask Transporter (VCT) places the MPC in the storage vault. The VCT is a rising hydraulic tower mobile crane, with redundant drop protection features, suspending the load from slings attached to the two towers, as opposed to a conventional gantry crane that lifts the load by winding a cable spool. The VCT is moved into position over the storage vault location, and as the towers are lowered, the MPC is lowered from the HI-TRAC transfer cask into the Cavity Enclosure Container (CEC).
The CEC provides the supporting structure for the MPC within the ISFSI concrete pad. A steel inner liner (divider shell) separates the MPC from the outer wall of the CEC, providing an annular flow path for air circulation. A steel shield ring within the inner liner is supported from above by triangular gussets welded to the divider shell. The gussets assist in centering the MPC as it is lowered into the CEC, and the shield ring reduces the radiation exposure to personnel working above the container. Careful alignment of the MPC is necessary when lowering the MPC into the CEC to clear the shield ring.
During the evolution of lowering the MPC into the storage vault, an observer (spotter) was positioned on a hydraulic lift adjacent to the VCT. The spotter was the only person positioned to directly observe the MPC as it was lowered. The VCT operator cannot directly observe the MPC and relies on information from the spotter. A Radiation Protection (RP) technician was stationed below and to the side of the ISFSI pad. Other personnel including the Cask Loading Supervisor (CLS), and Rigger In Change (RIC) Page 2 of 4 (04-2017)
U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY 0MB: NO. 3150-0104 EXPIRES: 3/31/2020 LICENSEE EVENT REPORT (LER)
CONTINUATION SHEET (See NUREG-1022, R.3 for instruction and guidance for completing this form http://www.nrc.gov/readinq-rm/doc-collections/nuregs/staff/sr1022/r30 Estimaled, the NRC may not conduct or sponsor, and a person is not required to respond to, the information coHection.
- 1. FACILITYNAME
- 2. DOCKET NUMBER
- 3. LER NUMBER YEAR San Onofre Nuclear Generating Station 072000-41 2018 SEQUENTIAL NUMBER
- - 001 were restricted from entering the area to maintain the worker exposure As Low As Reasonably Achievable (ALARA) and were not in a position.to observe the MPC download.
D. Description of Occurrence REV NO.
- - 0 On Friday, August 3, 2018, at approximately 12:45 PDT, as Holtec personnel were lowering the MPC into the storage vault, the bottom of the MPC contacted a gusset on the shield ring. The MPC tilted slightly, wedging it between the inner wall of the transfer cask and the shield ring. The VCT operator was monitoring the tower positions and was not observing the total weight of the load as it descended; consequently he did not detect that the slings were unloading. The spotter had moved the hydraulic lift for ALARA purposes without observing the MPC had stopped lowering and he was no longer positioned to directly observe the MPC movement. The spotter observed the slings had accumulated on the pad instead of the MPC, and did not recognize it was an abnormal condition. The CLS and RIC believed the MPC was lowering because from their perspective, the slings appeared to be taut.
At approximately 13:09 PDT, the RP technician reported the dose rate was elevated above normal levels, indicating the MPC had not lowered. Shortly afterwards, the Holtec Site Services Manager directed immediate action be taken place tension on the slings. At 13:30 PDT, the VCT was raised, fully lifting the MPC from the shield ring at 13:41 PDT. At 14: 14 PDT, it was confirmed the MPC had been fully lowered into the storage vault. A survey of the ISFSI pad confirmed the dose rates had returned to normal.
The Holtec Certificate of Compliance (CoC) No.72-1040, Technical Specification Section 5.2 "Transport Evaluation Program," item c.3 states, "The lifting equipment shall have redundant drop protection features which prevent uncontrolled lowering of the load." Technical Specification 5.2.c.3 was not met during the approximately 54 minutes the MPC was temporarily wedged in the transfer cask above the shield ring.
SCE initially determined the event was not reportable and discussed the event with NRC Region IV on Monday, August 6, and Tuesday, August 7. After additional discussion with the NRC inspection team during the week of September 10, SCE submitted a late 24-hour non-emergency notification under 10 CFR 72.75(d)(1 ), "An event in which important to safety equipment is disabled or failed to function as designed when: (i) The equipment is required by regulation, license condition or the certificate of compliance to be available and operable... to mitigate the consequences of an accident; and (ii) No redundant equipment was available and operable to perform the required safety function." This 60-day report is submitted under 10 CFR 72. 75(g), "Preparation and submission of written reports."
E. Cause Evaluation The ISFSI team initially failed to recognize the MPC misalignment and halt the download activity. A Root Cause Evaluation (RCE) and an Apparent Cause Evaluation (ACE) were completed by Holtec and SCE, respectively.
Holtec Management did not completely recognize the complexity and risks associated with fuel transfer operation while using a relatively new Holtec HI-STORM UMAX system design when performing a long duration campaign and thus did not implement all necessary program improvements or the necessary level of oversight. Holtec failed to challenge the design of the shield ring and did not identify the potential for unintended consequences. Page 3 of 4 U.S. NUCLEAR REGULATORY COMMISSION (04-2017)
/""Ati:o1r.i.,
LICENSEE EVENT REPORT (LER)
\\.... J CONTINUATION SHEET (See NUREG-1022, R.3 for instruction and guidance for completing this form http://www.nrc.gov/reading-rm/doc-collections/nuregs/staff/sr1022/r3fj APPROVED BY 0MB: NO. 3150-0104 EXPIRES: 3/31/2020
, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.
- 3. LER NUMBER YEAR San Onofre Nuclear Generating Station 072000-41 2018 SEQUENTIAL NUMBER
- - 001 REV NO.
- - 0 SCE Oversigh_t was not effective in pr~venting the event and failed to ensure Holtec provided technically accurate procedures, training to support procedure implementation, and sufficiently detailed guidance for the Oversight Specialists.
F. Corrective Actions
Completed Corrective Actions SCE directed Holtec to stop all work, allowing for the completion of the initial investigation and personnel briefings.
Holtec has incorporated independent experts into their design review process, expanding the review process to include members from site services and manufacturing, and will use an Independent Challenge Team to review new designs as well as changes with elevated potential consequences.
Corrective Actions
Procedural and programmatic revisions will be made, equipment modifications implemented, and revisions of the SCE Oversight program and training will be completed prior to resuming the spent fuel campaign. Additionally, enhancements will be made under the Corrective Action Program (CAP) to emphasize the importance of Operating Experience (OE) and Lessons Learned.
Continuous load monitoring equipment will be installed and utilized by the VCT operator to verify the MPC is not binding or misaligned as it is lowered into storage.
G. Safety Assessment
The MPC remained intact and was safely stored in the ISFSI. At no time during this event was there an impact on the health and safety of site personnel or the public. Calculations have shown the shield ring is structurally capable of supporting the weight of the MPC. Additionally, an analysis demonstrated the MPC confinement boundary has sufficient margin and would not be breached from a free vertical drop of twenty-five feet onto a rigid surface.
H. Additional Information - Operating Experience SONGS On July 22, 2018, the MPC download into the storage vault was delayed for 1.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> when the VCT operator observed a reduction in load. The MPC was raised, re-aligned, and successfully placed in storage. The redundant safety features remained operable as required. The cause of the delay was not fully evaluated at that time and has since been entered into the corrective action program and incorporated into lessons learned.
Callaway In July 2015 during a dry run, Callaway experienced contact with the shield ring and the crew realigned the MPC. A Caution Statement was added to the procedure at Callaway, however the potential for interference with the shield ring was inadequately addressed in the development of the procedures used at SONGS. Page 4 of 4