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| Quarter | Site | Title | Description | |
|---|---|---|---|---|
| 05000454/FIN-2010007-01 | 2010Q3 | Byron | Inadequate Procedures for Implementing FSAR Required Annulus Cooling | The inspectors identified a Severity Level IV NCV of 10 CFR 72.150, Instructions, Procedures, and Drawings. Specifically, the licensee failed to have procedures in place to ensure that the design basis peak fuel cladding temperature limit would not be exceeded during vacuum drying operations. The licensee entered this issue into its corrective action program and revised the procedure to provide monitoring criteria. The violation was determined to be of more than minor significance because, if left uncorrected, it could lead to a more safety significant event. Although the violation contributed to the likelihood of peak fuel cladding temperatures exceeding the safety limit, subsequent analysis by the licensee and the NRC determined that fuel cladding temperature limits were not exceeded during this event; therefore, the violation screened as having very low safety significance. |
| 05000454/FIN-2010007-03 | 2010Q3 | Byron | Licensee ISFSI Annulus Cooling System Important to Safety Classification | The inspectors identified an unresolved item associated with the licensees program that classifies ISFSI components and systems as either important to safety (ITS) or not important to safety (NITS). The inspectors identified that the licensee failed to have a procedure in place to classify ancillary pieces of equipment, not specifically classified in the Holtec FSAR, as ITS or NITS. The Holtec FSAR, Table 8.1.6 classifies ancillary pieces of equipment as ITS or NITS. The Holtec FSAR indicates that the maximum annulus cooling water temperature is 125oF during vacuum drying operations. This temperature can only be achieved through some active means, and at the Byron Station, is achieved through the use of an annulus cooling system. Under medium and high heat loads, failure of this system would result in annulus cooling water exceeding the125oF design basis limit absent some intervention. The system used by the licensee for HI-TRAC annulus cooling consists of a heat exchanger, submersible pump, temperature monitoring device, and chiller. The system is not classified as either ITS or NITS in the Holtec FSAR. The licensee purchased the chiller as commercial grade equipment and since the system was not identified within the Holtec FSAR, characterized the system as NITS. The licensee initiated IR 1116408, NRC Potential URIs from ISFSI Reactive Inspection, to determine whether the system needed to be re-designated as ITS. Subsequent to the completion of the inspection, the licensee utilized input from Holtec to make the ITS or NITS classification. Holtec Standard Procedure 345 is used to implement a graded classification approach, consistent with NUREG/CR-6407. Using the evaluation matrix in Holtec Standard Procedure 345 the licensee classified the cooling system as NITS. In Holtecs response to the licensee regarding its recommendation to classify the annulus cooling system as NITS, Holtec recommended the following: To preclude the possibility of peak cladding temperature exceeding 1058F, administrative measures should be taken by the licensee to monitor the operation of the system and mitigate the likelihood of the annulus water temperature rising above 125F by taking additional actions such as (a) regular monitoring of the device operability, (b) regular monitoring of the annulus bulk water temperature, and (c) procedurally establishing compensatory measures in order to mitigate the possibility of an adverse temperature condition. In the event of failure of the annulus cooling device which cannot be quickly restored (within 6 hours, based on the completion time for the similar condition in LCO 3.1.1 condition B from Amendment 5 of the Technical Specification), the cask should be backfilled with helium to the minimum limits as specified in Table 3-2, Appendix A, Amendment 3 of the Technical Specification (vacuum drying can be continued from that condition once the flushing system is restored). The inspectors reviewed the licensees revised procedures for implementation of the Holtec recommendations. However, this issue will remain unresolved pending further review of the system classification as NITS by the SFST office. (URI 05000454/2010007-03; 05000455/2010007-03; 07200068/2010002-03, Licensee ISFI Annulus System Important to Safety Classification.) |
| 05000454/FIN-2010007-02 | 2010Q3 | Byron | Non-Inert Atmosphere May Challenge Fuel Integrity | The inspectors identified a URI associated with the licensees adherence to Holtec CoC 1014, Amendment 3, Appendix B, Section 3.4.10, during vacuum drying operations. Specifically, Appendix B 3.4.10 states that users shall establish procedural and/or mechanical barriers to ensure that during loading operations and unloading operations, either the fuel cladding is covered by water, or the MPC is filled with an inert gas. SFST ISG-22 discusses that cladding and fuel damage may occur if: a) the fuel has pinhole leaks or hairline cracks; and b) air is introduced into a dry fuel canister while fuel is at an elevated temperature. The Holtec CoC defines intact fuel as fuel assemblies without known or suspected cladding defects greater than pinhole leaks or hairline cracks and which can be handled by normal means. The Holtec FSAR indicates that during vacuum drying operations, fuel cladding temperatures are designed to be less than 1058oF, but could be as high as 1040oF. The inspectors observed that while under vacuum, a hose rupture would allow air to flow back into the MPC. The licensee used commercial grade equipment hosing and valves, to complete the vacuum drying process. The licensee had no compensatory measures in place to promptly isolate and/or backfill the canister. The licensee documented this concern in its corrective action program under IR1116408, NRC Potential URIs from ISFSI Reactive Inspection. Currently, the licensee has stated that they have selected fuel with no known pinhole leaks or hairline cracks. This determination was made from a review of fuel sipping and chemistry records. The licensee has added additional contingency procedures to appropriately recognize a hose failure and backfill the canister with an inert gas. This will remain an unresolved issue pending further review of whether a postulated vacuum hose break would result in fuel damage. (URI 05000454/2010007-02; 05000455/2010007-02; 07200068/2010002-02, Non-Inert Atmosphere May Challenge Fuel Integrity.) |
| 05000454/FIN-2010007-04 | 2010Q3 | Byron | Thermal Models in FSAR Design Basis Analysis May Not be Conservative | The inspectors identified an unresolved item associated with peak cladding temperature thermal analyses during short term vacuum drying operations as described in the Holtec FSAR and the associated use of the Holtec FSAR at the Byron Station. SFST ISG-11 discusses that cladding temperature limits should not exceed 1058 oF during short term operations. During an independent review of the licensees failure to provide adequate cooling to the Byron Station ISFSI MPC during vacuum drying operations, a SFST technical reviewer assessed the Holtec FSAR Revision 5 design basis calculation for adequacy. When comparing the results of the reviewers model to the results provided by Holtecs model which were subsequently incorporated into the Holtec FSAR, Revision 5, a potential discrepancy was noted. The Holtec FSAR, Revision 5, states that during steady state vacuum drying of an MPC-32 canister with a heat load of 28.74 kilowatts and a shell temperature postulated at 125oF, fuel cladding temperatures will not exceed 1040oF. The SFST reviewers model calculated fuel cladding temperatures in excess of 1058 oF. The licensee documented this concern in its corrective action program under IR 1116408, NRC Potential URIs from ISFSI Reactive Inspection. The licensee commissioned canister specific two dimensional thermal analyses for each remaining canister in the licensees campaign. An additional safety factor was included in the licensees analyses to ensure that any discrepancies between the NRC model and the Holtec model would not result in peak cladding temperatures in excess of 1058oF. This unresolved issue will remain open pending additional SFST review of the design basis fuel cladding temperatures documented in the Holtec FSAR, Revision 5, and the use of this FSAR at the Byron Station. (URI 05000454/2010007-04; 05000455/2010007-04; 07200068/2010002-04, Thermal Models in FSAR Design Basis Analysis May Not Be Conservative.) |