ML030720220

Safety Evaluation of Topical Report No. 24370-TR-C-001, Alternate Rebar Splice-Bar-Lock Mechanical Splices.

ML030720220
Person / Time
Site:	Sequoyah
Issue date:	03/13/2003
From:	Anand R NRC/NRR/DLPM/LPD2
To:	Scalice J Tennessee Valley Authority
Anand R, NRR/DLPM, 415-1146
References
24370-TR-C-001, TAC MB5371
Download: ML030720220 (7)

Text

March 13, 2003 Mr. J. A. Scalice Chief Nuclear Officer and Executive Vice President Tennessee Valley Authority 6A Lookout Place 1101 Market Street Chattanooga, Tennessee 37402-2801

SUBJECT:

SEQUOYAH NUCLEAR PLANT, UNIT 1, SAFETY EVALUATION OF TOPICAL REPORT NO. 24370-TR-C-001, ALTERNATE REBAR SPLICE - BAR-LOCK MECHANICAL SPLICES (TAC NO. MB5371)

Dear Mr. Scalice:

On March 18, 2002, the Tennessee Valley Authority (TVA, the licensee) submitted Westinghouse Topical Report No. 24370-TR-C-001, Alternate Rebar Splice - Bar-Lock Mechanical Splices to the staff, supplemented by a letter dated December 10, 2002.

The staff has reviewed Topical Report No. 24370-TR-C-001, Alternate Rebar Splice -

Bar-Lock Mechanical Splices and found the Topical acceptable. The enclosed Nuclear Regulatory Commission (NRC) safety evaluation contains the staffs determination. However, this acceptance applies only to the Bar-Lock coupler assembly using American Society for Testing Maintenance A615 Grade 60 material in the #6 and #8 sizes for use on non-containment (i.e., shield building) applications at TVAs Sequoyah Units 1 and 2.

In accordance with the guidance provided on the NRC web site, we request that TVA publish an accepted version of this topical report within 3 months of receipt of this letter. The accepted version shall incorporate this letter and the enclosed safety evaluation between the title page and the abstract. It must be well indexed such that information is readily located. Also, it must contain in appendices historical review information, such as questions and accepted responses, and original report pages that were replaced. The accepted version shall include an "-A" (designated accepted) following the report identification symbol.

J. A. Scalice If the NRCs criteria or regulations change so that the conclusions in this letter are invalidated, thus making the topical report unacceptable, TVA will be expected to revise and resubmit its respective documentation, or submit justification for the continued applicability of the topical report without revision of the respective documentation.

If you have any questions concerning this matter, please contact Eva Brown at (301) 415-2315.

Sincerely,

/RA/

Raj K. Anand, Project Manager, Section 2 Project Directorate II Division of Licensing Project Management Office of Nuclear Reactor Regulation Docket No. 50-327

Enclosure:

Safety Evaluation cc w/encl: See next page

J. A. Scalice March 13, 2003 If the NRCs criteria or regulations change so that the conclusions in this letter are invalidated, thus making the topical report unacceptable, TVA will be expected to revise and resubmit its respective documentation, or submit justification for the continued applicability of the topical report without revision of the respective documentation.

If you have any questions concerning this matter, please contact Eva Brown at (301) 415-2315.

Sincerely,

/RA/

Raj K. Anand, Project Manager, Section 2 Project Directorate II Division of Licensing Project Management Office of Nuclear Reactor Regulation Docket No. 50-327

Enclosure:

Safety Evaluation cc w/encl: See next page DISTRIBUTION:

PUBLIC PDII-2 Reading File RAnand EBrown AHowe OGC KManoly JMa BClayton (Hard Copy)

ACRS SCahill, RII RTellson, RII ADAMS Accession No.ML030720220 OFFICE PDII-2\PM PDII-2\PM PDII-2\LA PDII-2\SC NAME EBrown RAnand BClayton AHowe DATE 3/11/03 3/11/03 3/11/03 3/12/03 Official Record Copy

Mr. J. A. Scalice SEQUOYAH NUCLEAR PLANT Tennessee Valley Authority cc:

Mr. Karl W. Singer, Senior Vice President Mr. Pedro Salas, Manager Nuclear Operations Licensing and Industry Affairs Tennessee Valley Authority Sequoyah Nuclear Plant 6A Lookout Place Tennessee Valley Authority 1101 Market Street P.O. Box 2000 Chattanooga, TN 37402-2801 Soddy Daisy, TN 37379 Mr. James E. Maddox, Acting Vice President Mr. D. L. Koehl, Plant Manager Engineering & Technical Services Sequoyah Nuclear Plant Tennessee Valley Authority Tennessee Valley Authority 6A Lookout Place P.O. Box 2000 1101 Market Street Soddy Daisy, TN 37379 Chattanooga, TN 37402-2801 Senior Resident Inspector Mr. Richard T. Purcell Sequoyah Nuclear Plant Site Vice President U.S. Nuclear Regulatory Commission Sequoyah Nuclear Plant 2600 Igou Ferry Road Tennessee Valley Authority Soddy Daisy, TN 37379 P.O. Box 2000 Soddy Daisy, TN 37379 Mr. Lawrence E. Nanney, Director Division of Radiological Health General Counsel Dept. of Environment & Conservation Tennessee Valley Authority Third Floor, L and C Annex ET 11A 401 Church Street 400 West Summit Hill Drive Nashville, TN 37243-1532 Knoxville, TN 37902 County Executive Mr. Robert J. Adney, General Manager Hamilton County Courthouse Nuclear Assurance Chattanooga, TN 37402-2801 Tennessee Valley Authority 6A Lookout Place Ms. Ann P. Harris 1101 Market Street 341 Swing Loop Road Chattanooga, TN 37402-2801 Rockwood, Tennessee 37854 Mr. Mark J. Burzynski, Manager Nuclear Licensing Tennessee Valley Authority 4X Blue Ridge 1101 Market Street Chattanooga, TN 37402-2801

SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION REQUEST FOR SAFETY EVALUATION OF TOPICAL REPORT NO. 24370-TR-C-001, ALTERNATE REBAR SPLICE - BAR-LOCK MECHANICAL SPLICES TENNESSEE VALLEY AUTHORITY SEQUOYAH NUCLEAR PLANT, UNIT 1 DOCKET NO. 50-327

1.0 INTRODUCTION

In a letter dated March 18, 2002, Tennessee Valley Authoritys (TVA, the licensee) Sequoyah Nuclear Plant (SQN) submitted a topical report for an alternate methodology for splicing reinforcing bars in concrete for nuclear safety-related applications at SQN. The topical report proposes that a Bar-Lock coupler system is now available for splicing reinforcing bars.

Presently, the SQN licencing basis does not address the use of this type of reinforcing bar splice. This topical report describes a qualification testing program and test results for the Bar-Lock coupler system. On July 9, 2002, and October 24, 2002, meetings were held between the U.S. Nuclear Regulatory Commission staff (the staff) and TVA. Subsequently, the staff issued a request for additional information dated December 4, 2002. The licensee provided response to the additional information in a letter dated December 10, 2002.

2.0 TEST PROGRAM Bechtel Corporation and Idaho National Engineering and Environmental Laboratory (INEEL) developed and performed a testing program for the Bar-Lock coupler system to assess its performance characteristics. TVA was heavily involved in the Bechtel/INEEL test program, and reviewed and approved the specifications, procedures and test plans associated with the procurement, testing, and installation of the Bar-Lock couplers. TVA civil engineers attended the vendor training session. TVA Engineering and Quality Assurance (QA) personnel witnessed the preparation of several test assemblies, and the testing of several specimens.

TVA reviewed and approved the testing program and performance analysis, prepared by INEEL.

The reinforcing bar used in the Bar-Lock coupler assembly testing program was American Society for Testing and Maintenance (ASTM) A615 Grade 60 material in #6 and #8 sizes. The mechanical properties for the reinforcing bars were tested in according to ASTM Designation A 370-96, Standard Test Methods and Definitions for Mechanical Testing of Steel Products; and ASTM Designation E 8-99, Standard Test Methods for Tension Testing of Metallic Materials.

Enclosure

The component parts of each Bar-Lock coupler consist of a steel tube, lock-shear bolts, and serrated rails. The steel tube is seamless hot-rolled in conforming to ASTM A-519, with minimum tensile strength in excess of 100 kilopound per square inch (ksi). The lock-shear bolt was made from American Iron and Steel Institute (AISI) 41L40 material, and were through-hardened over the entire length and further induction-hardened at the conical bolt tip. The serrated rails were made of ASTM CD1018 material, and were machined and then carburized to a depth of 0.032 inch The test specimen assemblies were made by steel construction workers using Bar-Locks assembly instructions in a normal field environment. Assembly of the test specimens was monitored by Bechtel Quality Control (QC) personnel. The Bar-Locks assemblies were tested in the same machine that had tested the mechanical properties of the reinforcing bars and in conformance with the same ASTM A 370-96 and E 8-99 standards.

Two reinforcing bar sizes (#6 and #8) of Bar-Lock coupler assemblies were statically tested.

The test was conducted using forty specimens of each of the two sizes of coupler assemblies.

The static test was performed according to the requirements of American Society of Mechanical Engineers (ASME)Section III, Division 2, Code for Concrete Reactor Vessels and Containment, (the Code) Section CC-4333.2.3(a), Static Tensile Tests for Mechanical Splices.

Forty specimens of each of the two sizes of the Bar-Lock coupler assemblies were tested for cyclic loadings. The cyclic test was performed according to the requirements of ASME Section III, Division 2, Code for Concrete Reactor Vessels and Containment, Section CC-4333.2.3(b),

Cyclic Tensile Tests for Mechanical Splices. The Code requires that three specimens of the bar-to-bar splice for each reinforcing bar size shall withstand 100 cycles of stress variation from 5 percent to 90 percent of the specified minimum yield strength of the reinforcing bar. In an effort to improve the cyclic durability assessment, after 100 cycles of loading required by the Code, several specimens were randomly selected to receive an additional 1000 cycles, and several other specimens were statically loaded to failure.

3.0 TECHNICAL EVALUATION

The Code requires six splice specimens for each bar size to be tensile tested statically to failure and three to be tested cyclically. The Code requires that the average tensile strength of the splices shall not be less than 90 percent of the actual tensile strength of the reinforcing bar being tested, nor less than 100 percent of the specified minimum tensile strength. Table CC-4334-1, Tensile Requirements for Mechanical Reinforcing bar splices and Welded Joints, of the Code lists a minimum yield strength of 60 ksi and minimum tensile strength of 90 ksi for ASTM 615 Grade 60 reinforcing bars.

The INEEL report states that the average tensile strength of the 40 #6 Bar-Locks assemblies is 106.2 ksi, which is 98.8 percent of the average #6 bar actual tensile strength. The average tensile strength of the 40 #8 Bar-Locks assemblies is 109.0 ksi, which is 99 percent of the average #8 bar actual tensile strength. None of the 80 specimens tested cyclically failed in any manner (e.g., bar break, or bar slip within the coupler). For those specimens that received additional 1000 cycles of loading, no obvious physical degradation was observed. For those specimens that passed 100 cycles of loading and then statically loaded to tensile failure, the measured tensile strengths were essentially the same as those tested statically to failure without the 100 cycles of loading. The report also states that no practical differences were

observed in the general character of the stress-strain curve of any of the 80 specimens tested statically, and no measurable slip was detected during the cyclic tests.

The staff finds the QA/QC program for the test specimens adequate. The phenomena of no measurable slip and the similarity in the stress-strain curves of the specimens tested demonstrate that the Bar-Locks assembly has delivered predictable results and qualifies as a viable reinforcing bar splicing system. The licensee has tested more specimens than that required by the Code, which increases the confidence level for the acceptance of the Bar-Locks assembly. The static and cyclic test methods and results have met the requirements of the Code. The additional tests of the 1000 cycles of loading and of the tensile test to failure after the 100 cycles of loading exceed the Code requirements.

4.0 CONCLUSION

Based on the information provided by the licensee, the staff determined that the licensee has developed and performed a reasonable test program for the Bar-Lock coupler assemblies, and that the test data demonstrate the adequacy of the proposed alternate methodology for connecting (splicing) reinforcing steel bars for nuclear-safety-related applications at the Sequoyah plant.

Principal Contributor: John Ma, NRR Date: March 13, 2003