ML14184A939
| ML14184A939 | |
| Person / Time | |
|---|---|
| Site: | Robinson  |
| Issue date: | 04/28/1992 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML14184A938 | List: |
| References | |
| NUDOCS 9205070125 | |
| Download: ML14184A939 (8) | |
Text
.oUNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION OF THE SECOND TEN-YEAR INTERVAL ISI HYDROSTATIC TEST PROGRAM RELIEF REQUESTS CAROLINA POWER & LIGHT COMPANY H. B. ROBINSON STEAM ELECTRIC PLANT, UNIT NO. 2 DOCKET NO. 50-261
1.0 INTRODUCTION
Technical Specification 4.0.1 for H. B. Robinson Steam Electric Plant, Unit No. 2 (HBR2), states that the inservice inspection and testing of the American Society of Mechanical Engineers (ASME) Code Class 1, 2, and 3 components shall be performed in accordance with Section XI of the ASME Boiler and Pressure Vessel Code and applicable Addenda, as required by 10 CFR 50.55a(g), except where specific written relief has been granted by the Commission pursuant to 10 CFR 50.55a(g)(6)(i). Pursuant to 10 CFR 50.55a(a)(3), alternatives to the requirements of paragraph (g) may be used if (i) the proposed alternatives would provide an acceptable level of quality and safety, or (ii) compliance with the specified requirements would result in hardship or unusual difficulties without a compensating increase in the level of quality and safety.
Pursuant to 10 CFR 50.55a(g)(4), ASME Code Class 1, 2, and 3 components (including supports) shall meet the requirements, except the design and access provisions and the preservice examination requirements set forth in the ASME Code,Section XI, "Rules for Inservice Inspection of Nuclear Power Plant Components," to the extent practical within the limitations of design, geometry, and materials of construction of the components. The regulations require that inservice examination of components and system pressure tests conducted during the second ten-year interval comply with the requirements in the latest Edition and Addenda of Section XI of the ASME Code incorporated by reference in 10 CFR 50.55a(b) on the date twelve months prior to the start of the 120-month inspection interval, subject to the limitations and modifications listed therein. The applicable Edition of Section XI of the ASME Code for HBR2, second 10-year inservice inspection (ISI) interval is the 1977 Edition through Summer 1978 Addenda. The components (including supports) may meet the requirements set forth in subsequent Editions and Addenda of the ASME Code incorporated by reference in 10 CFR 50.55a(b) subject to the limitations and modifications listed therein.
9205070125 920428 PDR ADOCK 05000261 P
-2 Pursuant to 10 CFR 50.55a(g)(5), if the licensee determines that conformance with an examination requirement of Section XI of the ASME Code is not practical for its facility, information shall be submitted to the Commission in support of that determination and a request made for relief from the ASME Code requirement. After evaluation of the determination, pursuant to 10 CFR 50.55a(g)(6)(i), the Commission may grant relief and may impose alternative requirements that are determined to be authorized by law, when relief will not endanger life, property, or the common defense and security, and is otherwise in the public interest, giving due consideration to the burden upon the licensee that could result if the requirements were imposed.
The licensee, Carolina Power & Light Company (CP&L), has submitted Relief Request Nos. 1, 2, 3, and 4, in a letter dated November 15, 1991, for the second 10-year ISI interval, which began in February 1982. The staff, with technical assistance from its contractor, the Idaho National Engineering Laboratory (INEL), has evaluated the subject requests for relief in the following sections.
2.0 EVALUATION The information provided by the licensee in support of the requests for relief from ASME Code requirements has been evaluated and the bases for granting relief from those requirements are documented below.
A. Request for Relief No. 1. Approval to Use ASME Code Case N-498 for Hydrostatic Pressure Tests on all Class 1 and 2 Pressure Retaining Components Code Requirement: Section XI, Table IWB-2500-1, Examination Category B-P, and Table IWC-2500-1, Examination Category C-H, require that hydrostatic pressure tests be performed in accordance with IWB-5222 for Class 1 components, and IWC-5222 for Class 2 components.
IWB-5222 requires that the Class 1 system hydrostatic test be conducted at a test pressure of 1.10 times the system nominal operating pressure that corresponds with 100% rated reactor power except when the test is conducted at temperatures above 100 0F to meet the requirements of IWB 5230.
IWC-5222 requires that the Class 2 system hydrostatic test pressure be at least 1.10 times the system pressure for systems with design temperature of 200"F or less, and at least 1.25 times the system pressure for systems with design temperature above 2000F.
Licensee's Code Relief Request:
Relief is requested from performance of the Code-required hydrostatic pressure tests for all Class 1 and Class 2 components. CP&L is requesting authorization to implement ASME Code Case N-498 into the HBR2, Second 10-Year Interval Inservice Inspection Program.
-3 Licensee's Basis for Requesting Relief: The licensee states that the system hydrostatic test requirements for the applicable Code article for HBR2 specify system pressurization that exceeds the nominal system operating pressure. In order to achieve static pressures of this level, abnormal system alignments and configurations are required. When these lineups are performed in radiation areas, the accumulated personnel exposure would significantly increase. In addition to valve manipulations, certain relief valves are required to be gagged and pipe hangers on the main steam system are required to be pinned to withstand static water loading versus steam loads. Using valves for hydrostatic test boundary isolation when they are not normally isolation valves potentially results in the need for additional maintenance due to abnormal wear from exceeding normal pressure conditions.
Performing hydrostatic tests can also generate a significant amount of wastewater, requiring processing and disposal.
For example, the hydrostatic testing of the residual heat removal (RHR) system at the containment vessel (CV) sump isolation valves could result in significant leakage into the CV sump due to the configuration of these double-disc gate valves, which have pressure equalization holes drilled in the upstream disc. Pressurizing the downstream side of these valves would tend to unseat the downstream disc, which would fill the disc innerspace and leak through the drilled disc into the CV sump. The nominal operating pressure test would significantly reduce, if not eliminate, this backleakage of water entering the sump. Maintenance actions to clean up or preclude this leakage would be exposure-intensive. Hydrotesting other portions of systems with high/low-pressure system interfaces also requires additional maintenance actions to preclude overpressurization of the lower-pressure components resulting in generation of additional wastewater and unwarranted exposure.
Licensee's Proposed Alternative Examination: The licensee proposes to use ASME Code Case N-498, "Alternative Rules for 10-Year Hydrostatic Pressure Testing for Class 1 and 2 Systems," in lieu of the Code-required hydrostatic pressure testing requirements of IWB-5222 and IWC-5222.
Staff Evaluation: ASME Code Case N-498 provides alternative rules for the 10-year hydrostatic pressure tests required by the ASME Code,Section XI, Table IWB-2500-1, Examination Category B-P, and Table IWC-2500-1, Examination Category C-H. Code Case N-498 has been reviewed and found acceptable by the NRC, and will be included in Revision 9 of Regulatory Guide 1.147. Pursuant to 10 CFR 50.55a(a)(3)(i), relief is granted based on the alternative examination provisions discussed in N-498. This alternative provides an acceptable level of quality and safety.
-4 B. Request for Relief No. 2, IWC-5222, Open Ended Portions of Class 2.RHR Suction From Reactor Building Sump Code Requirement:
Section XI, IWC-5222(c) of the 1977 Edition, Summer 1978 Addenda requires that for the purpose of the system hydrostatic test open ended portions of a suction or drain line from a storage tank extending to the first shutoff valve shall be considered as an extension of the storage tank. For open ended portions of discharge lines in nonclosed systems (such as containment spray header), any test that demonstrates unimpaired flow shall be acceptable in lieu of a system pressure test.
IWA-5244(b) states that in redundant systems where the buried components are nonisolable, the VT-2 visual examination shall consist of a test that determines the change in flow between the ends of buried components. In cases where an annulus surrounds the buried components, the areas at each end of the buried components shall be visually examined for evidence of leakage in lieu of a flow test.
Licensee's Code Relief Request:
Relief is requested from performing the unimpaired flow test of IWC-5222(c) and the VT-2 visual examination of IWA-5244(b) on the RHR system piping from the reactor building sump through penetrations P-46 and P-47 to containment isolation valves SI-860A and 860B.
Licensee's Basis for Requesting Relief:
The licensee states that there is no isolation method designed inside containment that will allow pressurization of these lines with water, nor is there any method available to provide sufficient water flow to these lines or means necessary to evaluate a flow difference between the ends of each line.
Although an annulus surrounds the subject piping, it is sealed so even if water pressure could be applied, inspection for water leakage is precluded by the design.
Licensee's Proposed Alternative Examination: The subject piping will be pressurized and tested at the containment post-accident design pressure of 42 psig during the containment integrated leak rate test. This is the maximum credible pressure that these lines will be subjected to during accident conditions. This test is more sensitive than the hydrostatic test of IWC-5222 and is performed for a longer duration. There are no relief valves in these sections of piping that govern system pressure.
Staff Evaluation:
As stated in IWC-5222(c), open ended portions of a suction or drain line from a storage tank extending to the first shutoff valve shall be considered as an extension of the storage tank. Later Editions of the Code (Winter 1980 Addenda) have separated this examination boundary statement from that requiring the unimpaired flow test (i.e.,
open ended portions of discharge lines in nonclosed systems).
This Code change was intended to clarify the two separate requirements.
-5 The subject piping extends from the suction side of the RHR pumps to the reactor building sump and is used for recirculation in the safety injection system. Relief is not required from the unimpaired flow test of IWC-5222(c) because the subject piping is considered an extension of the reactor building sump.
A VT-2 visual examination at each end of buried components surrounded by an annulus, required by IWA-5244(b), is acceptable in lieu of a flow test.
However, the annulus is sealed so inspection for water leakage is impractical if not impossible to perform. Imposition of this requirement on CP&L would cause a burden that would not be compensated for by an increase in quality or safety. The reactor building sump, with associated piping up to valves SI-860A and SI-860B, will be tested during the containment integrated leak rate test. The containment integrated leak rate test provides a reasonable assurance of continued inservice integrity. Pursuant to 10 CFR 50.55a(g)(6)(i), relief is granted from the requirements of IWA-5244(b).
Relief is not required from IWC-5222(c) as discussed above.
C. Request for Relief No. 3. Class 2 Nonsafety-Related Systems at Containment Penetrations Code Requirement: Section XI requires that a system hydrostatic pressure test of Class 2 pressure retaining components be performed in accordance with IWC-5222(a).
IWC-5222(a) requires the system hydrostatic test pressure to be at least 1.10 times the system pressure for systems with design temperature of 200OF or less, and at least 1.25 times the system pressure for systems with design temperature above 200 0F. The system pressure shall be the lowest pressure setting among the number of safety or relief valves provided for overpressure protection within the boundary of the system to be tested.
Licensee's Code Relief Request:
Relief is requested from performing a system hydrostatic pressure test on various nonsafety-related systems at containment penetrations.
Licensee's Basis for Requesting Relief:
The licensee states that due to the vintage of HBR2, the piping within these penetration boundaries was not constructed to Class 2 requirements. Regulatory Guide 1.26, Revision 2, "Quality Group Classifications and Standards For Water-,
Steam-, and Radioactive-Waste-Containing Components of Nuclear Power Plants," which is the basis used for classification of components for ISI testing at HBR2, does not require these penetrations to be classified as Quality Group B or Class 2; however, CP&L has optionally classified these lines as Class 2 solely because they are required to assure containment
-6 integrity. These reclassifications were done to assure that testing commensurate with the safety function of the component in question was performed. In the later Section XI ASME Code Editions that were used for HBR2's Second 10-year Interval Hydrostatic Test Program, rules have been addressed with regard to these optionally "upgraded/reclassified" components that indicate that it is the option of the owner, and not a requirement of Division 1 of Section XI, to apply all the rules of the Division to these components.
IWA-1320(e) of the 1986 Edition of Section XI states that if system safety criteria permit a system to be nonnuclear safety class and an owner optionally classifies and constructs that system, or a portion thereof, to Class 2 or Class 3 requirements, the application of the rules of IWC or IWD is at the option of the owner and is not a requirement of this Division.
Licensee's Proposed Alternative Examination:
None. The licensee states that the testing of these penetrations will be accomplished in accordance with 10 CFR Part 50, Appendix J, reactor containment leakage testing.
This test is performed at 42 psig, which is the design accident pressure for HBR2, and will provide adequate assurance of system integrity. This piping is also subject to the Section XI repair and replacement requirements.
Staff Evaluation: The subject piping systems at containment penetrations are nonsafety-related and classified Code Class 2. Later Editions of the Code give the owner the option of classifying nonnuclear safety class systems as Class 2 or Class 3 without requiring the Division 1 rules for inspection. Use of subsequent Editions and Addenda of the Code, which are incorporated by reference in paragraph (b) of 10 CFR 50.55a, is acceptable, pursuant to 10 CFR 50.55a(g)(4)(iv).
The staff hereby approves the use of paragraph IWA-1320(e) of the 1986 Edition at HBR2 for the various systems at the containment penetrations listed in the licensee's submittal.
Based on this approval, relief is not required.
D. Request for Relief No. 4, IWC-5222(a), Hydrostatic Pressure Test of Safety Injection Piping Code Requirement: Section XI, IWC-5222(a) requires the system hydrostatic pressure to be at least 1.10 times the system pressure for systems with design temperature of 200OF or less, and at least 1.25 times the system pressure for systems with design temperature above 2000F. The system pressure shall be the lowest setting among the number of safety or relief valves provided for overpressure protection within the boundary of the system to be tested.
Section XI, IWA-5213(d) requires a 4-hour holding time after attaining the test pressure and temperature conditions for insulated systems, and 10 minutes for noninsulated systems or components.
-7 Licensee's Code Relief Request:
Relief is requested from the Code required hydrostatic pressure testing at 1.25 times the design pressure, and from the 4-hour hold time for the safety injection piping from valves SI-868A, SI-868B, and SI-868C through penetrations P-64, P-62, and P-63 to check valves SI-873D, SI-873E, and SI-873F, respectively.
Licensee's Basis for Requesting Relief: The licensee states that the subject Code section requires that this portion of the system be tested at a pressure of 1.25 times the lowest relief valve setting that is provided for overpressure protection. This results in a test pressure of 2187.5 psig. Since no isolation is provided between these sections of piping and the reactor coolant system (RCS), this hydrostatic test must be performed with the RCS at or above the normal system pressure/temperature to avoid injection into the primary loop piping.
The lines in question are provided with relief protection at 1750 psi by valve SI-857B. The piping has a design pressure of 2500 psi downstream of valves SI-868A, B, and C and 1500 psi upstream. The downstream boundary for pressurization would be valves SI-875A, B, and C, which are check valves held closed by RCS pressure. The upstream pressurization boundary would be the valves SI-868A, B, and C. However, closing these normally locked open valves would require entry into the Limiting Condition for Operation for Technical Specification 3.3.1.3 in that the safety injection flowpaths would be isolated by closing the SI-868 valves. Alternatively, the test could be performed with the upstream pressurization boundary being motor-operated valves SI-870A and B. This would require substantially overpressurizing the upstream portion of the system with the SI-868 valves open, since the existing relief protection (valve SI-857B) would need to be gagged to achieve the required 2187.5 psi test pressure.
Additionally, in either case, testing at elevated pressures and temperatures using the RCS as one of the test boundaries is not considered prudent since the required test conditions leave little margin between the RCS pressure and the test pressure, leading to difficulty in controlling the test and creating the possibility of injecting into the primary.
Further, potential for damage to SI pumps exists if the SI-870 valves should open due to an SI signal during the test.
The proposed alternative testing, coupled with the design pressure of the piping being much greater than the system relief valve setting, will provide adequate verification of system integrity.
Licensee's Proposed Alternative Examination: The licensee states that these lines will receive a VT-2 visual examination during the conditions of a functional test (10-minute hold time) at operating pressure (approximately 1450 psig). This testing is consistent with the requirements of IWC-5210(a)(1) and IWC-5210(a)(2) for systems not required to operate during normal reactor operation.
Staff Evaluation: The licensee has sought relief from the Section XI hydrostatic pressure testing requirements for Class 1 and 2 systems by proposing to use Code Case N-498 as an alternative to the 1.25 times design pressure (see Relief Request No. 1).
This Code Case also imposes a 4-hour hold time at nominal operating pressure. The proposed alternative is to perform a VT-2 visual examination during the conditions of a functional test at operating pressure. Functional tests require a 10-minute hold time per IWA-5213(b). In a telephone conversation on January 3, 1992, the licensee described the limitations of the SI pumps in maintaining the 4-hour hold time and stated that the pump shut-off head is approximately 1450 psig (the proposed test pressure).
Even with alternating operation, the SI pumps could exceed their duty cycles and potentially be damaged. The Code-required hold time and hydrostatic test pressure are therefore impractical.
The proposed alternative examination provides reasonable assurance of the continued inservice structural integrity, giving due consideration to the burden upon CP&L if the requirements were imposed at HBR2. Therefore, pursuant to 10 CFR 50.55a(g)(6)(i), relief is granted as requested.
3.0 CONCLUSION
Paragraph 10 CFR 50.55a(g)(4) requires that components (including supports) that are classified as ASME Code Class 1, 2, and 3 meet the requirements, except design and access provisions and preservice requirements, set forth in applicable editions of ASME Code Section XI to the extent practical within the limitations of design, geometry, and materials of construction of the components. Pursuant to 10 CFR 50.55a(g)(5)(iii), the licensee determined that conformance with certain Code requirements is impractical for his facility and submitted supporting technical justification. Pursuant to 10 CFR 50.55a(g)(4)(iv), based on the approval to use the applicable portion of the 1986 Edition of the Code, relief is not required for Request for Relief No. 3. Pursuant to 10 CFR 50.55a(g)(6)(i), the staff has determined that certain requirements of the Code are impractical for HBR2, and relief may be granted for the issues described in Requests for Relief No. 2 (in part) and No. 4. It is determined that relief is not required for part of Request for Relief No. 2. Pursuant to 10 CFR 50.55a(a)(3)(i), the staff concludes that the licensee's proposed alternatives will provide an acceptable level of quality and safety. Such relief is authorized by law, will not endanger life, property, or the common defense and security, and is otherwise in the public interest. This relief is being granted giving due consideration to the burden upon the licensee that could result if the requirements were imposed on the facility.
Principal Contributor: T. McLellan Date:
April 28, 1992