ML20140F012
| ML20140F012 | |
| Person / Time | |
|---|---|
| Site: | Duane Arnold  |
| Issue date: | 06/06/1997 |
| From: | NRC (Affiliation Not Assigned) |
| To: | |
| Shared Package | |
| ML20140E965 | List: |
| References | |
| NUDOCS 9706120279 | |
| Download: ML20140F012 (14) | |
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g k UNITED STATES g j f
NUCLEAR REGULATORY COMMISSION
- WASHINGTON. D.C. 20066-0001 V...../
SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION OF THE SECOND 10-YEAR INTERVAL INSERVICE INSPECTION PROGRAM PLAN RE00ESTS FOR RELIEF I
fQB IES UTILITIES INC.
CENTRAL IOWA POWER COOPERATIVE l
CORN BELT POWER COOPERATIVE DUANE ARNOLD ENERGY CENTER DOCKET N0.50-33I I
1.0 INTRODUCTION
l The Technical Specifications (TSs) for the Duane Arnold Energy Center (DAEC) state that the inservice inspection (ISI) of the American Society of l 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 (B&PV) 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). The 10 CFR 50.55a(a)(3) states that alternatives to ;
the requirements of paragraph (g) may be used, when authorized by the NRC, 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 difficulty 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 pre-service 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 first 10-year interval and subsequent intervals comply
'Ath the requirements in the latest edition and addenda of Section XI of the
- 3ME Code incorporated by reference in 10 CFR 50.55a(b) 12 months prior to the start of the 120-month interval, subject to the limitations and modifications listed therein. The applicable edition of Section XI of the ASME Code for the DAEC second 10-year ISI interval is the 1980 Edition through Winter 1981 Addenda.
l ENCLOSURE 1 9706120279 970606 PDR ADOCK 05000331 p PDR v
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 l 10 CFR 50.55a(g)(6)(i), the Commission may grant relief and may impose l alternative requirements that are determined to be authorized by law, will not endanger life, property, or the common defense and security, and are.otherwise in the public interest, giving due consideration to the burden upon the licensee that could result if the requirements were imposed.
In a letter dated April 26, 1996, IES Utilities (licensee), submitted to the NRC its second 10-year ISI interval program plan requests for relief for the i
DAEC. The licensee also provided additional information in its letters dated l October 3, 1996, and January 21, 1997.
l 2.0 EVALUATION The staff, with technical assistance from its contractor, the Idaho National l Engineering and Environmental Laboratory (INEEL), has evaluated the i information provided by the licensee in support of its second 10-year ISI interval program plan requests for relief for the DAEC. Based on the information submitted, the staff adopts the contractor's conclusions and recommendations presented in the Technical Letter Report (TLR) enclosed.
The licensee, in Request for Relief HT-014, proposed an alternative to the 4-hour hold time prior to performing the VT-2_ visual examinations. associated with hydrostatic tests of the Class 2 high pressure coolant injection (HPCI) system piping and components on the water side, downstream of valves M0-2321 and M0-2300, extending to valves M0-2312, CV-2315, and M0-2318. The license proposed to implement the alternative rules for 10-year hydrostatic testing for Class 2 systems as provided in Code Case N-498-1 with the following exception: A system pressure test will be performed in accordance with IWC-5210(1), [IWA-5211(b)] for the above subject system or portion of a system not required to operate during normal reactor operation, but for which periodic system or component functional testing is performed to meet owner's requirements.
The test consists of performing the required visual (VT-2) inspections in conjunction with periodic HPCI turbine test performed in accordance with the
. ASME Section XI Inservice Testing Program. The VT-2 inspection will be performed once per period rather than once per interval. The test hold time will be a minimum of 30 minutes and a maximum of 60 minutes, starting when the TS flow and pressure requirements have been met.
l Both the code and Code Case N-498-1 specify pressure tests that include a 4-hour hold time prior to performing the VT-2 visual examination during the hydrostatic test of insulated systems. The staff determined that, under the circumstances presented, the 4-hour hold time for the subject system would cause an operational safety concern, because the required 4-hour hold time,
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during system operation, would cause the suppression pool water temperature t'o rise above that allowed by TSs. Under these test conditions, should an actual plant emergency occur, the additional actions required to bring the plant to a safe shutdown condition could be compromised.
The staff determined that requiring the licensee to perform the system leakage -
test at an elevated pressure with a 4-hour hold time on the subject portion of the HPCI system piping and components, would result in a burden without compensatSg increase in quality and safet/, given the hardship involved with code compliance and the safety of the propcad alternatives. Furthermore, the staff determined that the licensee's proposal to perform a VT-2 visual 4 examination once each period (at operating pressure for 30 to 60 minutes) in accordance with the pressure requirements of Code Case N-498-1 will enhanc.-
the detection of leakage in the HPCI System, providing reasonable assur'. of operational readiness.
In Request for Relief NDE-019, the licensee has proposed as an alternative to the code-required surface examination of the reactor vessel closure head nuts as specified in Table IWB-2500-1 of the 1980 Edition with the 1981 Addenda of ASME Section XI tt. perform a Visual VT-1 examination on the remaining reactor vessel closure head nuts (1/3) in wccordance with the 1989 Addenda of ASME Section XI. Based on a review of is.mination requirements for fxamination f Category E-G-1, it is noted that with the exception of the reactor pressure vessel closure head nuts and the closure studs (when removed), all other items
! require VT-1 visual examinations or volumetric examinations (as applicable).
When performing surface examinations in accordance with the 1980 Edition with the Winter 1981 Addenda, Item B6.10, the surface examination acceptance criteria is not provided, as it was in the course of preparation. Without clearly defined acceptance criteria, relevant conditions that reqcire corrective measures may not be adequately addressed. The 1989 Addenda of Section XI, Article IWB-3000, Acceptance Standards, IWB-3517.1, V!sual Examination, VT-1, describes relevant conditions that require corrective action prior to continued service of bolting and associated nuts.
Included for corrective action in IWB-3517.1 is the requirement to compare crack-like flaws to the flaw standards of IWB-3515 for acceptance. Surface examination acceptance criteria are typically limited to linear type flaws (i.e. cracking, aligned pitting and corrosion). Because the VT-1 visual examination acceptance criteria include the requirement for evaluation of crack-like indications and other relevant conditions requiring corrective action such as deformed or shered threads, localized corrosion, deformation of part, and other degradation t.schanisms, the staff determined that the VT-1 visual examination provides a more comprehensive assessment of the condition of the closure head nut. As a result, the staff determined that VT-1 visual examination provides an acceptable level of quality and safety. In addition, it is noteo that the 1989 Addenda of Section XI changes the requirement for the subject reactor pressure vessel closure head nns from surface to VT-1 visual exmination and provides appropriate accep+ nce criteria.
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i Based on the comprehensive assessment that the VT-1 visual examination provides, and considering that the 1989 Addenda and late editions of the code require only a VT-1 visual examination on reactor pressure vessel closure head nuts, the staff determined that the licensee's proposed alternative provides an acceptable level of quality and safety.
The licensee in Request for Relief NDE-020 proposed as an alternative to the calibration block reflector requirements of the code to continue the use of Calibration Blocks IE-30, IE-31, IE-32, IE-33, IE-3<' and IE-35 for future reactor pressure vessel (RPV) ultrasonic examinations. Furthermore, the licensee has proposed that all future calibration blocks will meet the design, fabrication, and material specification requirements of ASME Section XI, Appendix I and III, and Article 4 of ASME Section V, and will be provided with the documentation necessary to demonstrate compliance with these requirements.
The code requires that calibration blocks be of the same diameter, thickness, and material as the area to be examined. Article 4 of Section V specifies requirements for reflectors placed in calibration blocks. Each vessel calibration block is required to have 3-inch deep, side-drilled hole reflectors at 1/4T,1/2T, 3/4T, and milled notches on the surfaces corresponding to the inside and outside of the vessel.
The licensee procured the subject vessel calibration blocks when the : Tint was built. The existing calibratiet block designs satisfy the 1989 code design requirements with the exceptica c: two side-drilled holes. As a result of a concern regarding the examinatira sensitivity due to calibrations using the existing reflectors, the licensee provided information to support the use of
- the existing calibration blocks. General Electric Nuclear Energy report -
entitled, GERIS 2000 and Manual Exam Sensitivity for RPV Weld Examinations at the Duane Arnold Energy Center, document number GENE 9555-009-0197, addresses examination sensitivity and calibrations using the existing blocks and blocks meeting the code requirements.
Considering that the licensee is able to establish a distance amplitude curve with the existing reflectors that provides an examination sensitivity equal to or greater then that obtained from a 3-inch deep, side-drilled hole reflector, the staff determined that the scanning sensitivity established for the examinations provides an acceptable level of quality and safety. In addition, the licensee has verified that calibration block IE-30 is compatible with the ultrasonic equipment that will be used for future RPV examinations. Based on i the information provided, the staff determined that the continued use of the subject DAEC calibration standards will provide an acceptable level of quality tad safety.
- 3. CONCLUSIONS The staff has reviewed the information provided by the licensee for the DAEC second 10-year interval for Relief Requests HT-014, NDE-019, and NDE-020.
Based on the evaluation of Relief Request HT-014, the staff concluded that
4 l imposing the code requirements on the licensee will result in a burden without a compensating increase in quality and safety. The licensee's proposed hold
, system piping and components provides reasonable assurance of operational 1
readiness. Therefore, the licensee's proposed alternative contained in Request for Relief HT-014, is authorized pursuant to 10 CFR 50.55a(a)(3)(ii).
For Relief Requests NDE-019 and NDE-020, the staff concluded that the i licensee's proposed alternatives provide an acceptable level of quality and I safety. Therefore, the licensee's proposed alternatives contained in Requests i for Relief NDE-019 and NDE-020 are authorized pursuant to 10 CFR 50.55a(a)(3)(i).
Primary Contributor: Thomas K. McLellan Date: June 6,1997 1
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l l
TECHNICAL LETTER REPORT l
l' ON THE SECOND 10-YEAR INSERVICE INSPECTION INTERVAL RE0 VESTS FOR RELIEF l
IES UTILITIES. INC.
CENTRAL IOWA POWER COOPERATIVE CORN BELT POWER COOPERATIVE DUANE ARNOLD ENERGY CENTER DOCKET NO. 50-331
1.0 INTRODUCTION
By letter dated April 26, 1996, the licensee submitted Requests for Relief HT-014, NDE-019, and NDE-020 for the Duane Arnold Energy Center (DAEC) second 10-year interval inservice inspection program. In a letter dated October 3, 1996, IES Utilities clarified the requests which included revising Requests for Relief HT-014 and NDE-020. On November 18, 1996, a conference call was held between the NRC, the Idaho National Engineering and Environmental Laboratory (INEEL), and the licensee. As a result of this conference call, a letter dated January 21, 1997, was submitted. By this letter, the licensee provided further clarification and revised Request for Relief NDE-020. The INEEL staff has evaluated the subject requests for relief in the following sections.
2.0 EVALUATION The licensee submitted the subject requests for the second 10-year interval.
l The code of record for the DAEC second 10-year interval, is the American l
' Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code,Section XI, 1980 Edition, with the Winter 1981 Addenda. The information l
provided by the - ensee in support of the requests has been evaluated and the bases for dispe ion are documented below.
l 2.1 Relief Reauest HT-014.Section XI. Table IWC-2500-1. Examination Cateaorv C-H. Items C7.40 and C7.80. Hydrostatic Testino of the Hiah Pressure {
Coolant In_iection (HPCI) System Pioina and Components Code Reauirement: Section XI, Table IWC-2500-1, Examination Category C-H, Items C7.40 and C7.80, require a VT-2 visual examination during !
hydrostatic tests of Class 2 systems performed in accordance with IWC-5222 near the end of the interval. IWA-5213 states that for system hydrostatic tests, a 4-hour hold-time is required after attaining the test pressure and temperatute conditions for insulated systems, and a 10-minute hold-time for nonh,al.ted systems or components.
i Licensee's Proposed Alternative: In accordance with 10 CFR 50.55a(a)(3)(ii), the licensee proposed an alternative to the l ENCLOSURL
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4-hour hold-time prior to performing the VT-2 visual examinations associated with hydrostatic tests of the Class 2 HPCI system piping and components on the water side, downstream of valves M0-2321 and M0-2300, extending to valves M0-2312, CV-2315, and M0-2318, as stated.
"DAEC proposes to implement the alternative rules for 10-year hydrostatic testing for Class 2 systems as provided in Code Case N-498-1 with the following exception: A system pressure test shall be performed in accordance with IWC-5210(1), [IWA-5211(b)] for the above subject system or portion of a system not required to operate during normal reactor
- operation, but for which periodic system or component functional testing
! is performed to meet owner's requirements. This test shall consist of
! . performing the required visual (VT-2) inspections in conjunction with periodic HPCI turbine test performed in accordance with the ASME Section XI Inservice Testing Program (IST). This VT-2 inspection shall be performed once per period rather than once per interval. The test l
t hold time shall be a minimum of 30 minutes and a maximum of 60 minutes
, starting when the Technical Specification (TS) flow and pressure requirements have been met."
Licensee's Basis for the Proposed Alternative: (as stated) :
L " Hydrostatic pressure tests can be difficult to perform, often requiring
! complicated or abnormal valve line-ups in order to properly vent, fill, l and isolate the systems requiring testing.
" Operation of this system at the code-required pressure and temperature !
! for the required 4-hour test condition ' hold-time' in accordance with IWA-5213 would result in an undesirable torus water temperature.
"The DAEC TSs state in 3.7.G.2.c, 'If the suppression poui average water temperature is >105'F during testing which adds heat to the suppression pool, immediately suspend all testing which adds heat to the suppression pool, verify suppression pool average water temperature is <110*F once per hour, and restore suppression pool average temperature to 195'F within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> or be in at least HOT SHUTDOWN within the next 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> and COLD SHUTDOWN within the following 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />.
"A test was performed on August 28, 1996, in accordance with the IST Program during which the torus water temperature was trended. The average torus water temperature was 77.3*F at the beginning of the test.
The HPCI system was run for approximately 50 minutes to complete the testing requirements. The average torus water temperature was 101*F at the end of the 50 minutes. This is an increase in the torus water temperature of 23.7*F in 50 minutes (1*F every 2 minutes).
- "It has been determined that it would take four VT-2 qualified examiners i 15 minutes to walk down the HPCI system. This would allow a 35-minute
! hold-time for this particular case. During colder months of the year, ,
j the HPCI system may be run for a longer period of time since the torus J
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water temperature is colder at the beginning of the test, resulting in longer hold-time. For example, if the torus water temperature was 60*F at the beginning of the test, based on a l'F increase every 2 minutes and 15 minutes to perform the examination, a hold-time of 67 minutes would be reached (101*F minus 60*F, times 2, minus 15 minutes for examination).
"A research of past torus water temperatures during the winter months (November 1,1995, to April 1,1996) showed the following coldest temperature:
December 15, 1995 59.1*F January 16, 1996 59.l*F l March 13, 1996 59.7'F l
"With the pressure currently required by Section XI, elevated pressure hydrostatic test does not offer a commensurate increase in safety with cost benefit and place undue burden upon a licensee to perform these tests. Use of Code Case N-498-1 with a 30- to 60-minute hold-time rather l l than a 4-hour hold-time, and performing this test every period rather than every interval, will not jeopardize the public health and safety."
Evaluation: Both the code and Code Case N-498-1 specify pressure tests that include a 4-hour hold-time prior to performing the VT-2 visual examination during the hydrostatic test of insulated systems. The INEEL staff believes that, under the circumstances presented, the 4-hour hold-time for the subject system would cause an operational safety concern. This is because the required 4-hour hold-time, during system l l operation, would cause the suppression pool water temperature to rise l
! above that allowed by TSs. Under these test conditions, should an actual plant emergency occur, the additional actions required to bring the plant ,
to a safe shutdown condition could be compromised. Based on the above, l l it is concluded that compliance with the 4-hour hold-time would result in i a burden and could violate TSs requiring corrective action. i 1
The code requires the performance of a system hydrostatic test once per interval in accordance with the requirements of IPA-5000 for Class 1, 2, :
and 3 pressure-retaining systems. In lieu of the code-required '
hydrostatic test requirement at an elevated pressure, the licensee proposes to implement the alternatives to code requirements contained in Code Case N-498-1, " Alternative Rules for 10-Year System Hydrostatic Tecting for Class 1, 2, and 3 Systems," dated May 11, 1994.
, The system hydrostatic test, as stipulated in Section XI, is not a test ofthpstructuralintegrityofthesystem,butratheranenhancedleakage test. Hydrostatic testing only subjects the piping components to a small increase in pressure over the design pressure. Therefore, piping
'S.H. Bush and R.R. Maccary, " Development of In-Service Inspection Safety
. Philosophy for U.S.A. Nuc1'ar Power Plants," ASME, 1971.
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dead weight, thermal expansion, and seismic loads present far greater challenges to the structural integrity of a system. Consequently, the Section XI hydrostatic pressure test is primarily regarded as a means to enhance leak detection during the examination of components under pressure, rather than as a method to determine the structural integrity of the components. In addition, the industry experience indicates that leaks are not being discovered as a result of hydrostatic test pressures causing a prcexisting flaw to propagate through the wall. In most cases, leaks are being found when the system is at normal operating pressure.
Code Case N-498, " Alternative Rules for 10-Year System Hydrostatic Testing for Class 1 and 2 Systems," was previously approved for general use on Class I and 2 systems in Regulatory Guide 1.147, Rev. 9. Code Case N-498-1 requires a VT-2 visual examination at nominal operating pressure and temperature in conjunction with a system leakage test performed in accordance with paragraph IWA-5000 of the 1992 Edition of Section XI. System hydrostatic testing entails considerable time and radiation dose. The safety assurance provided by the enhanced leakage detectien gained from a slight increase in system pressure during a hydrostatic test may be offset or negated by the recessity to gag or remove code safety and/or relief valves (placing the system and, thus, the plant, in an off-normal state), erect temporary supports in steam lines, and expend resources to set up testing with special equipment and gages. Therefore, performance of system hydrostatic testing represents a considerable burden. ~ Giving consideration to the minimal amount of increased assurance provided by the increased pressure associated with a hydrostatic test versus the pressure for the system leakage test, and the hardship associated with performing the hydrostatic test, the INEEL staff finds that compliance with the Section XI hydrostatic testing requirements results in hardship and/or unusual difficulty without a compensating increase in the level of quality and safety.
Requiring the licensee to perform the system leakage test at an elevated pressure with a 4-hour hold-time on the subject portion of the HPCI system piping and components, results in a burder as noted above. The licensee proposes to perform a VT-2 visual examination once each period in accordance with the pressure requirements of Code Case N-498-1. The INEEL staff believes that~ performing the VT-2 visual examination once each period (at operating pressure for 30- to 60-minutes hold-time) will enhance the detection of leakage in the HPCI system, providing reasonable assurance of operational readiness. Therefore, it is recommended that the licensee's proposed alternative be authorized pursuant to 10 CFR 50.55a(a)(3)(ii).
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- 2.2 - Relief Reauest NDE-019. Examination Cateaory B-G-1. Item B6.10. Surface j Examination of the Reactor Vessel Closure Head Nuts 4
i Code Reauirement: Section XI, Table IWB-2500-1, Examination Category i B-G-1, Item B6.10 requires a 100% surface examination of all reactor 3 vessel closure head nuts. i e
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Licensee's Proposed Alternative: In accordance with 10 CFR 50.55a(a)(3)(1), the licensee proposed an alternative to performing the code-required surface examination of the subject reactor vessel closure head nuts as specified in Table IWB-2500-1 of the ASME Section XI,1980 Edition, with the Winter 1981 Addenda, as stated.
"IES Utilities Inc. proposes to perform a Visual VT-1 examination on the l remaining reactor vessel closure head nuts (one-third) in accordance with ,
the ASME Section XI, 1989 Addenda."
Licensee's Basis for the Proposed Alternative: (as stated)
" Table IWB-2500-1 of the ASME Section XI,1980 Edition, with the Winter 1981 Addenda, requires a surface examination to be performed on the reactor vessel closure head nuts. However, Table IWB-2500-1 does not provide the corresponding ' Examination Requirements / Figure Number' and
' Acceptance Standard.' These provisions were still in the course of preparation.
" Provisions for the ' Examination Requirements / Figure Number' and
' Acceptance Standard' for the reactor vessel closure head nuts were later incorporated in the ASME Section XI, 1989 Addenda. This addenda also L changed the examination method to a VT-1 visual examination.
"The DAEC has completed the surface examination on two-thirds of the reactor vessel closure head nuts for the current interval. The examination results have not shown any relevant indications.
"To perform the surface examination on the remaining one-third of the l reactor vessel closure head nuts would only have a small potential of increasing plant safety margins and a very disproportionate impact on expenditures of pisnt manpower. The visual VT-1 examination would detect the type of flaws that would be detrimental to the integrity of the nuts and, therefore, is an acceptable examination method."
Evaluation: The licensee has requested relief from performing the code-required surface examination on the remaining one-third sample of reactor pressure vessel closure head nuts. As an alternative, the licensee proposes to perform a VT-1 visual examination. Based on a review of examination requirements for Examination Category B-G-1, it is noted that with the exception of the reactor pressure vessel closure head nuts and the closure studs (when removed), all other items require VT-1 visual examinations or volumetric examinations (as applicable),
i Typical relevant conditions that would require corrective action prior to
, putting closure head nuts back into service would include corrosion, deformed or sheared threads, deformation, and degradation mechanisms
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(i.e., boric acid attack). The applicable code examination requirement for closure head nuts is a surface examination. Surface examination j procedures are typically qualified for the detection of linear-type flaws 1
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4 (cracks) with corresponding acceptance criteria for rejectable linear flaw lengths only. When performing surface examinations in accordance
' with the 1980 Edition, with the Winter 1981 Addenda, Item B6.10, the surface examination acceptance criteria is not provided, as it was in the course of preparation. Without clearly defined acceptance criteria, relevant conditions that require corrective measures may not be l adequately addressed.
L The 1989 Addenda of Section XI, Article IWB-3000, " Acceptance Standards',
IWB-3517.1, Visual Examination, VT-1," describes relevant conditions that require corrective action prior to continued service of bolting and associated nuts. Included for corrective action in IWB-3517.1 is the requirement to compare crack-like flaws to the flaw standards of IWB-3515 for acceptance. Surface examination acceptance criteria are typically limited to linear-type flaws (i.e., cracking, aligned pitting, and corrosion). Eacause the VT-1 visual examination acceptance criteria include the requirement for evaluation of crack-like indications and other relevant conditions requiring corrective action such as deformed or !
sheared threads, localized corrosion, deformation of part, and other ;
degradation mechanisms, it can be concluded that the VT-1 visual examination provides a more comprehensive assessment of the condition of the closure head nut. As a result, the INEEL staff believes that VT-1 visual examination provides an acceptable level of quality and safety.
In addition, it is noted that the 1989 Addenda of Section XI changes the requirement for the subject reactor pressure vessel closure head nuts from surface to VT-1 visual examination and provides appropriate acceptance criteria.
As an alternative to the coot .equired surface examination of reactor pressure vessel closure head nuts, the licensee proposed to perform a VT-1 visual examination. Based on the comerehensive assessment that the .
VT-1 visual examination provides, and considering that the 1989 Addenda and later editions of the code require only a VT-1 visual examination on reactor pressure vessel closure head nuts, an acceptable level of quality and safety is'provided. Therefore, it is recommended that the proposed alternative VT-1 visual examination be authorized pursuant to 10 CFR 50.55a(a)(3)(1). ;
2.3 Relief Reauest NDE-020. IWA-2232. Ultrasonic Examination Calibration Blocks Code Reauirement: Section XI, IWA-2232, Ultrasonic Examination, requires ultrasonic calibration blocks meet the design criteria of Article 4 of ASME Section V.
Licensee's Pronosed Alternative: In accordance with 10 CFR 50.55a(a)(3)(1), the licensee proposed an alternat.ive to the calibration block reflector requirements of the code. Specifically, the
[ licensee requested approval for continued use of calibration blocks
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IE-30, IE-31, IE-32, IE-33, IE-34, and IE-35, for future reactor pressure vessel (RPV) ultrasonic examinations, as stated.
"All fut'ure calibration blocks will meet the design, fabrication, and material specification requirements of ASME Section XI, Appendices I and III, and Article 4 of ASME Section V, and will be provided with the documentation necessary to demonstrate compliance with these requirements. A demonstration was conducted to verify that the vessel calibration block IE-30 is compatible with ultrasonic equipment that will be utilized for the vessel examination. The results were found to be acceptable under the 1989 Addenda of Section XI (edition which will be
. used for the Third 10-Year Interval.ISI Program) requirements and will be documented under IWA-2240 requirements. In addition, a comparison with the sensitivity obtained from an ASME standard block and the DAEC IE-30
. block showed that the DAEC calibration was slightly more sensitive."
Licensee's Basis for the Proposed Alternative: (as stated)
"The RPV calibration blocks currently being used at DAEC, when reviewed against the 1980 Edition, with the Winter 1981 Addenda of ASME Section XI and Section V, were identified as marginal in certain block design characteristics. This is because the requirements and examination techniques existing at the time of their fabrication were significantly 1 different from those employed today. The current block dimensions, while in compliance with the original fabrication requirements, satisfy all but two of the side-drilled hole dimensional requirements of the 1980 Edition, with the Winter 1981 Addenda, and the 1989 Addenda of Section XI code for calibration standards. . Calibration reflectors (side-drilled holes), though they do not meet the 1980 Edition, with the Winter 1981 and 1989 code requirements, have been proven adequate during previous inspections. Any alterations to the existing calibration standard would be undesirable since the potential is high that the alterations may effect comparisons of past and future calibration and examination results. . Compliance with ASME Section XI requirements to detect service-induced flaws requires traceability to previous examination i
results which is available using the existing calibration blocks. This review is supported by Regulatory Guide 1.150, Position C.2, which states in part, 'Where possible, the same calibration block should be used for successive inservice examinations of the RPV.' '
"A demonstration of the potential " edge effect" was performed on ASME standard block (block with 3-inch deep holes) and compared with the
[ results of the DAEC block. The results showed that the examinations l
conducted using the DAEC block were slightly more sensitive.
- " Based on the above, DAEC requests alternative examination from ASME i Section XI, (1980 W81 and 1989) requirements for calibration block design
- fabrication requirements, and material specifications (material of the calibration blocks has been verified to meet the material requirements of j both Article 4 of ASME Section V (1989), and Article 4 of ASME Section V t
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(1980 W81), in order to allow the continued use of the existing calibration blocks in the following table: calibration block IE-30, IE-31, IE-32, IE-33, IE-34, IE-35."
l Evaluation: The code requires that calibration blocks be'of the same diameter, thickness, and material as the area to be examined. Article 4 ,
of Section V specifies requirements for reflectors placed in calibration I blocks. Each vessel calibration block is required to have 3-inch deep, ;
l side-drilled hole reflectors at 1/4T,1/2T, and 3/4T, and milled notches i on the surfaces corresponding to the inside and outside of the vessel. !
, The licensee procured the subject vessel calibration blocks when the l 1 plant was built. The existing calibration block designs satisfy the 1989 I code design requirements with the exception of two side-drilled holes. l As a result of a concern regarding the examination sensitivity due to calibrations using the existing reflectors, the licensee provided l
information to support the use of the existing calibration blocks.
l General Electric Nuclear Energy report entitled, "GERIS 2000 and Manual Exam Sensitivity for RPV Weld Examinations at Duane Arnold Energy Center," document number GENE 9555-009-0197, addresses examination sensitivity and calibrations using the existing blocks and blocks meeting the code requirements. The theoretical and empirical information on the i
calibration block reflectors " edge effect" was discussed. The report
! concludes that, for the subject DAEC calibration blocks, angle beam l calibration on side-drilled hole reflectors,1 1/2 inches deep, result in l a calibration sensitivity slightly higher than would be obtained on the l code-required 3-inch deep, side-drilled hole reflectors.
Considering that the licensee is able to establish a distance amplitude ,
curve with the existing reflectors that provides an examination '
sensitivity equal to or greater than that obtained from a 3-inch deep, side-drilled hole reflector, it is reasonable to conclude that the scanning sensitivity established for the examinations will provide an acceptable level of quality and safety. In addition, the licensee has verified that calibration block IE-30 is compatible with the ultrasonic equipment that will be used for future RPV examinations. Based on the information provided, the INEEL staff believes that the continued use of the subject DAEC calibration standards will provide an acceptable level of quality and safety. In addition, the licensee has stated that new calibration blocks will be designed to meet code requirements.
Therefore, it is recommended that the proposed alternative be authorized
, pursuant to 10 CFR 50.55a(a)(3)(1). '
3.0 CONCLUSION
l The INEEL staff has reviewed the information provided by the licensee for the i
DAEC second 10-year inservice inspection interval for Relief Requests HT-014, I NDE-019, and NDE-020. Based on the evaluation of Relief Request HT-014, it
- has been determined that imposing the code requirements on the licensee will j result in a burden without a compensating increase in quality ant' safety. The l
I
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licensee's proposed hold-time prior to performing the VT-2 visual examination of the subject HPCI system piping and components provides reasonable assurance of operational readiness. Therefore, the INEEL recommends that for Relief Request HT-014, the licensee's proposed alternative be authorized pursuant to 10 CFR 50.55a(a)(3)(ii). For Relief Requests NDE-019 and NDE-020, it is concluded that the licensee's proposed alternatives provide an acceptable level of quality and safety. Therefore, it is recommended that the proposed alternatives be authorized pursuant to 10 CFR 50.55a(a)(3)(1).
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