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| {{#Wiki_filter:BN63097.001 B0T0 1106 DB05 1 Appendix E Fluid Jet Cutting of Davis-Besse RPV Head Materials | | {{#Wiki_filter:Appendix E Fluid Jet Cutting of Davis-Besse RPV Head Materials BN63097.001 B0T0 1106 DB05 1 |
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| BN63097.001 B0T0 1106 DB05 E-1 Appendix E Fluid Jet Cutting of Davis-Besse RPV Head Materials E.1 Introduction The formation of the wastage cavity in the reactor pressure vessel (RPV) head of the Davis Besse nuclear reactor was most likely due to a combination of degradation mechanisms. While the Root Cause Report fo r this incident identified boric acid corrosion as the primary mechanism for head wastage, subsequent observations and fluid flow modeling efforts suggest alternative mechanisms that may have significantly influenced wastage cavity formation. In addition to flow-assis ted corrosion (FAC), mechanical mechanisms for metal removal from the RPV head may also have played an important role. These mechanical mechanisms include water jet cutting and abrasive water jet cutting. If these mechanical material removal mechanisms were the dominant degradation mechanism for material removal, the wastage cavity could have formed in a relatively short (days to weeks) period of time, in contrast to the corrosion time (4 years) estimated in the Root Cause Report.
| | Appendix E Fluid Jet Cutting of Davis-Besse RPV Head Materials E.1 Introduction The formation of the wastage cavity in the reactor pressure vessel (RPV) head of the Davis Besse nuclear reactor was most likely due to a combination of degradation mechanisms. While the Root Cause Report for this incident identified boric acid corrosion as the primary mechanism for head wastage, subsequent observations and fluid flow modeling efforts suggest alternative mechanisms that may have significantly influenced wastage cavity formation. In addition to flow-assisted corrosion (FAC), |
| 1 E.2 Pure Water Jet Cutting The primary mechanism for material removal by water jet cutting is the conversion of the kinetic energy of the jet into the stagnation pressure at the point of impact on the target. The maximum pressure "P J", which can be produced (above the ambient static pressure) by such a jet, is related to the jet velocity "V 0" by the following relationship, P J = 1/2 V 0 2 (Eqn. 1) where is the density of the fluid in the jet. | | mechanical mechanisms for metal removal from the RPV head may also have played an important role. These mechanical mechanisms include water jet cutting and abrasive water jet cutting. If these mechanical material removal mechanisms were the dominant degradation mechanism for material removal, the wastage cavity could have formed in a relatively short (days to weeks) period of time, in contrast to the corrosion time (4 years) estimated in the Root Cause Report.1 E.2 Pure Water Jet Cutting The primary mechanism for material removal by water jet cutting is the conversion of the kinetic energy of the jet into the stagnation pressure at the point of impact on the target. |
| 2 At a temperature of 600°F and a pressure of 2000 psig, the specific volume of water is 0.02330 ft 3/lb, 3 which yields a density of 0.0248 lb/in | | The maximum pressure PJ, which can be produced (above the ambient static pressure) by such a jet, is related to the jet velocity V0 by the following relationship, PJ = 1/2 V02 (Eqn. 1) where is the density of the fluid in the jet.2 At a temperature of 600°F and a pressure of 2000 psig, the specific volume of water is 0.02330 ft3/lb,3 which yields a density of 0.0248 lb/in3. |
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| | BN63097.001 B0T0 1106 DB05 E-1 |
| BN63097.001 B0T0 1106 DB05 E-2 An evaluation of critical and optimum parameters for the material removal by water jet cutting was completed by Hashish. | |
| 4 The minimum pressure required to remove material by the impingement of a water jet was a pressure equal to the yield stress ( y) of the material. A detailed evaluation of the total specific energy required for water jet cutting yielded an "optimum" pressure "P o" for material removal in a ductile material as, P o = 2.5 y (Eqn. 2) where y is the yield stress for the ductile material.
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| 5 A typical yield stress for carbon steel at room temperat ure (75°F) is 50,000 lb/in
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| : 2. However, the yield stress for carbon steel is lower at reactor operating temperatures. As not ed by Glasstone and Sesonske, 6 the allowable stress for carbon steel (A302-B) under reactor conditions at 700°F is 27,000 lb/in
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| : 2. Hence, a reasonable estimate for the allowable stress for carbon steel at 600°F is approximately 30,000 lb/in
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| : 2. Therefore, the minimum and optimum pressures for water jet removal of carbon steel at reactor temperatures are approximately 30,000 lb/in 2 and 75,000 lb/in 2, respectively.
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| The water jet velocities required to begin material removal and the optimum velocity for material removal can be estimated by rearranging Equation 1 and solving for V | | An evaluation of critical and optimum parameters for the material removal by water jet cutting was completed by Hashish.4 The minimum pressure required to remove material by the impingement of a water jet was a pressure equal to the yield stress (y) of the material. A detailed evaluation of the total specific energy required for water jet cutting yielded an optimum pressure Po for material removal in a ductile material as, Po = 2.5 y (Eqn. 2) where y is the yield stress for the ductile material.5 A typical yield stress for carbon steel at room temperature (75°F) is 50,000 lb/in2. However, the yield stress for carbon steel is lower at reactor operating temperatures. As noted by Glasstone and Sesonske,6 the allowable stress for carbon steel (A302-B) under reactor conditions at 700°F is 27,000 lb/in2. Hence, a reasonable estimate for the allowable stress for carbon steel at 600°F is approximately 30,000 lb/in2. Therefore, the minimum and optimum pressures for water jet removal of carbon steel at reactor temperatures are approximately 30,000 lb/in2 and 75,000 lb/in2, respectively. |
| : 0. V 0 = (21/2 (Eqn. 3) where is the yield stress and 2.5 times the yield stress for the minimum and optimum material removal conditions. The results of these calculations suggest that a minimum fluid velocity of 2,386 feet per second is required to begin material removal. The fluid velocity for optimum material removal using only a water jet is 3,773 feet per second. These velocities are 2 to 3 times th e sonic velocity in air at 600°F BN63097.001 B0T0 1106 DB05 E-3 E.3 Abrasive Water Jet Cutting The material removal rate is greatly increas ed by the introduction of very fine abrasive materials into a water jet fluid flow stream.
| | The water jet velocities required to begin material removal and the optimum velocity for material removal can be estimated by rearranging Equation 1 and solving for V0. |
| This technology, called the abrasive water jet technique, has been developed for industrial applications over the past 25 years. In abrasive water jet technology, abrasives are incorporated in to a high-veloc ity water jet and the momentum of the water is transferred to the abrasive partic le, rapidly increasing the velocity of the particle.
| | V0 = (2/)1/2 (Eqn. 3) where is the yield stress and 2.5 times the yield stress for the minimum and optimum material removal conditions. The results of these calculations suggest that a minimum fluid velocity of 2,386 feet per second is required to begin material removal. The fluid velocity for optimum material removal using only a water jet is 3,773 feet per second. |
| Typical abrasive water jet fluid velocities are 300-600 m/s (984-1,968 ft/s) with abrasive mass flow rates of approximately 10 grams per second.
| | These velocities are 2 to 3 times the sonic velocity in air at 600°F BN63097.001 B0T0 1106 DB05 E-2 |
| 7 Current industrial app lications of abrasive water jet cu tting employ fluid flow rates of 0.5 gallons per minute (gpm) with an orifice diameter of 0.010 inch.
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| 8 Early investigations of the efficacy of abrasive water jet technology were completed by Hashish. Studies of the experimental conditions for the optimum abrasive water jet cutting of steel, cast iron, aluminum, and Inconel were presented by Hashish. The effect of abrasive type (garnet, s ilica sand and glass beads), abrasi ve flow rate, and stand-off distance were evaluated using a range of flow conditions and abrasives. Typical material removal rates for mild steel ove r a range of stand-off distances from the nozzle exit to the cutting surface at various flow rates are shown in Table E.1.
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| 9 Table E.1 Effect of Standoff Distance and Abrasive Flow Rate on the Material Removal Rate in Abrasive Water Jet Cutting of Mild Steel 9 Abrasive Flow Rate 4.3 g/s 7.3 g/s 10.7 g/s Standoff Removal Rate Distance (mm)(mm 3/sec)(mm 3/sec) (mm 3/sec) 2.5 22 34 95 5 34 42 72 10 32 51 64 20 30 42 55 50 18 22 50 75 10 18 43
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| BN63097.001 B0T0 1106 DB05 E-4 Additional comparisons of material removal rates for a range of materials and cutting parameters were also presented by Hashish 10 and are shown in Table E.2.
| | E.3 Abrasive Water Jet Cutting The material removal rate is greatly increased by the introduction of very fine abrasive materials into a water jet fluid flow stream. This technology, called the abrasive water jet technique, has been developed for industrial applications over the past 25 years. In abrasive water jet technology, abrasives are incorporated into a high-velocity water jet and the momentum of the water is transferred to the abrasive particle, rapidly increasing the velocity of the particle. Typical abrasive water jet fluid velocities are 300-600 m/s (984-1,968 ft/s) with abrasive mass flow rates of approximately 10 grams per second.7 Current industrial applications of abrasive water jet cutting employ fluid flow rates of 0.5 gallons per minute (gpm) with an orifice diameter of 0.010 inch.8 Early investigations of the efficacy of abrasive water jet technology were completed by Hashish. Studies of the experimental conditions for the optimum abrasive water jet cutting of steel, cast iron, aluminum, and Inconel were presented by Hashish. The effect of abrasive type (garnet, silica sand and glass beads), abrasive flow rate, and stand-off distance were evaluated using a range of flow conditions and abrasives. Typical material removal rates for mild steel over a range of stand-off distances from the nozzle exit to the cutting surface at various flow rates are shown in Table E.1.9 Table E.1 Effect of Standoff Distance and Abrasive Flow Rate on the Material Removal Rate in Abrasive Water Jet Cutting of Mild Steel9 Abrasive Flow Rate 4.3 g/s 7.3 g/s 10.7 g/s Standoff Removal Rate 3 |
| Table E.2 Material Removal Rate for Abrasive Water Jet Cutting of Various Materials 10 Material Removal rate mm 3/s) Aluminum 50-300 Steel 40-200 Cast Iron 50-250 Titanium 50-250 Inconel 40-200 E.4 Estimated Material Removal Rate Following the initiation of boric acid preci pitation and RPV head corrosion, ample amounts of abrasive material were available for incorporation into the fluid stream ejected from the CRDM nozzle crack. With hundreds of pounds of crystalline boric acid and the corrosion of about 195 in 3 of carbon steel (approximately 55 lb of steel yielding approximately 75 lb of Fe 3 O 4), there were significant quantities of abrasive materials that could be entrained in the high-velocity fluid jet striking th e interior surfaces of the wastage cavity. | | Distance (mm) (mm /sec) (mm3/sec) (mm3/sec) 2.5 22 34 95 5 34 42 72 10 32 51 64 20 30 42 55 50 18 22 50 75 10 18 43 BN63097.001 B0T0 1106 DB05 E-3 |
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| The Root Cause Report estimated that the leakage attributed to CRDM nozzle leaks during late 2001 was 0.1 to 0.2 gpm | | Additional comparisons of material removal rates for a range of materials and cutting parameters were also presented by Hashish10 and are shown in Table E.2. |
| : 11. Our calculations of CRDM crack leak rates, presented in Section 9.4, determined that th e CRDM Nozzle 3 leak rate was on the order of 0.17 gpm at this time. An estimate of the total materi al wastage that could have occurred due to this leak rate during this time period by abrasive jet cutting can be made by using data in Table E-1. Scaling the material removal rate for the 75 mm (3 inch) standoff distance at the lowest abrasive materi al flow rate (4.3 g/
| | Table E.2 Material Removal Rate for Abrasive Water Jet Cutting of Various Materials10 Material Removal rate mm3/s) |
| s) by the ratio of the flow rates (34% - 0.17 gpm/0.5gpm) yields a material removal rate of approximately 3.4 mm 3/s. At this material removal rate, the time required to excavate a wastage cavity of 195 in 3 (3,195,500 mm | | Aluminum 50-300 Steel 40-200 Cast Iron 50-250 Titanium 50-250 Inconel 40-200 E.4 Estimated Material Removal Rate Following the initiation of boric acid precipitation and RPV head corrosion, ample amounts of abrasive material were available for incorporation into the fluid stream ejected from the CRDM nozzle crack. With hundreds of pounds of crystalline boric acid and the corrosion of about 195 in3 of carbon steel (approximately 55 lb of steel yielding approximately 75 lb of Fe3O4), there were significant quantities of abrasive materials that could be entrained in the high-velocity fluid jet striking the interior surfaces of the wastage cavity. |
| : 3) would have been 939,853 seconds (261 hours = 10.8 days).
| | The Root Cause Report estimated that the leakage attributed to CRDM nozzle leaks during late 2001 was 0.1 to 0.2 gpm11. Our calculations of CRDM crack leak rates, presented in Section 9.4, determined that the CRDM Nozzle 3 leak rate was on the order of 0.17 gpm at this time. An estimate of the total material wastage that could have occurred due to this leak rate during this time period by abrasive jet cutting can be made by using data in Table E-1. Scaling the material removal rate for the 75 mm (3 inch) standoff distance at the lowest abrasive material flow rate (4.3 g/s) by the ratio of the flow rates (34% - 0.17 gpm/0.5gpm) yields a material removal rate of approximately 3.4 mm3/s. At this material removal rate, the time required to excavate a wastage cavity of 195 in3 (3,195,500 mm3) would have been 939,853 seconds (261 hours = 10.8 days). |
| BN63097.001 B0T0 1106 DB05 E-5 Therefore, under optimum abrasive water jet cutting conditions, the entire wastage cavity could have formed in a period of a couple of weeks. E.5 Evidence Supporting Mechanical Removal of Material from the Wastage Cavity No specific evaluations of the metallic particle content of the boric acid or corrosion deposits removed from the RPV head and wastage cavity near Nozzle 3 during 13 RFO were completed. However, two chemical analyses of the deposits removed from the | | BN63097.001 B0T0 1106 DB05 E-4 |
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| Davis-Besse reactor vessel head were completed by Framatome ANP in June 2002 and July 2002, respectively.12-13 The initial analyses on a number of specimens collected from the RPV were completed by Fender. | | Therefore, under optimum abrasive water jet cutting conditions, the entire wastage cavity could have formed in a period of a couple of weeks. |
| 11 This study noted that one of the specimens, "The dark colored chunk was quite hard and not easily crushed; a metallic strip coated with an adherent deposit was revealed after crushing." The chemical analysis was completed after the removal of the metal strip. | | E.5 Evidence Supporting Mechanical Removal of Material from the Wastage Cavity No specific evaluations of the metallic particle content of the boric acid or corrosion deposits removed from the RPV head and wastage cavity near Nozzle 3 during 13 RFO were completed. However, two chemical analyses of the deposits removed from the Davis-Besse reactor vessel head were completed by Framatome ANP in June 2002 and July 2002, respectively.12-13 The initial analyses on a number of specimens collected from the RPV were completed by Fender.11 This study noted that one of the specimens, The dark colored chunk was quite hard and not easily crushed; a metallic strip coated with an adherent deposit was revealed after crushing. The chemical analysis was completed after the removal of the metal strip. |
| | Subsequent chemical analyses were completed by Cyrus,13 who noted, Metallic fragments that could be readily isolated from the bulk deposit samples were removed. |
| | The remaining material in each sample was homogenized by grinding in an agate mortar and pestle. Portions of the homogenized samples were then segregated for analysis. |
| | Because smaller metallic particles remained in the samples, any metallic iron detected in the samples by x-ray diffraction was ignored. |
| | Since the chemical analyses of the materials removed from these metallic samples contained little chromium, it is evident that the source of this metal was not the degradation of the mirror insulation or the machining of CRDM nozzle flange surfaces during prior outages. Fender noted that, The most probable source of the iron is the carbon steel of the reactor vessel head.14 These observations support the case that mechanical removal of reactor pressure head material occurred during the formation of the wastage cavity. The mechanical removal of metallic fragments was likely a result of water jet cutting or abrasive water jet cutting of the RPV head during periods of high nozzle leakage late in Cycle 13. |
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| Subsequent chemical analyses were completed by Cyrus, 13 who noted, "Metallic fragments that could be readily isolated from the bulk deposit samples were removed. The remaining material in each sample was homogenized by grinding in an agate mortar and pestle. Portions of the homogenized samples were then segregated for analysis. Because smaller metallic particles remained in the samples, any metallic iron detected in the samples by x-ray diffraction was ignored."
| | E.6 Observation A major portion of the wastage cavity formation occurred during a relatively short period of time of the order of days to weeks, late in Cycle 13 and was due to abrasive water jet mechanisms that acted in conjunction with flow assisted boric acid corrosion. |
| | BN63097.001 B0T0 1106 DB05 E-6 |
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| Since the chemical analyses of the materials removed from these metallic samples contained little chromium, it is evident that the source of this metal was not the degradation of the mirror insulation or the machining of CRDM nozzle flange surfaces during prior outages. Fender noted that, "The most probable source of the iron is the carbon steel of the r eactor vessel head".
| | References |
| 14 These observations support the case that mechanical removal of reactor pressure head material occurred during the formation of the wastage cavity. The mechanical removal of metallic fragments was likely a result of water jet cutting or abrasive water jet cutt ing of the RPV head during periods of high nozzle leakage late in Cycle 13.
| | : 1. Root Cause Report: Significant Degradation of the Reactor Pressure Vessel Head, Davis Besse Nuclear Power Station Condition Report CR 2002-0891. Rev. 1, August 27, 2002, p. 24. |
| BN63097.001 B0T0 1106 DB05 E-6 E.6 Observation A major portion of the wastage cavity formati on occurred during a relatively short period of time of the order of days to weeks, late in Cycle 13 and was due to abrasive water jet mechanisms that acted in conjunction with flow assisted boric acid corrosion.
| | : 2. Thomas J. Labus and George A. Savanick, An Overview of Waterjet Fundamentals and Applications, Fifth Edition, 2001, WaterJet Technology Association, St. Louis, MO, p. 2.4. |
| BN63097.001 B0T0 1106 DB05 E-7 References
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| : 1. "Root Cause Report: Significant Degradation of the Reactor Pressure Vessel Head," | |
| Davis Besse Nuclear Power Station Condition Report CR 2002-0891. Rev. 1, August 27, 2002, p. 24. | |
| : 2. Thomas J. Labus and George A. Savanick, "An Overview of Waterjet Fundamentals and Applications," Fifth Edition, 2001, Wate rJet Technology Association, St. Louis, MO, p. 2.4. | |
| : 3. Joseph H. Keenan, Frederick G. Keyes, Philip G. Hill, and Joan G. Moore, Steam Tables, Thermodynamic Properties of Water, John Wiley and Sons, Inc., New York, 1969, p. 104. | | : 3. Joseph H. Keenan, Frederick G. Keyes, Philip G. Hill, and Joan G. Moore, Steam Tables, Thermodynamic Properties of Water, John Wiley and Sons, Inc., New York, 1969, p. 104. |
| : 4. M. Hashish, "Critical and Optimum Traverse Rates in Jet Cutting," Proceedings of the First U.S. Water Jet Symposium, Golden, CO, 1981, pp. 66-82. | | : 4. M. Hashish, Critical and Optimum Traverse Rates in Jet Cutting, Proceedings of the First U.S. Water Jet Symposium, Golden, CO, 1981, pp. 66-82. |
| : 5. Ibid , page 77. | | : 5. Ibid, page 77. |
| : 6. Samuel Glasstone and Alexander Sesonske, Nuclear Reactor Engineering , Van Nostrand Reinhold Co., New York, 1967, p. 813. | | : 6. Samuel Glasstone and Alexander Sesonske, Nuclear Reactor Engineering, Van Nostrand Reinhold Co., New York, 1967, p. 813. |
| : 7. M. Hashish, "Milling with Abrasive Water Jets: A Preliminary Investigation," Proceedings of the 4 th U.S. Water Jet Conference, Univ ersity of California, Berkeley, CA, August 26-28, 1987, p. 1. | | : 7. M. Hashish, Milling with Abrasive Water Jets: A Preliminary Investigation, Proceedings of the 4th U.S. Water Jet Conference, University of California, Berkeley, CA, August 26-28, 1987, p. 1. |
| : 8. "Waterjet Seminar White Paper," Flow In ternational Corporation, Kent, Washington USA, http://www.flowcorp.com. November 18, 2006, p. 25. | | : 8. Waterjet Seminar White Paper, Flow International Corporation, Kent, Washington USA, http://www.flowcorp.com. November 18, 2006, p. 25. |
| : 9. M. Hashish, "Milling with Abrasive Water Jets: A Preliminary Investigation," Proceedings of the 4 th U.S. Water Jet Conference, Univ ersity of California, Berkeley, CA, August 26-28, 1987, p. 7. | | : 9. M. Hashish, Milling with Abrasive Water Jets: A Preliminary Investigation, Proceedings of the 4th U.S. Water Jet Conference, University of California, Berkeley, CA, August 26-28, 1987, p. 7. |
| : 10. Ibid, page 15. | | : 10. Ibid, page 15. |
| : 11. "Root Cause Report: Significant Degradation of the Reactor Pressure Vessel Head," | | : 11. Root Cause Report: Significant Degradation of the Reactor Pressure Vessel Head, Davis Besse Nuclear Power Station Condition Report CR 2002-0891. Rev. 1, August 27, 2002, p. 21. |
| Davis Besse Nuclear Power Station Condition Report CR 2002-0891. Rev. 1, August 27, 2002, p. 21. | | : 12. Bruce A. Fender, Davis Besse Reactor Vessel Head Deposit Characterization Results, FRA-ANP Report 51-5018613-00, June 2002, p. 7. |
| : 12. Bruce A. Fender, "Davis Besse Reactor Vessel Head Deposit Characterization Results," FRA-ANP Report 51-5018613-00, June 2002, p. 7. | | : 13. Beverly H. Cyrus, Davis Besse Reactor Vessel Head Deposit Characterization Results (Second Batch, Nozzle #2 Removal), FRA-ANP Report 51-5018965-00, July 2002, p. 7. |
| : 13. Beverly H. Cyrus, ""Davis Besse Reactor Vessel Head Deposit Characterization Results (Second Batch, Nozzle #2 Removal)," FRA-ANP Report 51-5018965-00, July 2002, p. 7. | | BN63097.001 B0T0 1106 DB05 E-7 |
| BN63097.001 B0T0 1106 DB05 E-8 14. Bruce A. Fender, "Davis Besse Reactor Vessel Head Deposit Characterization Results," FRA-ANP Report 51-5018613-00, June 2002, p. 16.}} | | : 14. Bruce A. Fender, Davis Besse Reactor Vessel Head Deposit Characterization Results, FRA-ANP Report 51-5018613-00, June 2002, p. 16. |
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Revision 2 L-14-259, Firstenergy Nuclear Operating Company'S (Fenoc'S) Third Six-Month Status Report in Response to March 12, 2012 Commission Order Modifying Licenses with Regard to Reliable Spent Fuel Pool Instrumentation (Order Number EA-12-051)2014-08-28028 August 2014 Firstenergy Nuclear Operating Company'S (Fenoc'S) Third Six-Month Status Report in Response to March 12, 2012 Commission Order Modifying Licenses with Regard to Reliable Spent Fuel Pool Instrumentation (Order Number EA-12-051) ML14141A5252014-06-30030 June 2014 Staff Assessment of the Flooding Walkdown Report Supporting Implementation of Near-Term Task Force Recommendation 2.3 Related to the Fukushima DAI-ICHI Nuclear Power Plant Accident L-14-167, Report of Facility Changes, Tests and Experiments for the Period Ending May 26, 20142014-06-18018 June 2014 Report of Facility Changes, Tests and Experiments for the Period Ending May 26, 2014 ML14134A5172014-05-30030 May 2014 Staff Assessment of the Seismic Walkdown Report Supporting Implementation of Near-Term Task Force Recommendation 2.3 Related to the Fukushima DAI-ICHI Nuclear Power Plant Accident L-14-148, CFR 50.46 Report of Changes to or Errors in Emergency Core Cooling System Evaluation Models2014-05-19019 May 2014 CFR 50.46 Report of Changes to or Errors in Emergency Core Cooling System Evaluation Models ML14112A3152014-04-21021 April 2014 Review of Draft Plant-Specific Supplement 52 to the Generic Environmental Impact Statement for License Renewal of Nuclear Plants Regarding L-14-104, Firstenergy Nuclear Operating Co. Response to NRC Request for Information Pursuant to 10 CFR 50.54 (F) Regarding the Flooding Aspects of Recommendation 2.1 of the Near-Term Task Force Review of Insights from the Fukushima Dai-ichi Accident2014-03-11011 March 2014 Firstenergy Nuclear Operating Co. Response to NRC Request for Information Pursuant to 10 CFR 50.54 (F) Regarding the Flooding Aspects of Recommendation 2.1 of the Near-Term Task Force Review of Insights from the Fukushima Dai-ichi Accident ML14007A6702014-02-21021 February 2014 Interim Staff Evaluation Relating to Overall Integrated Plan in Response to Order EA-12-049 (Mitigation Strategies) ML14042A2942014-02-19019 February 2014 Mega-Tech Services, LLC, Technical Evaluation Report Regarding the Overall Integrated Plan for Davis-Besse Nuclear Power Station, TAC No.: MF0961 ML13340A1592013-11-26026 November 2013 Davis-Besse Nuclear Power Station Near-Term Task Force Recommendation 2.3 Seismic Walkdown Report Revision 1, Appendix a ML13340A1472013-11-26026 November 2013 Davis-Besse Nuclear Power Station & Perry Nuclear Power Plant - Response to RAI Associated with Seismic Aspects of Recommendation 2.3 of the Near-Term Task Force Review of Insights from the Fukushima Dai-ichi Accident (TAC Nos. MF0116 & MF0 ML13340A1632013-10-0909 October 2013 Davis-Besse Nuclear Power Station Near-Term Task Force Recommendation 2.3 Seismic Walkdown Report Revision 1, Appendix C to Appendix G ML13340A1622013-10-0909 October 2013 Davis-Besse Nuclear Power Station Near-Term Task Force Recommendation 2.3 Seismic Walkdown Report Revision 1, Appendix B (2 of 2) ML13340A1602013-10-0909 October 2013 Davis-Besse Nuclear Power Station Near-Term Task Force Recommendation 2.3 Seismic Walkdown Report Revision 1, Appendix B (1 of 2) ML13340A1582013-10-0909 October 2013 Davis-Besse Nuclear Power Station Near-Term Task Force Recommendation 2.3 Seismic Walkdown Report Revision 1 L-13-154, CFR 50.46 Report of Changes to or Errors in Emergency Core Cooling System Evaluation Models2013-05-28028 May 2013 CFR 50.46 Report of Changes to or Errors in Emergency Core Cooling System Evaluation Models L-13-157, Generic Safety Issue 191 Resolution Plan2013-05-15015 May 2013 Generic Safety Issue 191 Resolution Plan ML13009A3752012-12-12012 December 2012 Enclosure B to L-12-444, Calculation No. 32-9195651-000, Equivalent Margins Assessment of Davis-Besse Transition Welds for 52 EFPY - Non-Proprietary. L-12-347, FENOC Response to NRC Request for Information Pursuant to 10 CFR 50.54(f) Regarding Flooding Aspects of Recommendation 2.3 of Near-Term Task Force Review of Insights from Fukushima Dai-ichi Accident2012-11-27027 November 2012 FENOC Response to NRC Request for Information Pursuant to 10 CFR 50.54(f) Regarding Flooding Aspects of Recommendation 2.3 of Near-Term Task Force Review of Insights from Fukushima Dai-ichi Accident ML13135A2442012-08-10010 August 2012 Near-Term Task Force Recommendation 2.3 Seismic Walkdown Report, Appendix B - Seismic Walkdown Checklists (Swcs), Sheet 1 of 379 Through Sheet 201 of 379 ML13135A2432012-08-10010 August 2012 Near-Term Task Force Recommendation 2.3 Seismic Walkdown Report, Appendix a - Resumes and Qualifications ML13135A2422012-08-10010 August 2012 Near-Term Task Force Recommendation 2.3 Seismic Walkdown Report, Cover Through Page 176 2024-06-05
[Table view] Category:Technical
MONTHYEARL-23-214, Submittal of Relief Request for Impractical American Society of Mechanical Engineers Boiler and Pressure Vessel Code Section XI Examination Requirements2024-06-0505 June 2024 Submittal of Relief Request for Impractical American Society of Mechanical Engineers Boiler and Pressure Vessel Code Section XI Examination Requirements L-22-253, Submittal of Pressure and Temperature Limits Report, Revision 52023-01-10010 January 2023 Submittal of Pressure and Temperature Limits Report, Revision 5 L-22-211, Technical Specification 5.6.6 Steam Generator Tube Inspection 180-Day Report2022-09-29029 September 2022 Technical Specification 5.6.6 Steam Generator Tube Inspection 180-Day Report L-22-216, Submittal of Pressure and Temperature Limits Report. Revision 42022-09-27027 September 2022 Submittal of Pressure and Temperature Limits Report. Revision 4 L-22-149, Post Accident Monitoring Report2022-06-23023 June 2022 Post Accident Monitoring Report ML22202A4362022-04-0808 April 2022 Enclosure F: Updated Inputs to 52 EFPY P-T Operating Curves ML22202A4372022-03-0202 March 2022 Enclosure G: Framatome Inc. Document 86-9344713-000, Davis-Besse Reactor Vessel Embrittlement Fluence Reconciliation Through 60 Years ML21322A2892021-12-0909 December 2021 Approval of Plant-Specific Analysis of Certain Reactor Vessel Internal Components in Accordance with License Renewal Commitment No. 53 ML20302A3022020-09-25025 September 2020 1 to Technical Requirements Manual ML19255H0992019-10-10010 October 2019 Staff Assessment of Flooding Focused Evaluation L-19-189, 54010-CALC-01, Davis-Besse Nuclear Power Station: Evaluation of Risk Significance of Permanent ILRT Extension.2019-07-29029 July 2019 54010-CALC-01, Davis-Besse Nuclear Power Station: Evaluation of Risk Significance of Permanent ILRT Extension. ML22262A1522019-05-0101 May 2019 Framatome Inc., Document ANP-2718NP, Revision 007, Appendix G Pressure-Temperature Limits for 52 EFPY for the Davis-Besse Nuclear Power Station ML22202A4332019-04-30030 April 2019 Enclosure C: Framatome ANP-2718NP, Rev. 7, Appendix G Pressure-Temperature Limits for 52 EFPY for the Davis-Besse Nuclear Power Station ML18149A2812018-02-16016 February 2018 2017 ATI Environmental Inc. Midwest Laboratory Radiological Environmental Monitoring Program L-17-270, Notification of Emergency Core Cooling System (ECCS) Evaluation Model Change Pursuant to 10 CFR 50.462017-09-0101 September 2017 Notification of Emergency Core Cooling System (ECCS) Evaluation Model Change Pursuant to 10 CFR 50.46 ML17086A0322017-03-31031 March 2017 Enclosure B to L-17-105, Areva Report ANP-3542NP, Revision 1, Time-Limited Aging Analysis (TLAA) Regarding Reactor Vessel Internals Loss of Ductility at 60 Years ML17026A0082016-12-31031 December 2016 Areva Report ANP-3542NP, Time-Limited Aging Analysis (TLAA) Regarding Reactor Vessel Internals Loss of Ductility for Davis-Besse Nuclear Power Station, Unit No. 1 at 60 Years (Non Proprietary) L-16-229, Submittal of Pressure and Temperature Limits Report, Revision 32016-07-28028 July 2016 Submittal of Pressure and Temperature Limits Report, Revision 3 L-15-288, Response to NRC Letter. Request for Information, Per 10 CFR 50.54(f) Regarding Recommendations 2.1. 2.3. and 9.3. of the Near-Term Task Force Review of Insights from the Fukushima Dai-ichi Accident2015-10-0202 October 2015 Response to NRC Letter. Request for Information, Per 10 CFR 50.54(f) Regarding Recommendations 2.1. 2.3. and 9.3. of the Near-Term Task Force Review of Insights from the Fukushima Dai-ichi Accident L-14-289, Pressure and Temperature Limits Report. Revision 22014-09-22022 September 2014 Pressure and Temperature Limits Report. Revision 2 ML14134A5172014-05-30030 May 2014 Staff Assessment of the Seismic Walkdown Report Supporting Implementation of Near-Term Task Force Recommendation 2.3 Related to the Fukushima DAI-ICHI Nuclear Power Plant Accident L-14-148, CFR 50.46 Report of Changes to or Errors in Emergency Core Cooling System Evaluation Models2014-05-19019 May 2014 CFR 50.46 Report of Changes to or Errors in Emergency Core Cooling System Evaluation Models ML14112A3152014-04-21021 April 2014 Review of Draft Plant-Specific Supplement 52 to the Generic Environmental Impact Statement for License Renewal of Nuclear Plants Regarding ML14007A6702014-02-21021 February 2014 Interim Staff Evaluation Relating to Overall Integrated Plan in Response to Order EA-12-049 (Mitigation Strategies) ML14042A2942014-02-19019 February 2014 Mega-Tech Services, LLC, Technical Evaluation Report Regarding the Overall Integrated Plan for Davis-Besse Nuclear Power Station, TAC No.: MF0961 L-13-154, CFR 50.46 Report of Changes to or Errors in Emergency Core Cooling System Evaluation Models2013-05-28028 May 2013 CFR 50.46 Report of Changes to or Errors in Emergency Core Cooling System Evaluation Models ML13009A3752012-12-12012 December 2012 Enclosure B to L-12-444, Calculation No. 32-9195651-000, Equivalent Margins Assessment of Davis-Besse Transition Welds for 52 EFPY - Non-Proprietary. ML13008A0612012-08-10010 August 2012 Davis-Besse Near-Term Task Force Recommendation 2.3 Seismic Walkdown Report, Appendix C, Area Walk-By Checklists, Sheet 21 of 139 Through End L-15-328, Enclosure B, Bechtel Report No. 25593-000-G83-GEG-00016-000, Effect of Laminar Cracks on Splice Capacity of No. 11 Bars Based on Testing Conducted at Purdue University and University of Kansas for Davis-Besse Shield Building. Part 7 of 72012-07-30030 July 2012 Enclosure B, Bechtel Report No. 25593-000-G83-GEG-00016-000, Effect of Laminar Cracks on Splice Capacity of No. 11 Bars Based on Testing Conducted at Purdue University and University of Kansas for Davis-Besse Shield Building. Part 7 of 7 ML15299A1502012-07-30030 July 2012 Enclosure B, Bechtel Report No. 25593-000-G83-GEG-00016-000, Effect of Laminar Cracks on Splice Capacity of No. 11 Bars Based on Testing Conducted at Purdue University and University of Kansas for Davis-Besse Shield Building. Part 6 of 7 ML15299A1492012-07-30030 July 2012 Enclosure B, Bechtel Report No. 25593-000-G83-GEG-00016-000, Effect of Laminar Cracks on Splice Capacity of No. 11 Bars Based on Testing Conducted at Purdue University and University of Kansas for Davis-Besse Shield Building. Part 5 of 7 ML15299A1482012-07-30030 July 2012 Enclosure B, Bechtel Report No. 25593-000-G83-GEG-00016-000, Effect of Laminar Cracks on Splice Capacity of No. 11 Bars Based on Testing Conducted at Purdue University and University of Kansas for Davis-Besse Shield Building. Part 4 of 7 ML15299A1472012-07-30030 July 2012 Enclosure B, Bechtel Report No. 25593-000-G83-GEG-00016-000, Effect of Laminar Cracks on Splice Capacity of No. 11 Bars Based on Testing Conducted at Purdue University and University of Kansas for Davis-Besse Shield Building. Part 3 of 7 ML15299A1462012-07-30030 July 2012 Enclosure B, Bechtel Report No. 25593-000-G83-GEG-00016-000, Effect of Laminar Cracks on Splice Capacity of No. 11 Bars Based on Testing Conducted at Purdue University and University of Kansas for Davis-Besse Shield Building. Part 2 of 7 ML15299A1442012-07-30030 July 2012 Enclosure B, Bechtel Report No. 25593-000-G83-GEG-00016-000, Effect of Laminar Cracks on Splice Capacity of No. 11 Bars Based on Testing Conducted at Purdue University and University of Kansas for Davis-Besse Shield Building. Part 1 of 7 ML12209A2602012-07-26026 July 2012 Attachment 31, Fauske & Associates, Inc. Technical Bulletin No. 1295-1, BWR MSIV Leakage Assessment: NUREG-1465 Vs. MAAP 4.0.2 ML1017400422010-06-0404 June 2010 0800368.407, Rev. 0, Summary of Design and Analysis of Weld Overlays for Reactor Coolant Pump Suction and Discharge, Cold Leg Drain, and Core Flood Nozzle Dissimilar Metal Welds for Alloy 600 Primary Water Stress Corrosion Cracking Mitigati L-10-132, 0800368.408, Revision 0, Summary of Weld Overlay Ultrasonic Examinations for Reactor Coolant Pump Suction and Discharge Nozzle Welds, Core Flood Nozzle Welds, and Cold Leg Drain Nozzle Welds2010-04-25025 April 2010 0800368.408, Revision 0, Summary of Weld Overlay Ultrasonic Examinations for Reactor Coolant Pump Suction and Discharge Nozzle Welds, Core Flood Nozzle Welds, and Cold Leg Drain Nozzle Welds ML1002501322010-01-11011 January 2010 0800368.404, Revision 1, Leak-Before-Break Evaluation of Reactor Coolant Pump Suction and Discharge Nozzle Weld Overlays for Davis-Besse Nuclear Power Station, Enclosure B ML11301A2222008-12-0101 December 2008 Reference: Combined Heat and Power Effective Energy Solutions for a Sustainable Future ML0821900132008-08-0707 August 2008 Monthly Operating Reports Second Quarter 2008 L-08-105, Reactor Head Inspection Report2008-04-11011 April 2008 Reactor Head Inspection Report L-08-005, Submittal of the 2007 Organizational Safety Culture and Safety Conscious Work Environment Independent Assessment Report for Davis-Besse2008-01-27027 January 2008 Submittal of the 2007 Organizational Safety Culture and Safety Conscious Work Environment Independent Assessment Report for Davis-Besse ML0726105652007-09-17017 September 2007 Confirmatory Order, 2007 Independent Assessment of Corrective Action Program (FENOC) ML0708602822007-03-15015 March 2007 Review and Analysis of the Davis-Besse March 2002 Reactor Pressure Vessel Head Wastage Event, Appendix B, Crack Driving Force and Growth Rate Estimates ML0708602812007-03-15015 March 2007 Review and Analysis of the Davis-Besse March 2002 Reactor Pressure Vessel Head Wastage Event, Appendix a, Finite Element Stress Analysis of Davis-Besse CRDM Nozzle 3 Penetration ML0708602802007-03-15015 March 2007 Review and Analysis of the Davis-Besse March 2002 Reactor Pressure Vessel Head Wastage Event, Section 10. the Unique Nature of the Davis-Besse Nozzle 3 Crack and the RPV Head Wastage Cavity ML0708602762007-03-15015 March 2007 Review and Analysis of the Davis-Besse March 2002 Reactor Pressure Vessel Head Wastage Event, Section 9. Cfd Modeling of Fluid Flow in CRDM Nozzle and Weld Cracks and Through Annulus ML0708602712007-03-15015 March 2007 Review and Analysis of the Davis-Besse March 2002 Reactor Pressure Vessel Head Wastage Event, Section 8. Stress Analysis and Crack Growth Rates for Davis-Besse CRDM Nozzles 2 and 3 ML0708602842007-03-15015 March 2007 Review and Analysis of the Davis-Besse March 2002 Reactor Pressure Vessel Head Wastage Event, Appendix C, Cfd Analysis 2024-06-05
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Appendix E Fluid Jet Cutting of Davis-Besse RPV Head Materials BN63097.001 B0T0 1106 DB05 1
Appendix E Fluid Jet Cutting of Davis-Besse RPV Head Materials E.1 Introduction The formation of the wastage cavity in the reactor pressure vessel (RPV) head of the Davis Besse nuclear reactor was most likely due to a combination of degradation mechanisms. While the Root Cause Report for this incident identified boric acid corrosion as the primary mechanism for head wastage, subsequent observations and fluid flow modeling efforts suggest alternative mechanisms that may have significantly influenced wastage cavity formation. In addition to flow-assisted corrosion (FAC),
mechanical mechanisms for metal removal from the RPV head may also have played an important role. These mechanical mechanisms include water jet cutting and abrasive water jet cutting. If these mechanical material removal mechanisms were the dominant degradation mechanism for material removal, the wastage cavity could have formed in a relatively short (days to weeks) period of time, in contrast to the corrosion time (4 years) estimated in the Root Cause Report.1 E.2 Pure Water Jet Cutting The primary mechanism for material removal by water jet cutting is the conversion of the kinetic energy of the jet into the stagnation pressure at the point of impact on the target.
The maximum pressure PJ, which can be produced (above the ambient static pressure) by such a jet, is related to the jet velocity V0 by the following relationship, PJ = 1/2 V02 (Eqn. 1) where is the density of the fluid in the jet.2 At a temperature of 600°F and a pressure of 2000 psig, the specific volume of water is 0.02330 ft3/lb,3 which yields a density of 0.0248 lb/in3.
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An evaluation of critical and optimum parameters for the material removal by water jet cutting was completed by Hashish.4 The minimum pressure required to remove material by the impingement of a water jet was a pressure equal to the yield stress (y) of the material. A detailed evaluation of the total specific energy required for water jet cutting yielded an optimum pressure Po for material removal in a ductile material as, Po = 2.5 y (Eqn. 2) where y is the yield stress for the ductile material.5 A typical yield stress for carbon steel at room temperature (75°F) is 50,000 lb/in2. However, the yield stress for carbon steel is lower at reactor operating temperatures. As noted by Glasstone and Sesonske,6 the allowable stress for carbon steel (A302-B) under reactor conditions at 700°F is 27,000 lb/in2. Hence, a reasonable estimate for the allowable stress for carbon steel at 600°F is approximately 30,000 lb/in2. Therefore, the minimum and optimum pressures for water jet removal of carbon steel at reactor temperatures are approximately 30,000 lb/in2 and 75,000 lb/in2, respectively.
The water jet velocities required to begin material removal and the optimum velocity for material removal can be estimated by rearranging Equation 1 and solving for V0.
V0 = (2/)1/2 (Eqn. 3) where is the yield stress and 2.5 times the yield stress for the minimum and optimum material removal conditions. The results of these calculations suggest that a minimum fluid velocity of 2,386 feet per second is required to begin material removal. The fluid velocity for optimum material removal using only a water jet is 3,773 feet per second.
These velocities are 2 to 3 times the sonic velocity in air at 600°F BN63097.001 B0T0 1106 DB05 E-2
E.3 Abrasive Water Jet Cutting The material removal rate is greatly increased by the introduction of very fine abrasive materials into a water jet fluid flow stream. This technology, called the abrasive water jet technique, has been developed for industrial applications over the past 25 years. In abrasive water jet technology, abrasives are incorporated into a high-velocity water jet and the momentum of the water is transferred to the abrasive particle, rapidly increasing the velocity of the particle. Typical abrasive water jet fluid velocities are 300-600 m/s (984-1,968 ft/s) with abrasive mass flow rates of approximately 10 grams per second.7 Current industrial applications of abrasive water jet cutting employ fluid flow rates of 0.5 gallons per minute (gpm) with an orifice diameter of 0.010 inch.8 Early investigations of the efficacy of abrasive water jet technology were completed by Hashish. Studies of the experimental conditions for the optimum abrasive water jet cutting of steel, cast iron, aluminum, and Inconel were presented by Hashish. The effect of abrasive type (garnet, silica sand and glass beads), abrasive flow rate, and stand-off distance were evaluated using a range of flow conditions and abrasives. Typical material removal rates for mild steel over a range of stand-off distances from the nozzle exit to the cutting surface at various flow rates are shown in Table E.1.9 Table E.1 Effect of Standoff Distance and Abrasive Flow Rate on the Material Removal Rate in Abrasive Water Jet Cutting of Mild Steel9 Abrasive Flow Rate 4.3 g/s 7.3 g/s 10.7 g/s Standoff Removal Rate 3
Distance (mm) (mm /sec) (mm3/sec) (mm3/sec) 2.5 22 34 95 5 34 42 72 10 32 51 64 20 30 42 55 50 18 22 50 75 10 18 43 BN63097.001 B0T0 1106 DB05 E-3
Additional comparisons of material removal rates for a range of materials and cutting parameters were also presented by Hashish10 and are shown in Table E.2.
Table E.2 Material Removal Rate for Abrasive Water Jet Cutting of Various Materials10 Material Removal rate mm3/s)
Aluminum 50-300 Steel 40-200 Cast Iron 50-250 Titanium 50-250 Inconel 40-200 E.4 Estimated Material Removal Rate Following the initiation of boric acid precipitation and RPV head corrosion, ample amounts of abrasive material were available for incorporation into the fluid stream ejected from the CRDM nozzle crack. With hundreds of pounds of crystalline boric acid and the corrosion of about 195 in3 of carbon steel (approximately 55 lb of steel yielding approximately 75 lb of Fe3O4), there were significant quantities of abrasive materials that could be entrained in the high-velocity fluid jet striking the interior surfaces of the wastage cavity.
The Root Cause Report estimated that the leakage attributed to CRDM nozzle leaks during late 2001 was 0.1 to 0.2 gpm11. Our calculations of CRDM crack leak rates, presented in Section 9.4, determined that the CRDM Nozzle 3 leak rate was on the order of 0.17 gpm at this time. An estimate of the total material wastage that could have occurred due to this leak rate during this time period by abrasive jet cutting can be made by using data in Table E-1. Scaling the material removal rate for the 75 mm (3 inch) standoff distance at the lowest abrasive material flow rate (4.3 g/s) by the ratio of the flow rates (34% - 0.17 gpm/0.5gpm) yields a material removal rate of approximately 3.4 mm3/s. At this material removal rate, the time required to excavate a wastage cavity of 195 in3 (3,195,500 mm3) would have been 939,853 seconds (261 hours0.00302 days <br />0.0725 hours <br />4.315476e-4 weeks <br />9.93105e-5 months <br /> = 10.8 days).
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Therefore, under optimum abrasive water jet cutting conditions, the entire wastage cavity could have formed in a period of a couple of weeks.
E.5 Evidence Supporting Mechanical Removal of Material from the Wastage Cavity No specific evaluations of the metallic particle content of the boric acid or corrosion deposits removed from the RPV head and wastage cavity near Nozzle 3 during 13 RFO were completed. However, two chemical analyses of the deposits removed from the Davis-Besse reactor vessel head were completed by Framatome ANP in June 2002 and July 2002, respectively.12-13 The initial analyses on a number of specimens collected from the RPV were completed by Fender.11 This study noted that one of the specimens, The dark colored chunk was quite hard and not easily crushed; a metallic strip coated with an adherent deposit was revealed after crushing. The chemical analysis was completed after the removal of the metal strip.
Subsequent chemical analyses were completed by Cyrus,13 who noted, Metallic fragments that could be readily isolated from the bulk deposit samples were removed.
The remaining material in each sample was homogenized by grinding in an agate mortar and pestle. Portions of the homogenized samples were then segregated for analysis.
Because smaller metallic particles remained in the samples, any metallic iron detected in the samples by x-ray diffraction was ignored.
Since the chemical analyses of the materials removed from these metallic samples contained little chromium, it is evident that the source of this metal was not the degradation of the mirror insulation or the machining of CRDM nozzle flange surfaces during prior outages. Fender noted that, The most probable source of the iron is the carbon steel of the reactor vessel head.14 These observations support the case that mechanical removal of reactor pressure head material occurred during the formation of the wastage cavity. The mechanical removal of metallic fragments was likely a result of water jet cutting or abrasive water jet cutting of the RPV head during periods of high nozzle leakage late in Cycle 13.
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E.6 Observation A major portion of the wastage cavity formation occurred during a relatively short period of time of the order of days to weeks, late in Cycle 13 and was due to abrasive water jet mechanisms that acted in conjunction with flow assisted boric acid corrosion.
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References
- 1. Root Cause Report: Significant Degradation of the Reactor Pressure Vessel Head, Davis Besse Nuclear Power Station Condition Report CR 2002-0891. Rev. 1, August 27, 2002, p. 24.
- 2. Thomas J. Labus and George A. Savanick, An Overview of Waterjet Fundamentals and Applications, Fifth Edition, 2001, WaterJet Technology Association, St. Louis, MO, p. 2.4.
- 3. Joseph H. Keenan, Frederick G. Keyes, Philip G. Hill, and Joan G. Moore, Steam Tables, Thermodynamic Properties of Water, John Wiley and Sons, Inc., New York, 1969, p. 104.
- 4. M. Hashish, Critical and Optimum Traverse Rates in Jet Cutting, Proceedings of the First U.S. Water Jet Symposium, Golden, CO, 1981, pp. 66-82.
- 5. Ibid, page 77.
- 6. Samuel Glasstone and Alexander Sesonske, Nuclear Reactor Engineering, Van Nostrand Reinhold Co., New York, 1967, p. 813.
- 7. M. Hashish, Milling with Abrasive Water Jets: A Preliminary Investigation, Proceedings of the 4th U.S. Water Jet Conference, University of California, Berkeley, CA, August 26-28, 1987, p. 1.
- 8. Waterjet Seminar White Paper, Flow International Corporation, Kent, Washington USA, http://www.flowcorp.com. November 18, 2006, p. 25.
- 9. M. Hashish, Milling with Abrasive Water Jets: A Preliminary Investigation, Proceedings of the 4th U.S. Water Jet Conference, University of California, Berkeley, CA, August 26-28, 1987, p. 7.
- 10. Ibid, page 15.
- 11. Root Cause Report: Significant Degradation of the Reactor Pressure Vessel Head, Davis Besse Nuclear Power Station Condition Report CR 2002-0891. Rev. 1, August 27, 2002, p. 21.
- 12. Bruce A. Fender, Davis Besse Reactor Vessel Head Deposit Characterization Results, FRA-ANP Report 51-5018613-00, June 2002, p. 7.
- 13. Beverly H. Cyrus, Davis Besse Reactor Vessel Head Deposit Characterization Results (Second Batch, Nozzle #2 Removal), FRA-ANP Report 51-5018965-00, July 2002, p. 7.
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- 14. Bruce A. Fender, Davis Besse Reactor Vessel Head Deposit Characterization Results, FRA-ANP Report 51-5018613-00, June 2002, p. 16.
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