ML16141B200
| ML16141B200 | |
| Person / Time | |
|---|---|
| Site: | Oconee  |
| Issue date: | 05/05/1997 |
| From: | Labarge D NRC (Affiliation Not Assigned) |
| To: | Hampton J DUKE POWER CO. |
| References | |
| TAC-M98454, NUDOCS 9705090041 | |
| Download: ML16141B200 (7) | |
Text
'"'May 5,
1997 Mr. J. W. Hampton Vice President, Oconee Site Duke Power Company P. 0. Box 1439 Seneca, SC 29679
SUBJECT:
REQUEST FOR ADDITIONAL INFORMATION: HIGH PRESSURE INJECTION (HPI)
SYSTEM - OCONEE NUCLEAR STATION (TAC NO. M98454)
Dear Mr. Hampton:
As part of our continuing evaluation of the recent high pressure injection system weld crack on Unit 2 and associated concerns, the staff has identified a need for additional information. The information that is needed is.
described in the enclosure. Many of the questions were the result of our review of your letter dated May 2, 1997, "Justification for Continued Operation (JCO) of Oconee Unit 1 Based on Oconee Unit 2 HPI Line Leak."
These questions are indicated by an asterick (*).
We request that you respond to the JCO questions by May 7, 1997, and to the remaining questions by May 14, 1997.
Sincerely, ORIGINAL SIGNED BY:
David E. LaBarge, Senior Project Manager Project Directorate 11-2 Division of Reactor Projects -
I/II Office of Nuclear Reactor Regulation Docket Nos. 50-269, 50-270, and 50-287
Enclosure:
Request for Additional Information cc w/encl:
See next page Distributtion:
Docket File PUBLIC PD 11-2 Rdg.
SVarga HBerkow LBerry DLaBarge OGC ACRS 0
JJohnson, RII CCasto, RII 080060 To receive a copy of this document, Indicate In the box:
"C" = Copy without attachment/
closure "E" = Copy with attachment/enclosure "N"= No copy OFFICE PDII-2/P J/
PDII-2/A P
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- DLaBarge, LBerry
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!1 !g97 DOCUMENT NAME: G:\\OCONEE\\0C098454.RAI OFFICIAL RECORD COPY 9705090041 970505 PDR ADOCK 05000269 P
0 UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 May 5, 1997 Mr. J. W. Hampton Vice President, Oconee Site Duke Power Company P. 0. Box 1439 Seneca, SC 29679
SUBJECT:
REQUEST FOR ADDITIONAL INFORMATION: HIGH PRESSURE INJECTION (HPI)
SYSTEM - OCONEE NUCLEAR STATION (TAC NO. M98454)
Dear Mr. Hampton:
As part of our continuing evaluation of the recent high pressure injection system weld crack on Unit 2 and associated concerns, the staff has identified a need for additional information. The information that is needed is described in the enclosure. Many of the questions were the result of our review of your letter dated May 2, 1997, "Justification for Continued Operation (JCO) of Oconee Unit 1 Based on Oconee Unit 2 HPI Line Leak."
These questions are indicated by an asterick (*).
We request that you respond to the JCO questions by May 7, 1997, and to the remaining questions by.May 14, 1997.
Sin ly, David E. LaBarge, Senior Project Manager Project Directorate 11-2 Division of Reactor Projects -
I/II Office of Nuclear Reactor Regulation Docket Nos. 50-269, 50-270, and 50-287
Enclosure:
Request for Additional Information cc w/encl: See next page
Oconee Nuclear Station Units 1, 2, and 3 cc:
Mr. Paul R. Newton Mr. J. E. Burchfield Legal Department (PB05E)
Compliance Manager Duke Power Company Duke Power Company 422 South Church Street Oconee Nuclear Site Charlotte, North Carolina 28242-0001 P. 0. Box 1439 Seneca, South Carolina 29619 J. Michael McGarry, III, Esquire Winston and Strawn Ms. Karen E. Long 1400,L Street, NW.
Assistant Attorney General Washington, DC 20005 North Carolina Department of Justice Mr. Robert B. Borsum P. 0. Box 629 Framatome Technologies Raleigh, North Carolina 21602 Suite 525 1700 Rockville Pike Mr. G. A. Copp Rockville, Maryland 20852-1631 Licensing -
ECO50 Duke Power Company Manager, LIS 526 South Church Street NUS Corporation Charlotte, North Carolina 28242-0001 2650 McCormick Drive, 3rd Floor Clearwater, Florida 34619-1035 Senior Resident Inspector U. S. Nuclear Regulatory Commission Route 2, Box 610 Seneca, South Carolina 29678 Regional Administrator, Region II U. S. Nuclear Regulatory Commission Atlanta Federal Center 61 Forsyth Street, S.W., Suite 23T85 Atlanta, Georgia 30303 Max Batavia, Chief Bureau of Radiological Health South Carolina Department of Health and Environmental Control 2600 Bull Street Columbia, South Carolina 29201 County Supervisor of Oconee County Walhalla, South Carolina 29621 Mr. Dayne H. Brown, Director Division of Radiation Protection North Carolina Department of Environment, Health and Natural Resources P. 0. Box 27687 Raleigh, North Carolina 27611-7687
REQUEST FOR ADDITIONAL INFORMATION OCONEE NUCLEAR STATION CRACK IN THE PIPE/SAFE-END WELD CRACK IN HIGH PRESSURE INJECTION (HPI) LINE Note: Items with an asterisk also apply to the proposed Justification for Continued Operation (JCO) for Oconee Unit 1.
) Determination of the Root Cause
- a. Provide the complete results and conclusions from the laboratory, metallurgical examination of the cracked segment of piping.
- b. Provide the operational history for the normal charging/HPI injection system piping. State under what plant conditions is normal charging reduced or stopped (i.e., heating up, RCS leakage teeing, when load following, etc.).. State if there are any other conditions where all cooling, both normal charging and flow to the warming line, can be lost. Provide an estimate how often these events occur. Also, provide an estimate how often cold water is injected into a hot reactor (e.g., spurious safety injection signals).
- c. Provide a quantitative assessment of the interaction of turbulent penetration and HPI flow on the fatigue life of the pipe/safe-end weld.
- d. Provide an assessment of the effect of residual weld stresses and flow induced vibration of the sleeve on the root cause of the crack growth.
- e. Provide the basis for the recent modifications to this line.
(Replacement of the stop check valve.)
Provide an assessment of the effect of these modifications, the prior configuration, the gap in the thermal sleeve, and the operating characteristics of the line on the root cause.
- f. Provide a detailed explanation of the relationship between the gap or gaps in the thermal sleeve and cracking of the pipe/safe-end weld.
Discuss the potential for cracking of this weld with the thermal sleeve in place as well as out of position.
Explain why cracking of the pipe/safe-end weld should not be expected if the thermal sleeve is installed and in place per design.
- g. Provide a detailed explanation of the benefit of using a dual thermal sleeve, as stated in the JCO, in preventing cracking similar to that found in the pipe/safe-end weld in Unit 2.
-2 (2) Inservice Inspection Program
- a.
Provide a history of all examinations (volumetric, surface and visual) of the pipe/safe-end weld and adjacent piping and of the radiographic examination of the thermal sleeves in each unit of Oconee.
- b. Identify the materials used in the fabrication of the nozzle, safe end, piping, and pipe/safe-end weld. Identify whether the nozzle, safe end, and piping are wrought or cast.
- c. Identify the method used to perform the volumetric examination, the scope of the examination, the qualification procedure for determining whether cracks exist in the inspected material, and the results of the inspection. Describe any mockups that were used to qualify the UT inspection methods, including how representative the geometry and materials of the joint are represented by the mockup and the type of reflector, e.g., EDM notch, fatigue crack, etc.,
were used.
- d. Compare the materials in the calibration block to the materials in the HPI line.
- e.
Provide the bases supporting the frequency of inspection of Ultrasonic Testing, Radiographic Testing and Volumetric Testing, of the welds in Oconee Unit 1.
(3) Thermal Analysis
- a. Provide detailed dimensions of all components shown in Figure 1 of B&W LR:82:5463-08:01, page 21, including the insulation thickness.
- b. Provide thermal conductivity and diffusivity data of the metal and insulation components.
- c. Provide all internal and external heat transfer film coefficients and their basis.
- d. Provide the calculated temperature history distribution of the configuration shown in Figure 1.
(4) Fracture Analysis
- a. Provide a fracture analysis to determine the critical flaw size required to fracture the piping under normal loads during HPI injection or make-up conditions.
-3
- b. In determining the margins-to-failure, identify all assumptions and inputs into the analysis, including stresses and material characteristics.
- c. Determine the sensitivity of the critical flaw size and margin-to failure on the existence of the complex flaw geometry, i.e., 3600 NNinternal part through crack and through-wall cracking.
- d.
Determine the sensitivity of the critical flaw size and margin-to failure on the uncertainty in the mechanical and thermo-hydraulic loads at the pipe/safe-end weld.
- e.
Based on the root cause of the cracking, provide an assessment of the time to initiate and propagate a crack through the wall of the piping.
- f.
Provide a revised leak-before-break analysis based on the complex flaw geometry as found in the cracked and leaking pipe/safe-end weld.
(5) Other Configurations Identify if other similar configurations, e.g., rolled-in thermal sleeves in areas of large coolant temperature differences, of piping exist in the plant. Show that they are not susceptible to cracking from the same mechanism identified in the root cause investigation.
(6) Safety Implications
- a. Describe how the failure of one or more HPI lines is analyzed for the Oconee units, and describe the analyzed consequences.
- b.
Describe the limiting single failure and what equipment is relied on to mitigate the potential accident.
- c.
Review the Probabilistic Risk Assessment for Oconee to assess the risk significance of this event. Provide the results of the assessment, and state the actions that would be taken to reduce the potential risk.
(7)
Compensatory Actions
- a. Describe what actions, beyond those stated in the JCO, have been taken to prepare the operators for a potential HPI pipe break for the operating unit.
-4
- b. Describe what actions have been taken to limit the equipment that can be removed from service that is important to mitigating a potential HPI pipe break for the operating unit. Indicate if any administrative controls have been put in place to reduce the allowed outage times or increase the equipment required to be available.
- c. Describe what additional restrictions have been implemented regarding leakage monitoring, acceptance criteria and action statements over and above those described in the May 2, 1997, JCO for Oconee, Unit 1.
(8) Deficiency in Existing Fatigue Analyses
- a. The existing analysis of the HPI line is based on USAS B31.7, Class II standards. In light of the crack found in the pipe/safe-end weld, which was attributed to high-cycle fatigue, provide justification why the existing analysis of this HPI line is acceptable.
- b. Indicate if the pipe/safe-end weld was part of the original fatigue analysis of the nozzle.
(9) If the answer to Question 8b is yes, provide the design histograms used in the analysis.