ML050700300
| ML050700300 | |
| Person / Time | |
|---|---|
| Site: | Calvert Cliffs  |
| Issue date: | 03/11/2005 |
| From: | Holden C NRC/NRR/DLPM/LPD1 |
| To: | Vanderheyden G Calvert Cliffs |
| Guzman R, NRR/DLPM 415-1030 | |
| References | |
| EA-03-009, TAC MC5705 | |
| Download: ML050700300 (21) | |
Text
March 11, 2005 Mr. George Vanderheyden, Vice President Calvert Cliffs Nuclear Power Plant, Inc.
Calvert Cliffs Nuclear Power Plant 1650 Calvert Cliffs Parkway Lusby, MD 20657-4702
SUBJECT:
CALVERT CLIFFS NUCLEAR POWER PLANT, UNIT NO. 2 - RELAXATION OF THE REQUIREMENTS OF FIRST REVISED ORDER MODIFYING LICENSE (EA-03-009), REGARDING REACTOR PRESSURE VESSEL HEAD INSPECTIONS (TAC NO. MC5705)
Dear Mr. Vanderheyden:
By letter dated January 14, 2005 (ADAMS Accession No. ML050260665), Calvert Cliffs Nuclear Power Plant, Inc. (CCNPPI) requested relaxation from certain inspection requirements in the Nuclear Regulatory Commission (NRC) Order Modifying License EA-03-009 (Order) for Reactor Pressure Vessel (RPV) Head Penetration Nozzles for CCNPP, Unit No. 2 (CCNPP 2).
Additional information supporting your request was provided in letters dated March 4 (ADAMS Accession No. ML050680518) and March 8, 2005.
The NRC staff concludes that your proposed alternative UT examination of 50 control element drive mechanism (CEDM) penetration nozzles to a minimum of 1.2 inches above the highest point of the root of the J-groove weld and of 59 CEDM penetration nozzles below the J-groove weld to the maximum extent possible, provides reasonable assurance of the structural integrity of the RPV head, RPV penetration nozzles, and welds.
Further inspections of these RPV penetration nozzles in accordance with Section IV, paragraph C.(5)(b)(i), of the First Revised NRC Order EA-03-009 dated February 20, 2004, would result in hardship without a compensating increase in the level of quality and safety. Therefore, pursuant to Section IV, paragraph F, of the First Revised NRC Order EA-03-009 dated February 20, 2004, for good cause shown, the staff authorizes the proposed alternative inspections for the 50 RPV CEDM penetration nozzles above the highest point of the root of the J-groove weld and the 59 RPV penetration nozzles below the J-groove weld at CCNPP 2, subject to the following condition:
If the NRC staff finds that the crack-growth formula in industry report MRP-55 is unacceptable, CCNPP [the licensee] shall revise its analysis that justifies relaxation of the First Revised Order dated February 20, 2004, within 30 days after the NRC informs the licensee of an NRC-approved crack growth formula. If our [the licensees] revised analysis shows that the crack growth acceptance criteria are exceeded prior to the end of the current operating cycle, this relaxation can be rescinded and CCNPP shall, within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />, submit to the NRC written justification for continued operation. If the revised analysis shows that the crack growth acceptance criteria are exceeded during the subsequent operating cycle, CCNPP shall, within 30 days, submit the revised analysis for NRC review. If the revised analysis shows that the crack growth acceptance criteria are not exceeded during either the current operating cycle or the subsequent operating
G. Vanderheyden cycle, the licensee shall, within 30 days submit a letter to the NRC confirming that its analysis has been revised. Any future crack growth analyses performed for this and future cycles for reactor pressure vessel head penetrations must be based on an acceptable crack growth rate formula.
The details of the staffs review are contained in the enclosed safety evaluation. If you have questions regarding this matter, please contact Rich Guzman at 301-415-1030.
Sincerely,
/RA/
Cornelius F. Holden, Jr, Director Project Directorate I Division of Licensing Project Management Office of Nuclear Reactor Regulation Docket No. 50-318
Enclosure:
As stated cc w/encl: See next page
G. Vanderheyden cycle, the licensee shall, within 30 days submit a letter to the NRC confirming that its analysis has been revised. Any future crack growth analyses performed for this and future cycles for reactor pressure vessel head penetrations must be based on an acceptable crack growth rate formula.
The details of the staffs review are contained in the enclosed safety evaluation. If you have questions regarding this matter, please contact Rich Guzman at 301-415-1030.
Sincerely,
/RA/
Cornelius F. Holden, Jr, Director Project Directorate I Division of Licensing Project Management Office of Nuclear Reactor Regulation Docket No. 50-318
Enclosure:
As stated cc w/encl: See next page DISTRIBUTION:
PUBLIC PDI-1 R/F CHolden RLaufer RGuzman SLittle TChan OGC GMatakas GHill (2)
ACRS EReichart WKoo Accession No.: ML050700300 *Provided SE input by memo. No substantive changes made.
OFFICE PDI-1/PM PDI-1/LA EMCB/SC OGC PDI-1/SC DLPM/PDI NAME RGuzman SLittle TChan*
GLongo PTam for RLaufer CHolden DATE 3/11/05 3/11/05 3/11/05 SE DTD 3/11/05 3/11/05 3/11/05 OFFICIAL RECORD
Calvert Cliffs Nuclear Power Plant, Unit Nos. 1 and 2 cc:
President Calvert County Board of Commissioners 175 Main Street Prince Frederick, MD 20678 Carey Fleming, Esquire Counsel Constellation Energy 750 East Pratt Street, 17th floor Baltimore, MD 21202 Jay E. Silberg, Esquire Shaw, Pittman, Potts, and Trowbridge 2300 N Street, NW Washington, DC 20037 Lou Larragoite Calvert Cliffs Nuclear Power Plant 1650 Calvert Cliffs Parkway Lusby, MD 20657-4702 Resident Inspector U.S. Nuclear Regulatory Commission P.O. Box 287 St. Leonard, MD 20685 Mr. R. I. McLean, Administrator Radioecology Environ Impact Prog Department of Natural Resources Nuclear Evaluations 580 Taylor Avenue Tawes State Office Building Annapolis, MD 21401 Regional Administrator, Region I U.S. Nuclear Regulatory Commission 475 Allendale Road King of Prussia, PA 19406 Kristen A. Burger, Esquire Maryland People's Counsel 6 St. Paul Centre Suite 2102 Baltimore, MD 21202-1631 Patricia T. Birnie, Esquire Co-Director Maryland Safe Energy Coalition P.O. Box 33111 Baltimore, MD 21218 Mr. Loren F. Donatell NRC Technical Training Center 5700 Brainerd Road Chattanooga, TN 37411-4017
Enclosure SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION FIRST REVISED ORDER MODIFYING LICENSE (EA-03-009) RELAXATION REQUEST, EXAMINATION COVERAGE FOR REACTOR PRESSURE VESSEL HEAD PENETRATION NOZZLES CALVERT CLIFFS NUCLEAR POWER PLANT, UNIT NO. 2 CALVERT CLIFFS NUCLEAR POWER PLANT, INC.
DOCKET NUMBER 50-318
1.0 INTRODUCTION
The First Revised NRC Order EA-03-009 (Order), issued on February 20, 2004, requires specific examinations of the reactor pressure vessel (RPV) head and vessel head penetration (VHP) nozzles of all pressurized-water reactor (PWR) plants.Section IV, paragraph F, of the Order states that requests for relaxation of the Order associated with specific penetration nozzles will be evaluated by the NRC staff using the procedure for evaluating proposed alternatives to the American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code) in accordance with 10 CFR 50.55a(a)(3).Section IV, paragraph F, of the Order states that a request for relaxation regarding inspection of specific nozzles shall address the following criteria: (1) the proposed alternative(s) for inspection of specific nozzles will provide an acceptable level of quality and safety, or (2) compliance with this Order for specific nozzles would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety.
For Calvert Cliffs Nuclear Power Plant Unit 2 (CCNPP 2), and similar plants determined to have a high susceptibility to primary water stress-corrosion cracking (PWSCC) in accordance with Section IV, paragraph A and B, of the Order, the following inspections are required to be performed every refueling outage in accordance with Section IV, paragraph C.(5)(a) and paragraph C.(5)(b) of the Order:
(a)
Bare metal visual [BMV] examination of 100 percent of the RPV head surface (including 360E around each RPV head penetration nozzle). For RPV heads with the surface obscured by support structure interferences which are located at RPV head elevations downslope from the outermost RPV head penetration, a bare metal visual inspection of no less than 95 percent of the RPV head surface may be performed provided that the examination shall include those areas of the RPV head upslope and downslope from the support structure interference to identify any evidence of boron or corrosive product. Should any evidence of boron or corrosive product be identified, the licensee shall examine the RPV head surface under the support structure to ensure that the RPV head is not degraded.
(b)
For each penetration, perform a nonvisual NDE [nondestructive examination] in accordance with either (i), (ii), or (iii):
(i)
Ultrasonic testing of the RPV head penetration nozzle volume (i.e., nozzle base material) from 2 inches above the highest point of the root of the J-groove weld (on a horizontal plane perpendicular to the nozzle axis) to 2 inches below the lowest point at the toe of the J-groove weld on a horizontal plane perpendicular to the nozzle axis (or bottom of the nozzle if less than 2 inches
[See Figure IV-1]); OR from 2 inches above the highest point of the root of the J-groove weld (on a horizontal plane perpendicular to the nozzle axis) to 1.0-inch below the lowest point at the toe of the J-groove weld (on a horizontal plane perpendicular to the nozzle axis) and including all RPV head penetration nozzle surfaces below the J-groove weld that have an operating stress level (including all residual and normal operation stresses) of 20 ksi tension and greater (see Figure IV-2). In addition, an assessment shall be made to determine if leakage has occurred into the annulus between the RPV head penetration nozzle and the RPV head low-alloy steel.
(ii)
Eddy current testing or dye penetrant testing of the entire wetted surface of the J-groove weld and the wetted surface of the RPV head penetration nozzle base material from at least 2 inches above the highest point of the root of the J-groove weld (on a horizontal plane perpendicular to the nozzle axis) to 2 inches below the lowest point at the toe of the J-groove weld on a horizontal plane perpendicular to the nozzle axis (or the bottom of the nozzle if less than 2 inches
[See Figure IV-3]); OR from 2 inches above the highest point of the root of the J-groove weld (on a horizontal plane perpendicular to the nozzle axis) to 1.0-inch below the lowest point at the toe of the J-groove weld (on a horizontal plane perpendicular to the nozzle axis) and including all RPV head penetration nozzle surfaces below the J-groove weld that have an operating stress level (including all residual and normal operation stresses) of 20 ksi tension and greater (see Figure IV-4).
(iii)
A combination of (i) and (ii) to cover equivalent volumes, surfaces and leak paths of the RPV head penetration nozzle base material and J-groove weld as described in (i) and (ii). Substitution of a portion of a volumetric exam on a nozzle with a surface examination may be performed with the following requirements:
- 1.
On nozzle material below the J-groove weld, both the outside diameter and inside diameter surfaces of the nozzle must be examined.
- 2.
On nozzle material above the J-groove weld, surface examination of the inside diameter surface of the nozzle is permitted provided a surface examination of the J-groove weld is also performed.
Footnote 3 of the Order provides specific criteria for examination of repaired VHP nozzles.
By letter dated January 14, 2005, as supplemented by letters dated March 4 and 8, 2005, Calvert Cliffs Nuclear Power Plant, Inc. (the licensee), requested relaxation to implement an alternative to the requirements of Section IV, paragraph C.(5)(b)(i), of the First Revised NRC Order for RPV head penetration nozzles at CCNPP 2.
2.0 FIRST REVISED NRC ORDER EA-03-009 RELAXATION REQUEST FOR EXAMINATION COVERAGE FOR REACTOR PRESSURE VESSEL HEAD PENETRATION NOZZLES ABOVE THE J-GROOVE WELDS 2.1 First Revised NRC Order Requirements for Which Relaxation is Requested The licensee has requested relaxation from Section IV, paragraph C.(5)(b)(i) of the First Revised NRC Order. The specific relaxation requested is identified below:
2.2 Licensees Proposed Alternative The licensee seeks relaxation from the Order where inspection coverage is limited by inaccessible areas of 50 control element drive mechanism (CEDM) penetration nozzles for CCNPP, Unit No. 2, with respect to NDE, specifically ultrasonic testing (UT). The licensee stated that relaxation is requested from Section IV, paragraph IV.C.(5)(b)(i) of the Order from 2 inches above the highest point of the root of the J-groove weld (on a horizontal plane perpendicular to the nozzle axis).
The licensee proposes to meet the Order requirements, or to examine each CEDM nozzle above the J-groove weld to the maximum extent possible. The licensee stated the minimum UT examination coverage expected will be approximately 1.2 inches above the highest point of the J-groove weld.
2.3 Licensees Basis for Proposed Alternative The licensee stated that the Unit 2 CEDM penetrations have guide/thermal sleeves with a funneled-end installed inside the CEDM penetration to position the CEDM shaft. The licensee stated that above the J-groove weld there is a counterbore step on the inside diameter of the nozzle which reduces the annular gap of approximately 0.175 inch to 0.123 inch. Because of this, the thin gap scanning UT blade probe does not fit into the region where the gap width decreases.
The licensee stated that Units 1 and 2 have identical geometries for reactor vessel head nozzle design and fabrication. The analysis and evaluation performed in support of the 2004 Unit 1 refueling outage relaxation request remain valid and are applicable to the 2005 Unit 2 refueling outage relaxation request.
The licensee stated that the residual plus operating stresses are all below 20 ksi, both in the hoop and axial directions at an elevation 1.2 inches above the highest point of the J-groove weld on every CEDM penetration on the Calvert Cliffs reactor vessel head. Therefore, primary water stress-corrosion cracking (PWSCC) is not expected to initiate in the small region that is the subject of this relaxation request.
The licensee stated that it is possible to permanently remove the guide/thermal sleeves, allowing the insertion of a rotating ultrasonic probe, instead of a blade probe to achieve full coverage. However, the licensee stated that during the refueling outage, the effort to remove and re-install thermal sleeves (based on Unit 1 experience) is estimated to result in additional radiation exposure of approximately 31 person-rems and would cost approximately 7.5 million dollars.
The licensee stated that the in-core instrumentation nozzles and the RPV head vent nozzle will be ultrasonically tested 2 inches above the J-groove weld in accordance with the requirements of the Order. The licensee stated that where limitations exist that preclude the full examination coverage, the limitations will be noted and reported as required by Section IV.E of the Order.
The licensee stated that experience with the inspection of the CCNPP, Units 1 head, which is similar to the RPV head on Unit 2, confirms the inability to examine a full 2 inches above the J-groove weld for all scans of the CEDM nozzles using a blade probe. Therefore, based upon the information provided above, the licensee concluded that compliance with the requirements specified in the First Revised NRC Order would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety.
2.4 Evaluation The NRC staffs review of this request was based on criterion (2) of paragraph F of Section IV of the Order, which states:
[C]ompliance with this Order for specific nozzles would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety.
Regarding the required examination of the RPV head penetration nozzles, the licensee has demonstrated that hardship or unusual difficulty would result from implementing examinations to 2 inches above the highest point of the root of the J-groove weld of these nozzles, without a compensating increase in the level of quality and safety. The NRC staff reviewed the licensees hardship or unusual difficulty based upon dose implications on the workers subjected to performing examinations to the bottom of the nozzle without a compensating increase in the level of quality or safety.
The phenomenon of concern is PWSCC, which typically initiates in the areas of highest stress.
The area of CEDM penetrations that has the highest residual stress is the area adjacent to the J-groove attachment weld. Therefore, it is most likely that PWSCC will initiate in an area adjacent to the J-groove attachment weld.
The licensee proposed to examine the CEDM penetration nozzles to a minimum of 1.2 inches above the highest point of the root of the J-groove weld for those nozzles that could not achieve full coverage. The licensees proposed minimum inspection distance of the nozzle base material above the J-groove weld is supported by the licensees residual stress analysis of the CEDM nozzles at 0E, 11E, 29E, and 43E.
The licensee concluded that for all penetrations, the highest bounding, residual stress on the inside diameter (ID) surfaces at 1.2 inches above the highest point of the root of the J-groove weld is 19.9 ksi and occurs on the uphill side of the 11 degree nozzle. On the outside diameter (OD), the licensee stated that both hoop and axial stresses at 0.75 inch above the highest point of the root of the J-groove weld are below 7 ksi in all cases.
The licensee also had crack growth calculations performed for two different locations. The crack growth calculations were performed in accordance with the crack growth formula in Electric Power Research Institute (EPRI) Report Material Reliability Program (MRP) Report, MRP-55, Material Reliability Program (MRP Crack Growth Rates for Evaluation Primary Water Stress Corrosion Cracking (PWSCC) of Thick Wall Alloy 600 Material (MRP-55), Revision 1.
The NRC staff has made a preliminary assessment of the crack growth formula, but has not yet made a final determination on the acceptability of the subject industry report. Should the NRC staff determine the crack growth formula used by the licensee to be unacceptable, the licensee will be required to revise its analysis to incorporate an acceptable crack growth formula as described below.
If the NRC staff finds that the crack-growth formula in industry report MRP-55 is unacceptable, CCNPP [the licensee] shall revise its analysis that justifies relaxation of the First Revised Order dated February 20, 2004, within 30 days after the NRC informs the licensee of an NRC-approved crack growth formula. If our [the licensees] revised analysis shows that the crack growth acceptance criteria are exceeded prior to the end of the current operating cycle, this relaxation can be rescinded and CCNPP shall, within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />, submit to the NRC written justification for continued operation. If the revised analysis shows that the crack growth acceptance criteria are exceeded during the subsequent operating cycle, CCNPP shall, within 30 days, submit the revised analysis for NRC review. If the revised analysis shows that the crack growth acceptance criteria are not exceeded during either the current operating cycle or the subsequent operating cycle, the licensee shall, within 30 days submit a letter to the NRC confirming that its analysis has been revised. Any future crack growth analyses performed for this and future cycles for reactor pressure vessel head penetrations must be based on an acceptable crack growth rate formula.
The licensee concurred with the above statement in a letter dated March 8, 2005.
For the first calculation, the lower end of the crack was located 1.2 inches above the root of the J-groove weld. For the second calculation, the lower end of the flaw was placed at an elevation 2 inches above the root of the J-groove weld. The licensee concluded the results indicated there is little difference in the crack growths for flaws located at 1.18 inches above the weld or at 2 inches above the weld. A table of results is provided below:
Location Initial Flaw Depth Flaw Depth After 2 Years 1.18" Above the Weld 24.15%
24.24%
2.00" Above the Weld 24.15%
24.15%
Flaw depths are in terms of wall thickness.
The licensee stated that for circumferential flaws, the axial residual stresses decline very quickly with distances above the J-groove weld. The licensee stated that in the region above 1.2 inches above the highest point of the root of the J-groove weld, residual stresses are very low or are negative, so initiation and growth of circumferential flaws are not predicted for this region.
The licensee provided inspection data results of the 65 CEDM nozzle penetrations, 8 in-core instrumentation (ICI) nozzles and 1 vent-line penetration nozzle. Based on the inspection results, 15 of the CEDM nozzles were UT inspected at least 2 inches above the highest point of the root of the J-groove weld in accordance with the requirements of the First Revised NRC Order. All 8 ICI penetration nozzles and 1 vent-line penetration nozzle were UT examined in accordance with the requirements of the First Revised NRC Order. Fifty CEDM penetration nozzles which were UT examined did not meet the requirements of 2 inches above the highest point of the root of the J-groove weld (on a horizontal plane perpendicular to the nozzle axis) as required by the First Revised NRC Order EA-03-009, dated February 20, 2004. CEDM nozzle penetration #8 received the most limiting coverage of 1.2 inches above the root of the J-groove weld. A table of results is provided below.
Extent of UT Coverage in RVHP Nozzle Material Pen #
Nozzle Angle Coverage Above Weld Root on Uphill (in)
Coverage Below Weld Toe on the Downhill Side (in)
Circumferential Coverage Achieved (Degrees)
Scan Type (Blade Probe /
Rotating)
Axial Blade: A Circ Blade: C Examined to End of Nozzle Leak Path Assessment Possible? (Yes / No)
CEDM 1 0.0 1.70 1.00 360 C
No Yes CEDM 2 11.1
>2 0.51 360 C
No Yes CEDM 3 11.1 1.91 N/A 360 A/C Yes Yes CEDM 4 11.1 1.50 0.65 360 C
No Yes CEDM 5 11.1
>2 0.85 360 C
No Yes CEDM 6 12.0
>2 0.70 360 C
No Yes CEDM 7 12.0 1.71 0.75 360 C
No Yes CEDM 8 12.0 1.20 0.85 360 C
No Yes CEDM 9 12.0
>2 0.80 360 C
No Yes CEDM 10 22.6 1.92 0.45 360 C
No Yes CEDM 11 22.6 1.90 0.60 360 C
No Yes CEDM 12 22.6
>2 0.40 360 C
No Yes CEDM 13 22.6
>2 0.80 360 C
No Yes CEDM 14 24.1
>2 N/A 360 A
Yes Yes CEDM 15 24.1 1.90 0.50 360 C
No Yes CEDM 16 24.1
>2 0.40 360 C
No Yes CEDM 17 24.1
>2 0.45 360 C
No Yes CEDM 18 25.5 1.61 N/A 360 A
Yes Yes CEDM 19 25.5 1.50 0.70 360 C
No Yes CEDM 20 25.5 1.61 0.50 360 C
No Yes CEDM 21 25.5 1.80 0.60 360 C
No Yes CEDM 22 25.5 1.55 0.40 360 C
No Yes CEDM 23 25.5 1.61 0.40 360 C
No Yes CEDM 24 25.5
>2 0.40 360 C
No Yes CEDM 25 25.5
>2 0.74 360 C
No Yes CEDM 26 29.3 1.81 N/A 360 A
Yes Yes CEDM 27 29.3 1.75 0.60 360 C
No Yes CEDM 28 29.3
>2 0.40 360 C
No Yes CEDM 29 29.3 1.80 0.75 360 C
No Yes CEDM 30 29.3
>2 0.45 360 C
No Yes CEDM 31 29.3
>2 0.35 360 C
No Yes CEDM 32 29.3 1.84 0.50 360 C
No Yes CEDM 33 29.3
>2 0.75 360 C
No Yes CEDM 34 34.9 1.66 0.80 360 C
No Yes CEDM 35 34.9 1.48 0.40 360 C
No Yes CEDM 36 34.9 1.61 0.85 360 A/C No Yes CEDM 37 34.9 1.79 0.85 360 C
No Yes CEDM 38 38.5 1.63 N/A 360 A
Yes Yes CEDM 39 38.5 1.30 0.45 360 C
No Yes CEDM 40 38.5 1.30 0.40 360 C
No Yes CEDM 41 38.5 1.55 0.50 360 C
No Yes CEDM 42 38.5 1.75 0.45 360 C
No Yes CEDM 43 38.5 1.77 0.70 360 C
No Yes CEDM 44 38.5 1.27 0.65 360 C
No Yes CEDM 45 38.5 1.40 0.80 360 C
No Yes CEDM 46 41.8 1.56 N/A 360 A
Yes Yes CEDM 47 41.8 1.21 0.40 360 C
No Yes CEDM 48 41.8 1.50 0.45 360 C
No Yes CEDM 49 41.8 1.44 0.64 360 C
No Yes CEDM 50 41.8 1.58 0.60 360 C
No Yes CEDM 51 41.8 1.30 0.51 360 C
No Yes CEDM 52 41.8 1.60 0.63 360 C
No Yes CEDM 53 41.8 1.47 0.60 360 C
No Yes CEDM 54 42.5 1.60 0.55 360 C
No Yes CEDM 55 42.5 1.67 0.45 360 A/C No Yes CEDM 56 42.5 1.75 0.90 360 C
No Yes CEDM 57 42.5 1.60 0.40 360 C
No Yes CEDM 58 42.5 1.55 0.55 360 C
No Yes CEDM 59 42.5 1.47 0.65 360 C
No Yes CEDM 60 42.5 1.25 1.51 360 A
No Yes CEDM 61 42.5 1.60 0.50 360 C
No Yes CEDM 62 42.5 1.66 0.50 360 C
No Yes CEDM 63 42.5 1.36 0.50 360 C
No Yes CEDM 64 42.5 1.35 0.50 360 C
No Yes CEDM 65 42.5 1.37 0.50 360 C
No Yes ICI 66 54.8
>2 N/A 360 Rotating Yes Yes ICI 67 54.8
>2 N/A 360 Rotating Yes Yes ICI 68 54.8
>2 N/A 360 Rotating Yes Yes ICI 69 54.8
>2 N/A 360 Rotating Yes Yes ICI 70 54.8
>2 N/A 360 Rotating Yes Yes ICI 71 54.8
>2 N/A 360 Rotating Yes Yes ICI 72 54.8
>2 N/A 360 Rotating Yes Yes ICI 73 54.8
>2 N/A 360 Rotating Yes Yes Vent-Line 0-11
>2 N/A 360 Rotating/E CT Yes N/A The licensee also provided a table identifying the stress levels for the 50 CEDM nozzles which did not meet the requirement of 2 inches above the highest point of the J-groove weld (on a horizontal plane perpendicular to the nozzle axis) as required by the First Revised NRC Order EA-03-009, dated February 20, 2004. The table is provided below.
CEDM Number Nozzle Angle Minimum Axial Distance Achieved Above Uphill Weld Root (inches)
Stress Level Above the Uphill Weld Root at the Axial Distance for Nozzles Without Complete Coverage (ksi)
Minimum Axial Distance Achieved Above Downhill Weld Root for Nozzles with Coverage < 2" above Uphill Weld Root (inches)
Stress Level Above the Downhill Weld Root at the Axial Distance for Nozzles without Complete Coverage (ksi) 1 0
1.7 ID: 2.4 OD: -3.6 1.7 ID: 2.4 OD: -3.6 3
11.1 1.91 ID: 2.2 OD: -1.9 2.72 ID: 4.7 OD: 2.4 4
11.1 1.5 ID: 3.8 OD: -5.0 2.31 ID: 2.8 OD: 0.5 7
12.0 1.71 ID: 2.7 OD: -4.3 2.52 ID: 3.8 OD: 2.0 8
12.0 1.2 ID: 5.4 OD: -3.2 2.01 ID: 4.1 OD: -1.4 CEDM Number Nozzle Angle Minimum Axial Distance Achieved Above Uphill Weld Root (inches)
Stress Level Above the Uphill Weld Root at the Axial Distance for Nozzles Without Complete Coverage (ksi)
Minimum Axial Distance Achieved Above Downhill Weld Root for Nozzles with Coverage < 2" above Uphill Weld Root (inches)
Stress Level Above the Downhill Weld Root at the Axial Distance for Nozzles without Complete Coverage (ksi) 10 22.6 1.92 ID: 6.0 OD: -3.0 4.27 ID: 10.1 OD: 3.5 11 22.6 1.90 ID: 5.9 OD: -3.3 4.25 ID: 10.1 OD: 3.6 15 24.1 1.90 ID: 5.9 OD: -3.3 4.25 ID: 10.1 OD: 3.6 18 25.5 1.61 ID: 6.2 OD: -6.7 3.96 ID: 9.9 OD: 3.2 19 25.5 1.50 ID: 6.9 OD: -6.6 3.85 ID: 9.7 OD: 2.7 20 25.5 1.61 ID: 6.2 OD: -6.7 3.96 ID: 9.9 OD: 3.2 21 25.5 1.80 ID: 5.5 OD: -4.5 4.15 ID: 10.0 OD: 3.6 22 25.5 1.55 ID: 6.6 OD: -6.6 3.90 ID: 9.8 OD: 2.9 23 25.5 1.61 ID: 6.2 OD: -6.7 3.96 ID: 9.9 OD: 3.2 26 29.3 1.81 ID: 5.5 OD: -4.4 4.16 ID: 10.0 OD: 3.6 27 29.3 1.75 ID: 5.3 OD: -5.1 4.1 ID: 9.9 OD: 3.7 29 29.3 1.80 ID: 5.5 OD: -4.5 4.15 ID: 10.0 OD: 3.6 32 29.3 1.84 ID: 5.7 OD: -4.0 4.19 ID: 10.0 OD: 3.6 CEDM Number Nozzle Angle Minimum Axial Distance Achieved Above Uphill Weld Root (inches)
Stress Level Above the Uphill Weld Root at the Axial Distance for Nozzles Without Complete Coverage (ksi)
Minimum Axial Distance Achieved Above Downhill Weld Root for Nozzles with Coverage < 2" above Uphill Weld Root (inches)
Stress Level Above the Downhill Weld Root at the Axial Distance for Nozzles without Complete Coverage (ksi) 34 34.9 1.66 ID: 5.9 OD: -6.2 4.01 ID: 9.9 OD: 3.4 35 34.9 1.48 ID: 7.0 OD: -6.5 3.83 ID: 9.6 OD: 2.7 36 34.9 1.61 ID: 6.2 OD: -6.7 3.96 ID: 9.9 OD: 3.2 37 34.9 1.79 ID: 5.5 OD: -4.6 4.14 ID: 10.0 OD: 3.6 38 38.5 1.63 ID: 9.9 OD: -7.7 5.47 ID: 15.7 OD: 1.6 39 38.5 1.30 ID: 10.6 OD: -10.4 5.14 ID: 16.2 OD: 2.0 40 38.5 1.30 ID: 10.6 OD: -10.4 5.14 ID: 16.2 OD: 2.0 41 38.5 1.55 ID: 10.1 OD: -8.4 5.39 ID: 15.8 OD: 1.7 42 38.5 1.75 ID: 9.7 OD: -6.7 5.59 ID: 15.5 OD: 1.4 43 38.5 1.77 ID: 9.7 OD: -6.6 5.61 ID: 15.4 OD: 1.4 44 38.5 1.27 ID: 10.7 OD: -10.6 5.11 ID: 16.2 OD: 2.0 45 38.5 1.40 ID: 10.4 OD: -9.6 5.24 ID: 16.0 OD: 1.8 46 41.8 1.56 ID: 10.0 OD: -8.3 5.40 ID: 15.8 OD: 1.6 CEDM Number Nozzle Angle Minimum Axial Distance Achieved Above Uphill Weld Root (inches)
Stress Level Above the Uphill Weld Root at the Axial Distance for Nozzles Without Complete Coverage (ksi)
Minimum Axial Distance Achieved Above Downhill Weld Root for Nozzles with Coverage < 2" above Uphill Weld Root (inches)
Stress Level Above the Downhill Weld Root at the Axial Distance for Nozzles without Complete Coverage (ksi) 47 41.8 1.21 ID: 10.1 OD: -11.1 5.05 ID: 16.3 OD: 2.1 48 41.8 1.50 ID: 10.2 OD: -8.8 5.34 ID: 15.9 OD: 1.7 49 41.8 1.44 ID: 10.3 OD: -9.3 5.28 ID: 16.0 OD: 1.8 50 41.8 1.58 ID: 10.0 OD: -8.1 5.42 ID: 15.7 OD: 1.6 51 41.8 1.30 ID: 10.6 OD: -10.4 5.14 ID: 16.2 OD: 2.0 52 41.8 1.60 ID: 10.0 OD: -8.0 5.44 ID: 15.7 OD: 1.6 53 41.8 1.47 ID: 10.3 OD: -9.0 5.31 ID: 15.9 OD: 1.8 54 42.5 1.60 ID: 10.0 OD: -9.0 5.44 ID: 15.7 OD: 1.6 55 42.5 1.67 ID: 9.9 OD: -7.4 5.51 ID: 15.6 OD: 1.5 56 42.5 1.75 ID: 9.7 OD: -6.7 5.59 ID: 15.5 OD: 1.4 57 42.5 1.60 ID: 10.0 OD: -8.0 5.44 ID: 15.7 OD: 1.6 58 42.5 1.55 ID: 10.1 OD: -8.4 5.39 ID: 15.8 OD: 1.7 59 42.5 1.47 ID: 10.3 OD: -9.0 5.31 ID: 15.9 OD: 1.8 CEDM Number Nozzle Angle Minimum Axial Distance Achieved Above Uphill Weld Root (inches)
Stress Level Above the Uphill Weld Root at the Axial Distance for Nozzles Without Complete Coverage (ksi)
Minimum Axial Distance Achieved Above Downhill Weld Root for Nozzles with Coverage < 2" above Uphill Weld Root (inches)
Stress Level Above the Downhill Weld Root at the Axial Distance for Nozzles without Complete Coverage (ksi) 60 42.5 1.25 ID: 10.7 OD: -10.8 5.09 ID: 16.3 OD: 2.0 61 42.5 1.60 ID: 10.0 OD: -8.0 5.44 ID: 15.7 OD: 1.6 62 42.5 1.66 ID: 9.9 OD: -7.5 5.50 ID: 15.6 OD: 1.5 63 42.5 1.36 ID: 10.5 OD: -9.9 5.20 ID: 16.1 OD: 1.9 64 42.5 1.35 ID: 10.5 OD: -10.0 5.19 ID: 16.1 OD: 1.9 65 42.5 1.37 ID: 10.5 OD: -9.8 5.21 ID: 16.1 OD: 1.9 Based upon the inspection results provided from the tables above, most nozzles received considerable UT coverage, from the weld portion where the stresses are high to locations away from the weld where stresses decrease considerably. The licensee shows from the tables above, that the area of the nozzles that did not have complete UT coverage have low stresses.
The staff has determined that the likelihood of crack initiation and growth in these low stress areas is low.
The safety issues that are addressed by the inspections mandated by the Order are degradation (corrosion) of the low-alloy steel RPV head, and reactor coolant pressure boundary integrity. Based on the above information, the inspection performed by the licensee on the 50 CEDM nozzles, with a minimum coverage of 1.2 inches above the highest point of the root of the J-groove weld (on a horizontal plane perpendicular to the nozzle axis), provides reasonable assurance of the structural integrity of the RPV head, CEDM penetrantion nozzles, and welds.
2.5 Conclusion The NRC staff concludes that the licensees proposed alternative examination of the 50 CEDM nozzles, with a minimum coverage of 1.2 inches above the highest point of the root of the J-groove weld (on a horizontal plane perpendicular to the nozzle axis) provides reasonable assurance of the structural integrity of the RPV head, VHP nozzles, and welds. Further inspections of these CEDM nozzles in accordance with Section IV, paragraph C.(5)(b), or the First Revised NRC Order EA-03-009, dated February 20, 2004, would result in hardship without a compensating increase in the level of quality and safety. Therefore, pursuant to Section IV, paragraph F, of the Order, for good cause shown, the staff authorizes the proposed alternative inspection for the 50 CEDMs at CCNPP 2, subject to the following condition:
If the NRC staff finds that the crack-growth formula in industry report MRP-55 is unacceptable, the licensee shall revise its analysis that justifies relaxation of the First Revised Order within 30 days after the NRC informs the licensee of an NRC-approved crack growth formula. If the licensees revised analysis shows that the crack growth acceptance criteria are exceeded prior to the end of the current operating cycle, this relaxation is rescinded and the licensee shall, within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />, submit to the NRC written justification for continued operation. If the revised analysis shows that the crack growth acceptance criteria are exceeded during the subsequent operating cycle, the licensee shall, within 30 days, submit the revised analysis for NRC review. If the revised analysis shows that the crack growth acceptance criteria are not exceeded during either the current operating cycle or the subsequent operating cycle, the licensee shall, within 30 days, submit a letter to the NRC confirming that its analysis has been revised. Any future crack-growth analyses performed for this and future cycles for RPV head penetrations must be based on an acceptable crack growth rate formula.
3.0 FIRST REVISED NRC ORDER EA-03-009 RELAXATION REQUEST FOR EXAMINATION COVERAGE FOR REACTOR PRESSURE VESSEL HEAD PENETRATION NOZZLES BELOW THE J-GROOVE WELD 3.1 First Revised NRC Order Requirements for Which Relaxation is Requested The licensee has requested relaxation from Section IV, paragraph C.(5)(b)(i) of the First Revised NRC Order. The specific relaxation is identified below.
3.2 Licensees Proposed Alternative The licensee seeks relaxation from Section IV.C.(5)(b)(i) of the Order for UT each RPV head penetration nozzle (i.e., nozzle base material) to the bottom of the nozzle, specifically, missed examination coverage near the bottom of the CEDM nozzles due to instrument limitation.
The licensee proposes to meet the Order requirements, or to examine each CEDM nozzle below the J-groove weld to the maximum extent possible. The licensee stated the minimum UT examination coverage expected will be approximately 0.35 inch below the toe of the J-groove weld on the downhill side.
3.3 Reason for Relaxation Request The licensee stated that compliance with the requirements specified in the Order would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety.
3.4 Licensees Basis for Proposed Alternative The licensees relaxation request applies to all CCNPP 2 CEDM penetrations 1 through 65, except for nozzles 3, 14, 18, 26, 38, and 46, each of which were successfully scanned for the full length below the nozzle with an axial probe. The licensee stated that during the current UT examination of the Calvert Cliffs Unit 2 RPV head, difficulties were being encountered maintaining contact with the nozzle wall when using the Axial Blade Probe. The difficulties were encountered due to nozzle wall distortion particularly at the downhill side of the nozzle. The licensee stated that this condition worsens for those nozzles toward the periphery and is compounded by the position of the thermal sleeve that is anchored by the centering tabs located above the J-groove weld. Probe contact is dependent on maintaining a nominal gap dimension between the thermal sleeve and the nozzle ID as the probe is stroked axially and circumferentially around the nozzle. The design of the Circumferential Blade Probe is more robust and compliant than the Axial Blade Probe. The licensee stated that the Circumferential Blade Probe has a smaller footprint in the circumferential direction and has more spring force to keep the probe in contact with the nozzle. These features enable the Circumferential Blade Probe to provide better contact with the nozzle wall where nozzle distortion and thermal sleeve eccentricity exist.
The Circumferential Blade Probe has separate transducers for sending and receiving the ultrasonic signal. The transducers are arranged one above the other nominally 0.86 inch apart.
With this configuration, the lower transducer will not contact the inside wall on the nozzle until the upper transducer is inserted greater than approximately 0.86 inch into the nozzle. Since the scanning process requires that both transducers be in contact with the surface, the probe cannot scan the outer portion of the bottom of the nozzle. Based on the geometry involved in the transducer location and nozzle configuration, the portion that cannot be scanned is the portion extending from the bottom of the nozzle upward for a distance of approximately 0.56 inch.
3.5 Evaluation The NRC staffs review of this request was based on criterion (2) of paragraph F of Section IV of the Order which states:
[C]ompliance with this Order for specific nozzles would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety.
Regarding the required examination of the RPV head penetration nozzles, the licensee has demonstrated that hardship or unusual difficulty would result from implementing examinations to the bottom end of these nozzles, without a compensating increase in the level of quality and safety. The hardship identified by the licensee is due to nozzle wall distortion particularly at the downhill side of the nozzles. Due to the wall distortion, difficulties were encountered maintaining contact with the nozzle wall using the Axial Blade Probe. The licensee decided to change to a Circumferential Blade Probe. The licensee stated that the Circumferential Blade Probe is more robust and compliant than the Axial Blade Probe. The Circumferential Blade Probe has a smaller footprint in the circumferential direction and has more spring force to keep the probe in contact with the nozzle. This probe has two separate transducers for sending and receiving the ultrasonic signal and are arranged one above the other approximately 0.86 inch apart. Due to the configuration, the lower transducer will not contact the inside wall on the nozzle until the upper transducer is inserted greater than approximately 0.86 inch into the nozzle. Since the scanning process requires that both transducers be in contact with the surface, the probe cannot scan the outer portion of the bottom of the nozzle. The licensee stated that based on the geometry involved in the transducer location and nozzle configuration, the portion that cannot be scanned is the portion extending from the bottom of the nozzle upward for a distance of approximately 0.56 inch.
In a letter dated March 4, 2005, the licensee stated that examination of the bottom of the nozzle could be accomplished by surface examination. However, the licensee stated that this alternative would have prohibitive worker dose implications without a commensurate increase in quality or safety. Removal of the thermal guide sleeves to provide access for a rotating probe has similar dose implications that present hardship with no increase in safety or quality. The licensee also stated that the uninterrogated area involves a portion of the nozzle at the very bottom below the J-groove weld. At this area of the nozzle, the nozzle is essentially open-ended and the nozzle wall in this portion is not part of the reactor coolant system pressure boundary.
The phenomenon of concern is PWSCC, which typically initiates in the areas of highest stress.
The area of RPV head penetration nozzles that has the highest residual stress is the area adjacent to the J-groove attachment weld. Therefore, it is most likely that PWSCC will initiate in an area adjacent to the J-groove attachment weld.
The licensees proposed minimum inspection distance of the nozzle base material below the J-groove weld is supported by the licensees analysis which demonstrated that no flaw below that portion of the nozzle would propagate to a level adjacent to the J-groove weld within the next operating period (2 years). The licensee stated in a supplemental letter dated March 8, 2005, that a crack growth evaluation was performed using the methods of MRP-55 for crack growth caused by PWSCC at a head temperature of 594 EF. The licensee postulated through wall axial flaws extending from the bottom of the nozzle towards the weld to determine the maximum length of the flaws that would not grow to the bottom of the weld in a single 2-year inspection interval. The analysis was performed for four penetration angles. The results are tabulated below:
Location Downhill Side (A)
Uphill Side (B) 0E Nozzle 0.324" 0.324" 11E Nozzle 0.179" 0.386" 29E Nozzle 0.191" 0.361" 43E Nozzle 0.200" 0.360" The licensee has performed UT inspection on each CEDM nozzle to the maximum achievable axial distance below the toe of the J-groove weld. The minimum inspection distance below the toe of the J-groove weld on any CEDM nozzle was 0.35 inch on CEDM 31 on the downhill side.
CEDM 31 is a 29 degree nozzle, which according to the results of the licensees flaw tolerance evaluation must be inspected a minimum of 0.191 inch at this location. As shown in the table for the extent of UT coverage in reactor vessel head penetration nozzle material in Section 2.4, the minimum inspection distances achieved on every nozzle exceeded the minimum required distances based on the licensees flaw tolerance evaluation.
The licensee also provided a finite element analysis specific to Calvert Cliffs to determine the operating stresses in the CEDM nozzles. Results were used to define the loading and were previously submitted and reviewed in supplemental data packages dated April 9, 2003, January 30, 2004, April 13, 2004, and April 27, 2004 (ADAMS Accession Nos. ML031040010, ML040370331, ML041130293, and ML041240028, respectively). The finite element analysis was performed for the 42 ksi yield strength material used to fabricate the CEDM penetrations in Calvert Cliffs Unit 1. The yield strength for the material used to fabricate the CEDM penetrations in Calvert Cliffs Unit 2 is 37.5 ksi. As a result, the finite element method (FEM) analysis is bounding for Calvert Cliffs Unit 2. Based upon the information, the NRC staff finds the licensees FEM analysis to be acceptable.
The NRC staff notes that the referenced flaw tolerance evaluations discussed above were done for Calvert Cliffs Unit 1 RPV head. Since the design for Unit 2 RPV is identical, the use of the subject evaluation for Unit 2 is acceptable.
3.6 Conclusion Based upon the information provided by the licensee, the NRC staff finds the licensees proposed inspection of the CEDM nozzles below the J-groove weld to be acceptable, since the licensees UT inspection exceeded the minimum required distances below the toe of the J-groove weld based on the licensees flaw tolerance evaluation.
The licensees crack growth calculations were performed in accordance with the crack growth formula in EPRI MRP Report, MRP-55, Material Reliability Program (MRP Crack Growth Rates for Evaluation Primary Water Stress Corrosion Cracking (PWSCC) of Thick Wall Alloy 600 Material (MRP-55), Revision 1. The NRC staff has made a preliminary assessment of the crack growth formula, but has not yet made a final determination on the acceptability of the subject industry report. Should the NRC staff determine the crack growth formula used by the licensee to be unacceptable, the licensee will be required to revise its analysis to incorporate an acceptable crack growth formula as described below.
If the NRC staff finds that the crack-growth formula in industry report MRP-55 is unacceptable, CCNPP [the licensee] shall revise its analysis that justifies relaxation of the First Revised Order dated February 20, 2004, within 30 days after the NRC informs the licensee of an NRC-approved crack growth formula. If our [the licensees] revised analysis shows that the crack growth acceptance criteria are exceeded prior to the end of the current operating cycle, this relaxation can be rescinded and CCNPP shall, within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />, submit to the NRC written justification for continued operation. If the revised analysis shows that the crack growth acceptance criteria are exceeded during the subsequent operating cycle, CCNPP shall, within 30 days, submit the revised analysis for NRC review. If the revised analysis shows that the crack growth acceptance criteria are not exceeded during either the current operating cycle or the subsequent operating cycle, the licensee shall, within 30 days submit a letter to the NRC confirming that its analysis has been revised. Any future crack growth analyses performed for this and future cycles for reactor pressure vessel head penetrations must be based on an acceptable crack growth rate formula.
The licensee concurred with the above statement in a letter dated March 8, 2005.
4.0 CONCLUSION
The NRC staff concludes that the licensees proposed alternative UT examination for 50 control element drive mechanism (CEDM) penetration nozzles to a minimum of 1.2 inches above the highest point of the root of the J-groove weld and for 59 CEDM penetration nozzles below the J-groove weld to the maximum extent possible, provides reasonable assurance of the structural integrity of the RPV head, RPV penetration nozzles, and welds.
Further inspections of these RPV penetration nozzles in accordance with Section IV, paragraph C.(5)(b)(i), of the First Revised NRC Order EA-03-009 dated February 20, 2004, would result in hardship without a compensating increase in the level of quality and safety. Therefore, pursuant to Section IV, paragraph F, of the First Revised NRC Order EA-03-009 dated February 20, 2004, for good cause shown, the staff authorizes the proposed alternative inspections for the 50 RPV CEDM penetration nozzles above the highest point of the root of the J-groove weld and the 59 RPV penetration nozzles below the J-groove weld at CCNPP 2, subject to the following condition:
If the NRC staff finds that the crack-growth formula in industry report MRP-55 is unacceptable, CCNPP [the licensee] shall revise its analysis that justifies relaxation of the First Revised Order dated February 20, 2004, within 30 days after the NRC informs the licensee of an NRC-approved crack growth formula. If our [the licensees] revised analysis shows that the crack growth acceptance criteria are exceeded prior to the end of the current operating cycle, this relaxation can be rescinded and CCNPP shall, within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />, submit to the NRC written justification for continued operation. If the revised analysis shows that the crack growth acceptance criteria are exceeded during the subsequent operating cycle, CCNPP shall, within 30 days, submit the revised analysis for NRC review. If the revised analysis shows that the crack growth acceptance criteria are not exceeded during either the current operating cycle or the subsequent operating cycle, the licensee shall, within 30 days submit a letter to the NRC confirming that its analysis has been revised. Any future crack growth analyses performed for this and future cycles for reactor pressure vessel head penetrations must be based on an acceptable crack growth rate formula.
Principal Contributors: E. Reichart W. Koo Date: March 11, 2005