L-2014-005, Response to Request for Additional Information and Supplemental Information for Relief Request No. 13
| ML14030A183 | |
| Person / Time | |
|---|---|
| Site: | Turkey Point  |
| Issue date: | 01/09/2014 |
| From: | Kiley M Florida Power & Light Co |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| L-2014-005 | |
| Download: ML14030A183 (14) | |
Text
0 jAg 0 2014 L-2014-005 I=PLS 10 CFR 50.55a U. S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, D.C. 20555-0001 RE: Turkey Point Unit 3 Docket No. 50-250 Response to Request for Additional Information for Turkey Point Unit 3 And Supplemental Information for Relief Request No. 13 By letter L-2013-296, dated October 23, 2013, Agencywide Documents Access and Management System (ADAMS), Accession No. ML13318A010, Florida Power & Light Company (FPL) submitted Relief Request (RR) No. 13, for Turkey Point Unit 3, requesting relief from the American Society of Mechanical Engineers Boiler and Pressure Vessel Code for the alternate repair of degraded valve, 3-844A, in the common containment spray pump suction supply header. On December 4, 2013 via electronic mail by Ms. Audrey Klett, NRC Project Manager for Turkey Point Units 3 and 4, ADAMS Accession No. ML13338A696, the Nuclear Regulatory Commission (NRC) requested additional information to be provided for Turkey Point Unit 3 RR No. 13 by January 10, 2014.
The purpose of this letter is to supplement the RR No. 13 with additional information regarding the flaw of valve 3-844A and to respond to the NRC request for additional information. The enclosure to this letter contains the NRC's Request for Additional Information (RAI) questions for RR No. 13, and the corresponding FPL responses.
Attachment 1 provides a picture of valve 3-844 indicating the total size of through-wall flaw, and Attachment 2 provides the updated RR No. 13 with the supplemental information.
If there are any questions regarding this request, please contact Robert J. Tomonto, Turkey Point Licensing Manager, at (305) 246-7327.
Sincerely, Michael Kiley / " .
Site Vice-President ,,M AA , /4-1 L-6',4 Turkey Point Nuclear Plant Enclosure Attachments cc: Regional Administrator, Region II, USNRC Project Manager, NRR, USNRC Senior Resident Inspector, USNRC, Turkey Point Nuclear Plant Florida Power & Light Company 9760 S.W. 344"' Street Homestead, FL 33035
L-2014-005, Enclosure Page 1 of 5 FPL Letter L-2014-005 ENCLOSURE Florida Power & Light Company Turkey Point Nuclear Plant Unit 3 Responses to NRC Request for Additional Information For Relief Request No. 13
L-2014-005, Enclosure Page 2 of 5 NRC RAI No. 1 "The projected final flaw size at time of repair is projected to be the present 5/16 inch
[length] x 1/16 inch [width] measured. Ifthe monthly measurement increases from the present by 1/16 inch in either direction (allowing 1/16 inch for measurement uncertainty), then the growth rate will be re-examined to verify the structural analysis conclusions and predicted growth rate.
(a) Page 4 of the application states that daily walkdowns will be performed to observe significant leakage. Provide the leak rate (in gallons per minute) that the licensee would consider significant. Ifthe leakage does increase to the specified significant leak rate during service in the ensuing months, discuss the corrective actions.
(b) Clarify whether the licensee considers a length of 1/16 inches or 1/8 inches (1/16 inch + 1/16 inch for the measurement uncertainty) as the monthly measurement increase.
(c) If the monthly measurement indicates that the flaw grows more than the aforementioned length criterion, discuss whether any remedial actions will be taken, such as increasing the inspection frequency. If remedial actions will not be taken in this scenario, please justify why not.
(d) Discuss whether the physical location of the subject valve is conducive for the plant personnel to perform visual inspections during the daily walkdowns, measure the leakage, and to perform monthly measurements.
(e) Discuss whether the flaw on the valve is covered with insulation during normal operation. Ifyes, discuss whether the insulation will be removed for visual inspection during walkdowns."
FPL Response to RAI No. 1 a) Per design criteria for this system, the Turkey Point UFSAR section 6.2, states: "...The majority of valves, except those which perform a control function, are provided with backseats which are capable of limiting leakage to less than 1.0 cc per hour per inch of stem diameter, assuming no credit taken for valve packing..."
Assuming that the subject valve's backseat is capable of limiting the leakage to less than 1.0cc/hr, the leak rate that is considered significant for this valve is determined as follows: The valve stem diameter is 1.25 inches. Therefore, if the leakage increases to 25 drops per hour (1.25 inches x 1cc/hr x 0.0002642ga1/cc / 60 min./hr = 5.5E-6 gal/min=25 drops/hr), corrective actions will be initiated. Corrective actions include initiating repair/replacement of the valve.
b) A growth length of 1/16 inch (as measured) would be considered a significant increase warranting re-evaluation.
L-2014-005, Enclosure Page 3 of 5 c) Although the initial analysis of the flaw indication concluded that no growth is expected between discovery and the next refueling outage (March 2014), any measurable increase (more than the aforementioned length criterion) in the monthly measured flaw length will result in reevaluation of the flaw versus acceptance criteria and in an increased inspection frequency from daily to once per shift (three shifts per 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />). This will provide reasonable assurance that any fast-changing conditions that would require reevaluation of the flaw growth premise are monitored closely.
d) The physical location of the subject valve 3- 844A is in the Unit 3 Containment Spray Pump room, which is off the north-south hallway of the Unit 3 Auxiliary Building. This area is normally accessible for plant personnel to perform visual inspections during the daily walkdowns, measure the leakage, and to perform monthly flaw size measurements.
e) The subject valve 3 - 844A (including the area where the flaw location is found) is not covered with insulation during normal operation.
NRC RAI No. 2 "Page 3 of the application states that the flaw size of 5/16 inches long and 1/16 inches wide was obtained based on the direct measurement at the outside surface of the bonnet. The length of the flaw at the inside surface of the bonnet may be longer than 5/16 inches.
Discuss whether ultrasonic testing was conducted to measure the flaw size at the inside surface of the bonnet or bonnet thickness at the flaw location."
FPL Response to RAI No. 2 The flawed area is in a small uneven surface between the top of the bonnet (packing gland cast flange) and the capped packing gland leak off line. The location of the flaw and the configuration of the surface at the flaw location were evaluated by NDE Level III and radiography experts. They concluded that no meaningful information would be expected from ultrasonic testing or from radiography of the flawed area with the valve intact. A visual inspection performed December 3, 2013 indicated the flaw showed no signs of growth to date. The cavity internal wall was visible with no discernible voids, pinholes, or fissures. The cavity was "probed" with a 1/32 inch diameter wire. Maximum cavity depth measured with the wire was determined to be 1/16 " deep from the surface. The internal cavity wall was determined to be solid material with no holes, voids, pours or fissures that the 1/32" wire was able to be fit or pushed into. This information, along with the packing gland area inspection and measurement performed during a maintenance activity in 2007, provides reasonable assurance that there is not a large void behind the surface flaw. There has been no change in actual measured flaw dimensions since discovery.
L-2014-005, Enclosure Page 4 of 5 NRC RAI No. 3 "Page 4 of the application states that the subject valve will be repaired or replaced when the flaw length exceeds "the allowable and critical flaw size" of 5.63 inches and 23.4 inches in the circumferential and axial directions, respectively. Page 5 of the application refers the above sizes as "allowable critical size."
(a) Please clarify the "allowable and critical flaw size" and "allowable critical size" terminology. Please clarify whether the allowable flaw size is the same as the critical flaw size and whether the valve could fail catastrophically (or if it could become unstable and propagate uncontrollably) if the existing flaw reaches the critical flaw size. Explain whether the licensee will establish an allowable flaw size that is less than the critical flaw size to prevent such a catastrophic event so that actions can be taken before the flaw reaches its critical size.
(b) Justify why the allowable flaw size is the same as the critical flaw size.
(c) Discuss whether a crack growth rate criterion or a leak rate criterion should also be required to compliment the flaw size criterion as a defense-in-depth measure.
FPL Response to RAI No. 3 a) The "allowable flaw size" and "critical flaw size" are one and the same terminology used to describe the calculated allowable maximum flaw size to maintain structural integrity of the component based on operational parameters. These sizes (5.63 inches circumferentially and 24.3 inches longitudinally) are based on analysis of the packing gland area treated as a tube (pipe).
As stated in Paragraph 5.0 of the original Relief Request, negligible growth rate is predicted for the remainder of this fuel cycle. Therefore, a measurement 1/16" greater than the present measurements (which have not changed since discovery) would be the criteria for re-evaluation of the analysis that supports the present operability determination.
b) The critical flaw size is the calculated allowable flaw size beyond which the valve would not be expected to maintain structural integrity.
c) As a defense in depth, FPL will conservatively apply both a crack growth criterion and a leak rate criterion to administratively remain well within the acceptable flaw size analysis. These are summarized below:
- 1. A 1/16 inch growth rate per month (1/16" change in any monthly measurement): reanalyze evaluation of the flaw to maintain evaluation validity.
- 2. An increase from the existing imperceptible leak rate to greater than 25 drops per hour, initiate corrective action to repair/ replace valve.
L-2014-005, Enclosure Page 5 of 5 NRC RAI No. 4 "The corrosion report in the submittal concluded that the crack growth from corrosion for the subject valve is insignificant. The NRC staff notes that if a flaw can grow through the wall of the bonnet, then the crack growth rate must not be insignificant. Discuss why the flaw has been able to grow through the wall of the bonnet if the flaw growth from corrosion is insignificant."
FPL Response to RAI No. 4 The subject valve 3- 844A was fully disassembled under work order 37020508 during a Foreign Material Exclusion (FME) inspection completed in October 2007. At this time, the packing gland internal area was inspected and measured with the valve stem removed. The carbon spacer in the packing was noted as in good condition and reused.
This information provides reasonable assurance that there is not a long-term corrosion effect on the inside of the packing gland area and that there is not a large area of degradation (missing metal). The through-wall flaw appears to be a casting defect based upon it's void-like shape at the OD surface. Given the excellent corrosion resistance of CF8 casting to borated water, the through-wall leak path likely developed due to the gradual wash-out or removal of high temperature oxides from a casting defect rather than corrosion of sound metal. Therefore the conclusion is that the flaw growth rate is negligible.
NRC RAI No. 5 "Attachment 2 of the application contains a structural analysis performed by Structural Integrity Associates, Inc.. Page 4 of that analysis states that it used the following maximum operating conditions: a temperature of 205 degrees Fahrenheit (F) and a pressure of 180 pounds per square inch gauge (psig). The structural report's piping isometrics drawing, 5613-P-599-3, indicated that the design temperature and pressure are 300 degrees F and 200 psig, respectively. Discuss why the design conditions were not used in the structural calculation."
FPL Response to RAI No. 5 The word "design" should not have been used in paragraphs 3.2 and 3.5.1 of the Structural Integrity Associates, Inc analysis. The ASME Code does not require the use of design conditions for flaw evaluation. Section Xl flaw evaluation is normally based on the maximum temperature and pressure that would be expected for the period of plant operation until a repair is implemented. This is typically the maximum operating temperature and pressure unless the plant specifies other values to be used. Code Case N-513-3 specifies that maximum operating temperature and pressure are to be used when implementing the Code Case.
L-2014-005 Attachment 1
/
Additional portion of the flaw 1/32" and 3/8" from main Flaw Location (therefore total flaw length considered to be 11/16")
I Valve 3-844A (Partial Picture) I
L-2014-005 Attachment 2 Page 1 of 7 L-2014-005 Attachment 2 TURKEY POINT UNIT 3 RELIEF REQUEST No. 13
L-2014-005 Attachment 2 Page 2 of 7 TURKEY POINT UNIT 3 RELIEF REQUEST No. 13 Proposed Alternative In Accordance with 10 CFR 50.55a(a)(3)(ii)
Hardship or Unusual Difficulty Without Compensating Increase in Level of Quality and Safety 1.0 ASME Code Component(s) Affected The component associated with the relief request is valve 3-844A, which is the Turkey Point Unit 3 suction isolation valve for the "A" Containment Spray Pump (3P214A) from the common containment spray pump suction supply header.
The valve passively maintains the Containment Spray System suction piping integrity and provides maintenance isolation for the "A" Containment Spray Pump. The valve is normally maintained in the back-seated, locked-open position during Modes 1-4.
Valve 3-844A is a Quality Group B, ASME Class 2, an 8 inch manually-operated gate valve manufactured by Anchor-Darling, with Series 150 welding ends, and constructed of ASTM A-351 grade CF-8 cast stainless steel material. The valve and pump are located outside containment in the Auxiliary Building Unit 3 Containment Spray Pump room.
2.0 Applicable Code Edition The Code of Record for the Turkey Point Unit 3 Fourth 10-year inservice inspection interval is the 1998 Edition through 2000 Addenda of the American Society of Mechanical Engineers (ASME) Section Xl, "Rules for Inservice Inspection of Nuclear Power Plant Components" subject to the limitations and modifications in 10 CFR 50.55a(b).
3.0 Applicable Code Requirements ASME Section Xl Code, subsection IWC, "Requirements for Class 2 Components of Light-Water Cooled Power Plants," subparagraph IWC-3122.2, "Acceptance by Repair/Replacement Activity." ASME Section Xl, Subsection IWC, subparagraph IWC-3122.2 states in part that a component with flaws that exceed the acceptance standards of Table IWC-3410-1, is unacceptable for continued service until the component is corrected by a repair/replacement activity.
L-2014-005 Attachment 2 Page 3 of 7
4.0 Reason for Request
Florida Power & Light Company (FPL) has identified a through-wall flaw on the bonnet of valve 3-844A that exceeds the acceptance criteria of Table IWC-341 0-1, Acceptance Standards. While subparagraph IWC-3122.3 allows for acceptance by analytical evaluation per IWC-3600, it does not provide acceptance criteria for austenitic components. IWC-3600 states that the criteria of IWB-3600 may be applied, wherein Subarticle IWB-3640, "Evaluation Procedures and Acceptance Criteria for Austenitic Piping," it is stated that the evaluation procedures and acceptance criteria shall be the responsibility of the Owner and shall be subject to approval of the regulatory authority.
During a daily walk down (on 12/10/13) of valve 3 - 844A for the existing leak, an additional area of dried boric acid was identified approximately 3/8 inch away from the existing 5/16 inch flaw. A liquid penetrant examination was performed and a 1/32 inch indication was observed. As part of the evaluation, the area was cleaned and reinspected after 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />. The small area of boric acid was again visible. A new condition report was initiated (AR 01926346) to evaluate and address this condition.
A review of the previous inspection pictures revealed the same indication existed during the initial visual and liquid penetrant examination, but did not show the penetrant dye or evidence of leakage possibly due to dry boric acid or metal oxides blocking the leak path. As such, the indication was not recorded on the examination report.
Based on the initial flaw analysis under AR 01904263, the initial flaw for analysis should have been the 5/16 inch plus the 3/8 inch maximum distance from the flaw to the indication. This combination of the flaw area is allowed by ASME Section Xl (
Reference:
IWA 3300: Flaw Characterization). The combination of the flaw areas results in a flaw size for initial evaluation of 11/16 inches. Review of the flaw analysis, which resulted in a 5.63 inch circumferential critical flaw size allowed and a 23.4 inches allowable axial critical flaw size, results in the 11/16 inch flaw size being well within the acceptable critical flaw size criteria.
NRC Inspection Manual 9900: Technical Guidance, "Operability Determinations
& Functionality Assessments for Resolution of Degraded or Nonconforming Conditions Adverse to Quality of Safety" (dated April 16, 2008), Appendix C, "Specific Operability Issues," Item C.1 1, "Flaw Evaluation," addresses evaluations of ASME Class 2 and Class 3 system components with through-wall flaws. When ASME Class 2 or Class 3 components do not meet ASME Code acceptance standards, the requirements of a NRC-endorsed ASME Code Case, or NRC approved alternative, then a determination of whether the degraded or nonconforming condition results in a Technical Specification required system,
L-2014-005 Attachment 2 Page 4 of 7 structure, or component being inoperable, is required. This section of the manual also states that whenever a flaw does not meet ASME Code or construction code acceptance standards or the requirements of an NRC endorsed ASME code case, a relief request needs to be submitted in a timely manner after completing the operability determination process documentation.
The through-wall flaw is located on the bonnet near the top of the packing gland of valve 3-844A. This ASME Class 2 valve is in the 8 inch suction line to the "A" Containment Spray Pump. Valve 3-844A can not be isolated from the upstream common supply header of the Containment Spray System without taking both trains of the Containment Spray System out of service. With both trains inoperable, Technical Specifications (TS) Limiting Condition for Operation 3.6.2.1, Action b., would require to restore at least one train to operable status within 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br />, or to be in at least Hot Standby within the next 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br />. The Prompt Operability Determination (POD) evaluation concluded that the valve continues to be capable of performing its required safety functions and is not susceptible to sudden or catastrophic failure. Performing a Code repair/replacement activity now to correct the flaw would create a hardship based on the potential risks associated with unit shutdown, thermal stress cycling of plant components, and emergent equipment issues incurred during shutdown and startup evolutions, with no compensating increase in the level of quality and safety gained by immediate repair of the flaw.
Accordingly, FPL requests relief from the applicable code requirements to delay the repair/replacement activity until the next scheduled refueling outage or outage of sufficient duration requiring entry into Mode 5.
5.0 Proposed Alternative and Basis for Use The 10 CFR Section 50.55a(g)(4) specifies that ASME Code Class 1, 2, and 3 components must meet the requirements except for the design and access provisions and the pre-service examination requirements, set forth in the ASME Code Section Xl to the extent practical with the limitation of design, geometry and materials of construction of the components.
Paragraph 50.55a(a)(3) of 10 CFR Part 50 states in part that alternatives to the requirements of 10 CFR 50.55a(g) may be used when authorized by the NRC if the licensee demonstrates (i) the proposed alternatives would provide an acceptable level of quality and safety, or (ii) compliance with the specified requirements would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety.
FPL is requesting authorization of an alternative to the requirements of the ASME Code Section Xl, IWC-3122.2 pursuant to 10 CFR 50.55a(a)(3)(ii).
L-2014-005 Attachment 2 Page 5 of 7 FPL proposes to temporarily accept the as-found condition (i.e. through-wall flaw) to allow continued service operation until the next scheduled refueling outage or outage of sufficient duration requiring entry into Mode 5, instead of performing immediate flaw correction by a repair/replacement activity described in Code subparagraph IWC-3122.2, "Acceptance by Repair/Replacement Activity".
Performing a Code repair/replacement activity to correct the flaw would create a hardship based on the potential risks associated with unit shutdown, thermal stress cycling of plant components, and emergent equipment issues incurred during shutdown and startup evolutions, with no compensating increase in the level of quality and safety gained by immediate repair of the flaw.
Although the provisions of Code Case N-513-3, "Evaluation Criteria for Temporary Acceptance of Flaws in Class 2 & 3 Piping, Section Xl, Division I," do not apply directly to valves, the guidance of this Code Case was followed since it provides criteria for analytical evaluation, and rules for temporary acceptance of flaws in piping.
Specifically, Code Case N-513-3 Procedure (paragraph 2.0) Methodology was applied:
(a) Flaw size characterization is by visual examination and direct measurement: 11/16 inch in length and 1/16 inch in width.
(b) Flaw is characterized as through-wall coplanar flaw.
(c) The flaw is a single flaw.
(d) Flaw evaluation was performed and is attached to the POD (Attachment 2 of L-2013-296).
(e) FPL will perform a monthly PT examination of the area of manual valve 3-844A with the identified through-wall flaw to validate the analysis supporting the POD.
(f) FPL will perform a daily visual walkdown of manual valve 3-844A to confirm analysis from PT examinations remains valid, i.e. no new significant leakage.
(g) FPL will repair or replace manual valve 3-844A if the predicted flaw size from either periodic inspection or by flaw growth analysis exceeds the acceptance criteria (allowable and critical flaw lengths) of 5.63 inches and 23.4 inches in the circumferential and axial directions, respectively.
The structural analysis performed predicts negligible flaw growth for the remainder of Unit 3's present operating cycle (Cycle 27). The next outage is currently scheduled for March 2014. Therefore, the projected final flaw
L-2014-005 Attachment 2 Page 6 of 7 size at time of repair is projected to be the present 11/16 inch length x 1/16 inch width measured (total). If the monthly measurement increases by 1/16 inch in either direction, then the growth rate will be re-examined to verify the structural analysis conclusions and predicted growth rate.
(h) FPL will repair or replace manual valve 3-844A during the next scheduled Turkey Point Unit 3 Refueling Outage currently planned to begin in March 2014, or forced outage of sufficient duration requiring entry into Mode 5, whichever occurs earlier.
Augqmented Inspection FPL performed an extent of condition visual examination (method that found original flaw) at five of the most susceptible and accessible locations. The five locations examined were manual valves. Three susceptible locations are identical valves in the same service. The remaining two valves examined are 6 inch stainless steel manual valves in similar service (same fluid and service conditions). The inspections did not identify any evidence of unacceptable defects (no relevant indications, leakage or Dry Boric Acid) at the valves examined.
Flaw Evaluation The flaw evaluation is documented in the POD (Attachment 2 of L-2013-296),
which is the basis for considering the valve as operable, but degraded/non-conforming with compensatory measures.
The flaw was conservatively evaluated using a linear elastic fracture mechanics evaluation using the methods and acceptance criteria of ASME Section Xl non-mandatory Appendix H, "Evaluation of Flaws in Ferritic Piping." Applied loads for pressure, deadweight, thermal and seismic conditions were included. Overall, these loads are relatively minor due to the low pressure and temperature conditions, the plant configuration location adjacent to the pump suction nozzle anchor point, and the low seismic accelerations. Stress intensity factors and safety factors were applied per ASME Section Xl, Appendix H. The structural analysis evaluation calculated an allowable critical flaw size of 5.63 inch and 23.4 inch in the circumferential and axial directions, respectively. The measured flaw length is 11/16 inch circumferentially. Since the measured flaw size is significantly less than the allowable critical flaw sizes, there is substantial margin which ensures that structural integrity is maintained.
Additionally, a flaw growth evaluation was performed that considered potential effects of environmentally-assisted cracking, limited number of operating cycles and low resultant stresses and it concluded that flaw growth is not expected for the valve during the remainder of the current operating cycle. As such, valve 3-
L-2014-005 Attachment 2 Page 7 of 7 844A will retain its structural integrity until the flaw is removed via repair/replacement activity during the next refueling outage or forced outage of sufficient duration requiring entry into Mode 5.
Based on the flaw evaluation, it was determined that the through-wall flaw, is stable and the valve will not fail catastrophically under design loading or accident conditions.
6.0 Duration of Proposed Alternative The requested temporary Code relief will apply until Code repair/replacement activities are performed on the valve body either during the next scheduled refueling outage (or forced outage of sufficient duration requiring entry into Mode
- 5) or when the predicted flaw size exceeds acceptance criteria. The next scheduled Turkey Point Unit 3 refueling outage is planned to begin in March 2014.
7.0 Precedent This relief request is similar to the relief granted McGuire Nuclear Station, Unit 1, March 26, 2008, Accession Number ML080580577, which involved a through-wall flaw in an austenitic stainless steel ASME Class 2 valve, evaluated using the guidance of Code Case N-513-3.
8.0 Attachments
-No additional attachments from original submittals