ULNRC-06115, CFR 50.55a Request: Proposed Alternative to ASME Section XI Alternative Technical Requirements for Class 3 Buried Piping

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CFR 50.55a Request: Proposed Alternative to ASME Section XI Alternative Technical Requirements for Class 3 Buried Piping
ML14161A399
Person / Time
Site: Callaway Ameren icon.png
Issue date: 06/10/2014
From: Maglio S
Ameren Missouri
To:
Document Control Desk, Office of Nuclear Reactor Regulation
References
TAC MD6792, ULNRC-06115
Download: ML14161A399 (10)
v • d • e


Text

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WAmeren Callaway Plant MISSOURI June 10, 2014 ULNRC-06115 U.S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555-0001 10 CFR 50.55a Ladies and Gentlemen:

DOCKET NUMBER 50-483 CALLAWAY PLANT UNIT 1 UNION ELECTRIC CO.

10 CFR 50.55a REQUEST: PROPOSED ALTERNATIVE TO ASME SECTION XI REQUIREMENTS FOR CLASS 3 BURIED PIPING

Reference:

1) NRC letter, "Relief Request BR-10 for Third 10-Year Inservice Inspection Interval- Use of Polyethylene Pipe in Lieu of Carbon Steel Pipe in Buried Essential Service Water Piping System (TAC No. MD6792)," dated November 7, 2008 (Accession No. ML083100288)

Pursuant to 10 CFR 50.55a(a)(3)(i), Union Electric Company (Ameren Missouri) hereby requests NRC approval of attached relief request I4R-01 regarding paragraph IWA -4221 (b) of the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code,Section XI. This relief is requested for the remaining life of the Callaway Plant Unit 1, including plant life extension that has been sought through October 18, 2044, beginning with the fourth 10-year Inservice Inspection (lSI) interval, which begins December 19, 2014. The Code Edition applicable to the fourth 10-year Inservice Inspection interval for Callaway Plant is the 2007 Edition (up to and including the 2008 Addenda).

The requested relief is for an extension of the relief granted by the NRC for the current third 10-year lSI Interval, which supported replacement ofburied steel piping in Callaway's essential service water (ESW) system with polyethylene (PE) piping. For this repair/replacement activity, IWA-4221 (b) would have required the new/replacement piping to meet the original Construction Code requirements for the ESW piping. The applicable Construction Code (ASME Section III), however, did not provide rules for the design, fabrication, installation, examination and testing of PE piping.

............................................................................................................................ PO Box 620 Fulton, MO 65251 AmerenMissouri.com **************

STARS ~ Alliance

ULNRC-06115 June 10, 2014 Page2 No ASME Code Case providing conditions under which PE material may be used for ASME Section III, Class 3 buried piping systems has yet been endorsed by the NRC. Ameren Missouri therefore requests that relief from the noted Code requirements for the same buried PE ESW piping be extended for the remaining life of Callaway Plant, beginning with the fourth 10-year lSI interval, as described in the attached relief request.

The alternative to IWA-4221 (b) for which extension of approval is requested has provided an acceptable level of quality and safety. Replacement of the buried ESW steel piping with PE piping has provided an overall benefit to plant safety since PE piping is much more resistant to fouling and microbiologically induced corrosion, thus assuring improved long-term reliability of the risk-significant ESW system.

In the NRC Safety Evaluation Report (SER) attached to the letter dated November 7, 2008 (Reference

1) which approved relief request BR-10 for the current third lSI interval, the NRC cited a commitment for Ameren Missouri to:
  • Evaluate future investigations that would be performed by the industry to confirm the short-duration (3 0-day) stress allowables and applicable design factors for PE4 71 0 piping.
  • Evaluate future evolution of the fusion technique to validate structural integrity of the installed fusion joints.
  • Submit the results of the evaluations to the NRC, including, if necessary, a fourth 10-year lSI interval alternative request, prior to submittal of Callaway's inservice inspection plan for the fourth 10-year interval.

To satisfy this commitment, the attached relief request I4R-01 that describes the proposed alternative also provides the results ofthese evaluations.

This letter does not contain new commitments.

If there are any questions, please contact Jerry Doughty at 573-220-5145.

Sincerely,

.Lli\ott A. 0 Scott A. Maglio Manager, Regulatory Mfairs JPK

Attachment:

Relief Request I4R-01, "Proposed Alternative Technical Requirements to ASME Section XI Requirements for Replacement of Class 3 Buried Piping in Accordance with 10 CFR 50.55a(a)(3)(i)"

ULNRC-06115 June 10, 2014 Page 3 cc: Mr. Marc L. Dapas Regional Administrator U.S. Nuclear Regulatory Commission Region IV 1600 East Lamar Boulevard Arlington, TX 76011-4511 Senior Resident Inspector Callaway Resident Office U.S. Nuclear Regulatory Commission 8201 NRC Road Steedman, MO 65077 Mr. Fred Lyon Project Manager, Callaway Plant Office ofNuclear Reactor Regulation U.S. Nuclear Regulatory Commission Mail Stop 0-8B 1 Washington, DC 20555-2738

ULNRC-06115 June 10, 2014 Page4 Index and send hardcopy to QA File A160.0761 Hardcopy:

Certrec Corporation 4150 International Plaza Suite 820 Fort Worth, TX 76109 (Certrec receives ALL attachments as long as they are non-safeguards and may be publicly disclosed.)

Electronic distribution for the following can be made via Other Situations ULNRC Distribution:

F. M. Diya D. W. Neterer L. H. Graessle B. L. Cox S. A. Maglio T. B. Elwood M.G. Hoehn J. A. Doughty Corporate Communications NSRB Secretary STARS Regulatory Affairs Mr. John O'Neill (Pillsbury Winthrop Shaw Pittman LLP)

Missouri Public Service Commission

Attachment 1 to ULNRC-06115 Page 1 of 6 10 CFR SO.SSa Request 14R-01 Proposed Alternative Technical Requirements to ASME Section XI Requirements for Replacement of Class 3 Buried Piping in Accordance with 10 CFR 50.55a(a)(3)(i)

--Alternative Provides Acceptable Level of Quality and Safety--

1. ASME Code Component(s) Affected ASME Class 3 buried Essential Service Water (ESW) System supply and return piping replaced with high-density polyethylene (HOPE) piping in accordance with Relief Request 13R-10 during Callaway's third 10-year inservice inspection interval.

ESW Supply Piping Lines:

  • EF-003-AZC, A Train, 36-inch diameter, 411 feet
  • EF-007-AZC, B Train, 36-inch diameter, 518 feet ESW Return Piping Lines:
  • EF-083-AZC, A Train, 36 inch diameter, 279 feet
  • EF-140-AZC, B Train, 36 inch diameter, 288 feet

2. Applicable Code Edition and Addenda

The Code Edition and Addenda applicable to Callaway for its fourth lnservice Inspection (lSI) interval, that will begin December 19, 2014, will be ASME Boiler and Pressure Vessel Code,Section XI, Division 1, 2007 Edition through 2008 Addenda.

3. Applicable Code Requirement

ASME Section XI, IWA-4221(b) requires that "An item to be used for repair/replacement activities shall meet the Construction Code specified in accordance with (1), (2), or (3)," and ASME Section XI, IWA-4221(b)(1) requires that "When replacing an existing item, the new item shall meet the Construction Code to which the original item was constructed." ASME Section XI, IWA- 4221(c) states that as an alternative, Construction Code Cases may be used.

4. Reason for Request

The Construction Code of record for buried ASME Class 3 ESW piping is ASME Boiler and Pressure Vessel Code, Section Ill, Division 1 Subsection ND, 1974 Edition, through Summer 1975 Addenda. This Construction Code and later editions and addenda of this Construction Code do not provide rules for the design, fabrication, installation, examination and testing of piping constructed using polyethylene material. Union Electric Company Relief Request 13R-10 transmitted to the U.S. Nuclear Regulatory

Attachment 1 to ULNRC-06115 Page 2 of 6 Commission (NRC) through letter dated August 30, 2007, supplemented by letters dated April17, July 10, July 24, September 15, and October 9, 2008, provided conditions under which polyethylene material may be used for ASME Section Ill, Division 1, Class 3, buried piping systems. 13R-10 was accepted by the NRC as documented in letter dated October 31, 2008, and amended by letter dated November 7, 2008, with the following commitment:

[1] AmerenUE will evaluate future investigations performed by the industry to confirm the short-duration

{30-day) stress allowables and applicable design factors for PE4710 piping. [2] AmerenUE will also evaluate future evolution of the fusion technique to validate structural integrity of the installed fusion joints. [3] The results of the evaluations will be submitted to the NRC prior to submittal of Callaway's fourth 10-year interval/51 plan, and will include, if necessary, a fourth 10-year IS/ interval alternative request.

The NRC has determined that Callaway must submit an alternative request for the fourth 10-year lSI interval, therefore, this request is being submitted to allow the continued use of HDPE piping in those sections of the ESW system replaced with HDPE piping during the third lSI interval.

5. Proposed Alternative and Basis for Use Callaway proposes to continue use of the HDPE piping installed in the ESW system during the third lSI interval for the remaining life of Callaway Plant, beginning with the fourth lSI interval, which begins December 19, 2014. Following are the commitments agreed to in 13R-10, along with an updated evaluation or disposition for each commitment.

[1] AmerenUE will evaluate future investigations performed by the industry to confirm the short-duration (30-day) stress allowables and applicable design factors for PE4710 piping.

EPRI Report 1025254 Tensile Stress-Strain Properties and Elastic Modulus of PE 4710 Cell Classification 445574C High Density Polyethylene Pipe Material (2012), Section 3 states:

The results obtained in this study show that the three materials used in the testing are all qualified to PE 4710 cell classification 445574C [the same as used at Callaway] and meet all requirements of Code Case N755-1. The comparisons of test results and the allowable stress values in section 2.7 result in high safety factors of >4 for long-term duration (s50 years) allowable stress values in Code Case N755-1 (500 psi @ 140°F) and >3 for short-term (<5 minutes) duration allowable stress values. The report further recommends that the allowable stress values in Code Case N755-1 {5-minute short term of 400 psi @

176°F, interpolated for the EPRI testing as 306 psi @ 185°F) could be increased based on the tensile testing results. Although specific testing for load durations of up to 30 days at 175oF was not performed, test results do indicate that the allowable stresses for HDPE in Code Case N-755-1 are generally conservative by 3 to 4 orders of magnitude.

In addition to the results of EPRI Report 1025254 discussed above, it is important to recognize that all PE 4710 compounds are tested at more limiting conditions as part of the validation process in accordance

Attachment 1 to ULNRC-06115 Page 3 of6 with the requirements of Plastics Pipe Institute (PPI) TR-3, Policies and Procedures for Developing Hydrostatic Design Basis {HOB}, Pressure Design Basis (PDB), Strength Design Basis (SOB}, and Minimum Required Strength (MRS) Ratings for Thermoplastic Piping Materials or Pipe. Per PPI TR-3, in order to validate an HDB of 1000 psi at 140"F (the same HDB as the PE compound utilized for the Callaway ESW piping), a PE compound must be tested at 193"F and 690 psi for at least 3,800 hours0.00926 days <br />0.222 hours <br />0.00132 weeks <br />3.044e-4 months <br /> ("'158 days) or at 176"F and 775 psi for at least 11,300 hours0.00347 days <br />0.0833 hours <br />4.960317e-4 weeks <br />1.1415e-4 months <br /> ("'471 days).

As part of the validation process, the actual PE composition used for the Callaway ESW piping was tested at a higher temperature than the peak Callaway design temperature (tested at<!: 176"F versus the maximum design temperature of 175"F), and at an initial stress 21% more than that necessary to support the Callaway short-term allowable stress of 340 psi. Tests were performed at 775 psi versus a required stress of 640 psi to support the 0.50 Design Factor for Callaway.

Furthermore, the tests extended over a duration of more than thirty (30) times the maximum design duration of the Callaway post-accident design conditions. Tests extended over 943 days with test results remaining above 725 psi (equating to 362 psi allowable), versus the Callaway post-accident design duration of 30 days and 340 psi allowable. The following is a tabulation of the test results provided by DOW Chemical for the actual Callaway PE 4710 compound.

C.llaway PE4710 Elevated Temperature HydrosutlcTest Data callaway Condition Hydrostatic Test Data Safety Margin Tested Temperature tested Tested temperature. temperature.

nme,hrs Stress, psi Tlme,hrs Stress, psi versus callaway times/callaway stresses/callaway F F temperature design time design stress 175 720 340 176 7443 775 higher 10.3 2.3 175 720 340 176 9564 775 higher 13.3 2.3 175 720 340 176 17600 775 higher 24.4 2.3 175 720 340 176 14437 750 higher 20.1 2.2 175 720 340 176 21442 750 higher 29.8 2.2 175 720 340 176 21480 750 higher 29.8 2.2 175 720 340 176 21451 725 higher 29.8 2.1 175 720 340 176 21753 725 higher 30.2 2.1 175 720 340 176 22625 725 higher 31.4 2.1 The above test results provide conclusive evidence that the short term duration (30-day) stress allowables used for the Callaway HDPE Piping design are in fact conservative, resolving the question raised by the Regulator during review of the Callaway Relief Request 13R-10. In addition, Callaway actually used a heavier pipe wall than needed by design for the return piping (3.82" min wall vs. 2.24" required by design); therefore, additional design margin exists with the conservative short-term allowables actually incorporated in the design.

Conclusion (1): The allowable stress of 340 psi at 175 "F is a conservative value proven by actual test, and maintains a factor of safety of more than 2 (i.e. a Design Factor of 0.5 or Jess).

With respect to Design Factor, subsequent to submittal of the commitment Callaway actually decided to use the NRC-requested Design Factor of 0.50 for design of the HDPE piping system, in lieu of the

Attachment 1 to ULNRC-06115 Page 4 of6 industry recommended 0.63 for PE4710 (or 0.56 as originally proposed by Callaway). It may be noted that the latest versions of ASME Code Committee documents dealing with HOPE piping for nuclear applications have also invoked the 0.50 Design Factor for allowable stresses used in such design.

Conclusion (2): There are no unresolved issues with the Design Factor actually used in the Callaway design.

[2] AmerenUE will also evaluate future evolution of the fusion technique to validate structural integrity of the installed fusion joints.

The fusion technique used for the Callaway project was based on PPI, TR-33/2001, "Generic Butt Fusion Joining Procedure for Field Joining of Polyethylene Pipe," developed at the request of U.S. Department of Transportation for use on gas transmission piping. On-going testing has been performed by PPI over the years to validate the suitability of the TR-33 Fusing Procedure for different polyethylene materials, in different sizes and thicknesses. Initially this testing only involved fusing of 2DR11 and 8DR11 MOPE and HOPE (PE2406 and PE3408) piping to each other and to themselves (TR-33, 2001).

As ofthe time of the commitment to evaluate evolution of the fusing technique (ULNRC-05517, AmerenUE letter to NRC dated July 10, 2008) samples of PE2406 and PE3408 in sizes of 12DR6 through 22DR11 had been tested by PPI to validate the Standard Fusing Procedure for use with these larger sizes (TR-33, 2006). However, there had been no industry fusion testing of the new bimodal PE4710 material, or for any piping as large as the 36DR9.5 piping that was planned to be installed at Callaway.

DOW Chemical, the supplier of the DGDA 2490/92 PE4710 compound used for the Callaway pipe, had performed joint testing consisting of tensile, high speed tensile impact, quick burst and sustained pressure testing (> 1 year at elevated temperatures) on fused PE4710 piping up to 22DR9 in size, and those results were used as a basis for verifying fusibility of the material for the Callaway project (DOW letter to Ameren dated June 24, 2008).

Performance demonstration testing was subsequently performed by the Callaway project using the PPI Standard Fusing Procedure to validate fusibility of the actual PE4710 material, pipe diameter, wall thickness, and fusing machines to be employed. This involved 12 sample joints of 36DR9.5 pipe fused at the extremes of the fusing procedure, resulting in 48 coupons split into 96 test specimens. All96 test specimens passed the High Speed Tensile Impact Test.

During the course of installation, 208 butt-fused joints were made in the 36DR9.5 piping and all were examined by the Time-of-Flight Diffraction (TOFD) technique of ultrasonic examination. The acceptance criterion was "no indication of a flaw or void," resulting in a total of 5 rejected fusion joints. Four of these rejected joints involved very minor indications of voids, causing the joints to be re-made. One (1) out of 208 36DR9.5 joints contained a relatively large area of voiding, which was attributed to improper application of external force during the fusing process.

Attachment 1 to ULNRC-06115 Page 5 of6 In addition, all joints completed during the installation at Callaway were hydrostatically tested at 1.5 times the design pressure +10 psig, with no failures.

After the Callaway project was completed, the Plastics Pipe Institute continued with additional fusion testing under TR-33, using the same Standard Fusing Procedure with PE4710 material in sizes from 2DR11 through 36DR9 (reference TR-33, 2012). All of this testing reaffirmed that the standard fusing procedure applied at Callaway was appropriate for PE4710 material.

In the more than five years since the commitment was made to evaluate evolution of the fusion technique, extensive testing performed at Callaway and by the industry has reaffirmed applicability of the technique used during the project on 36DR9.5 piping consisting of PE4710 material. In addition, there have been no test results, no incidents in the industry, and no other evidence that would otherwise indicate non-suitability of the fusion technique applied at Callaway.

Conclusion (3): Structural integrity ofthe installed fusion joints in 36DR9.5 piping consisting of PE4710 material has been validated by test and experience.

[3] The results of the evaluations will be submitted to the NRC prior to submittal of Callaway's fourth 10-year interval/51 plan, and will include, if necessary, a fourth 10-year IS/ interval alternative request.

The above results are being submitted to the NRC prior to the submittal of Callaway's fourth 10-year interval lSI plan.

Pursuant to 10 CFR 50.55a(a)(3)(i), in lieu of the requirement of Section XIIWA- 4221(b)(1), this alternative to the original Construction Code provides an acceptable level of quality and safety for repair/replacement activities for ASME Class 3 buried piping.

6. Duration of Proposed Alternative The use of the proposed alternative is requested for the remaining life of the Callaway Plant, Unit 1, including plant life extension that has been sought through October 18, 2044.
7. Precedents (Optional)

The alternative to use HDPE piping in Callaway's ESW system was previously proposed in Relief Request 13R-10 submitted to the NRC via AmerenUE Letter ULNRC-05434 dated August 30, 2007, and was approved by NRC letter dated October 31, 2008, as supplemented by NRC letter dated November 7, 2008 (TAC No. MD6792).

to ULNRC-06115 Page 6 of6

8. References (Optional)

Tensile Stress-Strain Properties and Elastic Modulus of P£4710 Cell Classification 445574C High Density Polyethylene Pipe Material, EPRI, Palo Alto, CA: 2012. Technical Report 1025254.

Plastics Pipe Institute, TR-3, "Policies and Procedures for Developing Hydrostatic Design Basis (HDB),

Pressure Design Basis (PDB), Strength Design Basis (SDB), and Minimum Required Strength (MRS)

Ratings for Thermoplastic Piping Materials or Pipe" Summary of test data for Callaway PE4710 resin submitted by DOW Chemical to PPI for ISO 9080 CRS Listing, and transmitted by J. Zhou to J. E. O'Sullivan of Procon1, LLC, on January 22, 2014.

Plastics Pipe Institute, TR-33/2001, "Generic Butt Fusion Joining Procedure for Field Joining of Polyethylene Pipe."

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