WM 04-0032, 10 CFR 50.55a Request for Alternative Requirements for ASME Class 1 Items Connected to the Upper Portion (Steam Side) of the Pressurizer
| ML043140268 | |
| Person / Time | |
|---|---|
| Site: | Wolf Creek  |
| Issue date: | 11/02/2004 |
| From: | Muench R Wolf Creek |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| WM 04-0032 | |
| Download: ML043140268 (10) | |
Text
- WELF CREEK 'NUCLEAR OPERATING CORPORATION November 2, 2004 Richard A. Muench President and Chief Executive Officer WM 04-0032 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555
Subject:
Docket 50-482: 10 CFR 50.55a Request for Alternative Requirements for ASME Class 1 Items Connected to the Upper Portion (Steam Side) of the Pressurizer Gentlemen:
Pursuant to 10 CFR 50.55a(a)(3)(ii), Wolf Creek Nuclear Operating Corporation (WCNOC) requests approval of an alternative to certain ASME Boiler and Pressure Vessel Code, Section Ill requirements applicable to portions of the reactor coolant pressure boundary connected to the upper portion (steam side) of the pressurizer at the Wolf Creek Generating Station (WCGS). The proposed alternative is to allow certain piping and instrument lines, valves and supports to remain as designed and constructed to ASME Code Class 2 in lieu of upgrading the current design configuration and replacing these items with items constructed to ASME Section IlIl Subsection NB, Code Class 1 requirements.
Westinghouse Nuclear Safety Advisory Letter (NSAL), NSAL-00-006, "Pressurizer Upper Level Instrument Line Safety Classification," identified an issue regarding the safety classification of the pressurizer upper level instrument lines. The NSAL indicates that a break in an instrument line for the upper portion (steam side) of the pressurizer level instrumentation may result in a rapid depressurization of the Reactor Coolant System (RCS) sufficient to cause an Emergency Core Cooling System (ECCS) actuation. -This condition is inconsistent with the existing classification of the line as Safety Class 2. Specifically, a break in an instrument line connected to the pressurizer that results in an ECCS actuation should be classified as Safety Class 1 in accordance with ANSI N18.2 and 10 CFR 50.55a(c).
The basis supporting this 10 CFR 50.55a request is provided in the Attachment to this submittal. No commitments are identified in this submittal.
The replacement of the affected piping, tubing, valves and supports to ASME Boiler and Pressure Vessel Code, Section 1II,Class 1 requirements would be a hardship or unusual difficulty because the scope of the change would require substantial time and resources to upgrade plant design configuration and perform plant modification work to replace the affected items. WCNOC believes that upgrading of plant design configuration and replacement of the affected items would provide minimal safety benefit. Additionally, a modification of this type P.O. Box 411 / Burlington. KS 66839 1 Phone: (620) 364-8831.
An Equal Opportunity Employer M,'F/HCNVET
WM 04-0032 Page 2 of 2 would be costly in time, materials, personnel radiation exposure, and radioactive waste, and would not result in a compensating increase in the level of quality or safety.
If you have any questions concerning this matter, please contact me at (620) 364-4000 or Mr.
Kevin Moles at (620) 364-4126.
Sincerely, Richard . Muench RAM/rIg Attachment cc: J. N. Donohew (NRC), w/a D. N. Graves (NRC), w/a B. S. Mallett (NRC), w/a Senior Resident Inspector (NRC), w/a
Attachment to WM 04-0032 Page 1 of 8 10 CFR 50.55a Request Proposed Alternative In Accordance with 10 CFR 50.55a(a)(3)(ii)
-Hardship or Unusual Difficulty without Compensating Increase in Level of Quality or Safety--
- 1. ASME Code Component(s) Affected:
This request is for installed ASME Boiler and Pressure Vessel Code,Section III, Class 2 portions of the Reactor Coolant System (BB) and the Nuclear Sampling System (SJ),
including piping and instrument lines, valves and supports, connected to the pressurizer above the normal water level in the pressurizer. These piping and instrument lines and valves are shown on Piping and Instrumentation Drawing (P&ID) M-12BB02 (Updated Safety Analysis Report (USAR) Figure 5.1-1, Sheet 2), for the Reactor Coolant System (RCS), and on P&ID M-12SJ01 (USAR Figure 9.3-2, Sheet 1), for the Nuclear Sampling System. The items affected include: 1) approximately 540 feet of small bore piping and instrument tubing, 2) approximately 120 piping and tubing supports, and 3) 27 valves.
The instruments connected beyond the instrument manifold valves are not within the scope of the ASME Boiler and Pressure Vessel Code,Section III, rules as specified in Section 1II,paragraph NA-1130(c) and, therefore, are not included in the scope of this request.
The piping and instrument lines affected are described and listed below:
Piping from the three pressurizer upper instrumentation taps to the root valves, boundary valves and tubing downstream to the instrument manifold valves. (M-12BB02, Location D-7, C-7, C-6)
The pressurizer safety valve loop seal drain lines up to each boundary valve. (M-12BB02, Location G-7, G-6, G-5)
The piping from the tap in the pressurizer relief line BB-082-BCA-6", to the boundary valve in the pressurizer high point vent line (M-12BB02, Location E-7), and line BB-083-BCB-3/4" to pressurizer fill and vent valve BBV0085 (M-12BB02, Location F-7). It also includes the branch from BB-083-BCB-3/4" to the Nuclear Sampling System shown on drawing M-12SJ01 at Location G-7. This branch line extends to and includes the containment isolation valves for the pressurizer steam space sample line.
Attachment to WM 04-0032 Page 2 of 8 10 CFR 50.55a Request The lines and valves discussed above are tabulated below. The instrument manifold valve located at each instrument does not actually have an assigned number and is identified in the table by the associated instrument identification number.
P&ID Drawing: M-12BB02 DWG. Line(s) Root Valve Boundary Valves Location & Instrument Manifold Valves D-7 BB-111 -BCB-3/4" (piping) with BB-V0099 BB-VO100 1-1/2"x3/4" Reducer insert, BB-PT0455 Condensate Pot and 3/8" BB-LT0459 tubing (0.065" thickness)
C-7 BB-1 12-BCB-3/4" (piping) with BB-V0102 BB-V0103 1-112"x3/4" Reducer insert, BB-PT0456 Condensate Pot and 3/8" BB-LT0460 tubing (0.065" thickness)
C-6 BB-115-BCB-314" (piping) with BB-VO108 BB-VO110 1-1/2"x3/4" Reducer insert, BB-PT0457 Condensate Pot and 3/8" BB-PT0458 tubing (0.065" thickness) BB-LT0461 BB-LT0462 G-7 BB-088-BCB-3/4" (piping) BB-V0087 N/A G-6 BB-090-BCB-3/4" (piping) BB-V0088 N/A G-5 BB-092-BCB-3/4" (piping) BB-V0089 N/A E-7 BB-082-BCB-3/4" (piping) BB-V0295 N/A F-7 BB-083-BCB-3/4" (piping) BB-V0085 N/A F-7 BB-098-BCB-3/4" (piping) BB-V0086 N/A P&ID Drawing: M-12SJO0 DWG. Line(s) Root Valve Boundary Valves Location & Instrument Manifold Valves G-7 thru 3/8" tubing (0.065" thickness) BB-V0086 SJ-V0009 E-7 SJ-002-BCB-1" (piping) SJ-V0071 SJ-HV0013
04-0032 Attachment to WM Attachment to WM 04-0032 Page 3 of 8 10 CFR 50.55a Request
- 2. Applicable Code Edition and Addenda The piping, tubing, valves and supports identified in Part I of this request were designed, constructed and installed to a variety of editions and addenda of the ASME Boiler and Pressure Vessel Code, Section IlIl (referred to asSection III throughout the remainder of this request), depending on the applicable governing Design Specification. These editions and addenda range from the 1974 Edition with the Winter 1974 Addenda through the 1977 Edition. Additional specific provisions from later editions and addenda are also used as specified in the applicable Design Specification. Piping and tubing stress analysis performed by the site architectlengineer (Bechtel) was primarily to the 1974 Edition with Winter 1974 Addenda while the piping analysis performed by the NSSS designer (Westinghouse) was primarily to the 1974 Edition with the Winter 1975 Addenda. Site installation of these items was primarily to the 1974 Edition with Summer 1975 Addenda.
- 3. Applicable Code Requirement 10 CFR 50.55a(c) states, in part:
"(c) Reactor coolant pressure boundary.
(1) Components -which are part of the reactor coolant pressure boundary must meet the requirements for Class 1 components in Section 1114,5 of the ASME Boiler and Pressure Vessel Code, except as provided in paragraphs (c)(2), (c)(3), and (c)(4) of this section.
(2) Components which are connected to the reactor coolant system and are part of the reactor coolant pressure boundary as defined in §50.2 need not meet the requirements of paragraph (c)(1) of this section, Provided:
(i) In the event of postulated failure of the component during normal reactor operation, the reactor can be shut down and cooled down in an orderly manner, assuming makeup is provided by the reactor coolant makeup system; or"Section III paragraph NA-2110(c) requires that the Owner of a nuclear power plant, or his agent, shall be responsible for applying system safety criteria to classify the equipment in the nuclear power plant to be constructed in accordance with the rules of NA-2120 and NA-2130.
Section III paragraph NA-2120 states:
"Construction rules are specified for items which are designated Code Classes 1, 2, 3, CS, and MC. These Code classes are intended to be applied to the classification of items of a nuclear power system and containment system. Within these systems the Code recognizes the
Attachment to WM 04-0032 Page 4 of 8 10 CFR 50.55a Request different levels of importance associated with the function of each item as related to the safe operation of the nuclear power plant. The Code classes allow a choice of rules that provide assurance of structural integrity and quality commensurate with the relative importance assigned to the individual items of the nuclear power plant."
Section III paragraph NA-2131 requires that Class 1 items be constructed in accordance with the rules of Subsection NB.
- 4. Reason for Request Westinghouse Nuclear Safety Advisory Letter (NSAL), NSAL-00-006, "Pressurizer Upper Level Instrument Line Safety Classification," was issued April 3, 2000. This letter identified an issue where a break in an instrument line for the upper portion (steam side) of the pressurizer level instrument may result in a rapid depressurization of the RCS sufficient to cause an Emergency Core Cooling System (ECCS) actuation based on low pressurizer pressure. This condition is inconsistent with the existing classification of the line as Safety Class 2. Specifically, a break in an instrument line connected to the pressurizer that results in an ECCS actuation should be classified as Safety Class 1 in accordance with ANSI N18.2 and 10 CFR 50.55a(c).
This safety classification conflicts with the Class 2 classification of the pressurizer instrument lines originally provided by Westinghouse at the time of original design and licensing. This situation is the result of a change in Westinghouse design. In earlier Westinghouse designs, ECCS actuation would only occur with coincident low pressurizer level and low pressurizer pressure. Post Three Mile Island requirements only require low pressurizer pressure for ECCS actuation. The effect of this change was not addressed when Westinghouse made the change in the Reactor Protection System.
After review of the NSAL, ANSI N18.2, and the regulatory requirements, Wolf Creek Nuclear Operating Corporation (WCNOC) has concurred with the identified issue. The review performed by WCNOC also concluded that the scope applies to all Class 2 lines connected to the pressurizer steam space.
The affected piping, tubing, valves and supports at Wolf Creek Generating Station (WCGS), in Part 1 of this request, were designed and constructed as Class 2 in accordance with the rules of ASME Section III, Subsection NC. Replacing the affected piping, tubing, valves and supports to fully comply with ASME Section III Class 1 requirements would be a hardship or unusual difficulty because the scope of the change would require substantial resources. The estimated time for the potential removal and re-installation of approximately 540 feet of small bore piping and instrument tubing, 27 valves, and approximately 120 piping and tubing supports would be approximately 11,000 man-hours. The estimated additional engineering man-hours for upgrading the design configuration and issuing design change packages would be approximately 1,500 man-hours. This estimate does not include the considerable material cost associated with replacing ASME Class 2 components and materials with ASME Class 1
Attachment to WM 04-0032 Page 5 of 8 10 CFR 50.55a Request components and materials nor does it consider the additional radiation exposure that would be experienced during this process. Because of the location of the piping, tubing, valves and supports, the work could only be done during refueling outages.
Therefore, upgrading the current design configuration and replacing piping, tubing, valves and supports would be a hardship or unusual difficulty. As concluded in Part 5 of this request, replacing the affected items would not result in a compensating increase in the level of quality or safety.
- 5. Proposed Alternative and Basis for Use The proposed alternative is to allow the piping and instrument lines, valves and supports identified in Part 1 to remain as designed and constructed to ASME Code Class 2 in lieu of upgrading the current design configuration and replacing these items with items constructed to ASME Section III Subsection NB, Code Class 1 requirements. The basis for use of this proposed alternative in lieu of meeting ASME Section IlIl, Subsection NB, Code Class 1 is presented in the following paragraphs.
The piping, tubing and valves listed in Part I of this request were constructed as Class 2 in accordance with the rules of ASME Section 1II,Subsection NC. Supports of the subject piping and tubing lines were constructed as Class 2 in accordance with the rules of ASME Section III, Subsection NF. Construction as used in Section III Division 1 included requirements for materials, design, fabrication, examination, testing, inspection, and certification required in the manufacture and installation of items.
Although the items listed in Part 1 do meet most of the Section III requirements for Class I items, they do not meet all Section III requirements for Class 1 items and because compliance with 10 CFR 50.55a(c)(1) would require that the items meet all the requirements, these items can not be upgraded. For example, the valves do not meet the component certification requirements of Section 1I1,which require that a valve be stamped by an appropriate ASME Certificate Holder with the Class 1 identification mark and be certified by an appropriate ASME Certificate Holder on the Section III Code Data Report (Form NPV-1) as being in full compliance with Class 1 requirements.
To justify the proposed altemative, a comparison was made between the Section III requirements in Subsection NB for Class 1 and Subsection NC for Class 2 for the applicable editions and addenda described in Part 2. The comparison looked at each Article of Subsections NB and NC (covering the areas of materials, design, fabrication and installation, examination, testing, protection against overpressure, and nameplates, stamping and reports) and determined whether the differences were technical, quality or administrative requirements. Differences in Section III administrative requirements, such as certification and stamping, furnishing of a Stress Report, marking of items, etc.,
although affecting literal compliance, were determined to not reduce the quality or safety of the items. There were few differences in quality requirements between Class 1 and
Attachment to WM 04-0032 Page 6 of 8 10 CFR 50.55a Request Class 2 because most quality requirements are contained in the General Requirements Subsection NA and are equally applicable to both Class I and Class 2. No differences in quality requirements were identified that would reduce the quality or safety of the items.
For the items identified in Part 1 of this request, there were some differences in technical requirements between Class 1 and Class 2 in the areas of piping and tubing material examination (NB/NC-2510), valve design (NB/NC-3500), piping design (NB/NC-3600), examination of circumferential piping butt welds (NBINC-5220), and examination of springs in Class 1 component standard supports (NF-5410). However, replacing the affected items would provide minimal increase in quality and safety, as demonstrated in the following paragraphs discussing the technical requirement differences.
Material Examinations and Piping Design Inthe area of piping and tubing material examinations and piping design, the differences between the current installed Class 2 items and the Class 1 requirements could be eliminated by updating the applicable Design Specifications to include provisions from later editions and addenda of Section III that have been approved for use in 10 CFR 50.55a. For piping and tubing material examination, the later provisions of NB-2510(a) in the Summer 1983 Addenda exempted 1" and less seamless pipe, tubes and fittings from the examination requirements of NB-2500, thus making the Class 1 rules the same as Class 2 and eliminating the technical difference. WCNOC has previously incorporated this later provision in the Design Specification for replacement piping materials, but has not incorporated this provision into the Design Specification for instrument tubing and fittings. For piping design, there are considerable differences between Class I and Class 2 requirements but these differences were eliminated by the Summer 1975 Addenda change in NB-3630(d). This change allowed 1" and smaller Class 1 piping to be designed to NC-3600, thus making the Class I design rules the same as Class 2 and eliminating the technical differences. The NRC in 10 CFR 50.55a accepted the Summer 1983 Addenda containing these material examination provisions and the Summer 1975 Addenda containing these piping design provisions. If the design and construction had used the later NRC accepted addenda, the Class 2 installed configuration would meet Class 1 material examination and piping design requirements.
No increase in quality or safety would be realized by updating these Design Specifications or in upgrading the design configuration and replacing piping and tubing.
Valve Design In the area of valve design, the requirements in NB-3500 are considerably different than the requirements in NC-3500. However, the small valves identified in Part 1 of this request have been evaluated to the applicable requirements in NB-3500 and all the valves were found to meet the technical requirements of NB-3500 applicable to small valves. Therefore, there are no technical differences between the installed Class 2 valves and the requirements for Class 1 valves that would reduce the assurance that the valves will perform their intended safety function. No increase in quality and safety
Attachment to WM 04-0032 Page 7 of 8 10 CFR 50.55a Request would be realized by 'replacing the valves with i6al'es constructed to Class 1 requirements.
Examination of Circumferential Piping Butt Welds In the area of examination of circumferential piping butt welds, NB-5220 requires radiograph and surface examination of circumferential piping butt welds. NC-5222 requires radiograph only of these welds. The radiographs and surface exams in Class 1 assure volumetric quality of the welds and surface quality of the welds. Surface quality of the welds in Class 1 is to be verified because of Class 1 fatigue considerations and the design by analysis approach in Class 1 that reduces the design factor from 4 to 3.
Class 2 does not require the additional surface examinations of these welds because of its design by rule approach, which does not have specific fatigue requirements.
Because NB-3630(d) allows 1" and less Class 1 piping and tubing to be designed to Class 2 rules, the reduced design factor of 3 is not used, fatigue evaluation is not required, and special concern with surface quality in addition to volumetric quality is essentially eliminated. Therefore, the Class I requirement for surface examination of these welds will provide minimal increase in quality and safety. The use of Class 2 piping examination rules provide adequate assurance that these welds will perform their intended safety function of passive pressure boundary integrity.
Examination of Sprin-ls in Class 1 Supports In the area of examination of springs in component standard supports, NF-5410 states that springs in Class 1 component standard supports shall be examined by a surface examination. No such examination requirement exists for Class 2 springs in component standard supports. For branch line BB-098-BCB-3/4" to the Nuclear Sampling System tubing before valve BB-V0086, there is a Subsection NF Class 2 constant support (BB13-H510) containing a spring. As a Class 2 support, this spring did not receive a surface examination. This is a technical difference between the installed Class 2 support and the Class 1 requirements. However, the maximum load on this constant support during any loading condition is only 42 pounds, while the constant support was load rated by the manufacturer at 130 pounds in accordance with Subsection NF requirements, thus providing considerable margin in the function of the support. Not having received the surface examination may result in a minimal reduction in the quality and safety of the constant support; however, the support can be expected to perform its intended safety function based on the margin in available loading.
Conclusion From the preceding discussions, it is concluded that for the piping, tubing, and valves listed in Part I of this request, including their supports, the technical, quality and administrative differences between the Section III requirements for Class 1 and Class 2 construction would have minimal impact on the ability of these items to perform their intended safety function. However, even if a break failure should occur, the consequences of such an event would be bounded by the design-basis small break loss-of-coolant accident event for WCGS, which would be mitigated by the ECCS.
I,. , ; !I ; .i~
Attachment to WM 04-0032 Page 8 of 8 10 CFR 50.55a Request As demonstrated in Part 4 of this request, upgrading of the current design configuration and replacing the affected piping, tubing, valves and supports with items fully meeting Class 1 in accordance with Section l1l, Subsection NB would be a hardship or unusual difficulty. As demonstrated in this part, upgrading the current design configuration and replacing the affected piping, tubing, valves, and supports would provide minimal quality and safety benefit. Therefore, in accordance with 10 CFR 50.55a(a)(3)(ii), the basis for the proposed alternative demonstrates that compliance with Class 1 requirements of ASME Section III Subsection NB would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety.
- 6. Duration of Proposed Alternative WCNOC requests approval of the alternative proposed in Part 5 of this request for the life of the plant. No undue risk to the public health and safety is presented by this request.
- 7. Precedents Comanche Peak Steam Electric Station Letter, dated September 30, 2002, to USNRC:
Docket Nos. 50-445 and 50-446, "Relief Request A-2 for Unit I and A-9 for Unit 2 Relief from 10 CFR 50.55a Requirements for Class 1," and the associated NRC Safety Evaluation Report (SER) dated April14, 2003.
- 8. References Westinghouse Nuclear Safety Advisory Letter (NSAL-00-006), "Pressurizer Upper Level Instrument Line Safety Classification," dated April 3, 2000.