ML25142A364
| ML25142A364 | |
| Person / Time | |
|---|---|
| Site: | North Carolina State University |
| Issue date: | 05/22/2025 |
| From: | Hawari A North Carolina State University |
| To: | Office of Nuclear Reactor Regulation, Document Control Desk |
| References | |
| Download: ML25142A364 (1) | |
Text
College of Engineering Department or Nuclear Engineering Nuclear Reactor Program www.ne.ncsu.edu/nrp Campus Box 7909 2500 Stinson Drive Raleigh, NC 27695-7909 P: 919.515.7294 May 22, 2025 U.S. Nuclear Regulatory Commission Document Control Desk Washington, DC SUBJECT RESPONSE RESUBMITTAL TO THE REQUEST FOR ADDITIONAL INFORMATION FOR 297-NC STATE LICENSE RENEWAL AND POWER UPRATE RAI-10462-R1 License No. R-120 Docket No. 50-297 Please find enclosed a response to the Request for Additional Information for the License Renewal Request and Power Uprate related to the construction and condition of the reactor coolant systems and associated quality assurance.
If you have any questions regarding this amendment or require additional information, please contact Austin Wells (ajwells2@ncsu.edu) or by phone at (919) 515-3347.
I declare under penalty of perjury that the forgoing is true and correct. Executed on 22 May 2025.
Sincerely, Ayman I. Hawari, Ph.D.
Director, Nuclear Reactor Program North Carolina State University
Enclosures:
Resubmittal - Response to Request for Additional Information Sincerely, Ay A man I. Hawari, Ph.D.
Nuclear Reactor Program 1 l11 RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION FOR 297-NC STATE LICENSE RENEWAL AND POWER UPRATE RAI-10462-R1 NORTH CAROLINA STATE UNIVERSITY AT RALEIGH LICENSE NO. R-120; DOCKET NO. 50-297 MAY 22, 2025
- 1. Degradation of the NCSU PULSTAR reactor, the reactor coolant systems, and associated components is a function of time, pressure, temperature, and stress. The NCSU PULSTAR operates at atmospheric pressure (SAR 4.3) and nominal pool temperature of 70 °F-105°F (SAR Table 4-9) and therefore these factors in a reactor environment are not significant.
However, the reactor and its systems have been in service for approximately 60 years and the NRC staff need reasonable assurance of its continued operability and reliability, e.g., that the chances of a pipe failure and material degradation are highly unlikely, to allow the NRC staff to make a determination that these components and materials are not highly susceptible to failure over time.
The specific issues that are raised in relation to this question are discussed below.
I.
Provide a detailed description of the NCSU PULSTAR reactor coolant system to include information such as:
A. Joint designs and related specifications.
B. Pipe diameter and wall thickness (nominal and any measurements since installation, if performed).
C. All welding information such as material classification, material type and weld inspection records from original construction.
D. All piping, fittings, and valves primary material specifications and material type.
E. Design and any related specifications for all piping supports.
II.
Provide diagrams/drawings that shows all locations where the piping system penetrates the NCSU PULSTAR reactor pool and any other structures (such as walls and piping supports).
III.
Provide any history of deviation from the specified NCSU PULSTAR reactor pool water chemistry limits and operating temperature and the corrective action taken.
RESPONSE
All piping sizes, locations of transitions between schedules, locations of transitions between original and upgraded piping, and locations of valves, instrumentation, and supports are shown in Figure 1.
Nuclear Reactor Program 2 l11 I-A. Joint Design and Related Specifications: Original welds in the primary loop were pressure tested to 200 psi for 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br />, liquid penetrant tested, and radiographically examined under relevant codes and specifications [1][2][3].
All upgraded welds in the primary loop were visually inspected and pressure tested under relevant codes and specifications, with the welds on the 16N tanks visually inspected and pressure tested under associated vessel codes and specifications [4][5]. All upgraded threaded and welded pipe joints were completed in accordance with the applicable standards
[6][7].
I-B. Pipe Diameter and Wall Thickness: As shown in Figure 1, all piping located in the Mechanical Equipment Room (MER) is Schedule 10, transitioning to Schedule 40 when entering and leaving the Primary Piping Vault (PPV), and remaining Schedule 40 when routing to and from the reactor pool. Primary piping has a 10 in. diameter with 6 in. and 8 in. diameter sections immediately prior to and after the primary pump and heat exchanger. Piping diameters are labeled in Fig. 1.
I-C. Welding Information: Material classification and material type of original welds present in the primary system follow ASME Sec VIII [1968] parts UNF or UHA as applicable [3].
Material classification and material type of upgraded welds present in the primary system follow B31.1 [2010] [4]. Welds for the original and upgraded piping were performed by qualified welders and procedures [4][8].
I-D. Material Specifications and Material Type: Upgraded primary piping, fittings, flanges, and vessels are 304L, upgraded valves P-1A and P-3 are cast 316 (CF8M), and upgraded instrument weldolets, drains, and vents 2-1/2 or smaller are 316. Original piping and fittings are 304L, original lap-joint flanges interfacing with original valves P-1, P-2, and P-5 are 304L with A181 G1-2 flange rings, original flanges interfacing with P-4 are 304, and original valves are cast 304 (CF8).
All original piping, fittings, joints, and valves were inspected and found to meet all applicable quality standards [1][2][3]. Original valves (P-1, P-4, and P-5) comply with applicable standards [9][10][11].
All upgraded piping, fittings, joints, and valves were fabricated, installed, and inspected according to the code of construction and relevant standards [4][12][6][13][14][15]16][17].
I-E. Piping Support Design and Specifications: All piping supports (stands and hangers) were manufactured and replaced as part of the 2013 upgrade in accordance with applicable standards [4][18][19][20]. The locations of these supports are notated in Fig. 1 as PS-XX.
I-Supplemental: Primary Cooling Loop valves P-1 through P-5 are manually actuated gate valves which are visually inspected and actuated semiannually according to surveillance procedure PS-3-01-9:S1. During the visual inspection of the valves, the surrounding area and piping are also visually inspected. Operation of the valves is performed locally by means of a handwheel (P-5) or ratchet wrench (P-1) connected to the valve stem by an extension, which penetrates the concrete shielding blocks covering the valve pit (visible in the rear of the Valve Pit in Figure 2). P-1 and P-5 are cycled as a part of the semiannual maintenance and as required for general maintenance.
Nuclear Reactor Program 3 l11 II. Piping Penetrations: Figure 1 shows all locations where the piping system penetrates the NCSU PULSTAR reactor pool. Penetrations in the reactor pool and embedded piping sections are described in SAR Chapter 5. All other penetrations are wall penetrations; all wall penetrations have 1 in. radial clearance between the section of piping and the surrounding concrete. As such, wall penetrations do not offer structural support. When the piping initially transitions from the PPV to the MER, as well as when it returns to the PPV after moving through the primary pump and heat exchanger, the piping penetrates the wall of the MER/PPV. Penetrations also exist immediately preceding and following connections to the delay tanks, through the shielding wall within the PPV.
Penetrations in the reactor pool and embedded piping sections are described in SAR Chapter
- 5. The shaded material underneath the reactor pool in Figure 1 is the reinforced concrete foot casting of the reactor pool and biological shield. This foot casting has a total vertical thickness of 5 feet, with the embedded piping centerline located 1-9 from the base. This gives an approximate minimum thickness below and above the piping of 16 and 331/4 respectively.
The primary piping is embedded in the concrete foot casting and the biological shield between the base of the pool liner and the south face of the foot casting, where the pipe emerges into the valve pit. In the valve pit, the piping is immediately joined to the P-1 or P-5 valves. P-1 and P-5 are lap-jointed flanged valves secured to the primary piping by a bolted connection on both sides. They are mechanically supported by the short length of piping which extends from the foot casting to the valve flange, shown on the left side of Figure 2.
Primary piping penetrates the pool liner for supply and return as shown in Figure 1. These penetrations utilize Al-SS couplings to transition between the stainless steel piping, through the aluminum pool liner, and to aluminum piping located within the reactor pool. See Figure 3 for a detail drawing of this transition.
III. Pool Water Chemistry and Temperature: Per NCSU PULSTAR monitoring procedures of pH and resistivity, pool water chemistry is continually under surveillance. Reactor pool water temperature is constantly monitored via temperature probes. Based on these measurements, no documented history of deviation from specified reactor pool water chemistry limits or pool water temperatures has been observed.
Nuclear Reactor Program 4 l11 Figure 1. PULSTAR Reactor Primary Piping Schematic
Nuclear Reactor Program 5 l11 Figure 2. Valve Pit and View of P-1 and P-5 P-5 P-1 Valve Stem Extension
Nuclear Reactor Program 6 l11 Figure 3. Pool Liner Penetration Detail
Nuclear Reactor Program 7 l11
- 2. Although a Certified Material Test Report (CMTR) is not required for a Non-Power Production and Utilization Facility (NPUF), provide an equivalent written report or an equivalent quality assurance (QA) documentation that contains data and information that attests to the actual physical and chemical properties of the primary coolant system piping, fittings, and weld materials.
RESPONSE
Original welds in the primary loop were pressure tested to 200 psi for 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br />, liquid penetrant tested, and radiographically examined [1][2][3]. The primary loop was verified by the Atlanta Region of AEC Compliance Office in June 1971. These inspections designated no deviations from the standards for the primary coolant system.
All upgraded welds in the primary loop were visually inspected and received non-destructive testing according to the code of construction [4][5]. No deviations were noted with respect to the upgraded sections of the primary coolant system.
Nuclear Reactor Program 8 l11
- 3. Describe in detail any degradation of piping materials that is known or suspected to have occurred in the NCSU PULSTAR reactor. Discuss any other recurrence of this type of material degradation at other research and test reactors, if known, and how they apply to the NCSU PULSTAR reactor.
RESPONSE
No known piping degradation has been documented or is suspected. All piping between P-1 and P-5 (see Figure 1) is accessible and is visually inspected semiannually according to surveillance procedure PS-3-01-8:S1. Additionally, a visual inspection of key areas, such as in the mechanical equipment room (MER) and major components such as the primary pump and heat exchanger, is performed as part of each startup checklist. Primary Cooling Loop valves P-1 through P-5 are visually inspected and actuated semiannually according to surveillance procedure PS-3-01-9:S1. The primary piping at the transition from the biological shield foot to the valve pit has been inspected and verified to be in good condition. No evidence of deformation or degradation at this, or any point in the primary piping, has been found.
A minor leak from the primary cooling loop was detected in 1993 and determined to originate from the N-16 delay tank. The delay tank (at this time buried underground) was excavated, inspected, and hydrostatically tested, failing below its design pressure. A defective weld was identified as the root cause. A new delay tank of the same design was fabricated, tested satisfactorily according to the original quality standards, and installed in a newly constructed piping vault. This piping vault completely encloses all previously buried portions of the primary cooling system and provides access for inspection and maintenance while preventing soil-structure interaction. The new delay tank exhibited no degradation or deterioration during its lifetime and was replaced by the three-tank system installed as part of the power upgrade in 2013.
Nuclear Reactor Program 9 l11
- 4. The NCSU PULSTAR reactor primary coolant system is comprised of the reactor pool and liner, the 16 N delay tanks, the primary pump, the heat exchanger, a purification loop and associated piping (SAR 5.2). The primary coolant loop is modeled with primary components including the 16 N decay tank, coolant pump, heat exchanger and pipes connecting the components (SAR 4.6.2.1). Provide the frequency of the primary coolant loop utilization during reactor operation. Specify in your response the frequency when the primary coolant loop line has operated with:
- a. No water flow (not in use).
- b. Low water flow.
- c. Stagnant water flow.
RESPONSE
The primary coolant system is operated at a nominal flow rate of 500 gpm during reactor operation. Brief operations with natural circulation cooling are performed infrequently for educational labs (approx. twice per year) during which minimal flow is present in the primary coolant loop. Operations under natural convection cooling are permitted by the technical specifications and procedurally limited to 100 kW. Outside of natural convection operations, there are no operating conditions under which stagnant, low, or no water flow conditions occur.
Nuclear Reactor Program 10 l11
- 5. A "code of construction," also commonly referred to as a "building code," is a set of regulations established by local or state governments that define minimum standards for the design and construction of buildings, aiming to protect public health and safety by ensuring structures meet requirements for structural integrity, fire safety, plumbing, electrical systems, and accessibility features. Provide the "code of construction/building code(s)" used for the NCSU PULSTAR reactor pool and the primary coolant loop if different from the references given in SAR 3.1.3 and SAR 3.1.5.
RESPONSE
The standards for the construction and inspection of the original reactor facility presented in SAR Section 3 accurately describe the construction of the original reactor facility.
Additionally, sections of the primary coolant system replaced or modified during the 2013 power upgrade were constructed under ICC IBC-2011.
Nuclear Reactor Program 11 l11 Reference for Standards Applied to PULSTAR Construction:
- 1. ASTM #165-60T [1960]
- 2. ASTM E142-59T [1964]
- 4. ASME/ANSI B31.1 [2010]
- 6. ASME B-1.20.1 [1983 (R2006)]
- 7. ASME/ANSI B-16.25 [2012]
- 8. AWS D1.1/D1.1M [2010]
- 9. ASA B16.10 [1957, Face-to-Face and End-to-End Dimensions of Ferrous Valves]
- 10. ASA B16.5 [1968, Steel Pipe Flanges and Flanged Fittings]
- 11. MSS SP-42 [1959, Corrosion Resistant Gate, Globe, Angle, and Check Valves with Flanged and Butt Weld Ends]
- 12. ASME B16.5 [2009]
- 13. ASME B16.34 [2010]
- 14. ASTM A403 [2012]
- 15. ASTM A-351 [2012b]
- 16. ASTM A-193 [2012b]
- 17. ASTM A-194 [2012a]
- 18. MSS SP-58 [2009]
- 19. MSS SP-89 [2003]
- 20. MSS SP-69 [2003]