ML25027A415
| ML25027A415 | |
| Person / Time | |
|---|---|
| Site: | Dresden  |
| Issue date: | 01/27/2025 |
| From: | Amitava Ghosh NRC/NRR/DEX/ESEB |
| To: | |
| References | |
| Download: ML25027A415 (4) | |
Text
1 ASSESSMENT OF POTENTIAL HAZARDS FROM THE THREE RIVERS PIPELINE TO THE DRESDEN POWER STATION UNITS 1 AND 2-REDUCED DISTANCE TO THE METEOROLOGICAL TOWER AND PRESENCE OF THE PIPE MANIFOLD This assessment of potential hazards to the Dresden Power Station Units 1 and 2 (hereafter, Dresden Station) addresses the following scenarios:
- 1. Revised distance to the Meteorological Tower from the assumed location of a hypothetical pipeline rupture
- 2. Hazards posed by the pipeline manifold near the CPV Three Rivers Energy Center.
The staff assessment is given below.
- 1. Revised Distance to the Meteorological Tower The Meteorological Tower is not a safety-related structure at the Dresden Station. Originally, the distance to the Meteorological Tower from the closest point of the Alliance pipeline was assumed to be 1,259 ft. This distance has now revised to be 1,181 ft, a decrease of 78 ft (or a decrease by 6 percent).
Although the closes point of the Three Rivers pipeline is different for assessing the hazards at the nearest plant structure and the control room, the staff has assumed that the distances to these structures have similarly reduced, i.e., the distance are shortened by 78 ft. The revised distance to the nearest plant structure and the control room would be 3,288 ft and 3,623 ft, instead of originally assumed 3,366 ft and 3,701 ft, respectively, a decrease by approximately 2 percent for both.
In this assessment, only the overpressure from a guillotine rupture of the pipeline will be considered. Thermal radiation from a jet fire resulted from sudden rupture of the pipeline was assessed to cause a second degree burn to a human but would not compromise the integrity of the tower.
In this assessment, the staff assumed that it would take 20 minutes to close the isolation valves after the rupture has occurred, although the isolation vales are fitted automated valves that are designed to close in approximately 20 s. Results shown in Table 1 of the original NRC report show that the estimated overpressure at the Meteorological Tower, nearest plant structure, and control room are 0.08 psi, 0.04 psi, and 0.03 psi. They are significantly lower than 1 psi, the threshold suggested in RG 1.91. The staff notes that at this overpressure level, only glass windowpanes are expected to be damaged. In addition, the staff notes that the reactor building at the Dresden Station is designed to withstand a pressure drop of 6 psi from a tornado event.
Being 6 percent closer to the rupture point, the Meteorological Tower is expected to experience a small increase in overpressure, approximately 0.1 psi compared to approximately 0.08 psi estimated originally, significantly less than 1 psi. The nearest plant structure and the control room would experience even smaller increase in overpressure being at larger distances from the rupture point. Therefore, the staff expects that being closer to the assumed rupture point of
2 the pipeline would not result in overpressure levels detrimental to the safety of the plant structures.
- 2. Pipeline Manifold The manifold of the Three Rivers pipeline is near the CPV Three Rivers Energy Center. The location of the manifold is 41° 22 29 N and 88° 16 46 W. The manifold is located approximately 5,000 ft or 1 mi from the Dresden Station (Figure 1). The CPV Three River Energy Center is a 1,250 MW natural gas-fueled electric generation facility and will use the natural gas conveyed by the Three Rivers pipeline.
As can be seen in Figure 2, a portion of the pipeline is above ground and is exposed to open air.
Rest of the pipeline, especially near the Dresden Station, is below ground.
The staff finds that the pipeline near the manifold is most vulnerable to rupture being exposed to open air. Consequently, the vulnerability assessment made assuming a rupture close to the Dresden Station is conservative. As the CPV Three River Energy Center will receive the entire supply of natural gas through the Three Rivers pipeline, the quantity of natural gas released in a hypothetical rupture would be same irrespective of the rupture location. In addition, being further away from the Dresden Station (at least 5,000 ft away compared to 3,366 ft to the nearest plant structure from the assumed rupture location), the staff finds that the overpressure generated from a hypothetical rupture of the pipeline at the manifold location would be smaller at the Dresden Station than that estimated assuming a closer rupture point. The thermal radiation to be experienced by the plant structures would also be smaller because of larger distance.
Figure 1. Approximate location of the manifold with respect to the Dresden Station
3 Figure 2. Manifold under construction near the CPV Three Rivers Energy Center Staff Conclusion The staff, based on above discussion, concludes that although the plant structures are expected to experience a slightly higher overpressure and thermal radiation because of shortened distance to the hypothetical rupture point of the Three Rivers pipeline, the increase is negligible,
4 and the plant structures are not expected to be damaged as the estimated overpressure is below 1 psi.
Assuming the manifold area is most susceptible location of rupture of the pipeline being exposed above ground, the potential for damage to the plant structures from both overpressure and thermal radiation decreases because of larger distance.