NSUF 24-4977: Quantifying gamma irradiation tolerance of high-emissivity coatings on stainless steel
Radiative heat transfer between the reactor vessel outer surface and ex-vessel thermosyphons is a main thermal resistance for the Decay Heat Removal System (DHRS) of the Kairos Power Fluoride-Salt-Cooled High-Temperature Reactor (KP-FHR). The application of high-temperature stable emissivity-enhancing coatings to stainless steel is under investigation for the KP-FHR to improve DHRS performance, reduce system cost, and reduce plant footprint of the system. Selection of emissivity coatings for the KP-FHR has been informed by the concentrating solar power industry, where silicone-based paint-on coatings have been widely used on central receivers. These coatings increase emissivity by a factor of about 4 compared to as-received stainless steel and a factor of 2 compared to stainless steel oxidized at 550°C in air based on in-house testing at Kairos Power. While silicone-based emissivity coatings are effective and very practical to apply, further information on their radiation tolerance is required to qualify their use in nuclear applications since the silicone resin base of the coating is subject to degradation from gamma irradiation.
A gamma irradiation study of two leading paint-on emissivity coatings, HiE-Coat 840MX and Pyromark 2500, at multiple dose levels is proposed to inform whether this class of coating is suitable for nuclear applications. The irradiation will target a maximum dose of 1e9 rad on coated samples, which is above the 1e8 rad threshold where radiation damage to silicone-based thermosetting resin occurs based on previous literature. However, since previous research has shown mineral or glass fillers within silicone resins can increase radiation tolerance by a factor of ten, it is hypothesized that the emissivity-enhancing pigment fillers within HiE-Coat or Pyromark may aid radiation stability compared to silicone alone. Testing HiE-Coat, which has ceramic fillers, and Pyromark, which has graphite and metal oxide fillers, along with samples of each with pigment particles removed will allow determination of whether pigment fillers add radiation resistance and whether one class of filler is more radiation tolerant.
The coating irradiation test is proposed for the Advanced Test Reactor Canal Gamma Irradiation Facility, which is a useful test platform for this work since gamma dose rates cover KP-FHR ranges, total sample dose targets are achievable in reasonable irradiation periods, and neutron activation after testing is negligible allowing for simplified post-irradiation examination. The proposed irradiation will commence during the ATR 174A-1 outage and will be completed in 6 weeks or less, depending on dose rates in the facility. All pre- and post-irradiation characterization will be completed at Kairos Power laboratories. Sample tolerance to gamma irradiation will be quantified based on the following measurements: change in coating surface coverage after irradiation as measured by optical microscopy, change in coating emissivity after irradiation measured with a D&S AE1 Emissometer, change in sample mass, and change in coating thickness. Irradiated samples will also undergo a thermal cycling test program at Kairos laboratories which has been completed for unirradiated samples. If promising results on gamma irradiation tolerance are observed, Kairos Power will continue to develop and qualify high-emissivity coatings for upcoming reactor demonstration projects.
추가 정보
| 필드 | 값 |
|---|---|
| Award Announced Date | 2024-05-28T17:13:12.19 |
| Awarded Institution | Kairos Power LLC |
| Facility Tech Lead | Alina Montrose |
| Irradiation Facility | ATR Canal |
| PI | Kieran Dolan |
| PI Email | [email protected] |
| Project Type | RTE |
| RTE Number | None |