NSUF 16-651: Determining Structure Evolution in Isomolded Nuclear Graphite Under Stress
Graphite is an important material for a number of reactor systems and particularly for high temperature gas cooled reactors for which it comprises the bulk of the core material. Under neutron irradiation the graphite microstructure undergoes gross microstructural evolution resulting in similarly large property changes. [1] One area of historic and continuing research is that of irradiation creep of nuclear graphite. This irradiation creep, defined as the difference between the irradiation-induced growth of graphite in a stress-free condition and the irradiation-growth under a stressed condition, is of great technical importance to reactor design. As pointed out by Tsang and Marsden [2] , without the stress relief provided by irradiation creep, failure due to the elastic strain caused by irradiation-induced swelling of graphite would preclude its use. Irradiation creep (an inelastic strain) occurs over essentially all temperature and independently of thermal creep and has been modeled extensively with varying degrees of success. [3] While the classically understood model for dimensional change discusses the competition between inter-plane defect formation and annihilation of internal porosity. As irradiation progresses these internal interfaces and porosity become saturated and the graphite moves from densification into swelling. To date the porosity, or range of porosity of relevance to this mechanism has not been identified. The purpose of this work is to use already irradiated nuclear graphite that has been irradiated with and without an applied stress to map the change in internal porosity in the 0.01 to 10 micron pore range. The period of performance is less than 10 months.
Additional Info
| Field | Value |
|---|---|
| Abstract | Graphite is an important material for a number of reactor systems and particularly for high temperature gas cooled reactors for which it comprises the bulk of the core material. Under neutron irradiation the graphite microstructure undergoes gross microstructural evolution resulting in similarly large property changes. [1] One area of historic and continuing research is that of irradiation creep of nuclear graphite. This irradiation creep, defined as the difference between the irradiation-induced growth of graphite in a stress-free condition and the irradiation-growth under a stressed condition, is of great technical importance to reactor design. As pointed out by Tsang and Marsden [2] , without the stress relief provided by irradiation creep, failure due to the elastic strain caused by irradiation-induced swelling of graphite would preclude its use. Irradiation creep (an inelastic strain) occurs over essentially all temperature and independently of thermal creep and has been modeled extensively with varying degrees of success. [3] While the classically understood model for dimensional change discusses the competition between inter-plane defect formation and annihilation of internal porosity. As irradiation progresses these internal interfaces and porosity become saturated and the graphite moves from densification into swelling. To date the porosity, or range of porosity of relevance to this mechanism has not been identified. The purpose of this work is to use already irradiated nuclear graphite that has been irradiated with and without an applied stress to map the change in internal porosity in the 0.01 to 10 micron pore range. The period of performance is less than 10 months. |
| Award Announced Date | 2016-04-11T00:00:00 |
| Awarded Institution | None |
| Facility | None |
| Facility Tech Lead | Gordon Kohse |
| Irradiation Facility | None |
| PI | Lance Snead |
| PI Email | [email protected] |
| Project Type | RTE |
| RTE Number | 651 |