1. Copyright © Toyo Tanso Co., Ltd. All Rights Reserved TECS-14058 Irradiation Program for IG-110 and IG-430 Graphite for Evaluation of High Fluence Behavior E.Kunimoto 1, M.Yamaji 1, T.Konishi 1, Y.Katoh 2, M Snead 2, A.A. Campbell 2, J.Sumita 3, T.Shibata 3 Hangzhou, China, September 15-18, 2014 1. Toyo Tanso Co., Ltd. 2. Oak Ridge National Laboratory 3. Japan Atomic Energy Agency 15th International Nuclear Graphite Specialists Meeting

2. Copyright © Toyo Tanso Co., Ltd. All Rights Reserved 2 Contents 1.Introduction 2.Irradiation schedule 3.Irradiation behavior of IG-110 graphite 4.Irradiation behavior of IG-430 graphite 5.Summary

3. Copyright © Toyo Tanso Co., Ltd. All Rights Reserved 3 1. Introduction -- Japanese draft standard --  Draft standard was already issued by special committee of AESJ (Atomic Energy Society of Japan) (*1)  Composition of draft standard 1. General rules 2. Design standard for graphite components of HTGR 3. Material and product standard for graphite components of HTGR 4. In-service inspection and maintenance standard for graphite components of HTGR  Stress limit and consideration of oxidation,etc. in draft standard  Reasonable interpolation and extrapolation method in draft standard (*1) “Special committee on research on preparation for codes for graphite components in HTGR” (2008.4- 2009.3) Chair: T. Maruyama, Vice-chair: T. Oku Reference ： Expansion of Irradiation Data by Interpolation and Extrapolation for Design of Graphite Components in High Temperature Gas-cooled Reactor, JAEA-Research 2009- 008 ‘ Draft of standard for graphite core components in HTGR ’ (JAEA-Research 2009-042. English version) IG-110 graphite meets the technical criteria decided in the standard. Material property data on IG-110 graphite (including irradiation effects ) are listed in the standard.

4. Copyright © Toyo Tanso Co., Ltd. All Rights Reserved 4 1. Introduction -- Objective-- In the draft standard the interpolation and extrapolation of the design data on IG-110 graphite are carried out, but that should be verified. For that purpose, Toyo Tanso has started to irradiate IG-110 and IG-430 graphite, a promising candidate for the future reactor, at high temperatures to the higher fluence in the HFIR at ORNL. In the VHTR as a proven reactor operation conditions would be much more severe than those in the HTTR. Therefore, we need to expand the exiting irradiation data to the higher fluence region.

5. Copyright © Toyo Tanso Co., Ltd. All Rights Reserved 5 2. Irradiation schedule -- Irradiation plan in the HFIR -- Irradiation temperature : 300--1000ºC Neutron fluence : Area shown in the following figure Properties to be measured : Dimensions, Young’s modulus, CTE, etc. Grade : IG-110 and IG-430 Experimental Verification Planned Irradiation effect of dimensional change Pebble Bed type VHTR Region （ Prismatic type ） HTTR Design Code

6. Copyright © Toyo Tanso Co., Ltd. All Rights Reserved 6 2. Irradiation schedule 1. Pre-irradiation evaluation : 2010--2012 2. Irradiation : 2012--2015 3. PIE campaigns and evaluation : 2013--2017 All the range of HTGR design data will be covered by obtaining high fluence irradiation data on IG-110. For future HTGR use, irradiation of IG-430 graphite is being carried out. The results of pre-irradiation testing have demonstrated that the dimensions of the specimens are appropriate for irradiation testing. Part of the irradiation results have been established.

7. Copyright © Toyo Tanso Co., Ltd. All Rights Reserved 7 3. Irradiation behavior of IG-110 graphite -- Specimen Shapes and Orientation -- +Z(AX) +Y(TR) -X(TR) CRS (AX) TD4 (AX) 8 4 6 6 8 4 6 6 CRS(TR) TD4(TR) L=25 W=3 T=2.9 MB (AX) MB (TR) L=25 W=3 T=2.9 AX : Axial TR : Transverse MB : Multipurpose Beam CRS : Circular Rod Solid TD : Thermal Diffusivity Disk

8. Copyright © Toyo Tanso Co., Ltd. All Rights Reserved 8 3. Irradiation behavior of IG-110 graphite -- Dimensional Change and Dose-Effect Curve -- Dimensional Change of IG-110 graphite with Irradiation and Dose-Effect Curve Obtained by Interpolation and Extrapolation Reference(1) ： Expansion of Irradiation Data by Interpolation and Extrapolation for Design of Graphite Components in High Temperature Gas-cooled Reactor, JAEA-Research 2009- 008 ・ The results are consistent with the dose-effect curve. ・ About the irradiation data in high-temperature ranges, the temperature is checking now. We will review the results when more data is accumulated. Dose-Effect Curve

9. Copyright © Toyo Tanso Co., Ltd. All Rights Reserved 9 3. Irradiation behavior of IG-110 graphite -- Young's Modulus Change and Dose-Effect Curve -- Young's Modulus Change of IG-110 graphite with Irradiation and Dose-Effect Curve Obtained by Interpolation and Extrapolation ・ Irradiation increases Young's modulus. ・ The results at 400ºC are consistent with the dose-effect curve. ・ The data obtained at 600ºC show rates of increase higher than the dose-effect curve. We will review the results when more data is accumulated. E 0 : Young’s modulus of un- irradiated IG-110 graphite E : Young’s modulus of irradiated IG-110 graphite Dose-Effect Curve

10. Copyright © Toyo Tanso Co., Ltd. All Rights Reserved 10 3. Irradiation behavior of IG-110 graphite -- Thermal Conductivity Change and Dose-Effect Curve -- Thermal Conductivity Change of IG-110 graphite with Irradiation and Dose-Effect Curve Obtained by Interpolation and Extrapolation ・ Irradiation decreases thermal conductivity. ・ The results approximate the dose-effect curve. We will review the results when more data is accumulated. K 0 : Thermal conductivity of un- irradiated IG-110 graphite at the irradiation temperature K : Thermal conductivity of irradiated IG-110 graphite at the irradiation temperature

11. Copyright © Toyo Tanso Co., Ltd. All Rights Reserved 11 3. Irradiation behavior of IG-110 graphite -- Compressive Strength Change and Dose-Effect Curve -- ・ Irradiation increases strength. ・ The results approximate the dose-effect curves but with some variation. We will review the results when more data is accumulated. σ 0 : Strength of un-irradiated IG-110 graphite σ : Strength of irradiated IG-110 graphite Compressive Strength Change of IG-110 graphite with Irradiation and Dose-Effect Curve Obtained by Interpolation and Extrapolation

12. Copyright © Toyo Tanso Co., Ltd. All Rights Reserved 12 4. Irradiation behavior of IG-430 graphite -- Dimensional Change -- Dimensional change of irradiated IG-430 and IG-110 graphite ・ Both IG-430 and IG-110 graphite show similar behavior under low fluence region. ・ Some reports indicates that fluence of a turnaround point of IG-430 is lower than that of IG-110. We will review the results when more data in high temperature / high fluence region is accumulated. Error bar indicate on standard deviation

13. Copyright © Toyo Tanso Co., Ltd. All Rights Reserved 13 4. Irradiation behavior of IG-430 graphite -- Thermal Conductivity -- Irradiation effect on thermal conductivity of IG-430 and IG-110 graphite ・ After irradiation, the thermal conductivity of both IG-430 and IG-110 graphite decreases. ・ Comparing with IG-110 graphite, IG-430 graphite shows a smaller decrease in thermal conductivity with the same irradiation.

14. Copyright © Toyo Tanso Co., Ltd. All Rights Reserved 14 4. Irradiation behavior of IG-430 graphite -- Young’s Modulus -- Irradiation effect on Young’s modulus of IG-430 and IG-110 graphite ・ Both IG-430 and IG-110 graphite show similar behavior under irradiation. Error bar indicate on standard deviation

15. Copyright © Toyo Tanso Co., Ltd. All Rights Reserved 15 5. Summary 1.The comparison between irradiation data of IG-110 and dose-effect curve. The results of irradiation on IG-110 graphite in low-temperature ranges show good agreement with the dose-effect curve established in the draft standard. For high temperature ranges, we will verify consistency of the dose- effect curve by more data is accumulated. After all irradiation data is obtained, the dose-effects curve will be optimized. 2. The irradiation behavior of IG-430 and IG-110 graphite in low temperature / low fluence region is compared as follows: The changes in dimensions and Young's modulus are similar. The change of the IG-430’ thermal conductivity shows a smaller decrease rate.

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