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Goto, Minoru; Fujimoto, Nozomu; Shimakawa, Satoshi; Tachibana, Yukio; Nishihara, Tetsuo; Iyoku, Tatsuo
Proceedings of 5th International Topical Meeting on High Temperature Reactor Technology (HTR 2010) (CD-ROM), 8 Pages, 2010/10
In the High Temperature Engineering Test Reactor (HTTR), which is a Japanese block-type HTGR, reactivity is controlled by control rods (CRs) and burnable poisons (BPs). The CRs insertion depth into the core should be retained shallow during burnup period, because the large insertion depth leads to significant disturbance of the power distribution, and consequently fuel temperature rises above the limit. Thus, the controllable reactivity with the CRs during operation is small, and then reactivity control through the burnup period largely depends on the BPs. It has not been confirmed an effectiveness of BPs on reactivity control on block-type HTGRs. The HTTR succeeded in long-term high temperature operation, and its burnup reached about 370EFPD. Thereby it became possible to confirm the effectiveness of BPs on reactivity control on the HTTR using its burnup data. We focused on a burnup change in the CRs insertion depth into the core to confirm whether the BPs functioned as designed. Additionally, we compared the change in the CRs insertion depths between analysis results and the experimental data to confirm validity of a whole core burnup calculation with the SRAC/COREBN. As a result, the experimental data showed that although the CRs insertion depth into the core was increased with burnup, it was retained the allowable depth. Meanwhile, the analysis result of the CRs insertion depth was in good agreement with the experimental data.
Shinohara, Masanori; Tochio, Daisuke; Hamamoto, Shimpei; Inoi, Hiroyuki; Shinozaki, Masayuki; Nishihara, Tetsuo; Iyoku, Tatsuo
Proceedings of 5th International Topical Meeting on High Temperature Reactor Technology (HTR 2010) (CD-ROM), 7 Pages, 2010/10
HTTR constructed at the Oarai Research and Development Center of JAEA is the first HTGR in Japan. The reactor thermal power is 30 MW, the reactor maximum outlet coolant temperature is 850 
C in rated operation mode and 950 C in high temperature test operation mode. Main objectives of the HTTR are to establish and develop HTGR technology and to demonstrate process heat application. 30-days operation in rated operation mode and 50-days operation in high-temperature operation mode were performed to obtain various characteristic data of HTGR. The main test results are as follows :(1) CPF of the HTTR has excellent confinement ability of fission product which is the highest performance in the world. (2) The measurement temperature of the core internals is good agreement with the design value so that their structural integrity is maintained. (3) The intermediate heat exchanger keeps excellent heat transfer performance from beginning of operation.
prismatic VHTRJohnson, R.*; Sato, Hiroyuki
Proceedings of 5th International Topical Meeting on High Temperature Reactor Technology (HTR 2010) (CD-ROM), 8 Pages, 2010/10
Calculations are performed using CFD for flow of the helium coolant in the gap and coolant channels along with conjugate heat generation and heat transfer in the fuel compacts and graphite of a 350 MW prismatic reactor. Various scenarios are computed by varying the gap width from zero to 5 mm, varying the total heat generation rate to examine average and peak radial generation rates and variation of the graphite block geometry to account for the effects of shrinkage caused by irradiation. It is shown that the effect of increasing gap width causes increased maximum fuel temperature while providing significant cooling to the near-gap region. The maximum outlet coolant temperature variation is increased by the presence of gap flow and also by an increase in total heat generation with a gap present. The effect of block shrinkage is actually to decrease maximum fuel temperature compared to a similar reference case.
decomposition catalyst for iodine-sulfur processImai, Yoshiyuki; Kubo, Shinji; Goto, Minoru; Shimakawa, Satoshi; Tachibana, Yukio; Onuki, Kaoru
Proceedings of 5th International Topical Meeting on High Temperature Reactor Technology (HTR 2010) (CD-ROM), 4 Pages, 2010/10
Required performance of SO decomposition catalyst for Iodine-Sulfur process was investigated. Heat transfer area needed for shell and tube type SO decomposer exchanging heat from VHTR was calculated by applying Yagi-Kunii and Zukauskas's equation for filled layer-SiC tube and SiC tube-He gas flow heat transfer respectively and the minimum space velocity for catalyst was 1000 h
. To transform minimum space velocity to more universal kinetic rate constant, we introduced forward/reverse SO decomposition equation. To achieve equilibrium SO decomposition ratio above 0.5 MPa, rate constant k
should be more than 1.5 s for SO decomposition catalyst.
Shimakawa, Satoshi; Goto, Minoru; Nakagawa, Shigeaki; Tachibana, Yukio
Proceedings of 5th International Topical Meeting on High Temperature Reactor Technology (HTR 2010) (CD-ROM), 6 Pages, 2010/10
Capture cross section of carbon in thermal energy range has been regarded as unimportant in neutronics calculations on general reactor design, because of its infinitesimal value of only 3 mb at 2200 m/s. However, it is not negligible for design works for graphite-rich reactors, such as the High Temperature Gas-cooled Reactors (HTGRs). For the High Temperature Engineering Test Reactor (HTTR) of JAEA, five percent differences in capture cross section of carbon makes 0.24% change in thermal utilization factor of the four factor formula. This impact is for the HTTR with a core configuration of full-loaded core, named the packed core. In this case, change of multiplier factor will be equivalent to a change of thermal utilization factor. The impact of the cross section is dependent on an atomic number ratio of graphite/235-uranimu in reactor core. For more graphite-rich core such as the HTTR with ring core configuration, the five percent change of the cross section value makes a 0.47%
on multiplier factor. From our studies in the HTTR analysis, a value of capture cross section at 2200 m/s has been revised to 3.86 mb in evaluated nuclear data library of JENDL-4. Comparing with the value of JENDL4, the values in other libraries are about 10-15% smaller as 3.36 mb in ENDF/B-VII, 3.36 mb in JEFF-3.1 and 3.53 mb in JENDL-3.3. It was observed that discrepancy of a multiplier factor between former calculation and experiment of the HTTR showed disagreement in the evaluation of the critical approach tests. Monte Carlo calculation results using JENDL3.3 are overestimated about 0.4% with packed core configuration and 1.0% with ring core, respectively. In this report, the improvement of excess reactivity calculation for the HTTR with newly JENDL-4 is described.