Role of nuclear grade graphite in controlling oxidation in modular HTGRs

Windes, W. E.; Strydom, Gerhard; Kane, Joshua J.; Smith, Rebecca E

doi:10.2172/1167529

Cited by 16 publications

(8 citation statements)

References 52 publications

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“…Cu element makes the largest contribution to reduce the concentration of impurities in graphite. The HF is the best of reagent due to the lowest of total impurities which are obtained the graphite close to in low purity grades for nuclear graphite (1000 mg/kg) (Windes et al 2014). Several other elements like As, Ba, Ca, Ce, Eu Fe, Mg, Sm, and Th were also identified in the acid treatment sample but not identified in the non-treated acid sample.…”

Section: Resultsmentioning

confidence: 93%

“…of impurities elements can cause an increase of the oxidation rate of carbon graphite, such as; Pb, Bi (very strong accelerators), Li, Na, K, V, Mn, Co, Cu, Ag (strong accelerators) and Mg, Al, Si, S, Ca, Ti, Cr, Fe, Ni, Zn, Sr, Zr, Mo, Ba (weak to moderate accelerators) (Maahs and Schryer 1967). High purity nuclear grade graphite requires a maximum total impurity of 300 mg/kg, and low purity grades are allowed a maximum total impurity level of 1000 mg/kg (Windes et al 2014). The other impurity elements which need to be avoided in the nuclear grade graphite are those elements having a large neutron absorption cross-section such as B, Cd, and some rare earth element (Sm, Eu, Gd, Dy, Er, Yb, Ce, Th) (Sadanandam and Sharma 2016).…”

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confidence: 99%

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Determination of Elements in Acid Leaching of Graphite Using Instrumental Neutron Activation Analysis

Fisli¹,

Mustika²,

Sudirman³

et al. 2019

IJC

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Graphite material is extremely undissolvable to be turned into chemical solutions, therefore sample preparation is a serious problem faced in the determination of elemental impurity content in a graphite material. In this work, The nondestructive approach of instrumental neutron activation analysis (INAA) is applied to determine the concentration of multi-element in a graphite material, by employing both the forth floating process and the acid treatment method to the local Indonesian graphite. The sample was irradiated in the Rabbit system of G.A. Sywabessy Multi-Purpose Reactor at Serpong, Indonesia. The precision of the analysis was evaluated using certified reference materials which were obtained good performance with the most of concentration value in the range of 3 < zheta score < -3. Eleven elemental (Al, Sb, Co, Cu, La, Mn, Sc, Na, W, V, and Zn) concentration were determined in the forth floating process of the graphite. The Cu elemental is the most content with the value of 60,8 mg/kg or about 90% of total concentration content in graphite. Followed by the Sb content with a value of 5,5 mg/kg (about 8% of total impurities content in graphite). The remaining 2% includes the intermediate and the minor content of other impurity elements. After the acid treatment, the total concentration of impurities contained in the graphite material drastically decreases from 6.7% w/w to about 0,1; 0.6; and 0.59 % w/w for treatment employing the HF,  HNO3+H2SO4,and HF+HCl+H2SO4 acid reagent, respectively. Cu element makes the largest contribution to reduce the concentration of impurities in graphite which decreased from 60,675 mg/kg to 1,088 mg/kg; 925 mg/kg and 835 mg/kg for HF, HNO3+H2SO4 and HF+HCl+H2SO4 acid reagent, respectively. In addition, Sb element concentration dropped dramatically from 5,514 mg/kg to 93 mg/kg using HF reagents. The other trace elements (As, Ba, Ca, Ce, Eu, Fe, Mg, Sm, and Th) were also identified in the acid reagent treated graphite sample which are suspected to derivates from the impurity reagent and or from contamination during the sample preparation. The treated HF for graphite was obtained the low purity grades approach for nuclear graphite.

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Section: Resultsmentioning

confidence: 93%

mentioning

confidence: 99%

Determination of Elements in Acid Leaching of Graphite Using Instrumental Neutron Activation Analysis

Fisli¹,

Mustika²,

Sudirman³

et al. 2019

IJC

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“…Self-sustaining combustion means that the heat of the reaction itself is sufficient to maintain the process. Although most assessments of the 1986 Chernobyl accident describe the burning of the graphite moderator as a "graphite fire," some HTGR researchers dispute this terminology and go as far as to assert that "selfsustained oxidation is physically impossible in nuclear grade graphite" (Windes et al 2014). However, other analysts are not willing to make such unequivocal conclusions, conceding that self-sustaining oxidation reactions during air ingress can occur "in extreme situations" (Morris et al 2004) or are merely "difficult to achieve" (Areva 2010).…”

Section: Other Htgr Hazardsmentioning

confidence: 99%

"Advanced" isn't Always Better: Assessing the Safety, Security, and Environmental Impacts of Non-Light-Water Nuclear Reactors

Lyman¹

2021

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“…Graphite oxidation, an exothermic process, is an additional potential heat source within the core and must be considered in a D-LOFC accident. Significant air ingress is considered beyond design basis in a HTGR, and the contribution of graphite oxidation to fuel heat-up is thought to be limited by the maximum achievable flow of O 2 into the core through the postulated break [28][29][30][31][32]. For personal use only.…”

Section: Hypothetical Accident Progressionmentioning

confidence: 99%

Results of a Phenomena Identification and Ranking Table (Pirt) Exercise for a Severe Accident in a Small Modular High-Temperature Gas-Cooled Reactor

et al. 2019

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Canada has attracted specific interest from developers of nonwater-cooled small modular reactor (SMR) technologies, including concepts based on high-temperature gas-cooled reactors (HTGRs). It is anticipated that some research and development (R&D) will be necessary to support safety analysis and licensing of these reactors in Canada. The Phenomena Identification and Ranking Table (PIRT) process is a formalized method in which a panel of experts identifies which physical phenomena are most relevant to the reactor safety analysis and how well understood these phenomena are. The PIRT process is thus a tool to assess current knowledge levels and (or) predictive capabilities of models, thus providing direction to a focused R&D program. This paper summarizes the results of a PIRT process performed by a panel of experts at Canadian Nuclear Laboratories for a limiting or “worst-case” accident scenario at a generic HTGR-type SMR. Suggestions are given regarding the highest priority R&D items to support severe accidents analysis of these reactors.

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Role of nuclear grade graphite in controlling oxidation in modular HTGRs

Cited by 16 publications

References 52 publications

Determination of Elements in Acid Leaching of Graphite Using Instrumental Neutron Activation Analysis

Determination of Elements in Acid Leaching of Graphite Using Instrumental Neutron Activation Analysis

"Advanced" isn't Always Better: Assessing the Safety, Security, and Environmental Impacts of Non-Light-Water Nuclear Reactors

Results of a Phenomena Identification and Ranking Table (Pirt) Exercise for a Severe Accident in a Small Modular High-Temperature Gas-Cooled Reactor

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