Shielding Thickness of the Fuel Handling Hot Cell at the Spent Fuel Re-packaging Facility

Joon Gi Ahn 한국방사성폐기물학회 2022 한국방사성폐기물학회 학술논문요약집 Vol.20 No.2

For deep geological repository of the spent nuclear fuel, the fuel assemblies loaded in the storage cask are transferred to the disposal cask and the operation is performed in the fuel handling hot cell at the fuel re-packaging facility. As the fuel handling hot cell shielding is accomplished by the concrete wall and the viewing glass window, the required shielding thickness was evaluated for both materials. The ordinary concrete is applied to hot cell wall and two kinds of glasses, i.e., single layer of lead glass and double layer of lead glass and borosilicate glass, are considered for the viewing glass window. A bare spent PWR fuel assembly exposed to the environment in the hot cell was considered as the neutron and gamma radiation sources. The neutron and gamma transport calculations were performed using the MAVRIC program of the SCALE code system for the dose rate evaluation. The dose limit of 10 μSv/h is applied as the target dose to establish the required shielding thickness. The concrete wall of 94 cm thickness reduces the total dose rate to 6.9 μSv/h, which is the sum of neutron dose and gamma dose. Penetrating the concrete wall, both of the neutron dose and the gamma dose decrease constantly with shield thickness and the gamma dose is always dominant through whole penetrating distance. Single layer lead glass of 74 cm thickness reduces total dose rate to 6.2 μSv/h. Applying double layer shield glass combined of lead glass and borosilicate glass, the total dose rate reduces to 3.6 μSv/h at same shield thickness of 74 cm. Through the shield glass, gamma dose decreases rapidly and neutron dose decreases slowly compared with those for concrete wall. In result, neuron dose becomes dominant on the window glass shielding. The more efficient dose reduction of double layer glass is achieved by the borosilicate glass’s superior neutron shielding power. Thus, the use of double layer glass of lead glass and borosilicate glass is recommended for the viewing glass of the fuel handling hot cell. Finally, it is concluded that about 1 m thick concrete wall and 75 cm thick viewing glass window are sufficient for the radiation shielding of the hot cell at the spent fuel repackaging facility.

소듐붕규산염 유리의 표면 구조에 대한 분자 동역학 시뮬레이션 연구

권기덕 ( Ki Deok Kwon ),( Louise J. Criscenti ) 한국광물학회 2013 광물과 암석 (J.Miner.Soc.Korea) Vol.26 No.2

Borosilicate glass dissolution is an important chemical process that impacts the glass durability as nuclear waste form that may be used for high-level radioactive waste disposal. Experi-ments reported that the glass dissolution rates are strongly dependent on the bulk composition. Because some relationship exists between glass composition and molecular-structure distribution, eg, non-brid-ging oxygen content of SiO4 unit and averaged coordination number of B), the composition-dependent dissolution rates are attributed to the bulk structural changes corresponding to the compesitional variation, We examined Na borosilicate glass structures by performing classical molecular dynamics, MD, simulations for four different chemical compositions, xNa2O.B2O3.ySiO2, Our MD simulations de-monstrate that glass surfaces have significantly different chemical compositions and structures from the bulk glasses. Because glass surfaces forming an interface with solution are most likely the first dissolution-reaction occurring areas, the current MD result simply that composition-dependent glass dissolution behaviors should be understood by surface structural change upon the chemical composition change.

보로실리케이트 유리의 이온교환에 의한 고강도 투명방탄소재의 제조

김영환,심규인,임재민,최세영,Kim, Young-Hwan,Shim, Gyu-In,Lim, Jae-Min,Choi, Se-Young 한국군사과학기술학회 2010 한국군사과학기술학회지 Vol.13 No.6

Borosilicate glass (81% $SiO_2$-2% $Al_2O_3$-13% $B_2O_3$-4% $Na_2O_3$) was prepared, and the glass was ion exchanged in $KNO_3$ powder containing different temperature and time. The $K^+-Na^+$ ion exchange takes place at the glass surface and creates compressed stress, which raise the mechanical strength of the glass. The depth profile of $Na^+$ and $K^+$ was observed by electron probe micro analyzer. With the increasing heat-treatment time from 0min to 20min, the depth profile was increased from 17.1um to 29.4um, but mechanical properties were decreased. It was also found out that excessive heat treatment brings stress relaxation. The Vickers hardness, Fracture Toughness and bending strength of ion exchanged samples at $570^{\circ}C$ for 10min were $821.8H_v$, $1.3404MPa{\cdot}m^{1/2}$, and 953MPa, which is about 120%, 180%, and 450% higher than parent borosilicate glass, respectively. Transmittance was analyzed by UV-VIS-NIR spectrophotometer. Transmittance of ion exchanged borosilicate glass was decreased slightly at visible-range. It can be expected that transparent bulletproof materials in more light-weight and thinner by ion exchanged borosilicate glass.

지르코니아 첨가된 보로실리케이트 유리의 결정화

심규인,김영환,임재민,최세영,Shim, Gyu-In,Kim, Young-Hwan,Lim, Jae-Min,Choi, Se-Young 한국군사과학기술학회 2010 한국군사과학기술학회지 Vol.13 No.6

Borosilicate glass was prepared in the composition of 81% $SiO_2$, 4% $Na_2O$, 2% $Al_2O_3$, 13% $B_2O_3$. The albite phase($NaAlSi_3O_8$) increased with the $ZrO_2$(0~10wt.%) addition. For measurement of glass transition temperature($T_g$), crystallization temperature($T_{c,max}$) measured by differential thermal analysis. The $T_g$ and $T_{c,max}$ were $510{\sim}530^{\circ}C$ $650{\sim}670^{\circ}C$, respectively. The crystallized glass was heated at various conditions(temperature, time). After nucleation at $550^{\circ}C$ for 2hours prior to crystal growth at $650^{\circ}C$ for 4hours, the resulting Vickers hardness, fracture toughness and bending strength were about $736H_v$, $1.0779MPa{\cdot}m^{1/2}$, and 493MPa, which were 17%, 45% and 149% higher than parent borosilicate glass, respectively. Crystal size and transmittance of crystallized borosilicate glass were analyzed by FE-SEM, EDX and UV-VIS-NIR spectrophotometer. Transmittance of crystallized borosilicate glass was decreased with increasing $ZrO_2$(wt%) at visible-range. The results prove that light-weight bulletproof can be fabricated by the crystallization of borosilicate glass.

Lead-Borosilicate Glass계 LTCC용 유전체에 대한 고찰

윤상옥,오창용,김관수,조태현,심상흥,박종국,Yoon, Sang-Ok,Oh, Chang-Yong,Kim, Kwan-Soo,Jo, Tae-Hyun,Shim, Sang-Heung,Park, Jong-Guk 한국세라믹학회 2006 한국세라믹학회지 Vol.43 No.6

The effects of lead-borosilicate glass frits on the sintering behavior and microwave dielectric properties of ceramic-glass composites were investigated as functions of glass composition of glass addition ($10{\sim}50vol%$), softening point (Ts) of the glass, and sintering temperature of the composites ($500{\sim}900^{\circ}C$ for 2 h). The addition of 50 vol% glass ensured successful sintering below $900^{\circ}C$. Sintering characteristics of the composites were well described in terms of Ts. PbO addition in to the glass enhanced the reaction with $Al_{2}O_3$ to form liquid phase and $PbAl_{2}Si_{2}O_8$, which was responsible to lower Ts. Dielectric constant(${\epsilon}_r$), $Q{\times}f_0$ and temperature coefficient of resonant frequency (${\tau}_f$) of the composite with 50 vol% glass contents ($B_{2}O_{3}:PbO:SiO_{2}:CaO:Al_{2}O_3$ = 5:40:45:5:5) demonstrated 8.5, 6,000 GHz, $-70\;ppm/^{\circ}C$, respectively, which is applicable to substrate requiring a low dielectric constant. When the same glass composition was applied sinter $MgTiO_3\;and\;TiO_2,\;at\;900^{\circ}C$ (50 vol% glass in total), the properties were 23.8, 4,000 GHz, $-65ppm/^{\circ}C$ and 31.1, 2,500 GHz, $+80ppm/^{\circ}C$ respectively, which is applicable to filter requiring an intermidiate dielectric constant.

Alkali Borosilicate Glass for Vitrification of Molybdenum-rich Nuclear Waste

Seon-Jin Kim,Jung-wook Cho 한국방사성폐기물학회 2023 한국방사성폐기물학회 학술논문요약집 Vol.21 No.1

Vitrification is one of the best ways to immobilize high-level radioactive waste (HLW) worldwide over the past 50 years. Since the glass matrix has a medium (3.0-5.5 A) and short (1.5-3.0 A) periodicity, it can accommodate most elements from the periodic table. Borosilicate glass is the most suitable glass matrix for vitrification due to its high chemical durability, high waste-loading capacity, and good radiation resistance. Mo is a fission product contained in liquid waste generated in the process of reprocessing spent nuclear fuel and exists in the form of MoO4 2- in the glass. MoO4 2- forms a depolymerization region without directly connecting with the glass network former. When the concentration of Mo increases in the depolymerization region, it combines with nearby alkali or alkaline earth cations to form a crystalline molybdate phase. Phase separation and crystallization in the glass can degrade the performance of the material because it changes the physical and chemical properties of the glass. In particular, since alkali molybdate has high water solubility when it forms crystals containing radioactive elements such as Cs, there is a risk of leakage of radionuclides by groundwater during deep underground disposal. Therefore, in this study, the most stable glass-ceramic composition was developed using various alkali elements, and the difference in phase separation and crystallization behavior in glass and the stability of the solidified body were analyzed by structural analysis of the glass network and alkali molybdate. The cause of the difference in crystallization of alkali molybdate according to the type of alkali cation is structurally analyzed, and using this, research is conducted to increase the Mo content in the glass without crystallization.

중성자 차폐능 향상을 위한 붕규산유리 혼입 모르타르의 특성 분석

장보길 ( Jang Bo-kil ),김지현 ( Kim Ji-hyun ),정철우 ( Chung Chul-woo ) 한국건축시공학회 2017 한국건축시공학회 학술발표대회 논문집 Vol.17 No.2

Borosilicate glass was incorporated to improve the neutron shielding capability of concrete. Boron is a typical neutron shielding material, and it is contained in borosilicate glass. However, borosilicate glass causes alkali-silica reaction, which damages the concrete. Therefore, studied to reduce the expansion due to alkali-silica reaction and to improve the neuton shielding capability. The measurement of the expansion due to the alkali-silica reaction was based on ASTM C 1260. Experimental results show that the expansion due to alkali-silica reaction is reduced when borosilicate glass powder incorporated. In addition, the neutron shielding capability was significantly improved when the fine aggregate replaced with borosilicate glass.

EAF dust가 함유된 붕규산염계 결정화 유리의 미세구조 분석

안영수,강승구,김유택,이기강,김정환,Ahn, Y.S.,Kang, S.G.,Kim, Y.T.,Lee, G.K.,Kim, J.H. 한국결정성장학회 2006 한국결정성장학회지 Vol.16 No.2

Glassy specimen was obtained by melting and quenching a borosilicate glass frit miked with $10{\sim}80wt%$ EAF dust. The glass transition temperature, $T_g$ of glassy specimen was measured around $550^{\circ}C$ from the DTA curve and the eat treatment condition to crystallize a glassy specimen was selected as $700^{\circ}C$/1 hr. The spinel crystal peaks were found in XRD analysis for the glass containing dust > 70 wt%. For the glass-ceramics, however, the spinel peaks in a specimen containing dust > 40 wt%, and the spinel and willemite peaks in dust > 80 wt%. The crystals of several tens of nanometer with aspect ratio of $0.7{\sim}1.0$ were observed at a glassy specimen containing dust > 40 wt% by SEM which was not found by XRD analysis. For the glass-ceramics, the crystals were found in a specimen containing dust of even 10 wt% by SEM. The feature and distribution of crystals observed through the specimen for a glass-ceramics were diverse and not uniform. The crystals found in the glass-ceramics containing 70 wt% dust were hexahedral with an aspect ratio of around unity.

Sintering behavior and dielectric properties of ceramic/glass composites using lead borosilicate glass

윤상옥,김관수,심상흥,김신 한양대학교 세라믹연구소 2010 Journal of Ceramic Processing Research Vol.11 No.1

TiO2 and Al2O3 based ceramic/glass composites were prepared by a liquid phase sintering method using lead borosilicate (PBS)glass with a deformation temperature of about 627 oC. The non-reactive liquid phase sintering (NLPS) was conducted in both systems; there was no crystallization in the TiO2/PBS glass composite and although the crystallization of the anorthite-type phase occurred in the Al2O3/PBS glass composite, this phase might be crystallized from the PBS glass. The linear shrinkage behavior could be interpreted as one stage sintering for both systems. The dielectric constant (εr) of the TiO2/PBS glass composite was about 30, implying that an application to filters may therefore be shown to be appropriate. The temperature coefficient of the resonant frequency (τf), however, was +135 ppm/K and an improvement is necessary for the application to LTCC materials. The dielectric constant (εr) of the Al2O3/PBS glass composite was about 10 and an application to substrates may be proper.

폐 LCD판넬로부터 붕규산유리 발포체 제조를 위한 원료 유리 제조

오치훈 ( Chi Hoon Oh ),박윤국 ( Yoon Kook Park ),이철태 ( Chul Tae Lee ) 한국공업화학회 2016 공업화학 Vol.27 No.4

사용 후 발생되는 폐 LCD판넬용 유리의 재활용 방안을 마련하고자 별도의 전처리 없이 폐 LCD판넬을 습식분쇄함으로서 발포체 제조용 원료유리로 사용가능한 폐 붕규산유리의 회수 방법을 조사하였으며, 이렇게 회수된 폐 붕규산유리를 사용하여 발포체의 제조를 시도하였다. 입도 270 mesh 이하의 크기로 분쇄 조절된 폐 붕규산유리를 대상으로 폐 붕규산분말 100 g에 대해 발포제로서 탄소분을 0.3 중량 분율, 추가 발포조제로서 Na2CO3, Na2SO4, CaCO3를 각각 1.5 중량 분율이 되도록 첨가한 원료 유리분말을 발포소성온도 950 ℃에서 20 min간 발포를 진행함으로서 밀도가 0.3g/cm3 이하되는 발포체를 제조할 수 있었다. 또한 원료 유리에 추가적으로 SiO2 또는 H3BO3를 첨가함으로서 얻어지는 발포체에 효과적으로 개기공을 형성할 수 있었으며, 개기공의 형성은 흡음 등 새로운 기능을 가진 발포체의 제조 가능성을 보여주었다. In this article, the foamed body of glass was manufactured from the waste borosilicate glass produced by wet pulverization process without additional pretreatment which can be used as a recycling method for waste LCD panel glass. Each 100 g of pulverized waste borosilicate glass with the size of less than 270 mesh were mixed with 0.3 weight fraction of carbon and 1.5 weight fraction of Na2CO3, Na2SO4 and CaCO3 and let them foamed for 20 minutes at 950 ℃ to manufacture the foamed body having the density of less than 0.3 g/cm3. Additionally, adding SiO2 or H3BO3 to the mixture enabled the foamed body to have efficient formation of open pores which showed the possibility for producing the foamed body with new functionalities such as sound absorption.