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.

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.

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.

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

핵폐기물을 고화시키는 재료로 사용하는 붕규산염, borosilicate, 유리의 용해는 지충 처분장에 처리된 고준위 방사성 폐기물의 생태적 유출을 결정할 수 있는 중요한 화학반응이다. 습식 실험에서 유리의 용해속도, dissolution rate, 는 유리 화학조성에 의해 크게 좌우되는 것이 관찰된다. 유리의 bulk 구조의 규명한 분광분석 실험에 의하면 유리의 화학조성과 분자수준, molecular-level, 구조, 예: SiO4사면체의 연결구조와 B 원소의 배위구조, 사이의 상관관계가 존재한다. 따라서 화학조성에 따른 유리 용해도의 차이는 조성에 따른 bulk 내부구조의 변화로 이해되어 왔다. 그런데 유리표면은 수용액과 계면을 이루면서 용해과정에서 가장 직접적으로 반응하는 부분이기 때문에, 화학조성에 따른 표면구조 변화에 대한 지식 또한 필요하다. 본 논문에서는 분자 동역학, mo;ocu;ar dynamics, MD, 시뮬레이션을 사용하여 4가지의 다른 화학조성을 가지는 소듐붕규산염 유리, xNA2O.B2O3.ySiO2 화학조성, 에 대하여 bulk구조와 실험으로 얻기 어려운 표면, surface, 구조를 연구하였다. MD 시뮬레이션은 유리표면의 화학조성과 분자수준 구조가 bulk의 것과 매우 상이한 결과를 보여준다. 본 연구의 MD 시뮬레이션 결과는 화학조성에 따른 유리 용해도, 특히 초기 용해과정, 는 bulk구조의 변화보다 유리 표면구조의 변화에 의해 크게 좌우될 수 있다는 표면구조에 대한 이해의 중요성을 역설한다. 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.

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.

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.

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 韓國結晶成長學會誌 Vol.16 No.2

붕규산염계 유리 프리트에 중금속이 다량 함유된 전기로 EAF dust(전기로 제강분진, 이하 더스트)를 $10{\sim}80wt%$ 범위로 첨가한 후 용융하여 유리 시편을 얻었다. 제조된 유리의 DTA분석 결과로부터 유리전이온도, $T_g$가 $550^{\circ}C$ 부근임을 확인하였고 이로부터 결정화에 필요한 열처리 조건을 $700^{\circ}C$/10 hr으로 정하였다. 더스트 첨가량이 70wt% 이상인 유리시편은 XRD 분석 결과 spinel 결정 피크만이 나타났으며, 결정화 시편의 경우, 더스트 첨가량이 40wt% 이상부터 spinel 결정이, 80wt% 부터는 spinet과 willemite 피크가 함께 검출되었다. XRD 분석으로는 결정상이 검출되지 않았던 조성의 유리시편에서도 aspect ratio=$0.7{\sim}1.0$인 수십 nm 크기의 결정상 존재가 SEM으로 확인되었고 결정화 시편에서도 더스트 함량이 l0wt%부터 결정상이 관찰되었다. 결정화 시편에서 관찰된 결정상은 그 형태와 분포가 첨가량에 따라 다양하고 비균일 하였으나 더스트 첨가량이 70wt%인 시편에서는 aspect ratio가 1에 가까운 6면체 형상을 나타내었다. 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.

Reciprocating magnetorheological polishing method for borosilicate glass surface smoothness

Peng Zhang,Yu Zhen Dong,Hyoung Jin Choi,Chul-Hee Lee,Yong-Sheng Gao 한국공업화학회 2020 Journal of Industrial and Engineering Chemistry Vol.84 No.-

A new reciprocating magnetorheological (MR) method for polishing aflat borosilicate glass surface isproposed. A reciprocating MR polishing tester was designed to polish borosilicate glass, in whichsupplying MR polishingfluid uniformly could yield aflatter surface on the workpiece. The MR polishingfluid was prepared according to specific test requirements and the rheological properties andprecipitation rate were measured. The mechanism for polishing borosilicate glass was evaluated furtherby analyzing the surface morphology and surface profile. The transparency of the glass surface wasenhanced with an improvement of surface quality with pre-processing and reciprocating MR polishingprocess. The results demonstrated the effectiveness of the reciprocating MR polishing method, whichcould be used for polishing borosilicate glass.