A study of the Szilard-Chalmers reaction of ethyl iodide at low thermal neutron fluxes

1971 ◽  
Vol 24 (1) ◽  
pp. 25 ◽  
Author(s):  
BJ Brown ◽  
DJ Carswell
Keyword(s):  
Thermal Neutron ◽  
Neutron Irradiation ◽  
Solid Phase ◽  
Chemical Exchange ◽  
Irradiation Time ◽  
Iodine Concentration ◽  
Ethyl Iodide ◽  
Bond Rupture ◽  
Post Irradiation ◽  
Free Iodine

Results reported in this paper show that the simple interpretation of the Szilard-Chalmers reaction in ethyl iodide, viz. bond rupture of the radiohalide and absence of subsequent chemical exchange, is not entirely valid. The results also verify and explain the apparently anomalous radiohalide yield of zero for neutron irradiation of pure ethyl iodide in the absence of a γ flux. ��� At low neutron fluxes free radiohalide yields in the liquid phase have been shown to be a function of irradiation and post-irradiation time, γ pre-irradiation dose, and fast/thermal neutron ratio. These results are consistent with the hypothesis that exchange occurs at a rate which decreases as the free iodine concentration increases. ��� Neutron irradiation of ethyl iodide at 77�K produces radioactive iodine in a metastable free state which does not undergo recombination in the frozen solid phase. The rate of post-irradiation recombination between free iodine-128 and the thawed liquid organic phase is independent of irradiation time and was found to be significantly faster than the rate corresponding to neutron irradiation at room temperature.

Dissolution and recrystallization in modern shelf carbonates: evidence from pore water and solid phase chemistry

1993 ◽  
Vol 344 (1670) ◽  
pp. 27-36 ◽  
Keyword(s):  
Organic Matter ◽  
Pore Water ◽  
Solid Phase ◽  
Chemical Exchange ◽  
Isotope Composition ◽  
Geochemical Data ◽  
Carbonate Sediments ◽  
Pore Waters ◽  
Carbonate Minerals ◽  
Carbonate Production

We present an overview of geochemical data from pore waters and solid phases that clarify earliest diagenetic processes affecting modern, shallow marine carbonate sediments. Acids produced by organic matter decomposition react rapidly with metastable carbonate minerals in pore waters to produce extensive syndepositional dissolution and recrystallization. Stoichiometric relations among pore water solutes suggest that dissolution is related to oxidation of H 2 S which can accumulate in these low-Fe sediments. Sulphide oxidation likely occurs by enhanced diffusion of O 2 mediated by sulphide-oxidizing bacteria which colonize oxic/anoxic interfaces invaginating these intensely bioturbated sediments. Buffering of pore water stable isotopic compositions towards values of bulk sediment and rapid 45 Ca exchange rates during sediment incubations demonstrate that carbonate recrystallization is a significant process. Comparison of average biogenic carbonate production rates with estimated rates of dissolution and recrystallization suggests that over half the gross production is dissolved and/or recrystallized. Thus isotopic and elemental composition of carbonate minerals can experience significant alteration during earliest burial driven by chemical exchange among carbonate minerals and decomposing organic matter. Temporal shifts in palaeo-ocean carbon isotope composition inferred from bulk-rocks may be seriously compromised by facies-dependent differences in dissolution and recrystallization rates.

scholarly journals Microhardness of composite resins at different depths varying the post-irradiation time

2007 ◽  
Vol 15 (4) ◽  
pp. 305-309 ◽  
Author(s):  
Juliane Cristina Ciccone-Nogueira ◽  
Mariana Cristina Borsatto ◽  
Wanessa Christine de Souza-Zaron ◽  
Renata Pereira Ramos ◽  
Regina Guenka Palma-Dibb
Keyword(s):  
Irradiation Time ◽  
Composite Resins ◽  
Post Irradiation ◽  
Different Depths

scholarly journals Radioiodination and Purification of [131I]β-CIT and [131I]FP-CIT with an Automated Radiosynthesizer

2022 ◽  
Vol 15 (1) ◽  
pp. 96
Author(s):  
Elisabeth Plhak ◽  
Edith Gößnitzer ◽  
Reingard M. Aigner ◽  
Herbert Kvaternik
Keyword(s):  
Solid Phase ◽  
Single Photon ◽  
Photon Emission ◽  
Tropane Alkaloids ◽  
Radiochemical Yield ◽  
Emission Computed Tomography ◽  
Dopaminergic Dysfunction ◽  
Free Iodine ◽  
Iodine 131 ◽  
Photon Emission Computed Tomography

Dopaminergic transporter (DAT) imaging with single photon emission computed tomography (SPECT) is used to diagnose Parkinson’s disease and to differentiate it from other neurodegenerative disorders without presynaptic dopaminergic dysfunction. The radioiodinated tropane alkaloids [123I]FP-CIT and [123I]β-CIT enable the evaluation of the integrity of DATs. Commonly, the labeling of these compounds is performed by electrophilic substitution of the alkylstannylated precursors with radioactive iodine and following purification by HPLC or solid phase extraction (SPE). This work presents the first radioiodination of β-CIT and FP-CIT with no carrier added [131I]NaI on a Scintomics GRP synthesis module. Free iodine-131 and impurities were removed by SPE over a C-18 Sep-Pak cartridge. We achieved a radiochemical yield of >75% and a radiochemical purity of >98% with both compounds. Our development of an automated synthesis on a commercially available synthesizer ensures robust and efficient labeling of [131I]FP-CIT and [131I]β-CIT starting with low concentrated radioiodine.

scholarly journals PEMBUATAN SUMBER RADIASI GAMMA 137Cs DENGAN AKTIVITAS 20 mCi DARI PEB U3Si2-Al PASCA IRADIASI DALAM CONTAINER STAINLESS STEEL

2016 ◽  
Vol 21 (3) ◽  
Author(s):  
Aslina Br. Ginting ◽  
Yanlinastuti Yanlinastuti ◽  
Noviarty Noviarty ◽  
Boybul Boybul ◽  
Arif Nogroho ◽  
...  
Keyword(s):  
Stainless Steel ◽  
Gamma Radiation ◽  
Cation Exchange ◽  
High Activity ◽  
Radiation Source ◽  
Solid Phase ◽  
Test Results ◽  
Spent Fuel ◽  
Post Irradiation ◽  
Outer Capsule

PEMBUATAN SUMBER RADIASI GAMMA ISOTOP 137Cs DENGAN AKTIVITAS 20 mCi DARI PEB U3Si2-Al PASCA IRADIASI DALAM CONTAINER STAINLESS STEEL. Kegiatan uji pasca iradiasi pelat elemen bakar (PEB) U3Si2-Al banyak menghasilkan larutan dengan keaktifan yang sangat tinggi. Larutan tersebut mengandung isotop 137Cs, uranium serta transuranium yang mempunyai waktu paroh panjang dan berbahaya bagi lingkungan. Namun larutan tersebut memiliki nilai ekonomis tinggi karena dapat dimanfaatkan sebagai bahan baku untuk pembuatan sumber radiasi sinar gamma isotop 137Cs. Hal ini dapat membantu bidang industri dalam memenuhi kebutuhan sumber radioaktif dalam negeri karena selama ini kebutuhan isotop 137Cs di Indonesia masih tergantung dari industri luar negeri. Selain itu, pengadaan dan transportasi isotop 137Cs dari luar negeri serta dalam penggunaannya memerlukan persyaratan yang cukup ketat dari Badan Pengawas Tenaga Nuklir Nasional (BAPETEN), sehingga menyebabkan harga isotop 137Cs menjadi mahal sampai di Indonesia. Dengan alasan tersebut, BATAN sebagai lembaga litbang nuklir di Indonesia perlu mempelajari pembuatan sumber radiasi gamma isotop 137Cs dari larutan hasil pengujian bahan bakar nuklir U3Si2-Al pasca iradiasi. Manfaat isotop 137Cs sangat luas antara lain digunakan dalam menganalisis sampel lingkungan, industri migas, konstruksi, radiografi, perikanan, rumah sakit dan pertambangan. Pembuatan sumber radiasi gamma isotop 137Cs dimulai dari pengumpulan larutan hasil pengujian PEB U3Si2-Al. Larutan larutan hasil pengujian mengandung isotop 137Cs dan isotop lainnya dikumpulkan menjadi satu dalam botol dengan volume 65 mL. Pemisahan isotop 137Cs dari hasil fisi lainnya dilakukan dengan metode penukar kation menggunakan zeolit Lampung dengan berat 45 gr. Hasil pemisahan diperoleh 137Cs-zeolit dalam fasa padat dan isotop lainnya berada dalam fasa cair. Padatan137Cs-zeolit kering kemudian kemudian ditimbang dan diukur aktivitasnya menggunakan spektrometer-g. Hasil analisis dengan spektrometer-g diperoleh aktivitas padatan 137Cs-zeolit sebesar 20 mCi. Untuk menjadi sumber radiasi gamma 137Cs, padatan 137Cs-zeolit dengan aktivitas 20 mCi dikemas dengan cara memasukkan ke dalam inner-outer capsule terbuat dari stainless steel yang telah dirancang sebelumnya. Container stainless steel diproses menjadi sumber radiasi gamma tertutup (shield source) untuk selanjutnya disertifikasi oleh PTKMR-BATAN sebagai lembaga kalibtrator bahan radioaktif di BATAN.Kata kunci: Larutan proses PEB U3Si2-Al, radioaktif gamma, isotop 137Cs, penukar kation, zeolit Lampung dan container. MANUCFACTURING OF 137Cs GAMMA RAY SOURCE WITH ACTIVITY 20 mCi FROM PEB U3Si2-Al POST IRRADIATION IN STAINLESS STEEL CONTAINER. In the post-irradiation examination of fuel element plate (PEB) U3Si2-Al), a solution of high activity as a result of testing nuclear fuel stored in hotcell with enough volume. The solution can not be discarded as waste because it still contains fission isotop such as137Cs, uranium and transuranium, which has a long half life and dangerous for the environment. This can help the industry in order to fulfill the needs of a radioactive source in Indonesia, because until now 137Cs isotope is derived from foreign industries. In addition, the procurement and transportation of isotopes 137Cs require stringent requirements, because they have toget permission from the National Nuclear Energy Agency (BAPETEN), thus causing the price of high activity 137Cs isotopes becomes expensive to Indonesia. For these reasons, BATAN as nuclear R&D institutions in Indonesia need to study make isotopes 137Cs gamma radiation source, which is contained in the waste from spent fuel test results U3Si2-Al. Isotope 137Cs can be used very widely, such as in the analysis of environmental samples, the oil and gas industry, construction, radiography, fisheries, hospitals, and mining. Making isotope 137Cs gamma radiation source starting from the collection of waste from the test results PEB U3Si2- Al. Waste solution was collected in a bottle with volume 65 mL. Collection of 137Cs isotopes of other fission carried out using the method of cation exchange with weight 45 gr of zeolite Lampung. The results of separation are 137Cs-zeolite in the solid phase and the other isotopes are in the liquid phase. 137Cs-zeolite solid is then dried and then weighed and measured its activity using a spectrometer-g. Result of analisys by spectrometer-g was obtained acitivity of 137Cs-zeolite solids was 20 mCi.137Cs-zeolite solids then packed in sealed containers (shield source) capsule-shaped stainless steel and than certificate by PTKMR-BATAN.Keywords: Process wastle of PEB U3Si2-Al, gamma radioactive, isotope 137Cs, cation exchange, zeolite Lampung and container.

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