Optimization of moderator assembly for neutron flux measurement: experimental and theoretical approaches

Waheed, A.; Ali, N.; Baloch, Muzahir Ali; Qureshi, Akbar Ali; Munem, Eid A.; Rajput, Muhammad Usman; Jamal, Tauseef; Muhammad, Wazir

doi:10.1007/s41365-017-0213-z

Cited by 8 publications

(7 citation statements)

References 20 publications

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“…The neutron source was constructed by exposing a 0.3mm-thick layer of beryllium metal to the alpha radiation from the americium-241 source, allowing fast neutrons to be produced with a mean neutron energy of 4.2 MeV [8]. A 6 cm-thick layer of microcrystalline paraffin wax was used as a neutron moderator to reduce the fast neutrons to thermal energies of < 1 eV to increase the chances of neutron capture by the bismuth-209 atoms [9], and the thermal neutrons produced were used to irradiate a 10 g sample of bismuth beryllium acetate as shown in the irradiation setup diagram below (Fig. 4).…”

Section: 3neutron Irradiation Setupmentioning

confidence: 99%

“…Since then, this method of neutron generation by irradiating light elements such as beryllium, lithium, and fluorine with an intense alpha source has been incorporated into radioisotopic neutron sources used in nuclear laboratories throughout the world. The mechanism by which the neutrons are produced proceeds via an (α, n) reaction which requires a source of high energy alpha particles [2,26,27], such as the 9 Be(α, n) 12 C reaction in beryllium. In particular, polonium-210 has been frequently used as the alpha source for such applications due to its high alpha emission energy of 5.4 MeV [30,31], as well as a high specific activity of 4 kCi/g, which stems from its relatively low atomic mass and short half-life of 138 days [3].…”

Section: Introductionmentioning

confidence: 99%

“…Thus, a chain reaction can be initiated in a mixture of atoms of bismuth-209 and light elements, using an initial neutron source to transmute the bismuth atoms into that of polonium, which would themselves emit high-energy alpha particles that impact the light elements, causing further neutron production. Furthermore, 209 Bi and 9 Be are also able to cause neutron multiplication via a (n, 2n) reaction with fast neutrons [6], increasing the neutron population of the system.…”

Section: Introductionmentioning

confidence: 99%

“…To be suitable for sustaining neutron multiplication, the bismuth salt should contain a light element with high neutron yields from (α, n) reactions [7], e.g. 27 Al, 19 F, 10 B, 9 Be, as well as a high hydrogen content for neutron moderation, as the 209 Bi neutron capture cross section for 210 Po formation is greatly increased at thermal neutron velocities. Hence, bismuth beryllium acetate was used due to its high beryllium content, which is ideal for alpha-to-neutron conversion, as well as its intrinsic neutron multiplication and moderation properties.…”

Section: Introductionmentioning

confidence: 99%

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Development of a Science Demonstration Laboratory in National University of Singapore

Lim

Sow

2019

The Phys. Educat.

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Science demonstrations are a good way of promoting, teaching and learning science. This is provided that there exists carefully crafted “software” and communication methods to go along with the hardware. During the past few years, we have developed a Science Demonstration Laboratory at NUS aiming to play an active role in science outreach, science communication and science education. Our approach has evolved from an initial “show-and-tell” model to a more engaging “minds-on” approach where participants are consistently required to make predictions of the outcomes of scientific phenomena before witnessing the demonstrations. We also learnt that the education and development of talented science educators and communicators are crucial to ensure and project the effectiveness of a “hands-on”, “minds-on” approach to science education.

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Section: 3neutron Irradiation Setupmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Development of a Science Demonstration Laboratory in National University of Singapore

Lim

Sow

2019

The Phys. Educat.

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show abstract

“…Since then, this method of neutron generation by irradiating light elements such as beryllium, lithium, and uorine with an intense alpha source has been incorporated into radioisotopic neutron sources used in nuclear laboratories throughout the world. The mechanism by which the neutrons are produced proceeds via an (α, n) reaction which requires a source of high energy alpha particles [2,26,27], such as the 9 Be(α, n) 12 C reaction in beryllium. In particular, polonium-210 has been frequently used as the alpha source for such applications due to its high alpha emission energy of 5.4 MeV [30,31], as well as a high speci c activity of 4 kCi/g, which stems from its relatively low atomic mass and short half-life of 138 days [3].…”

Section: Introductionmentioning

confidence: 99%

Neutronic Chain Reactions for Polonium-210 Production

Lim

2023

Preprint

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The production of the industrially significant radionuclide polonium-210 from the neutron irradiation of bismuth metal and the subsequent beta decay of bismuth-210 is highly inefficient due to the small neutron capture cross section of bismuth-209. In this paper, we report a previously undescribed self-sustaining nuclear chain reaction involving self-propagating neutron multiplication in bismuth salts that allow for rapid and cost-effective production of polonium-210. The reaction proceeds in a cycle of three alternating elementary steps – the capture of neutrons by bismuth-209 and the subsequent formation of polonium-210, the emission of high-energy alpha particles by polonium-210, and the production of more neutrons from (α,n) and (n,2n) reactions on light element and bismuth-209 nuclei respectively. Furthermore, the high hydrogen density of the compound also confers it intrinsic neutron moderation properties, increasing the neutron capture cross section of bismuth-209 at thermal neutron energies. The chain reaction was proven to have successfully occurred by irradiating a sample of the bismuth salt with a 80 µCi neutron source and monitoring the activity levels of the reaction. It was found that the activity of the reaction increased exponentially after an initial stable period following a derived formula for polonium production trends for the reaction, thus validating the occurrence of the reaction. Furthermore, alpha spectroscopy confirmed that polonium-210 had been produced by characterising the 5.30 MeV alpha emission peak of the reaction in addition to using beta spectroscopy to identify the parent nuclide bismuth-210, further proving that the reaction was successful. Hence, this paper reports the successful initiation and characterisation of a novel nuclear chain reaction, and its potential applications offered by a method of rapidly producing large quantities of polonium-210.

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Optimization in nuclear systems

Koreshi

2022

Nuclear Engineering Mathematical Modeling and Simulation

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Optimization of moderator assembly for neutron flux measurement: experimental and theoretical approaches

Cited by 8 publications

References 20 publications

Development of a Science Demonstration Laboratory in National University of Singapore

Development of a Science Demonstration Laboratory in National University of Singapore

Neutronic Chain Reactions for Polonium-210 Production

Optimization in nuclear systems

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