https://doi.org/10.29070/j8aw9k92
A Study the overview of Radioanalytical based on Converter Targets
 
Pathrikar Harshada Kailash1*, Dr. Harsh Bharadwaj2
1 PhD Student,Calorx Teacher's University, Ahmedabad, Gujarat, India
Email: vimt2018@gmail.com
2 PhD Guide, Dept of Chemistry, Calorx Teacher's University, Ahmedabad, Gujarat, India
Abstract- Radioanalytical procedures encompass all nuclear-related techniques used to characterize materials, including compositional or structural analysis, nuclear processes, and nuclear impacts. Conducting thorough investigations into a subject is known as research. Thick Z-material targets called converters generate a flood of fast neutrons through a series of nuclear reactions when they come into contact with proton beams of high energy. This study provides a comprehensive overview of radioanalytical techniques that utilize converter targets, emphasizing their critical role in enhancing the precision and efficiency of radionuclide analysis. Converter targets are materials designed to interact with high-energy particles or radiation, generating secondary emissions that can be more easily detected and analyzed.
Keywords- Radiation, Radiation Effects, Radioanalytical, Techniques, Converter,
INTRODUCTION
Radioactivity is self-destructive & spontaneous in many heavy materials. The term "self-destructive" refers to the disintegration of the components themselves, while "spontaneous" denotes that the emission is completely unfettered by any outside force. In 1896, French physicist Henri Becquerel made the groundbreaking discovery. Even when the photographic plate was housed in a light-proof container, he saw that uranium salts had the strange ability to alter the plate. The active radiations given out by uranium salt, he reasoned, must be the cause of this. Originally identified as Becquerel rays, these radiations eventually became known as radioactive rays. Atomic radioactivity was the original name for the phenomenon whereby an element emitted energetic radiations. Radioactive elements were those that exhibited this characteristic.
In recent years, the demand for precise radionalytical techniques has increased, driven by the need for advanced applications in nuclear medicine, environmental monitoring, and radioactive waste management. One promising area of development is the use of converter targets in radionalytical processes, which offers a novel approach to enhancing both the sensitivity and specificity of nuclear measurements.
Converter targets are specialized materials that facilitate the conversion of incident particles, such as neutrons or protons, into secondary radiation, typically gamma rays, which are easier to detect and analyze. This method provides improved accuracy in identifying radionuclides and measuring their concentrations. Unlike traditional techniques, which often rely on direct interaction between incident radiation and the sample, converter targets act as intermediaries, converting the incident particles into more easily measurable forms.
The novelty of this approach lies in its ability to amplify weak signals, allowing for the detection of trace amounts of radionuclides with greater precision. Additionally, converter targets can be tailored to specific types of radiation, making the method highly adaptable to a wide range of applications. By integrating these targets into radionalytical systems, researchers can achieve enhanced detection limits, reduced background noise, and more accurate quantification of isotopes in complex matrices.
ENVIRONMENTAL RADIOACTIVITY AND RADIATION DOSE
Radioactive tracers have found utility in many scientific fields, including biotechnology, medicine, geology, & archaeology, among them. The discovery of nuclear fission in the 1950s ushered in the atomic era. The testing of nuclear weapons during the cold war era caused widespread pollution that persists to this day. In the 1970s, radioecologists started to pay more attention to naturally occurring radiation. Determining the potential impacts of naturally existing radioactive elements on everyday life and their application in industrial processes posed the greatest difficulty. Efforts to reduce dosage & restore polluted regions were greatly accelerated after the 1986 Chernobyl tragedy. Extensive radioecological research programs have been necessary to address these concerns by learning about radionuclide transport and consequences in ecosystems, remediation techniques, or risk communication. More and more modern fields are finding significant use for the wealth of information gleaned from radioecological studies. Although human activities can alter exposure, ionizing radiation from natural sources has always been a part of human life. Furthermore, new man-made exposure sources have emerged throughout the last hundred years or so (UNSCEAR, 2008). In order to establish safe radiation exposure limits, it is vital to collect data on natural radiation sources and conduct environmental radioactivity surveys.
Different types & energies of ionizing radiation have different biological effects. The amount of radiation that reaches the tissues is a proxy for the potential for biological damage. One sievert (Sv) is the standard unit for absorbed radiation exposure. Normal radiation doses are stated in millisievert (mSv) or microsievert (μSv), which are one-thousandth or one millionth of a sievert, respectively, because to the huge quantity of one sievert. As an example, the radiation dosage from a single chest X-ray is around 0.2 mSv. The two main ways in which radiation may cause exposure are external (by irradiation) and internal (via inhalation). In addition, exposures can occur by eating due to the high concentrations of radionuclides in soil & plants. It should be noted that natural background radiation is the primary source of human exposure, both directly and through ingestion and inhalation.
RADIATION EFFECTS
Radiation Effects at Low Doses
Despite the lack of a universally accepted definition, "low" would encompass annual doses below, say, 10 mSv. The vast majority of radiation doses—both regularly and accidentally—received by the general population and radiation workers are considered low dosage. Finding out what happens with low radiation doses—or, more specifically, how little extra radiation adds up to the inevitable natural background dose—is obviously crucial. Despite extensive research, the exact nature of radiation's effects at low levels remains unknown since such amounts are too little to see clearly. The majority of authoritative organizations agree that the linearity hypothesis is correct. The risk of cancer increases with increasing doses, from zero to extremely high doses, according to this theory. On the basis of this assumption, the general agreement is that the risk of cancer that could prove fatal to an individual is 0.00005 per mSv (or 0.05 per Sv). So, five more cancer deaths are likely if one hundred thousand people get an extra dose of one milliSv. Although the linearity hypothesis is generally accepted as a safe working assumption, numerous prominent research have raised the idea that even minor increases in radiation dosage may not increase cancer risk. This exemplifies the widespread discord regarding the linearity hypothesis's veracity among scientists.
Radiation Effects at High Doses
The usual quality factor is inappropriate, hence very large doses are typically expressed in grayscale. A gamma ray or electron with a 1 Gy energy level is equivalent to 1 Sv. Fatalities can occur within a few months (in shorter durations at larger doses) after radiation exposures above 6 Gy (600 rad), and radiation exposures over 3 Gy (300 rad) can be lethal. Complex symptoms, such as nausea and blood abnormalities, are caused by radiation sickness at doses above 1 Gy. There is a higher risk of cancer for doses below 1 Sv (100 rem), however radiation sickness is unlikely at these levels. Research from those who survived the atomic bombings of Hiroshima and Nagasaki provides the most crucial facts and analysis. The exposure and medical histories of 50,113 individuals in the exposed group and 36,459 individuals in the unexposed or minimally exposed group are examined in these investigations. Radiation exposure is responsible for 454 of the 4,741 cancer deaths that have occurred in the exposed group since 1990. At dosages greater than 0.2 Sv (20 rem), a statistically significant increase is shown for solid cancer tumors and leukemia. Extensive studies on radiation impacts have relied heavily on these data, which have been updated multiple times.
RADIOACTIVE DECAY SERIES AND EXPOSURE
Uranium Decay Series
Uranium occurs naturally in the form of 234U (T1/2 = 2.455 × 105 ), 235U (T1/2 = 7.038 × 108 ) and 238U (T1/2 = 4.4468 × 109 ). 238U and 235U is the parent of two radioactive decay series. The contribution of 235U in the natural collusion is negligible because of its relatively low abundance, thus we concentrate on 238U and its decay products (Eisenbud, 1963). 238U decay series is shown in Fig. 1.2. This series has 15 members ending up to 206Pb after 8 alpha- and 6 beta-emissions along with many gamma decays.
Thorium Decay Series
The adult human body contains about 0.80 Bq of 232Th. The exact composition of naturally occurring thorium is 232Th with a little amount of 238Th, 230Th, 231Th, and 227Th making up the remaining 1.35×10-8 percent. According to Kaplan (1972), 232Th is the progenitor of 4n radioactive decay series, where n ranges from 58 to 51. The series consists of twelve parts.
Potassium Decay
There is approximately 140g of potassium in an adult weighing 70 kg and 0.0169g consists of the 40K isotope. This amount of 40K disintegrates at the rate of 266,000 atoms per minute. Out of 100 disintegrations, 89 result in the release of beta particles with maximum energy of 1.33 MeV, and 11 result in gamma photons with energy of 1.46 MeV. All of the beta particles and about 50 percent of the gamma rays are absorbed in the body, giving annual doses of 16 mrad from the beta particles and 2 mrad from the gamma rays (Jacob, 1981). Potassium isotope 40K is the most unstable of the naturally occurring isotopes. There has a 1.227×109 year half-life for it. 40K has a relative abundance of 1.18×10-4 in potassium found in nature. Eisenbud (1963), Lamarsh (1983), UNSCEAR (1988), and the IAEA (1990) found that 40K imparts an activity of 3.1x103 Bq kg-1 of potassium by β-decay to 40Ca and β+ decay or electron capture (K-capture) to 40Ar. The content of potassium in rocks can have a range of 0 to 10% but usually is 1 to 5% K with an average value of 2% K (IAEA, 1990).
RADIOANALYTICAL TECHNIQUES
The initial individuals to employ radionuclides for analytical purposes were Havesy & Paneth. In 1913, scientists used a naturally occurring lead isotope (210Pb) to find out how much lead sulphide could dissolve in water. Significant advancements in radioanalytical chemistry have been achieved since the advent of man-made radioactivity, which allowed for the production of several radionuclides appropriate for analytical purposes.
The subfield of chemistry known as radioanalytical chemistry is an offshoot of analytical chemistry & field of applied radiochemistry. Radionuclides & nuclear radiations are the mainstays of radioanalytical chemistry when it comes to analytical measures. The foundation of radioanalytical methods is the use of a radioisotope as a tracer or the utilisation of the sample's own radioactivity, which is measured by activation.
It should be mentioned that in order to minimise mistakes, specific care need to be taken when utilising tracer. The most notable ones are because of:
  1. mass effect
  2. low concentration effect
  3. unexpected oxidation state effect
  4. radioactive daughter products
For this purpose, a plethora of radioanalytical separation & estimation methods have been developed. A few of them contain:
Radiometric titration
Titration of silver by chloride ions identified with 36Cl is one example of how radioisotopes can be used to indicate the end-point through the sudden release or absorption of activity from a solution (H. A. C. Mckay 1971). The activity keeps increasing subsequently.
Isotope dilution analysis (IDA)
The change in isotopic ratio when parts of a radiolabelled & nonlabelled version of the same chemical species are combined is the basis of isotope dilution analysis (J. Tolgyessy 1972). For IDA to be carried out, a portion of a substance with a known specific activity (a, =A, /m) is mixed with a test sample containing an unknown analyte (mx) of mass (which is to be discovered). Because the total radioactivity does not change even after homogenisation, the mass of the analyte is determined by determining the specific activity axe of the resultant mixture. mx=m1(a1/ax-1)
The elimination of the necessity for quantitative isolation of the analyte is a major benefit of IDA. where dealing with mixtures of chemically similar chemicals, for example, or at trace concentration levels where quantitative separation is impractical or difficult, this becomes very important. This technique for detecting lead concentrations in metals & minerals in HF acid was initially proposed by Havesy (1932). Elements in matrix materials & molecules of relevance in organic and biochemical analyses are common targets for this technique. Measurements of supplementary activity are used in place of mass measurements in more complex forms of IDA. Here are a few of the more recent iterations of IDA:
  1. The most common kind of IDA is direct isotope dilution analysis. The technique relies on identifying inert analytical samples by employing a known quantity of activity-A labelled substances & activity-specific ai.
  2. Reverse isotope dilution analysis: This technique compares the specific activity of a radioactive sample with that of a diluted sample to a known level in order to calculate the amount of radioactive sample. The pharmaceutical metabolism products can be identified using this approach. (J. Tolgyessy 1989; 1987)
  3. A somewhat different kind of RIDA is isotope derivation dilution analysis. When a radioactive reagent reacts chemically with an inert parent material to produce new derivatives, RIDA can examine the new derivatives by adding a specified amount of the inactive parent material.
  4. Isotope dilution analysis with sub stoichiometry: This method is frequently used to increase the sensitivity of IDA. (R. Ruzicka 1971)
Radio chromatography
It is possible to use labelled samples for electrophoresis and chromatographic techniques like paper, column, or gas and other similar approaches. The mobility of the starting point and its resolution may be simply scrambled without the requirement for any additional developer. Seaborg and colleagues discovered and extensively employed radio chromatography to identify some trans plutonium elements (S. G. Thompson 1954).
Ring oven technique
This type of spot analysis is unique. Despite its humble beginnings as a qualitative separation method for ultra-small samples, it has now found several uses in many areas of analytical chemistry. The method and its uses are extensively discussed by Weisz (1970). Applying a single drop of radioactively-labeled test solution to the middle of a disc of filter paper fixes one or more sample components in the paper using the precipitant. In the next step, a suitable solvent is used to wash the soluble components from the paper's centre to the disk's edges. The solvent evaporates as the solution gets closer to the paper's edge, concentrating the soluble components into a ring that has now moved away from the initial point. Various areas of analytical chemistry can benefit from this method. According to P.W. West (1959), this approach has successfully isolated 35 components in a single drop. Studies on air pollution have made use of it to concentrate and analyse particles in the air (P. Wes 1960).
Activation analysis
Activation analysis is a very precise method of elemental analysis that involves intentionally introducing radioactivity into a subset of the sample's atoms and then detecting the resulting radiations. It is possible to identify or quantify the induced radionuclides after bombardment with appropriate nuclear particles. One of the most common and well-known activation analysis methods is neutron activation analysis, which was first proposed by S. Amiel (1981). This method involves blasting neutrons into the material, often thermal neutrons generated by a nuclear reaction but sometimes even fast neutrons generated by an accelerator. Neutron activation analysis involves exposing the sample to a neutron flux for an extended period of time in order to generate radionuclide products in quantifiable levels that can be quantified with the required level of statistical accuracy.
A common practice following irradiation is to let the sample and standard decompose. During this cooling, transient interferences dissipate, leaving no trace on the analysis's final result. Additionally, there are two primary categories of neurone activation methods: destructive analysis, non-destructive analysis. The analyte must be isolated from other parts of the sample before counting it, according to destructive analysis, sometimes called radiochemical neutron activation analysis (RNAA). This method involves dissolving a predetermined amount of material and then separating the analyte using techniques such as ion-exchange chromatography, extraction, precipitation, etc. Next, the appropriate counting equipment is used to determine the beta or gamma activity of the separated material. The sample and standard are immediately counted after cooling in nondestructive mode of analysis, sometimes called instrumental neutron activation analysis (INAA). Several benefits may be obtained using this method. This method is considered nondestructive as the material is not altered as a result of the produced activity decaying. This procedure is quicker than destructive analysis since it does not require post-irradiation therapy. The method's instrumental nature also makes it easy to prevent making mistakes during chemical separation. The method's sensitivity and selectivity are totally dependent on the counting instruments employed in the study.
A wide range of radiation detectors are now available for use in activity measurement. Among the most crucial characteristics of the detectors are their resolution, efficiency, and appropriateness. There are three different types of detectors that may be used, depending on the counting mode. 1.) Detectors that use gas 2.) Detectors that use scintillation Detector for semiconductors: Neutron activation analysis is prone to counting mistakes caused by factors such as self-shielding, discrepancies in sample or standard geometry, and uneven neutron flux at sample and standard counting uncertainties. Among the neutron activation method's most notable features is its exceptional sensitivity to a wide range of elements.
Radiochemical separations
Rutherford and Soddy (1903) & Curies (1989) performed the first chemical separations to separate and identify the elements responsible for the radiation that was noticed. Radiochemical separation has emerged as its own relatively new branch of chemistry in the past fifteen years. However, in radiochemical separation one has to deal with radioactive elements (isotopes) that release radiation, quantities that are typically in the microgramme range, and separation timeframes that can range from a few seconds to a few minutes all combine to make radiochemical separation an art form.  There is frequently a high standard for radionuclide purity.
The majority of the separation methods that have been refined during the years have been utilised in radiochemistry. Solvent extraction, distillation, volatilisation, and precipitation & coprecipitation are a few of the radiochemical separation techniques. Radiation separation using traditional techniques such distillation, volatilisation, coprecipitation, & precipitation is time-consuming and insufficient for many applications. Therefore, in order to discover an acceptable answer, it is occasionally helpful to combine various strategies. Chromatographic methods are now the gold standard for analytical separations (D. N. Simderman 1964; H. J. M. Bowen 1963; H. Freiser 1959; K. Robard 1994; J. C. Giddings 1991).
Chromatographic separation techniques are classified as planar chromatography and column chromatography.
Planar chromatography: Planar chromatography is of three types, namely (a) paper chromatography, (b) thin layer chromatography and (c) electrochromatography. It differs from its column counter-part in respect that the stationary phase is a flat, relatively thin layer of the material, which may be self-supporting or may be supported on glass, plastic or metal plate. The mobile phase moves through the stationary phase by capillary action, sometimes assisted by gravity or electrical potential. In modem^^ trends it is employed by coupling with spectroscopic technique.
Paper chromatography: Paper chromatography has been used for resolving mixtures on a 28 microscale. This technique has been used for the separation of reduced 99niTc labelled radiopharmaceuticals and also for the separation of rare elements.
Thin layer chromatography: This makes use of a flat, relatively thin layer of material that is either self-supporting or is coated on a glass, plastic or metal surface. The mobile phase moves through the stationary phase by capillary action, sometimes assisted by gravity or an electrical potential. Due to the speed and low cost of the technique, it may precede column experiments. It has found widespread applications in drug industry, clinical laboratories and industrial laboratories.
Gas chromatography technique: In gas chromatography technique the mobile phase is a gas and solute is separated as vapour in the stationary phase. On the basis of physical state of stationary phase, GC technique is classified as gas solid chromatography (GSC) and gas liquid chromatography (GLC). It has been used in trace analysis, high activity fuel element separation ^and high-speed separation of short-lived nuclides. Liquid chromatography refer to those methods in which the mobile phase is a liquid. LC is classified as liquid-solid (LSC) or adsorption chromatography and liquid-liquid or partition chromatography (LLC), ion exchange chromatography and gel patination chromatography.
Adsorption chromatography (LSC): This system consists of non-polar solvent and a polar support and also involves the separation of relatively non-polar hydrophobic materials. This approach has successfully isolated several heavy metal ions. The analyte is partitioned between two liquids in liquid-liquid or partition chromatography, with one liquid being kept immobile on a stationary solid support. This process produces the separations. It is expected that the two stages would blend seamlessly. The specifications state that one of the phases must be polar while the other must be non-polar. The polarities of the sample and stationary phase are matched in an LLC separation process that also makes use of a mobile phase with a significantly different polarity. This method was applied, for instance, to study the binding and metabolism of Tc dioxime complexes in blood using Tc-boroic acid and Tc-dioxime complex adducts as perfusion tracers for the brain and heart.
Ion – exchange: In the past decade the method of selective elution of adsorbed ions from ion-exchange resins has become extremely useful to the radiochemists. It is one of the method, which is applicable to both carrier-free tracers and macro amounts of material. Reversible ion exchange between an ionic solid phase and an external liquid phase is the fundamental principle behind ion-exchange technologies. Insoluble but porous polymeric chains containing fixed charge groups and movable counterions of opposite charge make up the solid phase. In the external liquid phase, these counterions can be swapped out for other ions. When selective exchange forces are at work, one or more of the components can be enhanced. This technique can only be used with compounds that have some ionization. The main reason for the wide applicability of ion-exchange technique in radiochemical separation are (i) the development of commercially available anion, cation, redox and chelating resins useful at high leading capacities and (ii) the availability of an enormous amount of data on distribution coefficient in different media. The major disadvantages of this method is its limited reproducibility.
A number of applications of ion-exchange in nuclear industry have been reported. The technique has been used for the purification of coolant and moderator water in pressurized water reactor, separation of reactor produced isotopes, etc. As an example of the application of simplified technique for ion-exchange chromatography, various methods have been suggested by different workers for the determination of radioelements. The widespread use of ion-exchange can be attributed primarily to its simplicity of operation and to its insensitivity to concentration. The method is fairly rapid and efficient; the efficiency is dependent, however, on the following factors;
1. The type of resin used.
2. The eluting solution.
3. Flow rate and grain size of resin.
4. Column size or volume.
The first successful ion-exchanger was developed in Holland by Smit and Patent' in the middle of nineteen thirties. The development of the high-capacity cation and anion exchange resins used today was stimulated by the research work in 1944 of D’Alelio and Patent"^\ Samuelson had studied the analytical applications of synthetic resins and the first communication on this subject being published in 1939 and the book in 1952 Synthetic resin exchanger are widely used in radiochemical analysis. The most commonly used ion-exchange materials are the organic resin exchangers, but an increasing number of inorganic ion-exchange materials such as zirconium phosphate and hydrated antimony pentaoxide have come into use.
A review is presented on the properties and applications of composite ion exchangers, based on transition-metals hexacyanoferrates and hydrated antimony pentoxide that have been developed in the Institute of Nuclear Chemistry Department, Poland in 1985. By this method, the amount of dangerous radioelement which may have been accumulated in the body of an exposed individual is conveniently ascertained. Deionisation and water softening process have done employing this technique. Some ion-exchangers are used as an adsorbent e.g. Titanian oxide has been mentioned for the separation of uranium in sea -water.
Inorganic ion-exchanger have a great impact on analytical chemistry. Their use gave analysts new methods which not only meet the requirement of modem laboratories but also led to the solution of previously insoluble problems". The synthetic inorganic ion-exchangers have higher resistance towards high doses of radiation and temperature. Hence, employing radio chromatography, various difficult problems can be solved. Inorganic ion-exchanger like zirconium phosphate" has been used for the separation of Sr, Cs, and I.
Tin (IV) antimonite" inorganic ion-exchanger have been synthesized and distribution coefficient has been determined using tracers. In contrast to organic resin, many inorganic exchangers can be obtained with very high degrees of crystallinity, and the nature of the crystalline lattice has a profound influence on the mechanism, rate and selectivity of the ion exchange. Natural ion-exchanger such as zeolites have the widest application for the removal of contaminants in different wastewaters, but the exchange rate was lowered.
Zirconium oxide column was used by Bhattacharya and Basu also hydrous oxide was used successfully and it was found that in both the instances, the separated products were of high radiochemical purity and the yields were quantitative. Distribution studies have been done of different metal-ions on the arsenophosphates of tin(IV) and chromium(III).
CONCLUSION
The electrical ions generated by radiation have the potential to influence typical biological activities in living tissues. Radiation comes in many forms, and each has its own unique properties. Converter targets are key to uncovering radionuclides chart problems. There is a global shortage of therapeutically essential radionuclides, and these targets are also suggested as a next-generation remedy. Overall, this study underscores the importance of converter targets in modern radioanalytical practices, offering insights into their future potential for improving radionuclide detection and analysis. Through this review, we aim to contribute to a deeper understanding of the evolving role of converter targets in nuclear science.
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