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BackgroundEpithermal instrumental neutron activation analysis (EINAA) technique is used for the determination and estimation of the concentration levels of micronutrients such as Sodium (Na), Magnesium (Mg), Potassium (K), Calcium (Ca), Manganese (Mn), Copper (Cu) and Iodine (I) in breastmilk.AimTo examine the concentration of seven micro elements in the breastmilk of lactating mother who were exclusively breastfeeding.MethodsThis study employed quantitative experimental research where 27 lactating mothers voluntarily participated in the study from two health facilities in the Cape Coast Metropolitan area. Data was collected over a period of four weeks. A three millimetre (3mm) thick of flexible boron was used to cut off thermal neutrons in order to assess epithermal neutrons. This was done to create an activation energy which examines the amount of the 7 micro nutrients in the breastmilk. The standard reference materials used were the International Atomic Energy Agency (IAEA)-336; IAEA-407, IAEA-350 and National Institute of Standard and Technology (NIST) USA SRM 1577b. The Relative standardization method was used in the quantification of the elements.ResultsThe study achieved about 94.7% accuracy. The estimated health risk calculated showed that the concentrations of chlorine (Cl) and iodine (I) were high in the order I > Cl with all very far above the maximum Upper Limit (UL) of the daily Recommended Dietary Allowance (RDA) for all life stages except for children below 8 years.ConclusionMn is found in very high quantities in the diet consumed by the parents of babies. These children could be exposed to metabolic disorders or unexplained diseases in future without knowing their origin.

To polarize neutrons with energy beyond 0.1 eV, we developed a novel polarized proton spin filter based on dynamic nuclear polarization using photo-excited triplet electron spins. The spin filter consists of a single crystal of naphthalene doped with deuterated pentacene and has a size of $\varnothing15\times4 \, {\rm mm}^3$, allowing it to cover a wide beam diameter. It was operated in 0.35 T and at 90 K. We succeeded in polarizing neutrons in the energy range 0.1–10 eV using a RIKEN accelerator-driven compact neutron source. The averaged values of the proton and neutron polarization were $0.250\pm0.050$ and $0.076\pm0.015$, respectively.

The E_LIBANS project (INFN) aims at producing neutron facilities for interdisciplinary irradiation purposes among which pre-clinical research for BNCT. After the successful setting-up of the thermal neutron source based on a medical LINAC, a similar apparatus for epithermal neutrons has been developed. Both structures are based on an Elekta 18 MV coupled with a photoconverter-moderator system which deploys the (γ,n) reaction to convert the X-rays into neutrons. This communication describes the two neutron sources and the results obtained in their characterization.

Due to the complexity of finding formation porosity from the original “count rate” neutron tools that topic was covered in detail in Chapter 5. Now we turn our attention to all that followed the pioneering neutron logging tools and address the epithermal neutron tools and the compensated, (dual-detector) thermal neutron tools. In this chapter, we also provide a perspective of all the many combinations and permutations of the types of radioactive source, atomic particles propagated and detected, and the number of detectors and their spacings as used in what we may call the nuclear logging “zoo.”

In this study, the provenance of 42 obsidians from the Chalcolithic and Early Bronze Age levels of two settlements - Bakla Tepe and Liman Tepe - located on the Aegean coast of Anatolia were investigated with an interdisciplinary approach using fission-track (FT) dating, Instrumental Neutron Activation Analysis (INAA) and Epithermal Neutron Activation Analysis (ENAA). Some artefacts showed FT ages of a few thousand years. Apparent FT ages of the remaining samples are distributed over a wide range, from 0.53 +/- 0.03 to 1.43 +/- 0.20 Ma. After application of the size-correction method, most artefacts were distributed in a homogeneous group characterized by FT ages varying from 1.48 +/- 0.47 to 1.80 +/- 0.20 Ma, with a mean value of 1.65 +/- 0.05 Ma and low induced track density corresponding to low U content. The remaining 3 samples showed relatively high induced track densities. One of them has an apparent age of 0.53 +/- 0.03 Ma and a sizecorrected age of 1.02 +/- 0.07 Ma. The probable potential sources for the studied samples were identified as the island of Melos in the Aegean, and the central Anatolian sources - particularly the Golludag complex - through comparison of the FT data. INAA and ENAA studies have been carried out on 34 artefacts at the TRIGA Mark II research reactor of the University of Pavia. The identification of the sources was attained through cluster analysis of the chemical data. These results agree fully with those obtained by FT dating: most artefacts originated from the Melos-Dhemenegaki flow, and only 3 samples from central Anatolia. The current study provides a contribution to a better understanding of the circulation of obsidians in Anatolia.

To perform quantitative analysis of constituent elements, including light atoms, by time-of-flight (TOF) type neutron imaging, a new analysis method using epithermal neutrons excluding resonance dips has been proposed. The method is based on fitting the theoretical neutron transmission spectrum calculated from evaluated nuclear data to a measured neutron transmission spectrum. Compared to conventional imaging methods such as those using neutron radiography or neutron resonance analysis, it has the advantage of being able to evaluate multiple/light elements. We applied this technique to a pulsed neutron transmission experiment at the Hokkaido University Neutron Source. A stack of iron and carbon plates was measured as a model sample consisting of heavy and light elements. The evaluated elemental densities show reasonable agreements within an error of 10%.

The various dose components generated by epithermal neutron beams in tissue-equivalent materials have different spatial distributions that also depend on the size and volume of the irradiated volume. NCT dosimetry requires the separate determination of dose components having different LET, because of their different RBE. Monte Carlo simulations have been developed concerning the absorbed doses and thermal neutron fluences, to investigate the extent of the differences that may occur by changing the shape and size of the irradiated volumes. Moreover, the doses and fluences that occur if specific isotopes (10B, 14N, 157Gd) are added to water have been evaluated.

Analysis of Lunar Exploration Neutron Detector (LEND) neutron count rates for a large set of mid-latitude craters provides evidence for lower hydrogen content in the crater interiors compared to typical highland values. Epithermal neutron count rates for crater interiors measured by the LEND Sensor for Epithermal Neutrons (SETN) were compared to crater exteriors for 301 craters and displayed an increase in mean count rate at the ∼9-σ confidence level, consistent with a lower hydrogen content. A smaller subset of 31 craters also shows a significant increase in Optical Maturity parameter implying an immature regolith. The increase in SETN count rate for these craters is greater than the increase for the full set of craters by more than a factor of two.

In this article, we report a benchmark experiment of the tungsten reactivity worth under a super-critical state which has been conducted at the VENUS-II facility of CIAE in Beijing. The cylindrical tungsten target reactivity worth was measured and extracted as −1.234 ± 0.114 × 10−3 Δk/k using a period method. The resultant tungsten reactivity worth was compared with those from the MCNP Monte Carlo simulations with five evaluated libraries, i.e., ENDF/B-VII.0, ENDF/B-VII.1, CENDL-3.1, JENDL-4.0 and JEFF-3.2. It is found that the results from the MCNP simulations with ENDF/B-VII.0, ENDF/B-VII.1, JENDL-4.0 and JEFF-3.2 are overestimated, whereas that of CENDL-3.1 is underestimated, and those from the MCNP simulations with the ENDF/B-VII.1 and ENDF/B-VII.0 libraries show slight better agreement with the experiment data within errors. A correlation analysis was used to address these issues. We conclude that it is the discrepancy of the (n, γ) channel at the epithermal neutron region that mainly results in the difference between the measured and MCNP simulated tungsten reactivity worth values.

Specific design features and main characteristics of a compact accelerator-based epithermal neutron source for boron neutron capture therapy are described. High quality of the neutron flux generated by the accelerator-based source has been experimentally confirmed. The opportunities for medical use of the accelerator-based epithermal neutron source in oncological centers for boron neutron capture therapy are assessed.

Head and neck (HN) cancer is an endemic disease in Taiwan, China. Locally recurrent HN cancer after full-dose irradiation poses a therapeutic challenge, and boron neutron capture therapy (BNCT) may be a solution that could provide durable local control with tolerable toxicity. The Tsing-Hua Open Pool Reactor (THOR) at National Tsing-Hua University in Hsin-Chu, provides a high-quality epithermal neutron source for basic and clinical BNCT research. Our first clinical trial, entitled “A phase I/II trial of boron neutron capture therapy for recurrent head and neck cancer at THOR”, was carried out between 2010 and 2013. A total of 17 patients with 23 recurrent HN tumors who had received high-dose photon irradiation were enrolled in the study. The fructose complex of l-boronophenylalanine was used as a boron carrier, and a two-fraction BNCT treatment regimen at 28-day intervals was used for each patient. Toxicity was acceptable, and although the response rate was high (12/17), re-recurrence within or near the radiation site was common. To obtain better local control, another clinical trial entitled “A phase I/II trial of boron neutron capture therapy combined with image-guided intensity-modulated radiotherapy (IG-IMRT) for locally recurrent HN cancer” was initiated in 2014. The first administration of BNCT was performed according to our previous protocol, and IG-IMRT was initiated 28 days after BNCT. As of May 2017, seven patients have been treated with this combination. The treatment-related toxicity was similar to that previously observed with two BNCT applications. Three patients had a complete response, but locoregional recurrence was the major cause of failure despite initially good responses. Future clinical trials combining BNCT with other local or systemic treatments will be carried out for recurrent HN cancer patients at THOR.

To evidence the efficiency of cigarette filter we have determined the content of 27 major and trace elements in two brands of filter and filter-less cigarette tobacco, tobacco ash as well as new and spent filters. All measurements were performed by Epithermal Neutron Activation Analysis. We have found that the ash still contained between 71 and 86% of the initial amount of investigated elements excepting the more volatile As whose fraction represented only 28–32% of its original quantity. The possible implications of these findings were discussed.

I (G.J.Y.) was a graduate student the first time I met Dr. Salvatores in February 1994 in Cadarache, France. He was teaching a class (in French) on fast reactor physics. Among us was a bright Chinese student who had come to learn reactor physics the French way. The student’s French was a little less than perfect, so I was surprised when, at the end of the class, he raised his hand and asked Dr. Salvatores, “Are you really French?” Dr. Salvatores looked at him and replied with a smile, “Eh, non, je ne suis qu’un pauvre paysan italien!” (No, I’m only a poor Italian peasant!) The class had a good laugh. It did not take long for me to realize Dr. Salvatores was more than just a “pauvre paysan italien”. Massimo would later become my Ph.D. director, and we had many occasions to meet and share laughs around the world over the next 25 years. He was an outstanding scientist, mentor, and bon vivant. He was a model and an inspiration for several generations of French nuclear reactor physicists involved in the development of fast reactors and advanced fuel cycles. Dr. Salvatores initiated the integral experiment that is the subject of this article.

Five corals belonging to common scleractinian reef-building species, and collected from Gulf of Suez, Egypt were subjected to neutron activation analysis. The content of 26 elements: Na, Mg, Cl, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Zn, As, Br, Rb, Sr, Sb, I, Cs, Ba, La, Ce, Gd, Hf, Th, and U was experimentally determined. Ca and Sr have the highest content i.e. 38.4–39.5% and 0.73–0.78% respectively while, the content of all other elements was within the ranges reported for the worldwide corals. For a better understanding of the coral exoskeleton elemental content, the partition coefficient calculated for all determined elements showed a wide range of values varying from 2 × 10−4 in the case of Cl to 2 × 103 for Ce and other insoluble elements. Although all corals were collected in the vicinity of the Port Suez no traces of anthropogenic contamination were evidenced.

The review is devoted to the problems of the development of binary technologies of radiation therapy - neutron and photon-capture therapy of malignant neoplasms. These technologies are based on the principle of “biological” targeting: irradiation of a tumor with pre-delivered special preparations increasing energy release and the relative biological efficiency of primary radiation. The basis of methods, characteristics of sources of external irradiation and used preparations, and stages of development of technologies are described. The development and implementation of binary technologies attract a great number of researchers but are restrained by the shortage of operating sources of epithermal neutrons (reactors, neutron generators based on accelerators) and the lack of accurate radiation dosimetry planning systems that takes into account the dynamics and accumulation of drugs in tumors.

An epithermal neutron (0.5 eV < En < 10 keV) flux monitor developed for boron neutron capture therapy (BNCT) was optimized by Monte Carlo simulations. Based on this optimization study, the optimization results for each component of the epithermal neutron flux monitor were obtained. The simulation results indicated that the epithermal neutron flux monitor with optimal configuration was more efficiently applicable to precisely measure the epithermal neutron fluxes of BNCT neutron sources.

The purpose of this research is to conduct provenance study of the Nok sculptures in the I.P. Stanback Museum via instrumental neutron activation analysis (INAA). Several samples at different points on the sculptures were collected and then irradiated with thermal/epithermal neutrons from the PULSTAR reactor. INAA results indicate that (1) ceramic samples from the sculptures have different elemental concentrations from those of soil samples in which the sculptures may have been buried; (2) ceramic samples of the two different Nok sculptures share similar elemental concentrations; (3) ceramic firing processes cannot change the chemical composition of clay significantly.

A model for displacement cascade function was modified to account for the continuous variation of displacement density in the material in response to neutron exposure. The model is based on the Gaussian distribution of displacement energies of atoms in a material. Analytical treatment for moderated epithermal neutron field was given in which the displacement density was divided into two terms, discrete-resonance term and continuum term. Calculation are done for all isotopes using ENDF/B VII.1 data files and temperature dependent cross section library. Weighted elemental values were reported a fitting was performed to obtain energy-dependent formula of displacement density and reduce the number of parameters. Results relevant the present specification of the cascade function are tabulated for each element to enable calculation of displacement density at any value of displacement energy in the between 5 eV and 55 eV.

The results of experimental investigations of the spatial and energy distributions of the thermal and epithermal neutrons in a cassette fuel assembly, similar in design to that developed for the RITM-200 reactor core in the universal nuclear icebreaker, are presented. The measurements were performed using activation detectors with the isotopes 63Cu, 55Mn, and 197Au. It is shown that the structural nonuniformities of the fuel assembly (central water cavity, reactivity compensation system absorbing rod, strongly screened rods with consumable absorber) create significant thermal neutron flux nonuniformity over the cross-section of a fuel assembly. The flux distribution of epithermal neutrons with energy >0.4 eV is almost uniform. The experimental data are supported by calculations.

Radiative neutron capture was studied in the 70Zn(n,γ)71m,gZn reaction in order to determine the thermal neutron capture cross sections for the reactions. The resonance integrals were also measured to facilitate corrections for the epithermal neutron component. In addition, cross sections for the 64Zn(n,γ)65Zn and 68Zn(n,γ)69mZn reactions were determined. Through high-resolution γ-ray spectrometry in the 71mZn decay, a new set of γ-ray energies and intensities was obtained of roughly an order of magnitude greater precision than the previous set, and several transitions new to the decay scheme are proposed. The implications for the properties of the levels of 71Ga are discussed. More precise values of the decay half-lives for 69mZn, 71gZn, and 71mZn have been determined.

In the search for a suitable detector for demonstration neutron radiography measurements on the zero-power VR-1 training reactor at the Czech Technical University in Prague, some options were considered. Due to the reactor's low power and spatial limitations, an easy and practical solution had to be found. Self-developing films represent a flexible detection tool in x-ray imaging. Therefore, the goal of this study was to evaluate their potential for neutron detection. For this purpose, bare and converter covered films were studied in the thermal and epithermal neutron beams at the LVR-15 research reactor in Rez, Czech Republic.

Passive gamma ray spectrometry and neutron capture prompt gamma activation analysis (PGAA) were used to investigate powdered cow's milk samples [termed optimal (1), optimal (2) and optimal (3)] collected from local markets in the city of Cairo, Egypt. Standard material with a total average activity of 0.830 ± 0.2 μCi and a certified reference material [IAEA (A-14)] were used to study the accuracy of a passive multi-gamma ray measurement method. Three powdered milk samples of the same geometry and volume were used in this analysis. The specific activity of 226Ra ranged from 24.5 ± 2.1 to 114 ± 1.2 Bq/kg, 232Th from 8 ± 1 to 14 ± 1.2 Bq/kg and 40K from 444 ± 28 to 1826.1 ± 3.1 Bq/kg, all of which were higher than the activities corresponding to the United Nations Scientific Committee on the Effect of Atomic Radiation (UNSCEAR) (50, 50 and 500 Bq/kg for 226Ra, 232Th and 40K, respectively). The average dose rate at 1 cm for 40K ranged from 8.21E−02 ± 0.12 to 3.3E−1 ± 0.22 mSv/h/cm. We also showed that 208Tl81, 212Pb82 and 212Bi83 should be considered products of thorium. k0-PGAA was carried out using an integrated and calibrated prompt gamma ray system with a neutron flux of 106 n/cm2 per second. The thermal to epithermal neutron flux ratio (f) and cadmium ratio were measured using a thin gold foil technique (ration = 160). Different Cl concentrations were prepared as standards for k0-PGAA. The elemental concentrations of Na, Mg, Al, Ca, Mn, Fe, Cu, Ga, Zn, As, Se, Cs, Cd, In, Th and I were measured in the three powdered milk samples. The mean ± standard deviation ranges of the elements were as follows: Na = 1069 ± 49–1583 ± 53 ppm, Mg = 347 ± 13.64–385 ± 16.71 ppm, Al = 45 ± 1.30–72 ± 2.40 ppm, Fe = 5500 ± 110–7123 ± 130 ppm, Zn = 107 ± 3–123 ± 6 ppm, Ca = 4200 ± 72–5483 ± 81 ppm, Mn = 1269 ± 69–1784 ± 72 ppm, Pr = 1.7 ± 0.02–2.6 ± 0.07 ppm, Ga = 265 ± 5–293 ± 8 ppm, Cu = 57 ± 0.5–64 ± 0.9 ppm, In = 1000± 38.64–1574 ± 41.34 ppm, Cd = 6.1 ± 2.71–12.6 ± 4.11 ppm, I = 53 ± 0.09–62 ± 1.18 ppm, Cs = 4 ± 1.56–11 ± 4.22 ppm, As = 26 ± 0.66–29 ± 0.89 ppm, Se = 126 ± 4.8–144 ± 5.7 ppm, Th = 47 ± 1.0–78 ± 6.0 ppm.

The fundamental parity violation is enhanced by 10$^{6}$ times at maximum in several neutron induced compound nuclei. There is a theoretical prediction that fundamental T-violating effects can be also largely enhanced in compound nuclei implying that T-violation can be searched for by making very sensitive measurements. A T-violation search experiment using compound nuclei is planned at J-PARC. Polarized epithermal neutron beam, polarized nuclear target, and high count rate neutron detector are necessary for the experiment, and therefore a development of the neutron polarizer using polarized $^3$He is ongoing at J-PARC in JAEA. Recently, a clean vacuum system to fabricate $^3$He spin filters was constructed, and several $^3$He spin filters were fabricated. The current status of the development of the $^3$He spin filter was reported.

A new beam line has been designed based on the use of medical room of Tehran Research Reactor (TRR) for Boron Neutron Capture Therapy (BNCT) using MCNP4C Monte Carlo code. The medical room is located behind the east wall of the reactor pool. The designed beam line is an in-pool Beam Shaping Assembly (BSA) which is considered between the reactor core and the medical room wall. It was found that the final designed BSA can provide 2.96×109 n/cm2.s epithermal neutron flux with acceptable beam contaminations.

Cross sections for radiative neutron capture have been measured for the formation of 25-d $^{179}\mathrm{Hf}^{{m}_{2}}$ (${J}^{\ensuremath{\pi}}=25/{2}^{+}$) using targets of enriched $^{178}\mathrm{Hf}$. Based on irradiations using pure epithermal neutrons as well as mixed thermal + epithermal neutrons, the thermal cross section has been determined to be $\ensuremath{\sigma}=6(5)\phantom{\rule{0.16em}{0ex}}\ensuremath{\mu}\mathrm{b}$ and the resonance integral $I=1.63(5)\phantom{\rule{0.16em}{0ex}}\mathrm{mb}$. To enhance the determination of the cross sections, the energies and intensities of the $\ensuremath{\gamma}$ rays from the decay of $^{179}\mathrm{Hf}^{{m}_{2}}$ have been re-determined with improved precision. The half-life of $^{179}\mathrm{Hf}^{{m}_{2}}$ has been measured to be 24.91(27) d, in agreement with the previously accepted value. The analysis of the $^{179}\mathrm{Hf}^{{m}_{2}}$ decay required more precise spectrometry on competing $\ensuremath{\gamma}$ rays from the decay of $^{181}\mathrm{Hf}$, whose results are presented (along with that of the decay of $^{175}\mathrm{Hf}$) from irradiation of a source of natural Hf. The measured cross sections are compared with those of other high-spin neutron captures.

After publication of the paper, the authors noticed some errors in the list of authors and in the list of affiliations. Their correct version is given in this erratum.

In this study uranium (U) concentrations were determined in certified reference materials (CRMs) and in tree bark samples collected in “Cidade Universitária Armando de Salles Oliveira” (CUASO) USP, São Paulo. The barks were collected from different species namely Poincianella pluviosa and Tipuana tipu. These bark samples were cleaned, dried, grated and milled for the analyses by epithermal neutron activation analysis method (ENAA). This method consists on irradiating samples and U standard in IEA-R1 nuclear reactor with thermal neutron flux of 1.9 x 1012 n cm-2 s-1 during 40 to 60 seconds depending on the samples’ matrices. The samples and standard were measured by gamma ray spectroscopy. U was identified by the peak of 74.66 keV of 239U with half life of 23.47 minutes. Concentration of U was calculated by comparative method. For analytical quality control of U results, certified reference materials were analyzed. Results obtained for CRMs presented good precision and accuracy, with |Z score| ≤ 0.39. Uranium concentrations in tree barks varied from 83.1 to 627.6 ng g-1 and the relative standard deviations of these results ranged from 1.8 to 10 %.

An epithermal neutron beam has been designed for Boron neutron Capture Therapy (BNCT) at the thermal column of Tehran Research Reactor (TRR) recently. In this paper the whole body effective dose, as well as the equivalent doses of several organs have been calculated in this facility using MCNP4C Monte Carlo code. The effective dose has been calculated by using the absorbed doses determined for each individual organ, taking into account the radiation and tissue weighting factors. The ICRP 110 whole body male phantom has been used as a patient model. It was found that the effective dose during BNCT of a brain tumor is equal to 0.90Sv. This effective dose may induce a 4% secondary cancer risk.

The purpose of this study is to test the applicability of k 0 -INAA method at the Istanbul Technical University TRIGA Mark II research reactor. The neutron spectrum parameters such as epithermal neutron flux distribution parameter ( α ), thermal to epithermal neutron flux ratio ( f ) and thermal neutron flux ( φ th ) were determined at the central irradiation channel of the ITU TRIGA Mark II research reactor using bare triple-monitor method. HPGe detector calibrations and calculations were carried out by k 0 -IAEA software. The α , f and φ th values were calculated to be −0.009, 15.4 and 7.92·10 12 cm −2 s −1 , respectively. NIST SRM 1633b coal fly ash and intercomparison samples consisting of clay and sandy soil samples were used to evaluate the validity of the method. For selected elements, the statistical evaluation of the analysis results was carried out by z -score test. A good agreement between certified/reported and experimental values was obtained.

Boron neutron capture therapy (BNCT) is a biochemically targeted radiotherapy based on the nuclear capture and fission reactions that occur when non-radioactive boron-10, which is a constituent of natural elemental boron, is irradiated with low energy thermal neutrons to yield high linear energy transfer alpha particles and recoiling lithium-7 nuclei. Therefore, BNCT enables the application of a high dose of particle radiation selectively to tumor cells in which boron-10 compound has been accumulated. We applied BNCT using nuclear reactors for 167 cases of malignant brain tumors, including recurrent malignant gliomas, newly diagnosed malignant gliomas, and recurrent high-grade meningiomas from January 2002 to May 2014. Here, we review the principle and history of BNCT. In addition, we introduce fluoride-18-labeled boronophenylalanine positron emission tomography and the clinical results of BNCT for the above-mentioned malignant brain tumors. Finally, we discuss the recent development of accelerators producing epithermal neutron beams. This development could provide an alternative to the current use of specially modified nuclear reactors as a neutron source, and could allow BNCT to be performed in a hospital setting.

Thermalized neutrons arising at the surface of solar planets are produced from the interaction of cosmic rays with the nucleus consisting of surficial materials. The neutron energy spectrum in the range between thermal and epithermal regions at the lunar surface was investigated based on the combination of the isotopic variations of Sm and Gd caused by the thermal neutron-capture reactions in our previous study, with those of Dy, Er, and Yb caused by the epithermal neutron-capture reactions in this study. The detailed comparison of the systematic isotopic variations among Sm, Gd, Dy, Er, and Yb helps to construct a neutron energy spectrum at the surface of the Moon. Seven kinds of lunar soils at different depths of the drill core recovered from the Apollo 15 landing site (A-15) were used in this study. Isotopic variations of 164Dy/161Dy, 168Er/167Er, and 168Yb/174Yb were newly found in the A-15 samples, and showed the depth dependence caused by the interaction with cosmic-ray irradiation. In particular, the combination of the isotopic shifts of 168Er/167Er and 150Sm/149Sm could be effectively used to evaluate the epithermal neutron fluences of 5.4–8.1 × 10^17 n cm^−2 that were more than 10 times higher than thermal neutron fluences of 0.48–0.69 × 10^17 n cm^−2 reestimated in this study.