Delayed fast neutron as an indicator of burn-up for nuclear fuel elements

Akyurek, T.,Shoaib, S.B.,Usman, S. Korean Nuclear Society 2021 Nuclear Engineering and Technology Vol.53 No.10

Feasibility study of burn-up analysis and monitoring using delayed fast neutrons was investigated at Missouri University of Science and Technology Reactor (MSTR). Burnt and fresh fuel elements were used to collect delayed fast neutron data for different power levels. Total reactivity varied depending on the burn-up rate of fuel elements for each core configuration. The regulating rod worth was 2.07E-04 𝚫k/k/in and 1.95E-04 𝚫k/k/in for T121 and T122 core configurations at 11 inch, respectively. Delayed fast neutron spectrum of F1 (burnt) and F16 (fresh) fuel elements were analyzed further, and a strong correlation was observed between delayed fast neutron emission and burn-up. According to the analyzed peaks in burnt and fresh fuels, reactor power dependency was observed and it was determined that delayed neutron provided more reliable results at reactor powers of 50 kW and above.

A new dead-time determination method for gamma-ray detectors using attenuation law

T. Akyurek 한국원자력학회 2021 Nuclear Engineering and Technology Vol.53 No.12

This study presents a new dead-time measurement method using the gamma attenuation law andgeneralized dead-time models for nuclear gamma-ray detectors. The dead-time of the NaI(Tl) detectionsystem was obtained to validate the new dead-time determination method using very thin lead andpolyethylene absorbers. Non-paralyzing dead-time was found to be 8.39 ms, and paralyzing dead-timewas found to be 8.35 ms using lead absorber for NaI(Tl) scintillator detection system. These dead-timevalues are consistent with the previously reported dead-time values for scintillator detection systems. The gamma build-up factor's contribution to the dead-time was neglected because a very thin materialwas used.

Determination of Plutonium and Uranium Content and Burnup Using Six Group Delayed Neutrons

T. Akyurek,S. Usman 한국원자력학회 2019 Nuclear Engineering and Technology Vol.51 No.4

In this study, investigation of spent fuel was performed using six group delayed neutron parameters. Three used fuels (F1, F2, and F11) which are burnt over the years in the core of Missouri University ofScience and Technology Reactor (MSTR), were investigated. F16 fresh fuel was used as plutonium freefuel element and compared with irradiated used fuels to develop burnup and Pu discrimination method. The fast fission factor of the MSTR was calculated to be 1.071 which was used for burnup calculations. Burnup values of F2 and F11 fuel elements were estimated to be 1.98 g and 2.7 g, respectively. 239Puconversion was calculated to be 0.36 g and 0.50 g for F2 and F11 elements, respectively

Voltage dependent pulse shape analysis of Geiger-Müller counter

B. Almutairi,T. Akyurek,S. Usman 한국원자력학회 2019 Nuclear Engineering and Technology Vol.51 No.4

Detailed pulse shape analysis of a Geiger-Müller counter is performed to understand the pulse shapedependence on operating voltage. New data is presented to demonstrate that not all pulses generated ina GM counter are identical. In fact, there is a strong correlation between the operating voltage and thepulse shape. Similar to detector deadtime, pulse shapes fall in three distinct regions. For low voltageregion, where deadtime was reported to reduce with increasing voltage, pulse generated in this regionwas observed to have a fixed pulse width with a variable tail. The pulse width and fall time of the tail wasobserved to be a function of applied voltage; exponentially reducing with increasing voltage with anexponent of negative 6E-04 and 2E-03 respectively. The second region showed a pulse without anysignificant tail. During this time the detector deadtime was earlier reported to be at its minimum. Thehighest voltage region demonstrated a different deadtime mechanism where the second pulse wasreduced in width. During this time the deadtime seemed to be increasing with increasing voltage. Thisdata allows us to gain some unique insight into the phenomenon of GM detector deadtime not reportedthus far.

The Evaluation of Exogenous Melatonin Administration in Supraspinatus Overuse Tendinopathy in an Experimental Rat Model

Onur Kocadal,Murad Pepe,Nalan Akyurek,Zafer Gunes,Hatice Surer,Ertugrul Aksahin,Betul Ogut,Cem Nuri Aktekin 대한견주관절학회 2019 대한견주관절학회지 Vol.22 No.2

Background: Increased oxidative stress and inflammation play a critical role in the etiopathogenesis of chronic tendinopathy. Melatonin is an endogenous molecule that exhibits antioxidant and anti-inflammatory activity. The aim of this study was to evaluate the biochemi-cal and histopathological effects of exogenous melatonin administrations in supraspinatus overuse tendinopathy.Methods: Fifty rats were divided into the following four groups: cage activity, melatonin treatment, corticosteriod therapy, and control. Melatonin (10 mg/kg, intraperitoneal; twice a day) and triamcinolone (0.3 mg/kg, subacromial; weekly) were administered to the treat-ment groups after the overuse period. Biochemical and histopathological evaluations were performed on serum samples and biopsies obtained from rats. Plasma inducible nitric oxide synthase (iNOS), vascular endothelial growth factor (VEGF), total antioxidant status (TAS), total oxidant status (TOS), and oxidative stress index (OSI) levels were evaluated biochemically. Results: The TAS, TOS, OSI, iNOS, and VEGF values were significantly lower than the pre-treatment levels in rats receiving exogenous melatonin treatment (3 or 6 weeks) (p<0.05). TOS, iNOS, VEGF, and OSI values after 3 weeks of triamcinolone administration, and TOS, VEGF, and OSI levels after 6 weeks of triamcinolone application, were significantly lower than the pre-treatment levels (p<0.05). Conclusions: Exogenous melatonin application in overuse tendinopathy reduces oxidative stress and inflammation. Melatonin might be an alternative potential molecule to corticosteroids in the treatment of chronic tendinopathy.

Evaluation of the Radiation Pneumonia Development Risk in Lung Cancer Cases

Yilmaz, Sercan,Adas, Yasemin Guzle,Hicsonmez, Ayse,Andrieu, Meltem Nalca,Akyurek, Serap,Gokce, Saban Cakir Asian Pacific Journal of Cancer Prevention 2014 Asian Pacific journal of cancer prevention Vol.15 No.17

Background: Concurrent chemo-radiotherapy is the recommended standard treatment modality for patients with locally advanced lung cancer. The purpose of three-dimensional conformal radiotherapy (3DCRT) is to minimize normal tissue damage while a high dose can be delivered to the tumor. The most common dose limiting side effect of thoracic RT is radiation pneumonia (RP). In this study we evaluated the relationship between dose-volume histogram parameters and radiation pneumonitis. This study targeted prediction of the possible development of RP and evaluation of the relationship between dose-volume histogram (DVH) parameters and RP in patients undergoing 3DCRT. Materials and Methods: DVHs of 41 lung cancer patients treated with 3DCRT were evaluated with respect to the development of grade ${\geq}2$ RP by excluding gross tumor volume (GTV) and planned target volume (PTV) from total (TL) and ipsilateral (IPSI) lung volume. Results: Were admitted statistically significant for p<0.05. Conclusions: The cut-off values for V5, V13, V20, V30, V45 and the mean dose of TL-GTV; and V13, V20,V30 and the mean dose of TL-PTV were statistically significant for the development of Grade ${\geq}2$ RP. No statistically significant results related to the development of Grade ${\geq}2$ RP were observed for the ipsilateral lung and the evaluation of PTV volume. A controlled and careful evaluation of the dose-volume histograms is important to assess Grade ${\geq}2$ RP development of the lung cancer patients treated with concurrent chemo-radiotherapy. In the light of the obtained data it can be said that RP development may be avoided by the proper analysis of the dose volume histograms and the application of optimal treatment plans.

Visceral Leishmaniasis Mimicking Autoimmune Hepatitis, Primary Biliary Cirrhosis, and Systemic Lupus Erythematosus Overlap

Ozlem Guzel Tunccan,Abdurrahman Tufan,Gulcin Telli,Nalan Akyurek,Merve Pamukcuo?lu,Guldal Yılmaz,Kenan Hızel 대한기생충학열대의학회 2012 The Korean Journal of Parasitology Vol.50 No.2

Comparison of 2-Dimensional and 3-Dimensional Conformal Treatment Plans in Gastric Cancer Radiotherapy

Adas, Yasemin Guzle,Andrieu, Meltem Nalca,Hicsonmez, Ayse,Atakul, Tugba,Dirican, Bahar,Aktas, Caner,Yilmaz, Sercan,Akyurek, Serap,Gokce, Saban Cakir,Ergocen, Salih Asian Pacific Journal of Cancer Prevention 2014 Asian Pacific journal of cancer prevention Vol.15 No.17

Background: Postoperative chemoradiotherapy is accepted as standard treatment for stage IB-IV, M0 gastric cancer. Radiotherapy (RT) planning of gastric cancer is important because of the low radiation tolerance of surrounding critical organs. The purpose of this study was to compare the dosimetric aspects of 2-dimensional (2D) and 3-dimensional (3D) treatment plans, with the twin aims of evaluating the adequacy of 2D planning fields on coverage of planning target volume (PTV) and 3D conformal plans for both covering PTV and reducing the normal tissue doses. Materials and Methods: Thirty-six patients with stage II-IV gastric adenocarcinoma were treated with adjuvant chemoradiotherapy using 3DRT. For each patient, a second 2D treatment plan was generated. The two techniques were compared for target volume coverage and dose to normal tissues using dose volume histogram (DVH) analysis. Results: 3DRT provides more adequate coverage of the target volume. Comparative DVHs for the left kidney and spinal cord demonstrate lower radiation doses with the 3D technique. Conclusions: 3DRT produced better dose distributions and reduced radiation doses to left kidney and spinal cord compared to the 2D technique. For this reason it can be predicted that 3DRT will result in better tumor control and less normal tissue complications.

A multi-institutional analysis of sequential versus ‘sandwich’ adjuvant chemotherapy and radiotherapy for stage IIIC endometrial carcinoma

Cem Onal,Sezin Yuce Sari,Berna Akkus Yildirim,Guler Yavas,Melis Gultekin,Ozan Cem Guler,Serap Akyurek,Ferah Yildiz 대한부인종양학회 2019 Journal of Gynecologic Oncology Vol.30 No.3

Objective: To analyze the outcomes of sequential or sandwich chemotherapy (ChT) and radiotherapy (RT) in patients with node-positive endometrial cancer (EC). Methods: Data from 4 centers were collected retrospectively for 179 patients with stage IIIC EC treated with postoperative RT and ChT (paclitaxel and carboplatin). Patients were either treated with 6 cycles of ChT followed by RT (sequential arm; 96 patients) or with 3 cycles of ChT, RT, and an additional 3 cycles of ChT (sandwich arm; 83 patients). Prognostic factors affecting overall survival (OS) and progression-free survival (PFS) were analyzed. Results: The 5-year OS and PFS rates were 64% and 59%, respectively, with a median followup of 41 months (range, 5–167 months). The 5-year OS rates were significantly higher in the sandwich than sequential arms (74% vs. 56%; p=0.03) and the difference for 5-year PFS rates was nearly significant (65% vs. 54%; p=0.05). In univariate analysis, treatment strategy, age, International Federation of Gynecology and Obstetrics (FIGO) stage, pathology, rate of myometrial invasion, and grade were prognostic factors for OS and PFS. In multivariate analysis, non-endometrioid histology, advanced FIGO stage, and adjuvant sequential ChT and RT were negative predictors for OS, whereas only non-endometrioid histology was a prognostic factor for PFS. Conclusion: Postoperative adjuvant ChT and RT for stage IIIC EC patients, either given sequentially or sandwiched, offers excellent clinical efficacy and acceptably low toxicity. Our data support the superiority of the sandwich regimen compared to the sequential strategy in stage IIIC EC patients for OS.

Relations of Serum Visfatin and Resistin Levels with Endometrial Cancer and Factors Associated with its Prognosis

Ilhan, Tolgay Tuyan,Kebapcilar, Aysegul,Yilmaz, Setenay Arzu,Ilhan, Turkan,Kerimoglu, Ozlem Secilmis,Pekin, Aybuke Tazegul,Akyurek, Fikret,Unlu, Ali,Celik, Cetin Asian Pacific Journal of Cancer Prevention 2015 Asian Pacific journal of cancer prevention Vol.16 No.11

Background: The aims of this study were compare the serum visfatin and resistin levels between endometrial cancer (EC) patients and controls and evaluate their power to predict prognosis. Materials and Methods: This prospective study was conducted between March 2013 to June 2014 on the Gynecologic Oncology Department of the University of Selcuk, Konya, Turkey. A total of 42 EC patients and 42 controls were included and assessed for differences in serum visfatin and resistin levels, along with prognostic factors. Results: Endometrial cancer patients had significantly higher visfatin levels than control s (p: 0.011), associated with deep myometrial invasion (p: 0.019). In contrast the serum level of resistin did not significantly differ between EC patients and controls (p: 0.362). However, high resistin level in EC patients was associated with increase lymph node metastasis (p: 0.009). On logistic regression analysis, we found that serum visfatin elevation was associated with risk of myometrial invasion (OR: 1,091; 95%CI: 1.021-1.166; p: 0.010) and serum resistin with risk of lymph node metastasis (OR: 1.018; 95%CI: 1.000-1.035; p: 0.046). For myometrial invasion prediction, a serum visfatin level greater than 26.8 ng/mL demonstrated a sensitivity and specificity of 66.6 % and 96.4%, respectively. For lymph node metastasis prediction, the best cut-off for serum resistin level was 599ng/mL. A serum resistin level greater than this demonstrated a sensitivity and specificity of 87.5% and 77.1%, respectively. Conclusions: Our data suggest that serum visfatin is elevated in patients with EC and serum visfatin and resistin levels could be used to predict the risk of advance stage lesions.