Resonance data for self-shielding problems

The investigation of resonance self-shielding effects in macroscopic medium is important for the physics of nuclear reactors and shielding. The degree of consistency of evaluated resonance cross sections data and the requirements to the accurate presentation of self-shielding effects can be estimated by using the simplest benchmark data for resonance averaged functions of neutron transmission and self-indication cross section at arbitrary filter thickness n. We report the developed (for nonfissile nuclei) methods for description of cross sections and their functionals in the unresolved resonance range that aim to estimate properly the self-shielding effects and reveal the resonance structure in averaging intervals (groups)

Resonance Analysis in the Region of Unresolved Resonance

The independent analysis of new experimental data for 232Th cross sections in the unresolved region performed on the basis of the existing scheme and method of evaluation confirm the previously obtained average resonance parameters. The method of statistical modeling of the resonant cross-section structure in the unresolved resonance region, proposed and developed earlier by introducing the characteristic function of R-matrix elements distribution and the presentation of this by a ladder of fixed "resonances," is used for calculation of the self-shielding factors of 232Th. The results are given in comparison with those of the code NJOY and experimental data.JRC.D.5-Neutron physic

Neutron-Induced Activation Cross Sections on Hafnium Isotopes from the Threshold to 20 Mev

Results of new cross section measurements are presented for the following neutron-induced reactions : 178Hf(n,alpha)175Yb, 180Hf(n,alpha)177Yb, 177Hf(n,p)177Lug, 178Hf(n,x)177Lug, 180Hf(n,p)180Lu, 180Hf(n,n'gamma)180Hfm, 174Hf(n,2n)173Hf, 176Hf(n,2n)175Hf, and 177Hf(n,3n)175Hf obtained with activation technique. The irradiations were carried out at the 7-MV Van de Graaff accelerator at IRMM, Geel. Quasi monoenergetic neutrons with energies between 14.8 and 20.5 MeV were produced via the 3H(d,n)4He reaction at Ed = 1, 1.4, 2, 3, and 4 MeV. The 3H(p,n)3He reaction was employed for the production of neutrons in the 2-3 MeV energy range. Both natural and enriched samples were used to facilitate correction for interference between reactions leading to the same product. The radioactivity of the samples was determined by standard gamma-ray spectrometry using HPGe detector. The current measurements are compared with the data from other authors and Evaluated Nuclear Data Files. Cross sections for three of the studied reactions are reported for the first time.JRC.DG.D.5-Nuclear physic

Determination of the 232Th(n,gamma) Cross Section from 4 to 140 keV at GELINA

The neutron capture cross section of thorium has been masured in the energy region between 4 and 140 keV at the GELINA time-of-flight facility of the Institute for Reference Materials and Measurements in Geel, Belgium. The gamma-rays from capture events were detected by two C6D6 liquid scintillators, placed 14.37 m from the neutron source. The shape of the neutron flux was measured with a 10B-loaded ionization chamber. To obtain a detection efficienct independent of the gamma cascade and proportional to the total excitation energy, the pulsheight weighting technique was applied. The data have been normalized to the well-isolated and almost saturated 232Th resonance at 23.5 eV. The systematic uncertainties related to the normalization and weighting function, using an internal saturated resonance, are +- 1.5%. An additional systematic uncertainty of 0.5% results from the self-shielding and multiple scattering corrections. Between 4 and 140 keV, our date are +- 9 and 6.5% higher than the data of Kabayashi et al. and Macklin et al. respectively, and in good agreement with the data of Poenitz and Smith. below 15 keV our data deviate by up to 30% from the data reported by Wisshiak et al. Our dat have been analyzed in terms of average level parameters. The resulting parameters are consistent with the resolved resonance parameters deduced from the transmission measurements of Olsen et al.JRC.D.5-Neutron physic

Determination of the 232Th(n,gamma) Cross Section from 4 to 140 keV at GELINA.

Abstract not availableJRC.D-Institute for Reference Materials and Measurements (Geel

Locally Advanced Pancreatic Carcinoma - R 1-2 Resection or Bypass Procedure

Aim: Pancreatic cancer is an aggressive disease with poor prognosis. The radical surgical removal of the tumor (R0 resection) is a major determinant of postoperative survival. The aim of the study is an analysis of postoperative survival in patients with locally advanced pancreatic head carcinoma, where R1-2 pancreaticoduodenectomy or bypass surgery is performed.Materials and Methods: 288 patients with pancreatic head adenocarcinoma have been admitted to the Department of Surgery at the Naval Hospital, Varna for a period from January, 1995 until January, 2016. 115 (39.9%) underwent bypass surgery, and pancreaticoduodenectomy (Whipple or pylorus preserving) in combination with standard lymphadenectomy was performed on the remaining 173 (60.0%). Pancreaticoduodenectomy was defined as R0 resection in 122 (70.5%) patients, R1- in 43 (24.8%) and R2 - in the remaining 8 (4.6%) patients.Results: In the patient groups with R0 and R1 resection, the mean postoperative survival was significantly longer than that after a bypass surgery (18/13 vs 3/7 months) (

Liver Haemangioma

Aim: Hepatic haemangiomas (HHs) are the most common benign hepatic tumors. Elective surgery for giant HHs is still controversial. The aim of this retrospective study is an analysis of risk factors associated with the surgical treatment of HHs and the resulting postoperative complications.Materials and Methods: Forty-two patients underwent surgery for giant HHs at the Naval Hospital, Varna, Bulgaria between January, 2001 and December, 2014. Clinical presentation, diagnosis, treatment, and postoperative complications were analyzed.Results: Forty-one patients (97.6%) underwent elective surgery while in 1(2.4%) patient an emergency right hemihepatectomy had to be performed because of a ruptured haemangioma. The major indication for elective removal of HHs is abdominal pain. A total of 24 (57.1%) major liver resections and 18 (42.8%) enucleations were performed. Five patients had complications, including a biloma (n=2), a liver abscess (n=1), postoperative bleeding (n=1), and a wound infection (n=1). Resection and enucleation were both relatively safe with an acceptable complication rate (11.9%) and there was no mortality. The complication rates for enucleation and resection were 5.5% (1/18) and 16.6% (4/24), respectively, but the difference was not statistically significant (p=0.623). Clinical features including large tumor size (p=0.011), symptomatic tumors (p=0.013), increased blood loss (p=0.035), and prolonged operative time (p=0.005), indicating higher risks, were associated with an increase in the postoperative complications.Conclusion: Recent advances in surgical techniques and established perioperative management have now made it possible to perform liver resection or enucleation safely in most specialized units. Identifying the discriminatory factors that predict postoperative complications are important in establishing effective strategies for surgical procedures

Hepatopancreatoduodenectomy

Aim: We present our experience with a hepatopancreatoduodenectomy as a method of surgical treatment of lateral advanced malignant tumors of the gallbladder and analyze the clinical significance of this operating procedure.Materials and Methods: The study is retrospective (2005-2014) and includes four patients with locally advanced carcinoma of the gallbladder, engaging a hepaticocholedochus, the head of the pancreas and the duodenum with a spread to the retropancreatic lymph nodes, where a hepatopancreatoduodenectomy is performed.Results: Hemihepatectomy was performed in two of the patients, while the other two had liver resections, which involved a removal of two liver segments and part of Sg1. The postoperative mortality was 0%. Postoperative complications of grade I-II according classification of Dindo-Clavien were registred in two patients. The average survival was 13 months.Conclusions: Hepatopancreatoduodenectomy is a technical challenge and may be carried out with a low incidence of postoperative complications and zero mortality. This type of surgery is the only alternative for locally advanced carcinoma of the gallbladder and the extrahepatic bile duct

Duplication of the Extrahepatic Bile Ducts, Accessory Hepatic Lobe, Accessory Pancreas, Aberrant or Accessory Blood Vessels in Hepatoduodenal Ligament

Aim: Duplication of the extrahepatic bile ducts, accessory hepatic lobe, accessory pancreas, aberrant or accessory blood vessels in hepatoduodenal ligament are rare congenital malformations and the purpose of the present study.Materials and Methods: For the period 2005-2016, in the Department of Surgery at the Naval Hospital, Varna, the following distribution of diagnoses was established: four patients with a duplication of the extrahepatic bile ducts (n=2, duplication of d.cysticus; n=2, duplication of d.hepaticocholedochus), three patients with aberrant common hepatic artery, nine with aberrant right hepatic artery, ten patients with accessory rightl/left hepatic artery, one with an accessory pancreas, and six patients with accessory liver lobe with a diameter of 1 cm to 11 cm.Results: With one exception, in all patients described, the congenital malformations were asymptomatic and diagnosed as accidental intraoperative findings. The accessory pancreas located in the wall of the proximal jejunum was the reason for intermittent melena and anemic syndrome in one of the patients.Conclusions: Duplications of the abdominal organs are rare congenital malformations and are diagnosed in one in 4,500 autopsies. They are recorded more often in men from European ancestry. Intraoperative recognition of these malformations is important, especially in the era of laparoscopic surgery