Coupled neutronic/thermal-hydraulic hot channel analysis of high power density civil marine SMR cores

Core average power density of standard small modular reactors (SMR) are generally limited to 60–65 MW/m3, which is 40% lower than for a standard civil PWR in order to accommodate better thermal margins. While designing a SMR core for civil marine propulsion systems, it is required to increase its power density to make more attractive for future deployment. However, there are obvious thermal-hydraulic (TH) concerns regarding a high power density (HPD) core, which needs to be satisfied in order to ensure safe operation through accurate prediction of the TH parameters. This paper presents a coupled neutronic/thermal-hydraulic (TH) hot channel analysis of a HPD 375 MWth soluble-boron-free PWR core using 19.25% 235U enriched micro- heterogeneous ThO2-UO2 duplex fuel and 16% 235U enriched homogeneously mixed all-UO2 fuel with a 15 effective full-power-years (EFPY) core life. To perform this analysis the hybrid Monte Carlo reactor physics code MONK is coupled with sub-channel analysis TH code COBRA-EN. This approach is used to investigate the feasibility of different HPD marine PWR concepts and to identify the main TH challenges characterising these designs. To design HPD cores of between 82 and 111 MW/m3, three cases were chosen by optimizing the fuel pin diameter, pin pitch and pitch-to-diameter ratio. These cases have been studied to determine whether TH safety limits are satisfied by evaluating key parameters, such as minimum departure from nucleate boiling ratio, surface heat flux, critical heat flux, cladding inner surface and fuel centreline temperatures, and pressure drop. The results show that it is possible to achieve a core power density of 100 MW/m3 for both the candidate fuels, a ∼50% improvement on the reference design (63 MW/m3), while meeting the target core lifetime of 15 EFPY and remaining within TH limits. The size of the pressure vessel can therefore be reduced substantially and the economic competitiveness of the proposed civil marine PWR reactor core significantly improved

The Noncommutative Harmonic Oscillator based in Simplectic Representation of Galilei Group

In this work we study symplectic unitary representations for the Galilei group. As a consequence the Schr\"odinger equation is derived in phase space. The formalism is based on the non-commutative structure of the star-product, and using the group theory approach as a guide a physical consistent theory in phase space is constructed. The state is described by a quasi-probability amplitude that is in association with the Wigner function. The 3D harmonic oscillator and the noncommutative oscillator are studied in phase space as an application, and the Wigner function associated to both cases are determined.Comment: 7 pages,no figure

Hot channel analysis of a 333 MWth high power density civil marine core using 3D neutronic/thermal-hydraulic coupling of hybrid Monte Carlo MONK with sub-channel analysis COBRA-EN code

This paper presents a coupled neutronic/thermalhydraulic (TH) hot channel (HC) analysis of a high power density (HPD) 333 MWth soluble-boronfree PWR core using 18% U-235 enriched microheterogeneous ThO2-UO2 duplex fuel and 15% U-235 enriched homogeneously mixed all-UO2 fuel with a 15 effective full-power-years (EFPY) core life. This work utilizes the coupling of MONK as a hybrid Monte Carlo (MC) reactor physics code with subchannel analysis TH code COBRA-EN. This approach is used to investigate the feasibility of different HPD marine PWR concepts and to identify the main TH challenges characterising these designs. To design HPD cores of between 90 and 250 MW/m3, five cases were chosen by optimizing the fuel pin diameter (D), pin pitch (P) and pitch-to-diameter ratio (P/D). These cases have been studied to evaluate key TH parameters, such as MDNBR, surface heat flux, critical heat flux, cladding inner surface and fuel centreline temperatures, and pressure drop to determine whether TH safety limits are satisfied. The results show that it is possible to achieve a core power density of 120 MW/m3 for both the candidate fuels, a ∼90% improvement on the reference design and ∼18% greater than that of the Sizewell B PWR (101.6 MW/m3), while meeting the target core lifetime of 15 EFPY and remaining within TH limits. The size of the pressure vessel can therefore be reduced dramatically and the economic competitiveness of the proposed civil marine PWR reactor core significantly improved

Coupled neutronic/thermal-hydraulic hot channel analysis of high power density civil marine SMR cores

Core average power density of standard small modular reactors (SMR) are generally limited to 60–65 MW/m3, which is 40% lower than for a standard civil PWR in order to accommodate better thermal margins. While designing a SMR core for civil marine propulsion systems, it is required to increase its power density to make more attractive for future deployment. However, there are obvious thermal-hydraulic (TH) concerns regarding a high power density (HPD) core, which needs to be satisfied in order to ensure safe operation through accurate prediction of the TH parameters. This paper presents a coupled neutronic/thermal-hydraulic (TH) hot channel analysis of a HPD 375 MWth soluble-boron-free PWR core using 19.25% 235U enriched micro- heterogeneous ThO2-UO2 duplex fuel and 16% 235U enriched homogeneously mixed all-UO2 fuel with a 15 effective full-power-years (EFPY) core life. To perform this analysis the hybrid Monte Carlo reactor physics code MONK is coupled with sub-channel analysis TH code COBRA-EN. This approach is used to investigate the feasibility of different HPD marine PWR concepts and to identify the main TH challenges characterising these designs. To design HPD cores of between 82 and 111 MW/m3, three cases were chosen by optimizing the fuel pin diameter, pin pitch and pitch-to-diameter ratio. These cases have been studied to determine whether TH safety limits are satisfied by evaluating key parameters, such as minimum departure from nucleate boiling ratio, surface heat flux, critical heat flux, cladding inner surface and fuel centreline temperatures, and pressure drop. The results show that it is possible to achieve a core power density of 100 MW/m3 for both the candidate fuels, a ∼50% improvement on the reference design (63 MW/m3), while meeting the target core lifetime of 15 EFPY and remaining within TH limits. The size of the pressure vessel can therefore be reduced substantially and the economic competitiveness of the proposed civil marine PWR reactor core significantly improved

Vasopressin serum levels in patients with severe brain lesions and in brain-dead patients

Introduction: Patients with severe brain lesions (SBL) and brain-dead patients (BD) frequently present with vasopressin (AVP) secretion disorders. Objective: To evaluate AVID serum levels in SBL and BD patients. Design: Prospective, open label, observational trial. Setting: A general teaching hospital. Method: Three groups of adult subjects (age greater than or equal to 18y) of both sexes were included in this study: control group: 29 healthy volunteers; SBL group: 17 patients with Glasgow Coma Scale (GCS): less than or equal to8; and BD group: 11 brain-dead patients. Samples of venous blood were collected in the morning at rest from healthy volunteers and at 8 hourly intervals over a period of 24h from SBL and BID patients for AVP determinations. Concomitantly, some clinical and laboratorial variables were also recorded. Results: AVP serum levels (pg/ml) were [mean (SD); median]: control [2.2(1.1); 2.01; SBL [5.7(6.3); 2.9]; and BID [2.6(1.0); 2.81. AVID serum levels varied greatly in SBL patients, but without statistically significant difference in relation to the other groups (p=0.06). Hypotension (p=0.02), hypernatremia (p=0.0001), serum hyperosmolarity (p=0.0001) and urinary hypoosmolarity (p=0.003) were outstanding in BD patients when compared with SBL. Conclusions: The AVP serum levels did not demonstrate significant statistical difference between the groups, only showing a greater variability in SBL patients (manifested as serum spike levels). Hypernatremia and hyperosmolarity were present in BD patients, indicating a failure of the hypothalamic-pituitary system in AVP production and release.622A22623