Annual Report 2010 - Operation and Utilisation of the High Flux Reactor

The High Flux Reactor (HFR) at Petten is managed by the Institute for Energy (IE) of the EC - DG JRC and operated by NRG who are also licence holder and responsible for commercial activities. The HFR operates at 45 MW and is of the tank-in-pool type, light water cooled and moderated. It is one of the most powerful multi-purpose materials testing reactors in the world and one of the world leaders in target irradiation for the production of medical radioisotopes.JRC.F.4-Nuclear Reactor Integrity Assessment and Knowledge Managemen

Operation and Utilisation of the High Flux Reactor - Annual Report 2009

The High Flux Reactor (HFR) at Petten is managed by the Institute for Energy (IE) of the EC - DG JRC and operated by NRG who are also licence holder and responsible for commercial activities. The HFR operates at 45 MW and is of the tank-in-pool type, light water cooled and moderated. It is one of the most powerful multi-purpose materials testing reactors in the world and one of the world leaders in target irradiation for the production of medical radioisotopes.JRC.F-Institute for Energy and Transport (Petten

Navigator‐free metabolite‐cycled proton spectroscopy of the heart

Purpose Respiratory gating in cardiac water‐suppressed (WS) proton spectroscopy leads to long and unpredictable scan times. Metabolite cycling allows to perform frequency and phase correction on the water signal and, hence, offers an approach to navigator‐free cardiac spectroscopy with fixed scan time. The objective of the present study was to develop and implement navigator‐free metabolite‐cycled cardiac proton spectroscopy (MC nonav) and compare it with standard navigator‐gated WS (WS nav) and navigator‐free WS (WS nonav) measurements for the assessment of triglyceride‐to‐water ratios (TG/W) and creatine‐to‐water ratios (CR/W) in the intraventricular septum of the in vivo heart. Methods Navigator‐free metabolite‐cycled spectroscopy was implemented on a clinical 1.5T system. In vivo measurements were performed on 10 young and 5 older healthy volunteers to assess signal‐to‐noise ratio efficiency as well as TG/W and CR/W and the relative Cramér‐Rao lower bounds for CR. The performance of the metabolite‐cycled sequence was verified using simulations. Results On average, scan times of MC nonav were 3.4 times shorter compared with WS nav, while no significant bias for TG/W was observed (coefficient of variation = 14.0%). signal‐to‐noise ratio efficiency of both TG and CR increased for MC nonav compared with WS nav. Relative Cramér‐Rao lower bounds of CR decreased for MC nonav. Overall spectral quality was found comparable between MC nonav and WS nav, while it was inferior for WS nonav. Conclusion Navigator‐free metabolite‐cycled cardiac proton spectroscopy offers 3.4‐fold accelerated assessment of TG/W and CR/W in the heart with preserved spectral quality when compared with navigator‐gated WS scans

Cardiac- versus diaphragm-based respiratory navigation for proton spectroscopy of the heart

OBJECTIVES To study inter-individual differences of the relation between diaphragm and heart motion, the objective of the present study was to implement respiratory navigation on the heart and compare it against the established method of navigator gating on the diaphragm for single-voxel cardiac H-MRS. MATERIALS AND METHODS H-MRS was performed on a 1.5T system in 19 healthy volunteers of mixed age (range 24-75 years). Spectra were recorded in a 6-8 ml voxel in the ventricular septum using a PRESS (point-resolved spectroscopy) sequence and ECG gating. Water-unsuppressed data acquired with pencil beam navigation on the heart were compared to data with navigation on the diaphragm. Water-suppressed data were obtained to assess triglyceride-to-water ratios. RESULTS Water phase and amplitude fluctuations for cardiac versus diaphragm navigation did not reveal significant differences. Both navigator positions provided comparable triglyceride-to-water ratios and gating efficiencies (coefficient of variation (CoV) 7.0%). The cardiac navigator showed a good reproducibility (CoV 5.2%). DISCUSSION Respiratory navigation on the heart does not convey an advantage over diaphragm-based navigator gating for cardiac H-MRS, but also no disadvantage. Consequently, cardiac and diaphragm respiratory navigation may be used interchangeably

Long term out-of-pile thermocouple tests in conditions representative for nuclear gas-cooled high temperature reactors

During irradiation tests at high temperature failure of commercial Inconel 600 sheathed thermocouples is commonly encountered. As instrumentation, in particular thermocouples are considered safety-relevant both for irradiation tests and for commercial reactors, JRC and THERMOCOAX joined forces to solve this issue by performing out-of-pile tests with thermocouples mimicking the environment encountered by high temperature reactor (HTR) in-core instrumentation. The objective was to screen innovative sheathed thermocouples which would consecutively be tested under irradiation. Two such screening tests have been performed in high temperature environment (i.e. temperature in the range 1100–1150◦C) with purposely contaminated helium atmosphere (mainly CH4, CO, CO2, O2impurities) representative for high temperature reactor carburizing atmospheres. The first set of thermocouples embedded in graphite (mainly conventional N type thermocouples and thermocouples with innovative sheaths) was tested in a dedicated furnace at THERMOCOAX lab with helium flushing. The second out-of-pile test at JRC with a partly different set of thermocouples replicated the original test for comparison. Performance indicators such as thermal drift, insulation resistance and loop resistance were monitored. Through these long-term screening tests the effect of several parameters were investigated: niobium sleeves, bending, diameter, sheath composition as well as the chemical environment. SEM examinations were performed to analyze local damage (bending zone, sheath). The present paper describes the two tests, sums up data collected during these tests in terms of thermocouple behavior and describes further instrumentation testing work with fixed point mini cells for qualification under irradiation.JRC.F.4-Nuclear Reactor Integrity Assessment and Knowledge Managemen

Retrospective phase-based gating for cardiac proton spectroscopy with fixed scan time

BACKGROUND Respiratory motion is a major limiting factor for spectral quality and duration of in vivo proton MR spectroscopy of the heart. Prospective navigator gating is frequently applied to minimize the effects of respiratory motion, but scan durations are subject-dependent and hence difficult to predict. PURPOSE To implement cardiac proton MRS with fixed scan time by employing retrospective phase-based gating and to compare the proposed method to conventional navigator-gated MRS. STUDY TYPE Prospective. SUBJECTS Eighteen healthy volunteers (29.7 ± 7.8 years). FIELD STRENGTH/SEQUENCE 1.5, navigator-gated (16 averages without, 96 with water suppression [WS]) data acquisition as reference and navigator-free data acquisition with a fixed scan time (48 without WS, 304 with WS), cardiac-triggered point-resolved spectroscopy (PRESS). ASSESSMENT Navigator-free data acquisition with retrospective phase-based gating was compared with prospective navigator-gating. Navigator-free acquisition was repeated in 10 subjects to assess reproducibility. Scan time was assessed for prospective and retrospective gating. Retrospective phase-based gating was performed using a threshold based on the standard deviation (SD) of individual water (W) and triglyceride (TG) phases. STATISTICAL TESTS T-tests and Bland-Altman analysis. RESULTS The duration of the prospective navigator-gated scans ranged from 6:09 minutes to 21:50 minutes (mean 10:05 ± 3:46 min, gating efficiency 40.4 ± 10.5%), while data acquisition for retrospective phase-based gating had a fixed scan time of 11:44 minutes. Retrospective phase-based gating using a threshold of 1 × SD yielded a gating efficiency of 72.7 ± 4.3% and a coefficient of variation (CoV) of triglyceride-to-water ratios of 9.8% compared with the navigated reference. The intrasubject reproducibility of retrospective gating revealed a CoV of 9.5%. DATA CONCLUSION Cardiac proton MRS employing retrospective phase-based gating is feasible and provides reproducible assessment of TG/W in a fixed scan time. Since scan time is independent of respiratory motion, retrospective phase-based gating offers an approach to motion compensation with predictable exam time for proton MRS of the heart. LEVEL OF EVIDENCE 2 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2019;50:1973-1981

Long Term out-of-pile Thermocouple Tests in Conditions Representative for Nuclear Gas-cooled High Temperature Reactors

During irradiation tests at high temperature failure of commercial Inconel 600 sheathed thermocouples is commonly encountered. As instrumentation, in particular thermocouples are considered safety-relevant both for irradiation tests and for commercial reactors, JRC and THERMOCOAX joined forces to solve this issue by performing out-of-pile tests with thermocouples mimicking the environment encountered by the HTR in-core instrumentation. The objective was to screen innovative sheathed thermocouples which would consecutively be tested under irradiation. Two such screening tests have been performed in high temperature environment (i.e. temperature in the range 1100 - 11500C) with purposely contaminated helium atmosphere (mainly CH4, CO, CO2, O2 impurities) representative for High Temperature Reactor carburizing atmospheres. The first set of thermocouples embedded in graphite (mainly conventional N type thermocouples and thermocouples with innovative sheaths) was tested in a dedicated furnace at THERMOCOAX lab with helium flushing. The second out-of-pile test in Petten with a partly different set of thermocouples replicated the original test for comparison. Performance indicators such as thermocouples thermal drift, insulation resistance measurements and loop resistance measurements were monitored. Through these long-term screening tests several effects were investigated: niobium sleeves, bending, diameter, sheath composition as well as the chemical environment. SEM examinations were performed to analyze local damage (bending zone, sheath). The present paper describes the two experimentations, sums up data collected during these tests in terms of thermocouple behavior and describes further work, in particular to select suitable thermocouples equipped with fixed point mini cells for qualification under irradiation.JRC.F.4-Nuclear Reactor Integrity Assessment and Knowledge Managemen

Long term out-of-pile thermocouple tests in conditions representative for nuclear gas-cooled high temperature reactors

During irradiation tests at high temperature failure of commercial Inconel 600 sheathed thermocouples is commonly encountered. As instrumentation,in particular thermocouples are considered safety-relevant both for irradiation tests and for commercial reactors, JRC and THERMOCOAX joined forcesto solve this issue by performing out-of-pile tests with thermocouples mimicking the environment encountered by high temperature reactor (HTR) in-core instrumentation. The objective was to screen innovative sheathed thermocouples which would consecutively be tested under irradiation. Two suchscreening tests have been performed in high temperature environment (i.e. temperature in the range 1100–1150◦C) with purposely contaminated heliumatmosphere (mainly CH4, CO, CO2, O2impurities) representative for high temperature reactor carburizing atmospheres. The first set of thermocouplesembedded in graphite (mainly conventional N type thermocouples and thermocouples with innovative sheaths) was tested in a dedicated furnace atTHERMOCOAX lab with helium flushing. The second out-of-pile test at JRC with a partly different set of thermocouples replicated the original test forcomparison.Performance indicators such as thermal drift, insulation resistance and loop resistance were monitored. Through these long-term screening teststhe effect of several parameters were investigated: niobium sleeves, bending, diameter, sheath composition as well as the chemical environment. SEMexaminations were performed to analyze local damage (bending zone, sheath).The present paper describes the two tests, sums up data collected during these tests in terms of thermocouple behavior and describes further instru-mentation testing work with fixed point mini cells for qualification under irradiation.JRC.E.2-Safety of Irradiated Nuclear Material