Gamma noise to non-invasively monitor nuclear research reactors

Autonomous nuclear reactor monitoring is a key aspect of the International Atomic Energy Agency's strategy to ensure nonproliferation treaty compliance. From the rise of small modular reactor technology, decentralized nuclear reactor fleets may strain the capacities of such monitoring and requires new approaches. We demonstrate the superior capabilities of a gamma detection system to monitor the criticality of a zero power nuclear reactor from beyond typical vessel boundaries, offering a powerful alternative to neutron-based systems by providing direct information on fission chain propagation. Using the case example of the research reactor CROCUS, we demonstrate how two bismuth germanate scintillators placed outside the reactor vessel can precisely observe reactor criticality using so called noise methods and provide core status information in seconds. Our results indicate a wide range of applications due to the newly gained geometric flexibility that could find use in fields beyond nuclear safety.

First in-core gamma spectroscopy experiments in a zero power reactor

Gamma rays in nuclear reactors, arising either from nuclear reactions or decay processes, significantly contribute to the heating and dose of the reactor components. Zero power research reactors offer the possibility to measure gamma rays in a purely neutronic environment, allowing for validation experiments of dose estimates, computed spectra, and prompt to delayed gamma ratios. The resulting data can contribute to models, code validation and photo atomic/nuclear data evaluation. To date, most experiments have relied on flux measurements using TLDs, ionization chambers, or spectrometers set in low flux areas. The CROCUS reactor allows for flexible detector placement in and around the core, and has recently been outfitted with gamma detection capabilities to fulfill the need for in-core gamma spectroscopy, as opposed to flux. In this paper we report on the experiments and accompanying simulations of gamma spectrum measurements inside a zero power reactor core, CROCUS. It is a two-zone, uranium-fueled light water moderated facility operated by the Laboratory for Reactor Physics and Systems Behaviour (LRS) at the Swiss Federal Institute of Technology Lausanne (EPFL). Herein we also introduce, in detail, the new LEAF system: A Large Energy-resolving detection Array for Fission gammas. It consists of an array of four detectors – two large ø 127 254 mm Bismuth Germanate (BGO) and two smaller ø 12 50 mm Cerium Bromide (CeBr3) scintillators. We describe the calibration and characterization of LEAF followed by first in-core measurements of gamma ray spectra in a zero power reactor at different sub-critical and critical states, and different locations. The spectra are then compared to code results, namely MCNP6.2 pulse height tallies. We were able to distinguish prompt processes and delayed peaks from decay databases. We present thus experimental data from hitherto inaccessible core regions. We provide the data as validation means for codes that attempt to model these processes for energies up to 10 MeV. We finally draw conclusions and discuss the future uses of LEAF. The results indicate the possibility of isotope tracking and burn-up validation.

Delayed gamma fraction determination in the zero power reactor CROCUS

Gamma rays are an inextricable part of a nuclear reactor’s radiation field, and as such require characterization for dose rate estimations required for the radiation protection of personnel, material choices, and the design of nuclear facilities. Most commonplace radiation transport codes used for shielding calculations only included the prompt neutron induced component of the emitted gamma rays. The relative amount of gamma rays that are emitted from delayed processes – the delayed gamma fraction – amount to a significant contribution, e.g. in a typical zero power reactor at steady state is estimated to be roughly a third. Accurate predictions of gamma fields thus require an estimation of the delayed content in order to meaningfully contribute. As a consequence, recent code developments also include delayed gamma sources and require validation data. The CROCUS zero power research reactor at EPFL is part of the NEA IRPhE and has therefore been characterized for benchmark quality experiments. In order to provide the means for delayed gamma validation, a dedicated experimental campaign was conducted in the CROCUS reactor using its newly developed gamma detection capabilities based on scintillators. In this paper we present the experimental determination of the delayed gamma fraction in CROCUS using in-core neutron and gamma detectors in a benchmark reactor configuration. A consistent and flexibly applicable methodology on how to estimate the delayed gamma fraction in zero power reactors has hitherto not existed – we herein present a general experimental setup and analysis technique that can be applied to other facilities. We found that the build-up time of relevant short lived delayed gamma emitters is likely attributed to the activation of the aluminium cladding of the fuel. Using a CeBr3 scintillator in the control rod position of the CROCUS core, we determined a delayed gamma fraction of (30.6±0.6)%.

D2 receptor occupancy under recommended and high doses of olanzapine: an iodine-123-iodobenzamide SPECT study

The aim of this study was to compare the degree of striatal dopamine D2 receptor availability in patients treated with recommended (5-20 mg, mean dose 11.9 +/- 6.3 mg daily) and higher doses (25-40 mg, mean 32.1 +/- 5.6 mg daily) of the novel antipsychotic drug olanzapine by means of [123I] IBZM Single photon emission computed tomography (SPECT). The results were compared to those of a group of 10 untreated, healthy, age- and sex-matched controls. The degree of dopamine D2 receptor occupancy in the patient group was correlated with the presence of extrapyramidal symptoms (EPS). A total of 20 patients who met the DSM III R criteria for schizophrenia or schizoaffective disorder received a clinically effective antipsychotic monotherapy with olanzapine. The mean daily dose of olanzapine ranged from 0.05-0.6 mg/kg body weight. The dopamine D2 receptor binding was reduced in all patients treated with olanzapine. Specific IBZM binding expressed as the [STR-BKG]/BKG ratio ranged from 0.13-0.61 (healthy controls 0.95). The D2 receptor availability revealed an exponential dose-response relationship (r = - 0.85, p < 0.001). The frequency of EPS induced by olanzapine was considerably lower. Only one patient, treated with 40 mg olanzapine, suffered from severe EPS symptoms and had to be given biperiden. There were no significant differences in the presence of EPS symptoms between patients with recommended doses and those with higher doses of olanzapine.

Clinical and biological findings in a case with 48-hour bipolar ultrarapid cycling before and during valproate treatment

BACKGROUND

The rare cases of patients with 48-hour ultrarapid cycling allow close investigation of mood cycles in affective disorders, because rhythmic changes in psychopathologic state and biological parameters happen very precisely.

METHOD

A 67-year-old white man who had experienced bipolar 48-hour ultrarapid cycling (DSM-IV 296.80) for several years was studied without any medication and then again studied 4 weeks later during treatment with valproate (1800 mg/day).

RESULTS

Objective and self ratings revealed pronounced manic states 1 day and depressed states the following day, which were found to be accompanied by rhythmic fluctuations in behavior and electroencephalographic parameters, blood cortisol and growth hormone levels (both elevated on depressive days), and urinary metanephrine (dopamine metabolite) and norepinephrine levels (both elevated on manic days). Using single photon emission computed tomography, regional blood flow in the left thalamus was lower than in the right thalamus on the manic day, while symmetric perfusion of the thalamus was found on the depressive day. Under valproate treatment, the patient remitted completely, and significant rhythmic changes in most of the biological parameters were no longer detectable.

CONCLUSION

The biological findings in this patient with bipolar 48-hour ultrarapid cycling, which correspond to those in other types of affective disorders, suggest that disturbances in the diencephalon-pituitary axis may be especially correlated to pathologic changes of mood.

In vivo effects of olanzapine on striatal dopamine D(2)/D(3) receptor binding in schizophrenic patients: an iodine-123 iodobenzamide single-photon emission tomography study

Olanzapine is a new atypical antipsychotic agent that belongs to the same chemical class as clozapine. The pharmacological efficacy of olanzapine (in contrast to that of risperidone) has been shown to be comparable to that of clozapine, but olanzapine has the advantage of producing a less pronounced bone marrow depressing effect than clozapine. The specific aims of this study were (a) to assess dopamine D(2)/D(3) receptor availability in patients treated with olanzapine by means of iodine-123 iodobenzamide [(123)I]IBZM single-photon emission tomography (SPET), (b) to compare the results with findings of [(123)I]IBZM SPET in patients under treatment with risperidone and (c) to correlate the results with the occurrence of extrapyramidal side-effects (EPMS). Brain SPET scans were performed in 20 schizophrenic patients (DSM III R) at 2 h after i.v. administration of 185 MBq [(123)I]IBZM. Images were acquired using a triple-head gamma camera (Picker Prism 3000 XP). For semiquantitative evaluation of D(2)/D(3) receptor binding, transverse slices corrected for attenuation were used to calculate specific uptake values [STR-BKG]/BKG (STR=striatum; BKG=background). The mean daily dose of olanzapine ranged from 0.05 to 0.6 mg/kg body weight. The dopamine D(2)/D(3) receptor binding was reduced in all patients treated with olanzapine. Specific IBZM binding [STR-BKG]/BKG ranged from 0.13 to 0.61 (normal controls >0.95). The decreased D(2)/D(3) receptor availability revealed an exponential dose-response relationship (r=-0.85, P<0.001). The slope of the curve was similar to that of risperidone and considerably higher than that of clozapine as compared with the results of a previously published study. EPMS were observed in only one patient, presenting with the lowest D(2)/D(3) availability. The frequency of EPMS induced by olanzapine (5%) was considerably lower than the frequency under risperidone treatment (40%). Our findings suggest an exponential relationship between the daily dose of olanzapine striatal and decreased D(2)/D(3) striatal binding availability. The results are consistent with the findings of in vitro experiments reporting a higher D(2)/D(3) receptor affinity and a similar 5HT(2) receptor affinity of olanzapine as compared with clozapine. Thus, the decreased tendency to induce EPMS at therapeutic doses is not due to the limited occupancy of striatal D(2)/D(3) receptors in vivo. Patients are protected from EPMS by other intrinsic effects of the drug, i.e. the combination of both D(2)/D(3) and 5HT(2) receptor antagonism.

Iodine-123-iodobenzamide SPECT assessment of dopamine D2 receptor occupancy in riperidone-treated schizophrenic patients

The recently introduced neuroleptic, risperidone, was expected to block fewer dopamine D2 receptors than typical neuroleptics (e.g., haloperidol), but at comparable potency. The aim of this study was to evaluate the degree of dopamine D2 receptor occupancy in relation to the neuroleptic dosage and to correlate the findings with the presence of extrapyramidal symptoms (EPS). Additionally, the data were compared to previous iodobenzamide (IBZM) SPECT findings in patients treated with other neuroleptics, haloperidol and clozapine.

METHODS

In 20 patients with schizophrenia [Diagnostic and Statistical Manual of Mental Disorders (Third Edition-Revised)] treated with mean daily doses of risperidone ranging from 0.029 to 0.128 mg/kg body weight, SPECT was performed 2 hr after intravenous injection of 185 MBq 123I-IBZM, a selective dopamine D2 receptor ligand. Striatal IBZM binding was assessed by calculating a striatal/frontal cortex ratio, expressed as a percentage of the control value.

RESULTS

Selective dopamine D2 receptor binding of the ligand was reduced in all treated patients, with binding values ranging from 7% to 68%. The degree of occupancy displayed an exponential dose-response relationship (r = -0.86; p < 0.0001). The slope of the curve was between those of haloperidol and clozapine but was closer and more similar in shape to the curve of haloperidol. Extrapyramidal symptoms were observed in 8 of 20 patients with binding values between 7% and 47%. However, there was no clear relationship between the degree of receptor occupancy and the presence of EPS.

CONCLUSION

The findings suggest an exponential dose-response relationship between the daily dosage of risperidone and the dopamine D2 receptor occupancy. The blockade of specific striatal IBZM binding found under therapy with risperidone is between those of haloperidol and clozapine. The dose-response curve for risperidone, however, shows greater similarity to that of haloperidol.

[Structural magnetic resonance tomography in diagnosis and research of Alzheimer type dementia]

One of the most widely used neuroimaging procedures in Psychiatry and Neurology is magnetic resonance imaging (MRI). MRI has gained the position of a standard investigation in the differential diagnosis of dementia syndromes. In the clinical diagnosis of Alzheimer's disease (AD) MRI helps to improve the diagnostical accuracy. Recently new MRI-based techniques for performing volumetric measurement of cortical and subcortical structures have been developed. First reports indicate that MRI-based volumetric measurements can be accurate in differentiating AD patients from cognitively normal elderly individuals. These new techniques may be useful adjunct in assessing the clinical diagnosis of AD. Results could also yield insight in the fundamental pathology of the degenerative disease. It is the objective of this chapter to summarize and comment on the significance of MRI in the diagnosis and research of AD. Future directions are outlined, including the use of microscopic MRI, the differentiation of white matter signal hyperintensities and the combined evaluation of structural MRI and functional imaging techniques.

D2-dopamine-receptor occupancy during treatment with haloperidol decanoate

We investigated in an open, explanatory study a total of 24 patients meeting DSM-III-R criteria for schizophrenia. Eighteen patients were treated for at least 4 weeks with a fixed dose of orally administered haloperidol for at least 4 weeks (mean daily dosage ranging from 0.07 to 0.35 mg/kg b.w.), and 6 patients received haloperidol decanoate with a fixed dose for at least 4 months (dosage range 50-150 mg/4 weeks; calculated mean daily dosage ranging from 0.02 to 0.09 mg/kg b.w.). One week after injection of haloperidol decanoate, the single photon emission computed tomography examination was performed. Our data suggest that D2-dopamine-receptor occupancy of 50 mg/4 weeks haloperidol decanoate 1 week after injection corresponds to an oral dose of 4.5 mg/day haloperidol.

The pharmacokinetics and pharmacodynamics of lisuride in healthy volunteers after intravenous, intramuscular, and subcutaneous injection

The plasma concentration of lisuride and prolactin have been measured in twelve healthy male volunteers after IV, IM or SC injection of 25 micrograms lisuride hydrogen maleate as an aqueous solution. After IV administration the plasma lisuride fell in two phases with half-lives of 14 min and 1.5 h. Total clearance was 13 ml.min-1.kg-1. After IM and SC injection the plasma concentrations peaked at 12 to 15 min and the profiles were similar to that found after IV administration. The systemic availabilities were 90% and 94%, respectively. Prolactin concentrations were reduced by a maximum of 60% relative to the normal circadian rhythm after all three routes of administration. The treatments were well tolerated, the only adverse reactions reported by some of the volunteers being mild, transient dizziness, tiredness, and nausea.

Influence of the pineal gland on pituitary function in humans

In 14 men and 14 women we examined the relationship between melatonin and the secretion of pituitary hormones. Blood pressure, and the serum concentrations of melatonin, catecholamines, prolactin, thyrotropin, growth hormone, and cortisol were determined every 3-4 hr for 24 hr. In the normal, basal (unstimulated) condition there were no significant correlations (p greater than 0.05) between the systolic blood pressure and dopamine (r = 0.09), norepinephrine (r = 0.26), or epinephrine (r = 0.27), nor were there significant correlations between melatonin and dopamine (r = -0.01), norepinephrine (r = -0.26), or growth hormone (r = 0.17). The concentrations of melatonin correlated positively with those of prolactin (r = 0.56, p less than 0.05 for men and r = 0.58, p less than 0.001 for women) and thyrotropin (r = 0.62, p less than 0.001 for all subjects), but not with those of cortisol (r = 0.004, p greater than 0.05). We speculate that the increase in melatonin at night leads to a decrease in dopaminergic activity; the diminished release of dopamine may lead to a simultaneous increase in thyrotropin and prolactin.