Hands-on Maintenance Research Articles

Virtual Reality in Education and the Co-construction of Immediacy

AbstractVirtual reality (VR) in educational settings is often promoted by commercial actors as a way to experience environments outside the classroom and a soon-to-be part of everyday teaching and learning. This study follows the development of an educational software package in a Swedish municipality that combines VR technology with 360° live footage from museums and science centers to enable students to visit these spaces from the classroom via their headsets. By focusing on the workarounds and configurations intuitively performed by teachers, students, museum staff, and technicians in this pilot project, different kinds of articulation work performed to make the technology fit with local conditions are identified, from hands-on repair and maintenance to the facilitation of interaction and presence. The collective effort put into making the technology disappear and create a feeling of unmediated experience or immediacy shows how global imaginaries about VR as an immersive technology are enacted by the participants, at the same time as the work put into the project made them challenge the idea of VR as a new everyday technology. This tension between the desire for immediacy and the hands-on work in the physical environment that goes into fulfilling these imaginaries points to the need for local production of educational technologies that recognizes their co-constructive, embodied, and situated nature.

Analysis of radiation conditions in the CFETR ion cyclotron resonance heating antenna

An ion cyclotron resonance heating (ICRH) antenna will be installed in the equatorial port plug of the China Fusion Engineering Test Reactor (CFETR) for heating ions and electrons in plasma. This study reports the latest neutronic modeling and analyses of antenna for the subsequent optimization of the shielding design, with radiation damage, nuclear heating, gas generation of key components, and shutdown dose rate (SDDR) used as main indicators. Results showed that the nuclear heating of the BP was extremely high, thus posing a high risk to the structure, highlighting the necessity of further upgrading the shielding performance. In addition, the SDDR was more than 100 μSv/hr 12 days after the shutdown, rendering hands-on maintenance in the areas at a short time challenging. Meanwhile, key contributors to higher SDDR have been analyzed.

Dust contamination of Divertor Remote Handling System in ITER Hot Cell: A novel approach to model complex superficial radiation sources

Activated dust produced by the erosion of plasma-facing components entails a significant radiation source for ITER and, generally, for all tokamaks aiming for operation under high neutron exposure. In-Vessel remote-handling operations will mobilise the dust, which will be deposited on the remote-handling tools used, for which hands-on maintenance is expected. To ensure safe maintenance of the remote-handling equipment, a dedicated decontamination process in the Hot Cell is required. Evaluating the radiation fields produced by the contaminated equipment is central to minimising radiation exposure to personnel. In this study, we present a nuclear analysis of the Divertor Remote Handling System during its transfer and decontamination process. Past computational limitations regarding superficial sources definition and high uncertainties on the dust model have been overcome by implementing a novel methodology and following an alternative approach. Two surface-dependent dust distributions over the complex geometry surfaces were considered to evaluate the dose rates according to the different contamination levels during the process phases. A scoping analysis was performed to determine the amount of dust that would comply with project requirements in each phase of the process. Improvement margins were identified in the quantification of the amount of dust and Hot Cell layout.

A-174 More Timely Patient Care Amidst Healthcare Staffing Shortages, Reducing Blood Specimen Tube Barcode Errors for Continuous Flow in an Automated Laboratory System

Abstract Background The Core Laboratory at Henry Ford Hospital utilizes total laboratory automation to support chemistry, hematology and coagulation analyzers, processing approximately 10 000 specimens daily. Testing and reporting delays can occur when the system encounters a specimen tube barcode error. Specimens will stop moving and causes approximately a 2-minute per error production pause while the error is resolved. This induces congestion for all other specimens in line behind the error. The seemingly trivial minutes of congestion leads to a domino effect, resulting in reduced line productivity, a temporary limit of testing capacity and prolonged TATs. The laboratory receives specimen tubes with labels generated from over 600 printers. The system encounters 200–250 errors daily associated with barcode read failures of various types. Errors account for an estimated loss of ∼320 h of staff productivity per month. Methods Automation line error files, manually recorded data from lab staff, observations of automation line errors occurring in real time, data from a printer maintenance blitz and barcode printer service requests were used in root cause analysis. Three progressive Kaizens events were organized in 2022 to induce rapid process change through focused chartering of events and actions. A probing study designed to induce controlled defects and stoppages helped recognize where congestion on the line was occurring. Simulation of barcode application errors allowed an understanding of the impact of label application. Staff and line productivity loss analysis predicted the potential opportunity of error reduction. Results Fifty-five percent of the barcode errors were caused by improper label application and 45% were poor print quality of the barcode on the label. Of the label application defects, 55% were caused by the label being placed upside-down, of which 34% were caused by the label format used by our Emergency Department. Print quality issues such as faded or pitted printing labels accounted for 45% of errors. The printer preventive maintenance blitz successfully reduced print quality errors by 30%. Converting to a more robust printer in two high-volume areas resulted in zero print quality errors over three months. Barcode label format changes were 100% effective in eliminating upside-down as a root cause. Conclusion Elimination of barcode line errors can recover 2.0 FTEs in three divisions per month, while increasing automation line productivity and a cost approximately$150 000 per year in work delays and unnecessary rework. The Kaizen approach to problem-solving allowed for rapid brainstorming amongst multiple teams. Altered label format allowed built-in engineering control by mistake-proofing the process and making label positioning irrelevant. Identification of areas where high volumes of labels were being printed and replacing those printers with more robust printers reduced service calls and eliminated printer causal factors since these printers require less hands-on maintenance. Finally, instituting preventative label printer maintenance and total quality management reduces or prevents errors associated with print quality. Sustaining mechanisms include continued real-time data documentation and communication of defects, collaboration with colleagues in Nursing for further root cause analysis of barcode application defects.

Early-Stage Radiation Safety Analysis for the Spallation Neutron Source Second Target Station Bunker Operations

The Second Target Station project at Oak Ridge National Laboratory will develop a cold neutron source to meet growing experimental needs. This paper describes calculations of the residual dose rates associated with the monolith shield plug and the beamline bunker, two key conventional operations and radiation safety features. While neutron production is active, the instrument hall outside the bunker must be generally accessible with dose rates of less than 0.25 mrem/h. When neutron production is halted, the bunker must be accessible for hands-on maintenance operations. These two requirements form the cause for the assessments reported herein of residual dose rates caused by the monolith shield plug and residual dose rates in the bunker. The monolith shield plug was shown to not produce significant dose rates inside the bunker after a 20-year lifetime, and the residual dose rates inside the bunker for the case of an operating beamline were shown to reasonably allow for hands-on maintenance. These calculations are based on preliminary design models of the relevant systems. Additionally, an example showing the significance of considering neutron supermirror physics in transport calculations that track nuclide production and destruction rates to produce gamma sources for residual dose rate calculations is included. The example shows that if neutron supermirror physics is not considered, dose rate fields may be significantly underpredicted.

Dose rate analysis for a pre-conceptual design of the high energy beam transport section in the IBTF

A pre-conceptual design study to evaluate the Breeding Blanket (BB) performance has been carried out because the BB, producing heat energy and tritium, is a key component for the fusion demonstration reactor. The Integrated Breeding Test Facility (IBTF) is based on an accelerator-driven system using a 40 MeV deuteron beam with a maximum current of 10 mA. Accelerated deuteron reacts with a solid beryllium target to generate neutrons. The total yield of the produced neutrons is estimated to be 6.68E+15 n/sec. The forward direction neutrons irradiate the tritium breeding unit, while the backscattered neutrons through the beam pipes activate the Deuteron Accelerator Unit (DAU) components that require temporary human access maintenance.Therefore, this study did a dose rate analysis for the pre-conceptual design of the High Energy Beam Transport (HEBT) section in the DAU during maintenance. The HEBT section is divided into regions A and B. For the reference HEBT model, the dose rate in only region B satisfies the human access requirement (dose rate ≤ 100 uSv/h) during short-term maintenance (STM) and long-term maintenance (LTM). To reduce the dose rate, the beam pipe material was changed to Al6063, which has a low weight fraction of Mn and Ni compared to SS304. A lead shutter was also used to shield the dose rate from the test cell. As a result, the dose rate in region A is lower than 100 uSv/h during the STM with a cooling time of 1 week. The dose rate in region B satisfies the hands-on maintenance requirement (dose rate ≤ 10 uSv/h). The dose rate in region A is lower than 100 uSv/h except for near the beam pipe during the LTM. The dose rate in region B is lower than 10 uSv/h. The dose rate in the HEBT section is increased as the LTM is repeated. However, the increasing rate of the dose is reduced as the LTM repeats. Neutron transport calculation was performed by SRC-UNED-v3.1.4 with the TENDL2019 cross-section library, and the gamma source was estimated using FISPACT-Ⅱ with the TENDL 2017 cross-section library.

Assessment of shutdown dose rates in the ITER Collective Thomson Scattering system and in equatorial port plug 12

The ITER Collective Thomson Scattering (CTS) system will be the main diagnostic responsible for measuring the velocity distribution function of fusion-born alpha particles in the plasma. As the CTS diagnostic is integrated in the equatorial port plug 12 (drawer 3), with direct apertures to the port interspace where maintenance hands-on operation will be carried out, it is essential to assess the shutdown dose rates (SDDR) in these maintenance areas. In this work, the D1S-UNED3.1.4 Monte-Carlo transport code, based on the implementation of the direct-one-step methodology in MCNP5 v1.60, was used to estimate the dose rate level 12 days (106 s) after shutdown in the port interspace. The results show that the CTS system does not contribute significantly to the SDDR in the area where hands-on maintenance is foreseen with contribution to dose rates less than 1 µSv/h. This is consistent with previous estimates, although with the most recent model of the CTS design there is a slight increase of the SDDR values. This deviation can be attributed to design changes and improved shielding modelling and/or most importantly, to statistical fluctuations of the D1S simulations. From a neutronics point of view, the increase in the SDDR falls within the range of the statistical fluctuations, and the design is still compliant with the radiation safety ALARA principle aiming at minimizing radiation doses, and there is no requirement for further design optimizations.

Investigation of the possibility of L-band SRF cavities for medium-beta heavy ion multi-charge-state beams

The possibility of 1288 MHz (L-band) SRF elliptical cavity to accelerate heavy ion multi-charge-state (up to 5 charge states) beams is being investigated for accelerating energy higher than 200 MeV/u. This cavity is a potential energy upgrade for heavy ions linac accelerators such as the Facility for Rare Isotope Beams (FRIB) in the United States of America and Rare Isotope Science Project (RISP) in Korea. One of possible disadvantages of the L-band frequency structure is its small longitudinal acceptance. It should be sufficiently large for transporting the ions with the limited beam loss ensuring accelerator hands-on maintenance. The analytic study was performed and it showed a promising result using 1288 MHz cavities. In addition, from beam loss point of view, the study deduced that 1288 MHz linac frequency could be the limit for medium-beta heavy ion up to 5 charge states beam accelerators. This paper is the result of the detailed beam dynamics simulation for the linac performance using TRACK code to confirm the analytic result. The result shows that the longitudinal acceptance is large enough for medium-beta heavy ion with 5 charge state beams.

Evaluation of a simplified approach in food safety management systems in the retail sector: A case study of butcheries in Flanders, Belgium and Lancashire, UK

The EFSA BIOHAZ panel published a scientific opinion proposing a new approach in food safety management, adapted to the needs of small retail businesses such as grocery, butcher, bakery, fishmonger and ice cream shops. The opinion is aiming at a more hands-on development and maintenance of their food safety management system, based on prerequisite programs and hazard analysis critical control point-principles. In this paper, the added value of the EFSA opinion is evaluated by comparing requirements with existing legislation and applied guidelines relevant for butchers, and to assess perceptions about introduced changes by this opinion for small independent butcheries in Flanders, Belgium and in North-West England, UK as a case study. Results show that the conditions for flexibilities, as stated in the EFSA opinion, could lead to difficulties in interpretation among Member States. Also, the hazard analysis approach applied in the two main UK guides to good practice appeared to be similar to the simplified approach proposed by EFSA. For Belgium, the main difference is that in the Belgian guide to good practice hazards are ranked and critical control points are identified for the preparation and selling of fresh meat, minced meat and meat preparations. The specification of prerequisite programs and related activities in the EFSA opinion can be an important step towards harmonization among EU Member States. Assessing the perceptions of ten UK and ten Belgian butchers revealed that the hazard analysis approach and the thirteen prerequisite requirements proposed by EFSA, are generally positively experienced by the butchers. However, the introduction of the proposal ‘Monthly microbiological tests’ to verify cleaning and disinfection activities is rejected by all the Belgian butchers and by the majority of the UK butchers. This proposal will not ease their job and the necessity of these tests should be reconsidered.

Abstract 2276: Performance and cost comparison of circulating tumor DNA detection platforms

Abstract Purpose The field of circulating cell free DNA (cfDNA) testing is quickly developing. Multiple platforms to detect hotspot mutations in ctDNA are available, including Bio-Rad droplet digital PCR (ddPCR), BioCartis Idylla, Roche COBAS z480 and Sysmex BEAMing. These platforms vary in the amount of plasma required, the method of ctDNA isolation, the number of hotspots analyzed, and the costs per sample. These factors can impact the applicability of a specific platform in the analysis of ctDNA. In this study we compared these platforms in terms of sensitivity and total costs per sample. Methods The platform comparison was performed as follows: 1. Plasma from six metastatic colorectal cancer (mCRC) patients with known tissue KRAS mutation status was analyzed according to the manufacturers’ protocols. 2. Sensitivity was tested using six constructed reference samples with seven KRAS hotspot mutations at various total input (10ng, 50ng) and mutant allele frequencies (0%, 0.04%, 0.50%); each in four replicates. 3. Twelve mCRC patients were analyzed using equal amounts of ctDNA for each platform. 4. Total costs per sample were evaluated, including costs for consumables, technician hands-on time, equipment and maintenance. Results 1. In six mCRC samples BEAMing (3ml plasma) detected 5/6 mutations, ddPCR and Idylla (both 1ml plasma) 4/6 mutations and COBAS z480 (2ml plasma) 3/6 mutations. 2. In constructed reference samples ddPCR (65%) and BEAMing (46%) yielded the highest sensitivity. With 10ng input BEAMing and COBAS z480 produced “Too little DNA” errors in 60% and 100% of cases, respectively. 3. In twelve mCRC samples, eight had more than 10ng ctDNA and four had less. All platforms were fully concordant for samples with more than 10ng input. Detection rate across twelve samples: Idylla detected 7/11 detectable mutations, COBAS z480 and BEAMing both detected 5/11, ddPCR detected 4/10. 4. BEAMing has the highest cost per sample (€486-€821) whereas ddPCR has the lowest cost per sample (€39-€298). Conclusions A direct comparison of ctDNA mutation detection platforms is complex and should take into account the differences in input and output specifications of the platforms. Factors such as complexity of analysis (Idylla is a low complexity platform, whereas BEAMing requires more specialized training), total costs (varying from ddPCR to BEAMing), sensitivity (ddPCR and BEAMing yielded the highest sensitivity) and the number of mutations evaluated vary greatly between the platforms. All these factors influence ctDNA analysis and will have to be considered when choosing a specific platform for a specific (clinical) question, or when comparing results between studies. Our data provide insight in the comparative performance of four commercial ctDNA analysis platforms, allowing future users to make an informed decision regarding a platform. Acknowledgement Powered by Health~Holland, Top Sector Life Sciences & Health, grant LSHM16047-H005. Citation Format: Daan C. Vessies, Marjolein J. Greuter, Karlijn L. van Rooijen, Theodora C. Linders, Mirthe Lanfermeijer, Kalpana L. Ramkisoensing, Flore E. Grijseels, Boris van Doorn, Gerrit A. Meijer, Miriam Koopman, Veerle M. Coupé, Geraldine R. Vink, Remond J. Fijneman, Daan van den Broek. Performance and cost comparison of circulating tumor DNA detection platforms [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 2276.

Decontamination tests of dust under load for the ITER Blanket Remote Handling System

Radioactive dust will accumulate in the vacuum vessel (VV) of ITER after plasma operations. Consequently, the ITER Blanket Remote Handling System (BRHS) will be deployed into the VV to stably handle the blanket modules 1.5 m long, weighing up to 4.5 ton with high positioning accuracy. The BRHS itself must also undergo regular hands-on decontamination and maintenance in the Hot Cell Facility (HCF). However, the workers will be exposed to any activated dust that remains on BRHS component surfaces after remote decontamination. Past studies estimated the contaminated surface area of the BRHS, however, in this study, decontamination tests were performed and the dose rate to maintenance workers was calculated using the Monte Carlo N–Particle Transport Code (MCNP5). Decontamination tests were performed by using multiple test pieces of varying surface roughness made from SUS329J4L and two different types of brushes (nylon and SUS304) to simulate decontamination of the BRHS surface. Tungsten dust was pressed on the test pieces to simulate the loading by the rollers. After the test pieces were brushed the surface of each test piece was observed by using both optical and scanning electron microscopes. Dust was reduced by approximately 99% in all cases where the SUS304 brush was used regardless of surface roughness. The decontamination rate was used to estimate how much dust will be able to be cleaned from the BRHS surface. This paper describes the optimal decontamination tools with respect to the BRHS surface conditions to calculate and hopefully reduce the dose rate to maintenance workers so as to optimize the BRHS maintenance plan in the HCF.

Neutronic effects of the ITER Upper Port environment update in C-model

This paper presents analysis of neutronic effects carried out with the newly developed MCNP model of the ITER Upper Port (UP) environment integrated into the neutronics C-Model of the ITER tokamak machine. C-Model includes only the standard ITER components and generic port plugs. With a number of other important updates in addition to the description of the UP environment, the new C-Model R180430 has been issued 30/04/2018, and currently is the ITER-reference model to be used in any ITER-related neutronics analysis. One of ITER’s design targets is to maintain a limit of 100 μSv/h for Shut-Down Dose Rate (SDDR) after 12 days of cooling time in the areas of envisaged personnel access with hands-on maintenance. In case of UP, the maintenance access is planned inside of UP duct where Inter-Space Structure (ISS) will be installed. Therefore, neutronics analysis has been focused on estimations of SDDR inside the UP duct and, following the ALARA principle, on finding the UP design solutions for reduction of dose. This task has been accomplished by 3D visualization of the SDDR map at UP duct, and drawing SDDR isosurfaces which revealed areas of dose hot spots and the radiation streaming pathways. Such information allows an understanding of the weak areas of the UP shielding and the formulation of the means for potential improvement of the radiation conditions in the UP duct area. The R2Smesh code has been used in SDDR calculations, with capability to plot distributions of decay gamma sources and revealing which radioactive materials are dominant contributors to SDDR. Comparison with the previous version of the ITER generic model called C-lite V2R150304MOD shows that the newly created C-Model R180430 demonstrated similar SDDR at the UP ISS maintenance corridors.

Evaluation of radiation environment in the target area of fragment separator HFRS at HIAF

In this work, the radiation environment in the target area of a fragment separator is evaluated using FLUKA code. The energy deposition in quadrupole coils is presented to provide guidance for a radiation-resistant magnets design. Results show that neutrons dominate in the prompt radiation field. A compact shielding design is recommended for high radiation areas along with the minimization of air activation in the tunnel in order to minimize the radiation effect on nearby beam lines. The displacements per atom results for the graphite target and copper coils indicate that the effect is insignificant. In addition, the activation level of the target is estimated for workers under possible hands-on maintenance condition.

ITER hot Cell—Remote handling system maintenance overview

ITER is a large scale fusion device designed to study the high temperature fusion reaction between tritium and deuterium. The success of a tokamak-type fusion reactor will depend to a great extent on developing reliable and safe methods of carrying out routine maintenance and repairs remotely. Remote Handling System (RHS) is used to perform remotely the maintenance inside the vacuum vessel. RHS will be contaminated during exposure inside ITER Vacuum Vessel with activated dust, tritium and beryllium. RHS will be transported to the Hot Cell Facility to be remotely decontaminated before its hands-on maintenance operation. RHS maintenance is made of repair, changing parts, testing and re-commissioning activities.In this paper the results of concept design engineering investigation of the routine remote maintenance and repair is developed. Maintenance requirements for a nuclear fusion facility are rather similar to those of JET (David et al. 2005 [1]), but magnified (Lässer et al., 2012 [2]; Loughlin et al., [3]). A dedicated facility of a unique scale is planned to support ITER remote maintenance activities.

Neutronics analysis for integration of ITER diagnostics port EP10

Shutdown dose rate calculations have been performed on an integrated ITER C-lite neutronics model with equatorial port 10. A ‘fully shielded’ configuration, optimised for a given set of diagnostic designs (i.e. shielding in all available space within the port plug drawers), results in a shutdown dose rate in the port interspace, from the activation of materials comprising equatorial port 10, in excess of 2000μSv/h. Achieving dose rates of 100μSv/h or less, as required in areas where hands-on maintenance can be performed, in the port interspace region will be challenging. A combination of methods will need to be implemented, such as reducing mass and/or the use of reduced activation steel in the port interspace, optimisation of the diagnostic designs and shielding of the port interspace floor. Further analysis is required to test these options and the ongoing design optimisation of the EP10 diagnostic systems.

Development of the charge exchange type beam scraper system at the J-PARC

Improvement in injection beam quality at the Japan Proton Accelerator Research Complex 3-GeV rapid cycle synchrotron is to mitigate beam loss at the injection section. We developed a charge-exchange type scraper system with a thin carbon foil to collimate the beam halo in the injection beam line of the synchrotron. The key issue to realize the scraper is a reduction of the beam loss induced by the multiple-scattering effect of charge-exchange foil placed at the scraper head. In order to determine the adequate foil thickness, a charge-exchange efficiency of a carbon foil and particle-tracking simulation study of the collimated beam have been performed assuming a realistic halo at the scraper section. Using the results of this study, we chose the thickness of a 520μg/cm2 as the scraper foils to mitigate radiation dose around the L3BT scraper section. A charge-exchange scraper system that prevents the emission of radioactive fragments of the carbon foil was build. The system was put into operation to prove its effectiveness in eliminating the beam halo. From the result of a preliminary beam experiments, we confirmed that the installed scrapers eliminate a transverse beam tail or halo. After two days of operation with beam collimation, the radiation dose level around the scraper section was a tolerable one for the hands-on maintenance.

A case study of machinery maintenance protocols and procedures within the UK utilities sector

Failure to conduct periodic fixed-time-to (or scheduled) maintenance on off-highway plant and equipment represents a significant health and safety hazard and major litigation risk for utility contractors completing service excavation and reinstatement works on public highways. Mini-excavators are a ubiquitous mobile plant item used for such tasks and have recently been responsible for several major injuries and fatalities involving workers and members of the public in the United Kingdom (UK). The research utilises the method of triangulation to examine the maintenance practices of utility contractors in the UK. Findings from the research reveal that a combination of prevailing market forces and internal ‘company’ pressures have inadvertently removed knowledgeable and trained operators, site foremen and managerial supervisors from hands-on maintenance inspections. Rather, ‘virtual’ maintenance protocols and procedures are adopted by head office but rarely fully implemented on-site. The research concludes with pragmatic recommendations and direction for future research.

Hydrogen species in diamond: Molecular dynamics simulation in bulk diamond for fusion applications

For an electron cyclotron resonance heating system, a diamond window seems to be the only material able to withstand the high microwave power and radiation effects and at the same time act as a tritium barrier. Therefore it is important to understand the evolution of hydrogen isotopes in diamond. Both, hydrogen content and radiation can quite rapidly degrade its excellent properties. Hydrogen isotopes can be introduced in the material by two processes: (1) during the growth process of synthetic samples and (2) as a neutron radiation effect when devices are exposed to a fusion irradiation environment. In the last case, both device performance (thermal, optical and dielectric properties degradation) and hands-on maintenance of the window (tritium inventory), demand a good knowledge of hydrogen species concentrations and their evolution with lattice damage.In this paper, a classical molecular dynamics study analyses the hydrogen equilibrium sites in diamond, and also their bulk and interstitial vibrational characteristics, including isotopic shifts. Some interesting results are presented and discussed. We confirm that the bond-centred site is the more stable configuration for H. Vibrational studies show lines in the C–H stretching region. Isotopic studies reveal ratios close to the theoretical ones for BC and ET sites. On the contrary, the AB site vibrations obtained suggest the existence of a local carbon oscillation.

Nuclear analysis and shielding optimisation in support of the ITER In-Vessel Viewing System design

The In-Vessel Viewing System (IVVS) units proposed for ITER are deployed to perform in-vessel examination. During plasma operations, the IVVS is located beyond the vacuum vessel, with shielding blocks envisaged to protect components from neutron damage and reduce shutdown dose rate (SDR) levels. Analyses were conducted to determine the effectiveness of several shielding configurations. The neutron response of the system was assessed using global variance reduction techniques and a surface source, and shutdown dose rate calculations were undertaken using MCR2S.Unshielded, the absorbed dose to piezoelectric motors (PZT) was found to be below stable limits, however activation of the primary closure plate (PCP) was prohibitively high. A scenario with shielding blocks at probe level showed significantly reduced PCP contact dose rate, however still marginally exceeded port cell requirements. The addition of shielding blocks at the bioshield plug demonstrated PCP contact dose rates below project requirements. SDR levels in contact with the isolated IVVS cartridge were found to marginally exceed the hands-on maintenance limit. For engineering feasibility, shielding blocks at bioshield level are to be avoided, however the port cell SDR field requires further consideration. In addition, alternative low-activation steels are being considered for the IVVS cartridge.

Activation characteristics due to beam loss and energy dependency of its criteria for 100 MeV proton linac

Beam loss criterion such as 1 W/m for an uniformly distributed loss has been applied at high power proton or heavy ion accelerator. It has been accepted based on the exposure level due to radioactive accelerator components during a hands-on maintenance and is a very important factor in shielding analysis of such high power, high energy accelerators. Well-developed Monte Carlo codes and inventory codes, which have been used for an activity calculation, were confirmed by benchmarking of published experimental data. The modular style method (PHITS+DChain-SP) and all-in-one style method (Fluka) using Monte Carlo code were applied to verify the criterion. The beam loss at bulk target and one-point loss at beam pipe and a uniformly distributed loss were simulated. The dose distribution and the decay scheme were compared with the control level of a hands-on maintenance. It was proved that more considerations were required instead of taking 1 W/m simply as the beam loss criterion. Especially the energy dependency effect was discussed mainly.