| 1. |
- Fachinger, J, et al.
(författare)
-
Behaviour of spent HTR fuel elements in aquatic phases of repository host rock formations
- 2006
-
Ingår i: Nuclear Engineering and Design. - 0029-5493. ; 236:5-6, s. 543-554
-
Tidskriftsartikel (refereegranskat)abstract
- One back-end option for spent HTR fuel elements proposed for future HTR fuel cycles in the EC is an open fuel cycle with direct disposal ofconditioned or non-conditioned fuel elements. This option has already been chosen in Germany due to the political decision to terminate the useof HTR technology. First integral leaching investigations at Research Centre Juelich on the behaviour of spent HTR fuel in salt brines, typical ofaccident scenarios in a repository in salt, proved that the main part of the radionuclide inventory cannot be mobilised as long as the coated particlesdo not fail. However, such experiments will not lead to a useful model for performance assessment calculations, because a failure of the coatingsby corrosion will not occur during experimental times of a few years. In order to get a robust and realistic model for the long-term behaviour inaqueous phases of host rock systems, it is necessary to understand the barrier function of the different parts of an HTR fuel element, i.e. the matrixgraphite, the different coating materials, and the fuel kernel.Therefore, our attention is focused on understanding and modelling the barrier performance of the different parts of an HTR fuel element withrespect to their barrier function, and on the development of an overall model for performance assessment. In order to understand this behaviour,it is necessary to start with investigations of unirradiated material, and to proceed with experiments with external gamma irradiation to determinethe effects of oxidising radiolysis species. Further experiments with irradiated material have to be performed to investigate the influence of theirradiation damage, and finally an investigation has to be made of the irradiated material plus additional gamma irradiation. Experimental data arenow available for the diffusive transport of radionuclides in the water-saturated graphite pore system, the corrosion rates of unirradiated graphitewith and without external gamma irradiation and unirradiated and irradiated silicon carbide, and for the dissolution rates of UO2 and (Th,U)O2 fuelkernels with and without external gamma irradiation. All investigations were performed in aquatic phases from salt, granite, and clay host rock.
|
|
| 2. |
- Grambow, M., et al.
(författare)
-
Using application benchmark call graphs to quantify and improve the practical relevance of microbenchmark suites
- 2021
-
Ingår i: Peerj Computer Science. - : PeerJ. - 2376-5992. ; 7
-
Tidskriftsartikel (refereegranskat)abstract
- Performance problems in applications should ideally be detected as soon as they occur, i.e., directly when the causing code modification is added to the code repository. To this end, complex and cost-intensive application benchmarks or lightweight but less relevant microbenchmarks can be added to existing build pipelines to ensure performance goals. In this paper, we show how the practical relevance of microbenchmark suites can be improved and verified based on the application flow during an application benchmark run. We propose an approach to determine the overlap of common function calls between application and microbenchmarks, describe a method which identifies redundant microbenchmarks, and present a recommendation algorithm which reveals relevant functions that are not covered by microbenchmarks yet. A microbenchmark suite optimized in this way can easily test all functions determined to be relevant by application benchmarks after every code change, thus, significantly reducing the risk of undetected performance problems. Our evaluation using two time series databases shows that, depending on the specific application scenario, application benchmarks cover different functions of the system under test. Their respective microbenchmark suites cover between 35.62% and 66.29% of the functions called during the application benchmark, offering substantial room for improvement. Through two use cases-removing redundancies in the microbenchmark suite and recommendation of yet uncovered functions-we decrease the total number of microbenchmarks and increase the practical relevance of both suites. Removing redundancies can significantly reduce the number of microbenchmarks (and thus the execution time as well) to similar to 10% and similar to 23% of the original microbenchmark suites, whereas recommendation identifies up to 26 and 14 newly, uncovered functions to benchmark to improve the relevance. By utilizing the differences and synergies of application benchmarks and microbenchmarks, our approach potentially enables effective software performance assurance with performance tests of multiple granularities.
|
|
| 3. |
- Grambow, M., et al.
(författare)
-
Using Microbenchmark Suites to Detect Application Performance Changes
- 2023
-
Ingår i: Ieee Transactions on Cloud Computing. - : Institute of Electrical and Electronics Engineers (IEEE). - 2168-7161 .- 2372-0018. ; 11:3, s. 2575-2590
-
Tidskriftsartikel (refereegranskat)abstract
- Software performance changes are costly and often hard to detect pre-release. Similar to software testing frameworks, either application benchmarks or microbenchmarks can be integrated into quality assurance pipelines to detect performance changes before releasing a new application version. Unfortunately, extensive benchmarking studies usually take several hours which is problematic when examining dozens of daily code changes in detail; hence, trade-offs have to be made. Optimized microbenchmark suites, which only include a small subset of the full suite, are a potential solution for this problem, given that they still reliably detect the majority of the application performance changes such as an increased request latency. It is, however, unclear whether microbenchmarks and application benchmarks detect the same performance problems and one can be a proxy for the other. In this paper, we explore whether microbenchmark suites can detect the same application performance changes as an application benchmark. For this, we run extensive benchmark experiments with both the complete and the optimized microbenchmark suites of the two time-series database systems InfluxDB and VictoriaMetrics and compare their results to the results of corresponding application benchmarks. We do this for 70 and 110 commits, respectively. Our results show that it is possible to detect application performance changes using an optimized microbenchmark suite if frequent false-positive alarms can be tolerated.
|
|
