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論文

ROSA/LSTF test on nitrogen gas behavior during reflux condensation in PWR and RELAP5 code analyses

竹田 武司; 大津 巌

Mechanical Engineering Journal (Internet), 5(4), p.18-00077_1 - 18-00077_14, 2018/08

We conducted an experiment focusing on nitrogen gas behavior during reflux condensation in PWR with ROSA/LSTF. The primary pressure was lower than 1 MPa under constant core power of 0.7% of volumetric-scaled (1/48) PWR nominal power. Steam generator (SG) secondary-side collapsed liquid level was maintained at certain liquid level above SG U-tube height. Nitrogen gas was injected stepwise into each SG inlet plenum at certain constant amount. The primary pressure and degree of subcooling of SG U-tubes were largely dependent on amount of nitrogen gas accumulated in SG U-tubes. Nitrogen gas accumulated from outlet towards inlet of SG U-tubes. Non-uniform flow behavior was observed among SG U-tubes with nitrogen gas ingress. The RELAP5/MOD3.3 code indicated remaining problems in predictions of the primary pressure and degree of subcooling of SG U-tubes depending on number of nitrogen gas injection. We studied further non-uniform flow behavior through sensitivity analyses.

論文

Uncertainty analysis of ROSA/LSTF test by RELAP5 code and PKL counterpart test concerning PWR hot leg break LOCAs

竹田 武司; 大津 巌

Nuclear Engineering and Technology, 50(6), p.829 - 841, 2018/08

An experiment was conducted for OECD/NEA ROSA-2 Project using LSTF, which simulated 17% hot leg intermediate-break LOCA in PWR. Core uncovery started simultaneously with liquid level drop in crossover leg downflow-side before loop seal clearing, and water remaining occurred on upper core plate. Results of uncertainty analysis with RELAP5/MOD3.3 code clarified influences of combination of multiple uncertain parameters on peak cladding temperature within defined uncertain ranges. An experiment was performed for OECD/NEA PKL-3 Project with PKL. The LSTF test simulated PWR 1% hot leg small-break LOCA with steam generator secondary-side depressurization as accident management measure and nitrogen gas inflow. Some discrepancies appeared between the LSTF and PKL test results for primary pressure, core collapsed liquid level, and cladding surface temperature probably due to effects of differences between LSTF and PKL in configuration, geometry, and volumetric size.

論文

ROSA/LSTF tests and posttest analyses by RELAP5 code for accident management measures during PWR station blackout transient with loss of primary coolant and gas inflow

竹田 武司; 大津 巌

Science and Technology of Nuclear Installations, 2018, p.7635878_1 - 7635878_19, 2018/00

Three tests were carried out with LSTF, simulating accident management (AM) measures during PWR station blackout transient with loss of primary coolant under assumptions of nitrogen gas inflow and total-failure of high-pressure injection system. As AM measures, steam generator (SG) depressurization was done by fully opening relief valves, and auxiliary feedwater was injected into secondary-side simultaneously. Conditions for break size and onset timing of AM measures were different. Primary pressure decreased to below 1 MPa with or without primary depressurization by fully opening pressurizer relief valve. Nonuniform flow behaviors were observed in SG U-tubes with gas ingress depending on gas accumulation rate in two tests that gas accumulated remarkably. The RELAP5/MOD3.3 code indicated remaining problems in predictions of primary pressure, SG U-tube liquid levels, and natural circulation mass flow rates after gas inflow and accumulator flow rate through analyses for two tests.

論文

RELAP5 uncertainty evaluation using ROSA/LSTF test data on PWR 17% cold leg intermediate-break LOCA with single-failure ECCS

竹田 武司; 大津 巌

Annals of Nuclear Energy, 109, p.9 - 21, 2017/11

 被引用回数:1 パーセンタイル:64.68(Nuclear Science & Technology)

An experiment was conducted for the OECD/NEA ROSA-2 Project using LSTF, which simulated a cold leg intermediate-break loss-of-coolant accident with 17% break in a PWR. Assumptions were made such as single-failure of high-pressure and low-pressure injection systems. In the LSTF test, core dryout took place because of rapid drop in the core liquid level. Liquid was accumulated in upper plenum, SG U-tube upflow-side and inlet plena because of counter-current flow limiting (CCFL). The post-test analysis by RELAP5/MOD3.3 code revealed that peak cladding temperature (PCT) was overpredicted because of underprediction of the core liquid level due to inadequate prediction of accumulator flow rate. We found the combination of multiple uncertain parameters including the Wallis CCFL correlation at the upper core plate, core decay power, and steam convective heat transfer coefficient in the core within the defined uncertain ranges largely affected the PCT.

論文

ROSA/LSTF test and RELAP5 analyses on PWR cold leg small-break LOCA with accident management measure and PKL counterpart test

竹田 武司; 大津 巌

Nuclear Engineering and Technology, 49(5), p.928 - 940, 2017/08

An experiment using PKL was performed for the OECD/NEA PKL-3 Project as a counterpart to a previous test with LSTF on a cold leg small-break loss-of-coolant accident with an accident management measure in a PWR. The rate of steam generator secondary-side depressurization was controlled to achieve a primary depressurization rate of 200 K/h as a common test condition. In both tests, rapid recovery started in the core collapsed liquid level after loop seal clearing. Some discrepancies appeared between the LSTF and PKL test results for the core collapsed liquid level, the cladding surface temperature, and the primary pressure. The RELAP5/MOD3.3 code indicated a remaining problem in the prediction of primary coolant distribution. Results of uncertainty analysis for the LSTF test clarified the influences of the combination of multiple uncertain parameters on peak cladding temperature within the defined uncertain ranges.

論文

ROSA/LSTF test on nitrogen gas behavior during reflux cooling in PWR and RELAP5 post-test analysis

竹田 武司; 大津 巌

Proceedings of 25th International Conference on Nuclear Engineering (ICONE-25) (CD-ROM), 11 Pages, 2017/07

An experiment focusing on nitrogen gas behavior during reflux cooling in a PWR was performed with the LSTF. The test conditions were made such as the constant core power of 0.7% of the volumetric-scaled PWR nominal power and the primary pressure of lower than 1 MPa. The steam generator (SG) secondary-side collapsed liquid level was maintained at a certain liquid level above the SG tube height. Nitrogen gas was injected stepwise into each SG inlet plenum at a certain constant amount. The primary pressure and the SG U-tube fluid temperatures were greatly dependent on the amount of nitrogen gas accumulated in the SG U-tubes. Non-uniform flow behavior was observed among the SG U-tubes with nitrogen gas ingress. The RELAP5/MOD3.3 code indicated remaining problems in the predictions of the primary pressure and the SG U-tube fluid temperatures after nitrogen gas inflow.

論文

ROSA/LSTF tests and RELAP5 posttest analyses for PWR safety system using steam generator secondary-side depressurization against effects of release of nitrogen gas dissolved in accumulator water

竹田 武司; 大貫 晃*; 金森 大輔*; 大津 巌

Science and Technology of Nuclear Installations, 2016, p.7481793_1 - 7481793_15, 2016/00

AA2016-0048.pdf:5.15MB

 被引用回数:1 パーセンタイル:76.09(Nuclear Science & Technology)

Two tests related to a new safety system for PWR were performed with ROSA/LSTF. The tests simulated cold leg small-break loss-of-coolant accidents with 2-inch diameter break using an early steam generator (SG) secondary-side depressurization with or without release of nitrogen gas dissolved in accumulator (ACC) water. The pressure difference between the primary and SG secondary sides after the actuation of ACC system was larger in the test with the dissolved gas release than in the test without the dissolved gas release. No core uncovery and heatup took place because of the ACC coolant injection and two-phase natural circulation. The RELAP5 code predicted most of the overall trends of the major thermal-hydraulic responses after adjusting a break discharge coefficient for two-phase discharge flow under the assumption of releasing all the dissolved gas at the vessel upper plenum.

論文

ROSA/LSTF experiment on a PWR station blackout transient with accident management measures and RELAP5 analyses

竹田 武司; 大津 巌

Mechanical Engineering Journal (Internet), 2(5), p.15-00132_1 - 15-00132_15, 2015/10

An experiment on a PWR station blackout transient with accident management (AM) measures was conducted using the ROSA/LSTF under an assumption of non-condensable gas inflow to primary system from accumulator tanks. The AM measures considered are SG secondary-side depressurization by fully opening safety valves in both SGs with start of core uncovery and coolant injection into the secondary-side of both SGs at low pressures. The primary pressure started to decrease when the SG primary-to-secondary heat removal resumed soon after the SG secondary-side coolant injection. The primary depressurization worsened due to the gas accumulation in SG U-tubes after accumulator completion. The RELAP5 code indicated remaining problems in the predictions of the SG U-tube collapsed liquid level and primary mass flow rate after gas ingress. The SG coolant injection flow rate was found to significantly affect the peak cladding temperature and the ACC actuation time through RELAP5 sensitivity analyses.

論文

ROSA/LSTF experiment on accident management measures during a PWR station blackout transient with pump seal leakage and RELAP5 analyses

竹田 武司; 大津 巌

Journal of Energy and Power Sources, 2(7), p.274 - 290, 2015/07

An experiment on accident management (AM) measures during a PWR station blackout transient with leakage from primary coolant pump seals was conducted using the ROSA/LSTF under an assumption of non-condensable gas inflow to the primary system from accumulator tanks. The AM measures are steam generator (SG) secondary-side depressurization by fully opening safety valves (SVs) in both SGs and primary-side depressurization by fully opening SV in pressurizer with the start of core uncovery and coolant injection into the SG secondary-side at low pressures. The decrease was accelerated in the primary pressure when the SG primary-to-secondary heat removal resumed soon after the coolant injection into the SG secondary-side. The primary depressurization worsened due to the gas accumulation in the SG U-tubes after accumulator completion. Remaining problems in the RELAP5 code include the predictions of pressure difference between the primary and SG secondary sides after the gas inflow.

論文

ROSA/LSTF experiment on AM measures during a PWR station blackout transient with pump seal leakage and RELAP5 POST-TEST analysis

竹田 武司; 大津 巌

Proceedings of 23rd International Conference on Nuclear Engineering (ICONE-23) (DVD-ROM), 10 Pages, 2015/05

An experiment on accident management (AM) measures during a PWR station blackout transient with the TMLB' scenario and leakage from primary coolant pump seals was conducted using the ROSA/LSTF under an assumption of non-condensable gas inflow to the primary system from accumulator tanks. The AM measures are steam generator (SG) secondary-side depressurization by fully opening safety valves (SVs) in both SGs and primary-side depressurization by fully opening SV in pressurizer with the start of core uncovery and coolant injection into the SG secondary-side at low pressures. The decrease was accelerated in the primary pressure when the SG primary-to-secondary heat removal resumed soon after the coolant injection into the SG secondary-side. The primary depressurization worsened due to the gas accumulation in the SG U-tubes. The RELAP5 code indicated remaining problems in the predictions of the primary pressure and SG U-tube collapsed liquid level.

論文

ROSA/LSTF experiment on a PWR station blackout transient with AM measures and RELAP5 post-test analysis

竹田 武司; 大津 巌; 与能本 泰介

Proceedings of 22nd International Conference on Nuclear Engineering (ICONE-22) (DVD-ROM), 10 Pages, 2014/07

An experiment on a PWR station blackout transient with the TMLB' scenario and accident management (AM) measures was conducted using the ROSA/LSTF at Japan Atomic Energy Agency under an assumption of non-condensable gas inflow to the primary system from accumulator tanks. The AM measures proposed in this study are steam generator (SG) secondary-side depressurization by fully opening safety valves in both SGs with the incipience of core uncovery and coolant injection into the secondary-side of both SGs at low pressures. The LSTF test revealed the primary pressure started to decrease when the SG primary-to-secondary heat removal resumed soon after the coolant injection into the SG secondary-side. The primary depressurization worsened due to the gas accumulation in the SG U-tubes after the completion of accumulator coolant injection. The RELAP5 code indicated remaining problems in the predictions of SG U-tube liquid level and primary mass flow rate after the gas ingress.

論文

OECD/NEA ROSA project experiment on steam condensation in PWR horizontal legs during large-break LOCA

竹田 武司; 大津 巌; 中村 秀夫

Journal of Energy and Power Engineering, 7(6), p.1009 - 1022, 2013/06

Separate-effect experiment simulating steam direct-contact condensation on emergency core cooling system (ECCS) water in PWR cold legs during reflood phase of large-break LOCA was conducted in OECD/NEA ROSA Project using the Large Scale Test Facility (LSTF). A new test section was furnished in the downstream of the LSTF break unit horizontally attached to the cold leg. Significant condensation of steam appeared in a short distance from the simulated ECCS injection point, and the steam temperature in the test section decreased immediately after the initiation of the ECCS water injection. Total steam condensation rate estimated from the difference between steam flow rates at the test section inlet and outlet was in proportion to the simulated ECCS water mass flux until the complete condensation of steam. Clear images of high-speed video camera were successfully obtained on droplet behaviors through the viewer of the test section, especially for annular mist flow.

論文

LSTF test on cet performance during PWR hot leg small-break LOCA and RELAP5 analysis

竹田 武司; 大津 巌; 中村 秀夫

Proceedings of 15th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-15) (USB Flash Drive), 12 Pages, 2013/05

An OECD/NEA ROSA-2 Project experiment was conducted with the LSTF simulating a PWR hot leg small-break LOCA with a break size equivalent to 1.5% cold leg break under an assumption of total failure of HPI system as a counterpart to PKL-2 Project test. Major test objectives are to clarify responses of CETs versus cladding surface temperature at both of high- and low-pressure conditions corresponding to the pressure range of LSTF and PKL. Core uncovery took place in both phases with no reflux condensate. The observed peak temperature in the core was higher in the low-pressure phase because of longer core uncovery duration though core power and primary pressure were lower than in the high-pressure phase. One-dimensional representation of the core by RELAP5/MOD3.2.1.2 code indicated a limitation in the accuracy of CET responses. The lack in the multi-dimensional steam flow representation had a difficulty in the correct prediction of the peak steam temperature at the core exit.

論文

OECD/NEA ROSA Project experiment on steam condensation in PWR horizontal legs during large-break LOCA

竹田 武司; 大津 巌; 中村 秀夫

Proceedings of 20th International Conference on Nuclear Engineering and the ASME 2012 Power Conference (ICONE-20 & POWER 2012) (DVD-ROM), 11 Pages, 2012/07

Separate-effect experiment simulating steam condensation on emergency core cooling system (ECCS) water in PWR cold legs during reflood phase of large-break loss-of-coolant accident (LBLOCA) was conducted in OECD/NEA ROSA project using the Large Scale Test Facility (LSTF). The boundary test conditions were defined based on PWR LBLOCA analysis by RELAP5/MOD3.2.1.2 code considering typical Japanese safety analysis conditions. Significant condensation of steam appeared in a short distance from the simulated ECCS injection point, and the steam temperature in the test section decreased immediately after the initiation of the ECCS water injection. Fluid temperature distribution at 50 mm downstream from the ECCS injection point was significantly non-uniform, but became almost uniform in less than 350 mm. Clear images of high-speed video camera were obtained on droplet behaviors through the viewer at 200 mm downstream from the ECCS injection point, especially for annular mist flow.

論文

ROSA/LSTF装置を用いた将来型炉の安全系に関する研究

与能本 泰介; 大津 巌; 中村 秀夫; 近藤 昌也; Svetlov, S.*

日本機械学会第8回動力・エネルギー技術シンポジウム講演論文集, p.215 - 220, 2002/06

日本原子力研究所では、軽水炉の安全性評価・確認のために整備した一連の研究施設を用いて、将来型原子炉の安全性解析手法や最適設計手法の高度化を目指した研究を進めている。主たる対象は、近い将来に安全審査が行われる可能性のある大型軽水炉(APWR+, ABWR-II)であるが、いわゆる革新的原子炉も検討対象に含まれている。この計画では、ROSA/LSTF装置等の大型の熱水力装置を用いて実証的な実験,現象理解や性能把握のための基礎実験,コード整備を行う。本論文では、APWR+の新型安全系やAM策の評価のために重要な自然循環について、これまでの関連する実験結果の概要をまとめ、非一様流動の把握,解析が最重要であることを述べる。また、革新的原子炉用の非常用熱交換器での凝縮現象に関し、ロシアのSPOT実験を用いた将来の相関式の評価、並び、二相流流動と伝熱の同時計測を特徴とする基礎実験についてまとめる。

論文

Thermal-hydraulic research on future reactor systems in the ROSA program at JAERI

与能本 泰介; 大津 巌; Svetlov, S.*

Proceedings of 3rd Korea-Japan Symposium on Nuclear Thermal Hydraulics and Safety (NTHAS-3), p.521 - 528, 2002/00

原研では、将来型軽水炉システムの熱水力に関する研究計画を進めている。本論文では本計画の概要と最近の二つの研究内容を紹介する。初めに、SG二次側冷却による長期崩壊熱除去手法の評価のためには、蒸気発生器伝熱管群での非一様流動挙動解析手法の検討が重要であることを述べる。我が国の産業界が計画中の次世代加圧水型炉APWR+では、このような崩壊熱除去システムの使用が計画されている。次に、革新的原子炉用の非常用熱交換器に関し、ロシアのSPOT実験データを用いた検討について紹介する。この検討では、実験に用いられた曲がりや短い直線部を有する伝熱管の管内凝縮伝熱量が、十分長い直管で得られた凝縮相関式を用いて数%の精度で予測できることが示された。

論文

光ファイバーボイドプローブによる気泡速度計測へのウェーブレットの適用

大津 巌; 近藤 昌也; 与能本 泰介; 安濃田 良成

日本機械学会2001年度年次大会講演論文集, Vol.1, p.7 - 8, 2001/00

光ファイバープローブを用いたレーザードップラー流速計は、気泡接触前に気泡界面からの反射波を測定する場合、触針式プローブを用いする手法と較べ、プローブ-気泡間の流体的干渉を避けるうえで有利であると考えられる。この計測法の特性を検討するため、垂直管(内径10mm)の水中で上昇する空気プラグを測定し、13500コマ/秒で撮影したVTR画像で校正した。気泡速度7.76及び18.6cm/sの実験で測定したドップラー信号を周波数の時間的変化を捉えられるウェーブレット変換法で周波数解析した結果、気泡がプローブに接触する直前、ドップラー計測で得た速度が、画像から得た速度に対し急速に低下する時間的特性を明確に捉えられた。真の気泡速度を得るためには、この気液界面にプローブ先端が最接近した時間のデータを排除する必要があることがわかった。

論文

ROSA/LSTF experiments on low-pressure natural circulation heat removal for next-generation PWRs

与能本 泰介; 大津 巌

Proceedings of 12th Pacific Basin Nuclear Conference (PBNC 2000), Vol.1, p.317 - 329, 2000/00

蒸気発生器(SG)二次側除熱により事故後の崩壊熱除去を行うPWRにおいては、大気圧近傍圧力での自然循環除熱挙動を明らかにすることが重要である。本論文では、ROSA/LSTF装置を用いて、これに関して行った二つの実験について述べる。いずれの実験でもSG伝熱管群で気液二相が上下に分離した伝熱管(停滞管)と凝縮を伴いつつ二相流が流れる伝熱管が共存する非一様な観測された。停滞管では熱伝達が生じないため、非一様流動は一次系からSG二次側へ実効的な伝熱面積を減少させる効果がある。現行解析コードでは、この効果をモデル化できないため、自然循環挙動を適切に予測することはできない。重力注入水中の溶存空気の影響を検討した実験では、伝熱管への溶存空気の蓄積が観測されたが、7時間に渡る実験期間中に伝熱劣化は見られなかった。これは、空気が、伝熱に寄与しない停滞管に選択的に蓄積したことによる。この結果は、SG二次側除熱と重力注入を用いて、冷却材喪失事故後の長期冷却を行うシステムの有望性を示すものである。

論文

Secondary-side depressurization during PWR cold-leg small break LOCAs based on ROSA-V/LSTF experiments and analyses

浅香 英明; 安濃田 良成; 久木田 豊*; 大津 巌

Journal of Nuclear Science and Technology, 35(12), p.905 - 915, 1998/12

 被引用回数:15 パーセンタイル:22.13(Nuclear Science & Technology)

原子炉冷却系の2次側減圧操作は、種々の事故シナリオにおいて炉心の冷却を維持する上で有効であると考えられている。特に1次系の冷却材損失を防ぎつつ炉心冷却を促進できる観点から注目されている。PWR小破断LOCA時に高圧注入系が不動作の場合について、2次側減圧操作の有効性をROSA-V/LSTF実験とRELAP5解析により検討した。2次側減圧速度と減圧開始時間が炉心水位や燃料被覆管表面最高温度(PCT)に与える影響を種々の破断面積について解析的に調べた。その結果、PCTは破断面積が1%から1.5%の間で最も高くなることが示された。また、極大PCTを制限するための減圧速度と減圧開始時間に関する条件を明らかにした。さらに、減圧速度の限界についても論じられている。

論文

Core liquid level responses due to secondary-side depressurization during PWR small break LOCA

浅香 英明; 大津 巌; 安濃田 良成; 大貫 晃; 久木田 豊*

Journal of Nuclear Science and Technology, 35(2), p.113 - 119, 1998/02

 被引用回数:10 パーセンタイル:32.67(Nuclear Science & Technology)

原子炉冷却系の減圧操作は、種々の事故シナリオにおいて炉心の冷却を維持する上で有効であると考えられている。特にPWRの2次系減圧操作は、1次系の冷却材損失を防ぎつつ炉心冷却を促進できる観点から注目されている。PWR小破断LOCA時に高圧注入系の全系統が不作動の場合について、2次系減圧速度と破断面積が炉心水位挙動に与える影響についてLSTF実験とREFLA/TRACコードによる解析により調べた。その結果、2.5%以下の任意の破断について、炉心の著しい温度上昇を防ぐためには約200K/h以上の2次系減圧操作が必要であることを明らかにした。また、2次系減圧操作時における1次系内の特徴的な熱水力挙動を明らかにした。

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