核電專業(yè)英語(yǔ)學(xué)習(xí)(必考)

1、第1章 應(yīng)知應(yīng)會(huì)的單詞與專業(yè)術(shù)語(yǔ)1.1. 原子核、核子及相關(guān)術(shù)語(yǔ)21質(zhì)子 proton中子 neutron電子 electron核子 nucleon核 nucleus （pl.）nuclei原子 atom光子 photon正電子 positron量子 quantum, quanta (pl.)電子伏特 electron-volt (eV)兆電子伏特 mega electron-volt (MeV)同位素 isotope原子序數(shù) atomic number質(zhì)量數(shù) mass number超鈾元素 transuranium element元素周期表 periodic table熱中子 thermal

2、 neutron快中子 fast neutron復(fù)合核compound nucleus 1.2. 相關(guān)元素與材料1.2.1. 核燃料與增殖材料鈾 uranium（U）钚 plutonium（Pu）氘，重氫 deuterium，heavy hydrogen氚 tritium混合氧化物燃料（MOX燃料）Mixed (Uranium and Plutonium) OXide fuel二氧化鈾 uranium dioxide濃縮鈾 enriched uranium貧鈾 depleted uranium碳化鈾 uranium carbide釷 thorium鋰 lithium錒系元素 actinide

3、element易裂變的 fissile可裂變的、可裂變物質(zhì) fissionable 增殖同位素 fertile isotope核嬗變 nuclear transmutation轉(zhuǎn)化 conversion1.2.2. 其它核材料及核電廠用材料慢化劑 moderator輕水 light water重水 heavy water石墨 graphite冷卻劑 coolant氦 helium液態(tài)金屬 liquid metal鈉 sodium包殼 cladding鋁 aluminium鎂 magnesium鋯 zirconium鋯合金 zircaloy不銹鋼 stainless steel控制材料 cont

4、rol material通量展平flux-shaping銀 silver銦 indium鎘 cadmium可燃毒物 burnable poison硼 boron硼酸 boric acid鋰 lithium鈹 beryllium乏燃料 spent fuel因科鎳，因康 INCONEL不銹鋼 stainless steel奧氏體不銹鋼 austenitic stainless steel鐵素體不銹鋼 ferritic stainless steel馬氏體不銹鋼 martensitic stainless steel1.3. 核反應(yīng)及相關(guān)術(shù)語(yǔ)衰變 decay裂變 fission聚變 fusion核反

5、應(yīng) nuclear reaction鏈?zhǔn)椒磻?yīng) chain reaction截面 cross section微觀截面 microscopic cross section宏觀截面 macroscopic cross section吸收截面 absorbing cross section散射截面 scattering cross section靶恩 barn緩發(fā)中子 delayed neutron瞬發(fā)中子 prompt neutron瞬發(fā)臨界 prompt criticality易裂變的 fissile可裂變的 fissionable慢化 morderate / slow down增殖比 breed

6、ing ratio燃耗 burnup反應(yīng)性 reactivity中子循環(huán) neutron cycle裂變產(chǎn)物 fission product臨界 criticality瞬發(fā)臨界 prompt critical通量 flux氙 xenon碘 iodine錒系（元素）actinide反應(yīng)性價(jià)值 reactivity worth慢化劑溫度系數(shù)  moderator  temperature  coefficient反應(yīng)性系數(shù)  reactivity  coefficient剩余反應(yīng)性  excess  reactivity燃料比功

7、率  fuel  specific  power倍增因子 multiplication factor有效增殖系數(shù) effective multiplication factor；effective multiplication constant 無(wú)限介質(zhì)增殖系數(shù) infinite multiplication factor； infinite multiplication constant 快中子增殖系數(shù) fast fission factor 熱中子利用系數(shù) thermal utilization factor 不泄漏幾率 nonleakage probabil

8、ity逃脫共振俘獲幾率 resonance escape probability四因子公式 four-factor formula多普勒增寬 Doppler broadening*總集成中子通量/總積分中子通量 Total Integrated Neutron Flux = Integrated Flux or Fluence (注量) = Neutron density ´ Velocity ´ Time 單位：n/m3× m/s × s = n/m2 1.4. 反應(yīng)堆壓水堆 Pressurized Water Reactor (PWR)沸水堆 Boi

9、ling Water Reactor (BWR)加拿大重水鈾反應(yīng)堆（坎杜堆）CANadian Deuterium and Uranium reactor (CANDU) / pressurized heavy water reactor (PHWR)英國(guó)氣冷堆（美諾克斯堆）British gas-cooled Magnox reactor高溫氣冷堆 high temperature gas-cooled reactor (HTGR)快中子增殖反應(yīng)堆 fast breeder reactor (FBR)輕水堆 Light Water Reactor (LWR)先進(jìn)反應(yīng)堆 advanced rea

10、ctor超臨界水反應(yīng)堆 supercritical water reactor歐洲壓水堆（第三代反應(yīng)堆之一） European Pressurized water Reactor (EPR)（美國(guó)）先進(jìn)壓水堆600/1000（第三代(+)反應(yīng)堆之一） AP(WR)600 / 10001.5. 核電廠部件、設(shè)備與系統(tǒng)燃料芯塊 fuel pellet燃料元件 fuel element燃料棒 fuel rod燃料組件 fuel assembly定位格架 spacer grid法蘭 flange密封環(huán) seal ring阻力塞 plug(上/下)腔室 (upper / lower ) plenum 堆

11、芯，活性區(qū) core反應(yīng)堆壓力容器 Reactor Pressure Vessel (RPV)上封頭 upper closure head液壓螺栓拉伸機(jī)(張緊機(jī)) hydraulic stud tensioner 包覆層 clad (碳鋼表面的防腐蝕堆焊層)控制棒 control rod控制棒組件 Control Element Assembly (CEA)可燃吸收棒 burnable absorber rod控制棒驅(qū)動(dòng)機(jī)構(gòu) Control Element Drive Mechanism (CEDM)變送器 transmitter信號(hào)調(diào)理 signal regulation吊籃 barrel進(jìn)

12、/出口接管 inlet / outlet nozzle冷/熱端，冷/熱腿，冷/熱管段 cold / hot leg反應(yīng)堆堆內(nèi)構(gòu)件 reactor vessel internals腫脹 swelling腐蝕 corrode, corrosion侵蝕 erode, erosion氧化 oxidation, oxidize完整性 integrity反應(yīng)堆冷卻劑泵（主泵） Reactor Coolant Pump (RCP)屏蔽泵 canned (motor) pump軸封泵 shaft seal pump反應(yīng)堆冷卻劑系統(tǒng)（一回路系統(tǒng)）Reactor Coolant System (RCS)核蒸汽供應(yīng)

13、系統(tǒng) Nuclear Steam Supply System (NSSS)一回路 primary loop/circuit一回路系統(tǒng)/主回路系統(tǒng) primary system二回路 secondary loop穩(wěn)壓器 pressurizer (PRZ)波動(dòng)管 surge line汽水分離器 moisture separator干燥器（二/三級(jí)汽水分離器）steam dryer安全閥 safety valve卸壓閥 relief valve溢流閥 overflow valve主蒸汽隔離閥 main steam isolation valve單向閥 check valve止回閥 non-retur

14、n valve主蒸汽聯(lián)箱 main steam header 給水調(diào)節(jié)閥 feed regulating valve蒸汽發(fā)生器 Steam Generator (SG)主蒸汽管 Main Steam Line (MSL)汽輪機(jī) steam turbine汽水分離再熱器 Moisture Separator Reheater (MSR)給水泵 feed (water) pump上充泵 charging pump凝汽器 condenser發(fā)電機(jī) (electric) generator安全殼 containment地基，基礎(chǔ) foundation煙道 stack貫穿件 penetration核島

15、nuclear island常規(guī)島 conventional island核電廠配套子項(xiàng) Balance of Plant (BOP)一回路輔助系統(tǒng) auxiliary system for primary loop化學(xué)與容積控制系統(tǒng)（化容系統(tǒng)） Chemical and Volume Control System (CVCS)專設(shè)安全設(shè)施 Engineered Safety Feature (ESF)余熱排出系統(tǒng) Residual Heat-Removal System (RHRS)應(yīng)急堆芯冷卻系統(tǒng) Emergency Core Cooling System (ECCS),安注系統(tǒng)Safet

16、y Injection (SI) System直接注射系統(tǒng) direct vessel injection (DVI)換料水箱 In-containment Refueling Water Storage Tank (IRWST)(乏)燃料貯存水池 (spent) fuel storage pool燃料裝卸系統(tǒng) fuel handling system堆芯補(bǔ)水箱 core makeup tank蓄壓箱 accumulator機(jī)組 unit輔助噴淋 auxiliary spray柴油發(fā)電機(jī) Diesel generator自動(dòng)保護(hù)系統(tǒng) Automatic Protective System (A

17、PS)自動(dòng)降壓系統(tǒng) automatic depressurization system (ADS)儀控系統(tǒng) Instrumentation and Control System (I & C system)開(kāi)關(guān)設(shè)備，開(kāi)關(guān)柜 switch gear 蒸汽軸封系統(tǒng)，壓蓋蒸汽密封系統(tǒng) gland steam system汽輪機(jī)旁路管 turbine bypass line 輔助給水泵 auxiliary feedwater pump汽動(dòng)給水泵 turbine driven feedwater pump 導(dǎo)管conduit冷凝水泵condensate pump 冷凝水增壓泵 condensat

18、e booster pump水潤(rùn)滑軸承 water lubricated bearing 人孔 man way檢修孔 accessory port熱電偶 thermocouple加熱節(jié)點(diǎn)熱電偶 heated junction thermocouple干簧管開(kāi)關(guān) reed switch流量限制器 flow restrictor節(jié)流孔版 orifice1.6. 反應(yīng)堆運(yùn)行運(yùn)行 operation運(yùn)行工況 operating condition操縱員 operator維護(hù) maintenance監(jiān)督、監(jiān)視surveillance 監(jiān)督試樣 surveillance specimen輻照監(jiān)督管 irr

19、adiation surveillance capsule輻照監(jiān)督試樣盒 surveillance specimen compartment硼濃度 boron concentration稀釋 dilution / dilute硼注入 boron  injection停堆 shutdown緊急停堆 scram / trip停役 outage換料停堆 refueling outage / refueling shutdown換料 refuel卸料  discharge倒料  shuffling滿功率運(yùn)行 full power operation負(fù)荷跟蹤 lo

20、ad following甩負(fù)荷 load shedding, load rejection(控制棒等的)插入 insertion(控制棒等的)抽出 withdrawal反應(yīng)堆調(diào)節(jié)系統(tǒng) Reactor Regulating System (RRS)(蒸汽發(fā)生器)排污、下泄 blowdown規(guī)程 procedure技術(shù)規(guī)格 technical specification瞬態(tài)，瞬變 transient安裝調(diào)試 installation and commissioning冷態(tài)試驗(yàn)  cold  functional  test熱態(tài)試驗(yàn)  hot  fu

21、nctional  test(反應(yīng)堆)啟動(dòng)試驗(yàn) (reactor) start up test退役 decommissioning主控室 main control room方位角偏差 azimuthal tilt徑向功率分布 radial power distribution 軸向功率分布 axial power distribution燃料管理方案fuel management scheme燃料-包殼交互作用fuel-clad interaction effect芯塊-包殼交互作用 (PCI) pellet-clad interaction(燃料)柵格、晶格 lattic

22、e積水垢 fouling 去污 cleansing(水的)凈化 purify (v), purification (n)1.7. 反應(yīng)堆安全核安全 nuclear safety安全功能  safety  function衰變熱 decay heat余熱 residual heat空泡系數(shù) void coefficient法律 law法規(guī) regulation / code 聯(lián)邦管理法規(guī) Code of Federal Regulations (CFR)法案（美） Act導(dǎo)則 guidance, guide安全1/2/3級(jí)safety class 1/2/3可靠性 relia

23、bility容限，裕量，邊界margin堆芯熱裕量core thermal margin堵管裕量 tube plugging margin運(yùn)行安全裕量 operating margin標(biāo)準(zhǔn)，準(zhǔn)則 criterion，復(fù)數(shù)形式: criteria概率安全分析 Probabilistic Safety Analysis (PSA)概率風(fēng)險(xiǎn)分析 Probabilistic Risk Analysis (PRA)確定論安全分析 deterministic safety analysis初步安全分析報(bào)告 Preliminary Safety Analysis Report (PSAR)最終安全分析報(bào)告

24、Final Safety Analysis Report (FSAR)安全評(píng)價(jià)報(bào)告 safety evaluation report事件 incident事故 accident后果 consequence嚴(yán)重事故 severe accident堆芯損毀 core damage堆芯融化 core meltdown全廠斷電 station blackout冷卻劑喪失事故（失水事故）Loss-of-coolant Accident (LOCA)反應(yīng)性引入事故 Reactivity Insertion Accident (RIA)未能緊急停堆的預(yù)計(jì)瞬變 Anticipated Transient Wi

25、thout Scram (ATWS)失電 Loss of Power失流 Loss of flow先漏后破leak before break (LBB)故障安全，失效保護(hù) fail-safe單一故障準(zhǔn)則 single-failure criterion共因故障 common cause failure固有安全性 inherent safety非能動(dòng)安全 passive safety冗余性 redundancy多樣性 diversity多層屏障 multiple barrier縱深防御 defense in depth潛熱latent heat 焓，熱函 sensible heat, entha

26、lpy定期安全檢查 periodic safety inspection許可證 license監(jiān)管 regulation核安全準(zhǔn)則 nuclear safety criteria三哩島事故 Three Mile Island (TMI) accident切爾諾貝利事故 Chernobyl accident工作不正常，故障 malfunction失效 failure假設(shè)始發(fā)事件 postulated initiating events事故工況 accident condition嚴(yán)重事故 severe accident事故處理 accident management設(shè)計(jì)基準(zhǔn)事故 design b

27、asis accident負(fù)荷喪失事故 loss of electrical load accident主給水喪失事故 loss of main feed water accident卡棒事故 stuck rod accident彈棒事故 rod ejection accident堵管裕量 tube plugging margin管道甩擺限制 pipe whip restraint在役檢查 inservice inspection承壓熱沖擊 pressurized thermal shock1.8. 放射性與輻射防護(hù)放射性 radioactivity散射 scatter折射 deflect,

28、deflection衍射 diffraction穿透 penetrate, penetration交互作用 interact, interaction電離 ionization湮滅 annihilate (v.), annihilation (n.)衰減 attenuate(v.), attenuation(n.)入射離子 projectile輻射防護(hù) radiation protection輻射，射線 radiation, ray輻照，（向外）輻射 irradiation內(nèi)照射 internal exposure外照射 external exposure職業(yè)照射（劑量） occupation

29、al dose注量 fluence宇宙射線 cosmic rayX射線 x-raya / b / g 射線 a / b / g ray保健物理 health physics屏蔽 shielding生物屏蔽 biological shield劑量 dose劑量當(dāng)量 dose equivalent集體劑量 collective dose個(gè)人劑量 individual dose攝入，攝取 ingest, ingestion吸入 inhale, inhalation昏迷 coma絞痛 cramp腹瀉 diarrhea顫抖 tremor嘔吐 vomit身體的 somatic 軀體反應(yīng) somatic e

30、ffect輻照病變 radiation sickness 征兆 symptom治療 therapy幸存者 survivor活化產(chǎn)物 activation product廢水 effluent天然本底 natural background希弗 sivert譜 spectrum雷姆 rem氡 radon合理可行盡量低 as low as reasonably achievable (ALARA)放射性廢物處理 radioactive waste disposal高放廢物 high-level (radioactive) waste低放廢物 low-level (radioactive) waste

31、1.9. 有關(guān)機(jī)構(gòu)國(guó)際原子能機(jī)構(gòu) International Atomic Energy Agency (IAEA)美國(guó)機(jī)械工程師學(xué)會(huì) American Society of Mechanical Engineers (ASME)美國(guó)核管會(huì) Nuclear Regulatory Commission (NRC/USNRC)美國(guó)能源部 Department Of Energy (DOE)世界核電運(yùn)營(yíng)者協(xié)會(huì) World Association of Nuclear Operators (WANO)國(guó)際輻射防護(hù)委員會(huì) International Commission on Radiological

32、Protection (ICRP)中國(guó)國(guó)家原子能機(jī)構(gòu) China Atomic Energy Authority （CAEA）國(guó)家環(huán)?？偩?State Environment Protection Administration of China1.10. 其它術(shù)語(yǔ)1.10.1. 表示方向橫向 lateral縱向 longitudinal徑向 radial垂直于 perpendicular to垂直/立式安裝 vertically mounted環(huán)向 circumferential軸向 axial周邊 periphery1.10.2. 材料術(shù)語(yǔ)腐蝕 corrosion應(yīng)力腐蝕開(kāi)裂 stress

33、corrosion cracking斷裂 rapture, fracture, break破口 breach腫脹 swelling氣蝕 cavitation點(diǎn)蝕/孔蝕 pitting縫隙腐蝕 crevice corrosion沖蝕 erosion流動(dòng)加速腐蝕FAC flow accelerated corrosion耗蝕 wastage 凹陷，凹痕(SG tube) dent疲勞 fatigue老化 ageing降級(jí) degradation磨損 wear微動(dòng)磨損 fretting wear蠕變 creep應(yīng)力 stress應(yīng)變 strain蠕變強(qiáng)度 creep strength抗拉強(qiáng)度 ten

34、sile strength屈服強(qiáng)度 yield strength斷裂強(qiáng)度 rapture strength斷裂韌性 fracture toughness零延性轉(zhuǎn)變溫度nil-ductility transition temperature 基準(zhǔn)性能 baseline property熱應(yīng)力 thermal stress輻照腫脹 irradiation swelling焊接 weld堆焊 deposit welding, overlaying, build-up welding, surface welding密封焊 seal weld對(duì)接焊 butt weld焊縫 weld seam焊接熱影響

35、區(qū) heat affected zone (HAZ)鍛造 forge鍛件 forging1.10.3. 核電工程術(shù)語(yǔ)征購(gòu) procurement安裝 erection調(diào)試 commissioning廠址 site招標(biāo) call for bid, call for tender商務(wù)標(biāo) commercial offer 技術(shù)標(biāo) technical offer開(kāi)工 commencement合同 contract 不可更改的合同 firm contract 分包合同 subcontract承諾，任務(wù) commitment工地，工作現(xiàn)場(chǎng) job site技術(shù)要求 technical requiremen

36、t 技術(shù)規(guī)格 technical specification不符合項(xiàng) non-conformance交貨 delivery倉(cāng)庫(kù) warehouse施工計(jì)劃 construction schedule離岸價(jià)格 Free on Board (FOB)到岸價(jià)格 Cost Insurance and Freight (CIF) EPC合同-設(shè)計(jì)采購(gòu)建造，Engineering, Procurement & Construction電網(wǎng) power grid輸變電系統(tǒng) distribution system 1.10.4. 其它化合物 compound混合物 mixture質(zhì)量 mass動(dòng)量 m

37、omentum能量 energy勢(shì)能 potential (energy)動(dòng)能 kinetic energy慣性 inertia半衰期 half-life平均自由程mean free path燃料循環(huán) fuel cycle熱點(diǎn) hot spot熱管因子 hot-channel factor偏離泡核沸騰比 departure from nucleate boiling ratio (DNBR)傳熱 heat transfer換熱器 heat exchanger導(dǎo)熱 heat conduction對(duì)流 convection熱輻射 thermal / heat radiation干度 quality

38、蒸汽 steam預(yù)應(yīng)力鋼筋混凝土 prestressed reinforced concrete / prestressed concrete鋼筋混凝土 reinforced concrete鐵鋼沙混凝土 Steel shot concrete筋，鋼筋束 tendon流量分配 flow distribution電網(wǎng) power grid公共事業(yè)，業(yè)主 utility業(yè)主 owner承包商 contractor分包商 sub-contractor壓降 pressure drop壓差differential pressure水位 (water) level水位指示 level indication

39、規(guī)定，條款；保障；裝備 provision地震 earthquake地震的 seismic颶風(fēng) tornado暖通空調(diào) Heating, Ventilation and Air Conditioning (HVAC)熱阱 heat sink惰轉(zhuǎn) coastdown惰轉(zhuǎn)流量coastdown flow 功率失常激增，功率漂移 power excursion 減輕，緩解 v. mitigate, n. mitigation公差、容差 allowance間隙，公差 clearance權(quán)重因子 weighting factor1.11. 有必要了解的詞匯與短語(yǔ)根據(jù)經(jīng)驗(yàn) as a rule of thu

40、mb以數(shù)量級(jí) by orders of magnitude早期故障, 初期故障 incipient failure 消除 eliminate, elimination導(dǎo)出，起源 derive, derivation, deduce, deduction機(jī)理，原理 mechanism, approach, principle, theory敏感的 susceptible 敏感性 susceptibility有毒的 toxic急劇的 acute遺傳 inherit遺傳性的 hereditary高度 altitude假定，假設(shè) postulate, postulation可滲透的, 有滲透性的 pe

41、rmeable不可滲透的 impermeable脆性破裂 brittle fracture脆化 embrittlement韌性 toughness延展性 ductility1.12. AP1000核電廠相關(guān)術(shù)語(yǔ)非能動(dòng)余熱導(dǎo)出系統(tǒng) passive decay heat removal system爆破閥 squib valve第2章 閱讀理解題練習(xí)2.1. Passage 1As a result reactor designers have paid great attention to the inherent safety of reactors which can be achieved

42、 by negative temperature and power coefficients and fail-safe control systems. It can be said with some confidence that present-day thermal reactors are safe in the sense that under no conceivable circumstance can they explode like a bomb, and control systems have been designed which can, in the eve

43、nt of any malfunction on the part of the reactor or its associated plant, automatically and rapidly shut down the reactor, i.e. make it subcritical by a substantial amount, in a very few seconds.1. According to the paragraph, inherent safety of reactors can be achieved by . （C）A. the operators;B. po

44、sitive temperature and positive power coefficients;C. negative temperature and negative power coefficients;D. passive safety system and positive power coefficients.2. The best title of the passage may probably be . （D）A. fail-safe control system；B. thermal reactor safety and operation;C. automatic p

45、rotective system;D. inherent safety design of reactors.2.2. Passage IIThe biological shield should contain some hydrogen compound to slow down fast neutrons, and be dense enough to attenuate gamma radiation effectively. Concrete satisfies both these requirements fairly well and is suitable for landb

46、ase reactors. Barytes (重晶石) concrete, containing the heavy element barium, and steel-shot concrete have been used for biological shields. They are more dense than ordinary concrete, with improved shielding properties, however their higher cost offsets this advantage. The biological shield for a mari

47、ne reactor, which is usually a fairly compact pressurized water reactor, must satisfy a minimum space and weight requirement. This leads to a shield design which consists typically of alternate layers of water (for fast neutron slowing) and steel (for gamma ray attenuation).3. According to the above

48、 passage, is not possible for constructing biological shield? （C）A. steel; B. concrete;C. graphite; D. paraffin wax.4. Which of the following sentences is not true? （D）A. The biological shield is designed mainly to slow down fast neutrons and attenuate gamma radiation.B. The marine reactor uses alte

49、rnative steel and water layers as its biological shield.C. The combination of heavy element concrete and steel bars could improve the shielding properties.D. The biological shield should use hydrogen element to slow down fast neutron and attenuate gamma radiations.2.3. Passage IIIIn order to mitigat

50、e the effects of large release of steam (an potentially of radioactivity) in the containment, two full capacity independent safety systems are provided; the reactor building spray system and the reactor building emergency coolers. The systems are designed to provide cool water to condense discharge

51、steam and to prevent containment pressure from reaching its design limit. Individual systems differ considerably but a typical system may be described as follows; The initial capacity of the systems in removing heat from the containment atmosphere is typically 253GJ/hr.When a containment pressure of

52、 4psig is reached, the emergency coolers of the reactor building are actuated. In their post accident mode, the system consists of three units each with a fan and an emergency cooler. As the reactor building air is circulated across a tubular heat exchanger, a portion of steam is condensed. These co

53、olers alone would be capable of returning the containment pressure to near atmospheric within 24 hr after an accident. When the pressure reaches a level of 10 psig, the second safety system, the reactor building spray system, is automatically actuated. It consists of a pump, piping, headers, and spr

54、ay nozzles arranged uniformly under the containment dome. It can spray borated water into the reactor building at a rate of 11.35m3/min. A sodium hydroxide additive is also provided in the spray water to increase the retention of iodine, and hence, to reduce its concentration in the containment atmo

55、sphere in the event of a sizable breach of fuel cladding.5. Two full capacity independent safety systems are provided for the design purpose of . （A）A. condensing the steam released into the containment when pressure exceeds design limit.B. maintaining the high pressure in the containmentC. discharg

56、ing large amount of steam D. mitigating the effect of radiation hazard to the containment.6. The reactor building spray system will be actuated automatically . （C）A. after 24 hours after the accident;B. immediately after the accident;C. when the containment pressure reaches a level of design limit;D. when the air in the containment is circulat