WO1996000966A1 - Reduction of the neutron dose of a reactor vessel - Google Patents
Reduction of the neutron dose of a reactor vessel Download PDFInfo
- Publication number
- WO1996000966A1 WO1996000966A1 PCT/SE1995/000709 SE9500709W WO9600966A1 WO 1996000966 A1 WO1996000966 A1 WO 1996000966A1 SE 9500709 W SE9500709 W SE 9500709W WO 9600966 A1 WO9600966 A1 WO 9600966A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- sub
- fuel
- channels
- fuel assembly
- channel
- Prior art date
Links
- 239000000446 fuel Substances 0.000 claims abstract description 130
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 47
- 230000000712 assembly Effects 0.000 claims abstract description 18
- 238000000429 assembly Methods 0.000 claims abstract description 18
- 238000009835 boiling Methods 0.000 claims abstract description 8
- 238000000034 method Methods 0.000 claims abstract description 6
- 230000000903 blocking effect Effects 0.000 claims abstract 5
- 239000000463 material Substances 0.000 claims description 6
- 239000002826 coolant Substances 0.000 claims description 3
- 229910001093 Zr alloy Inorganic materials 0.000 description 3
- 229910000831 Steel Inorganic materials 0.000 description 2
- 238000005253 cladding Methods 0.000 description 2
- 238000005336 cracking Methods 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 239000008188 pellet Substances 0.000 description 2
- 229910001220 stainless steel Inorganic materials 0.000 description 2
- 239000010935 stainless steel Substances 0.000 description 2
- 239000010959 steel Substances 0.000 description 2
- 235000013382 Morus laevigata Nutrition 0.000 description 1
- 244000278455 Morus laevigata Species 0.000 description 1
- QCWXUUIWCKQGHC-UHFFFAOYSA-N Zirconium Chemical compound [Zr] QCWXUUIWCKQGHC-UHFFFAOYSA-N 0.000 description 1
- 230000004323 axial length Effects 0.000 description 1
- 239000000498 cooling water Substances 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 230000004907 flux Effects 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 238000001956 neutron scattering Methods 0.000 description 1
- 239000003758 nuclear fuel Substances 0.000 description 1
- OOAWCECZEHPMBX-UHFFFAOYSA-N oxygen(2-);uranium(4+) Chemical compound [O-2].[O-2].[U+4] OOAWCECZEHPMBX-UHFFFAOYSA-N 0.000 description 1
- 230000000149 penetrating effect Effects 0.000 description 1
- 230000002093 peripheral effect Effects 0.000 description 1
- 125000006850 spacer group Chemical group 0.000 description 1
- 238000011144 upstream manufacturing Methods 0.000 description 1
- FCTBKIHDJGHPPO-UHFFFAOYSA-N uranium dioxide Inorganic materials O=[U]=O FCTBKIHDJGHPPO-UHFFFAOYSA-N 0.000 description 1
- 229910052726 zirconium Inorganic materials 0.000 description 1
Classifications
-
- G—PHYSICS
- G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
- G21C—NUCLEAR REACTORS
- G21C11/00—Shielding structurally associated with the reactor
- G21C11/06—Reflecting shields, i.e. for minimising loss of neutrons
-
- G—PHYSICS
- G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
- G21C—NUCLEAR REACTORS
- G21C3/00—Reactor fuel elements and their assemblies; Selection of substances for use as reactor fuel elements
- G21C3/30—Assemblies of a number of fuel elements in the form of a rigid unit
- G21C3/32—Bundles of parallel pin-, rod-, or tube-shaped fuel elements
- G21C3/322—Means to influence the coolant flow through or around the bundles
-
- G—PHYSICS
- G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
- G21C—NUCLEAR REACTORS
- G21C3/00—Reactor fuel elements and their assemblies; Selection of substances for use as reactor fuel elements
- G21C3/30—Assemblies of a number of fuel elements in the form of a rigid unit
- G21C3/32—Bundles of parallel pin-, rod-, or tube-shaped fuel elements
- G21C3/326—Bundles of parallel pin-, rod-, or tube-shaped fuel elements comprising fuel elements of different composition; comprising, in addition to the fuel elements, other pin-, rod-, or tube-shaped elements, e.g. control rods, grid support rods, fertile rods, poison rods or dummy rods
- G21C3/328—Relative disposition of the elements in the bundle lattice
-
- G—PHYSICS
- G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
- G21C—NUCLEAR REACTORS
- G21C5/00—Moderator or core structure; Selection of materials for use as moderator
- G21C5/02—Details
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E30/00—Energy generation of nuclear origin
- Y02E30/30—Nuclear fission reactors
Definitions
- the present invention relates to method for reducing the proportion of fast neutrons leaking out of a reactor core in a boiling water reactor.
- the reactor core comprises a plura ⁇ lity of fuel assemblies and is surrounded by a reactor vessel. Water flows upwards through the fuel assemblies and part of the water is thereby transformed into steam.
- a fuel assembly comprises a number of vertical channel-formed parts, so-called sub-channels, to accommodate fuel bundles.
- a fuel bundle comprises a plurality of fuel rods arranged between a bottom tie plate and a top tie plate. Openings are provided between adjacent sub-channels such that water and steam may flow between the sub-channels.
- the invention also relates to a device for improving the neutron moderation at the upper part of a fuel assembly.
- the invention also relates to a fuel assembly of the kind described above, comprising a device for improving the neutron moderation at the upper part of the fuel assembly.
- a reactor core in a boiling water reactor comprises a plurality of vertical fuel assemblies of substantially square cross section.
- the fuel assemblies are arranged in a regular lattice.
- the core is surrounded by a moderator tank as well as by a pressure-maintaining reactor vessel.
- the core is immersed into water which serves both as coolant and as neutron moderator, that is, it slows down the neutrons released during the nuclear reaction.
- the space between the moderator tank and the reactor vessel is water-filled.
- a fuel assembly comprises a plurality of vertical fuel rods, each one containing a column of pellets of a nuclear fuel arranged in a cladding tube. The water flows upwards through the fuel assembly whereby part of the water is transformed into steam.
- Another way is to replaced the fuel rods in those fuel assem ⁇ blies which are located nearest the reactor vessel by rods of a non-fissile material, for example stainless steel or zirco ⁇ nium.
- rods of a non-fissile material for example stainless steel or zirco ⁇ nium.
- One object of the invention is to suggest a method for redu ⁇ cing the proportion of fast neutrons leaking out of the reac- tor core, hence reducing the proportion of fast neutrons reaching the reactor vessel and the moderator tank.
- the object is fulfilled with as small a reduction of the active core, that is, that part of the core which comprises fuel, and with as high a utilization of the fuel as possible.
- Another object of the invention is to provide a device which reduces the proportion of steam at the upper part of a fuel assembly, thus improving the neutron moderation at the upper part.
- An improved neutron moderation leads to a reduction of the proportion of fast neutrons leaking out of the fuel assembly.
- Still another object of the invention is to suggest a fuel assembly for a boiling water reactor, which fuel assembly has an improved neutron moderation at its upper part.
- Figure 1 is a schematic picture of the composition of a boil ⁇ ing water reactor.
- Figure 2 shows an example of a known fuel assembly in a verti ⁇ cal section through the line C-C in figure 3.
- Figure 3 shows the same fuel assembly as Figure 2 in a view perpendicular to a horizontal plane through the line A-A in Figure 2.
- Figure 4 is a schematic picture of a fuel assembly according to the invention in a vertical section through the line D-D in Figures 5 and 8.
- Figure 5 shows a first embodiment of a fuel assembly in Figure 4 in a view perpendicular to a horizontal plane through the line B-B.
- Figure 6 is a perspective view of a device for reducing the proportion of steam at the upper part of a fuel assembly according to the invention.
- Figure 7 shows the volumetric proportion of steam ( ⁇ ) in a sub-channel as a function of the distance (1) from the inlet section of the fuel assembly.
- Figure 8 shows a second embodiment of a fuel assembly in Figure 4 in a view perpendicular to a horizontal plane through the line B-B.
- Figure 9 is a schematic picture of a third embodiment of a fuel assembly according to the invention.
- Figure 10 shows a horizontal section of part of a reactor core comprising fuel assemblies according to the invention.
- the reactor shown in Figure 1 comprises a reactor core 1 containing one or more vertical fuel assemblies, control rods 2 which are used, inter alia, for stopping and starting the reactor, a moderator tank 3 which surrounds the core, steam separators 4 which separate the steam formed in the reactor from the water in the reactor.
- the reactor is surrounded by a pressure-maintaining reactor vessel 5.
- the reactor vessel is filled with water to a level some distance above the reactor core.
- the fuel assembly 6 illustrated in Figures 2 and 3 is enclosed in a fuel channel 7 of substantially square cross section.
- the fuel channel is provided with a hollow support member 8 of cruciform cross section, which is secured to the four walls of the fuel channel.
- the fuel channel with the support member surrounds four vertical channel-formed parts 9a - 9d, so- called sub-channels, with an at least substantially square cross section.
- the four sub-channels each includes a fuel bundle 15a - 15d.
- Each fuel bundle comprises fuel rods 10 arranged in a symmetrical lattice of 4x4 rods.
- the fuel rods are kept in their positions by a number of so-called spacers 11, placed between a top tie plate 12 and a bottom tie plate 13.
- a fuel rod consists of a number of cylindrical pellets of uranium dioxide stacked on top of each other and enclosed in a cladding tube of Zircaloy.
- Moderator water and cooling water flow into the fuel assembly from below through an inlet section 14.
- the spaces between the fuel rods within each sub-channel are flown through by water, as is the cruciform channel 25 formed by the support member.
- the support member 8 is provided with a number of axially distributed openings 26 allowing water and steam to flow between the sub-channels.
- Figure 4 shows a vertical section through the line D-D in Figure 5, which shows a first embodiment of a fuel assembly 20a according to the invention, and Figure 8, which shows a second embodiment of a fuel assembly 20b according to the invention.
- the fuel assembly in Figure 5 has four sub-channels 9e, 9f, 9g and 9h. To reduce the number of generated neutrons in the fuel assembly, the fuel bundle has been removed from the sub-assembly 9h and replaced by a top plug 16h.
- the top plug is arranged at the upper part of the fuel assembly and the function thereof is to restrict the upward water flow in the sub-channel and instead force the water to flow into adjacent sub-channels 9e and 9g, through the openings 26a, between the plugged sub-channel and the adjacent sub-channels, which are arranged upstream of the top plug.
- the top plug is formed so as to block those openings 26b, between the plugged sub-channel and adjacent sub-channels, which are arranged downstream of the top plug. In this way, the water flow is increased at the upper parts of the adjacent sub-channels.
- the increased water flow provides a reduced proportion of steam, which results in an increased neutron moderation and hence a reduced number of fast neutrons.
- the proportion of steam is increased somewhat in the lower parts of the adjacent sub-channels, which does not matter so much since the proportion of steam is low there.
- the plugged sub ⁇ channel 9h contains no steam but only water and hence consti- tutes a good moderator for fast neutrons arriving from the other sub-channels in the fuel assembly as well as from other surrounding fuel assemblies.
- FIG. 6 shows the top plug 16h, which comprises a tubular part 27, one end of which is provided with a bottom part 17 and the other end of which is open.
- the top plug has a sub ⁇ stantially square cross section.
- the cross section substan ⁇ tially corresponds to the cross section of that sub-channel in which the top plug is arranged.
- the bottom part is provided with a number of openings 18 allowing a certain flow of water to take place through the top plug.
- the bottom part serves as a strong restrictor of the upward water flow in the sub ⁇ channel.
- the task of the tubular part is to block the openings between the sub-channels downstream of the bottom part, thus preventing water and steam from penetrating into the upper part of the plugged sub-channel from adjacent sub-channels.
- the top plug may be made from, for example Zircaloy or stain ⁇ less steel.
- the length of the plug is optimized to obtain the best effect with respect to reduction of the steam content. To attain improved moderation in the upper part of the fuel assembly, the length of the plug should be smaller than half the length of that sub-channel in which it is arranged.
- Figure 7 shows the result of calculations made, on the one hand, on the unplugged fuel assembly 6 shown in Figures 2 and 3, which has one fuel bundle in each sub-channel, and, on the other hand, on the first embodiment of the plugged fuel assem- bly 20a shown in Figures 4 and 5, where a fuel bundle is remo ⁇ ved and replaced by a top plug.
- Figure 7 shows in the form of a diagram how the steam content ⁇ (the proportion of steam per volume) varies with the distance 1 from the inlet section of the fuel assembly for a sub-channel.
- Curve F shows the steam content versus the distance from the inlet section of the fuel assembly for the four sub-channels 9a, 9b, 9c, 9d in the unplugged fuel assembly.
- Curve E shows the steam content versus the axial length for that sub-channel 9f which is furthest away from the plugged sub-channel 9h in the plugged fuel assembly 20a.
- Curve G shows the steam content versus the distance from the inlet section of the fuel assembly for those sub-channels 9e and 9g, one side of which adjoins the plugged sub-channel 9h, in the plugged fuel assembly 20a.
- the diagram shows that the steam content is reduced heavily at the upper part of those sub ⁇ channels, one side of which adjoins the plugged sub-channel.
- the steam content increases somewhat in the sub-channel located furthest away from the plugged sub-channel. In the plugged sub-channel there is no steam, that is, the steam content is zero for all distances 1. In those cases where two plugged channels are used, the steam content at the upper part of the fuel assembly is, of course, reduced still further.
- Figure 8 shows a second embodiment of a fuel assembly accor ⁇ ding to the invention.
- the fuel assembly has four sub-channels 9e, 9f, 9g and 9h.
- two fuel bundles are removed from the sub-channels 9h and 9e, and each removed fuel bundle is replaced by a top plug 16h and 16e.
- the top plug is arranged at the upper part of the fuel assembly.
- Figure 9 shows a third embodiment of a fuel assembly 21 accor ⁇ ding to the invention.
- all the fuel rods are removed and at least some of them are replaced by rods 22 of a non-fissile material, for example stainless steel or Zircaloy.
- rods 22 of a non-fissile material, for example stainless steel or Zircaloy.
- a top plug 16i of the same kind as the one shown in Figure 6 is arranged.
- At least certain of the openings 18 are arranged such that the non- fissile rods are able to run through these openings.
- Figure 10 shows a horizontal section of part of a reactor core comprising plugged fuel assemblies according to the first 20a and the second 20b embodiment of the invention.
- the object of the invention is to reduce the dose of fast neutrons to which the reactor vessel 5 and the moderator tank 3 are exposed.
- Fuel assemblies with one or more plugged sub-channels are arranged in the positions which are located furthest out in the core, that is, nearest the moderator tank and the pressure vessel. Depending on the distance of the sub-channels to the vessel walls, fuel assemblies are arranged with one or two plugged sub-channels. The fuel assemblies are turned such that the plugged sub-channels are facing the moderator tank.
- the plugged sub-channels increase the amount of moderated water between the fuel and the reactor vessel, increases the modera ⁇ tion in the unplugged sub-channels, and reduces the generation of neutrons in the immediate vicinity of the reactor vessel.
- unplugged fuel assemblies 6 are arranged, that is, fuel assemblies with one fuel bundle in each sub-channel.
- the removed fuel bundles may be assembled so as to constitute one whole fuel assembly and be loaded into a suitable position in the core, or they may be assembled into a fuel assembly with two or three fuel bundles according to the invention and be used in the peripheral parts in the core.
Landscapes
- Physics & Mathematics (AREA)
- Engineering & Computer Science (AREA)
- Plasma & Fusion (AREA)
- General Engineering & Computer Science (AREA)
- High Energy & Nuclear Physics (AREA)
- Structure Of Emergency Protection For Nuclear Reactors (AREA)
- Monitoring And Testing Of Nuclear Reactors (AREA)
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
SE9402293-6 | 1994-06-29 | ||
SE9402293A SE505976C2 (sv) | 1994-06-29 | 1994-06-29 | Förfarande, anordning samt bärnslepatron för reducering av en reaktortanks neutrondos |
Publications (1)
Publication Number | Publication Date |
---|---|
WO1996000966A1 true WO1996000966A1 (en) | 1996-01-11 |
Family
ID=20394565
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/SE1995/000709 WO1996000966A1 (en) | 1994-06-29 | 1995-06-13 | Reduction of the neutron dose of a reactor vessel |
Country Status (2)
Country | Link |
---|---|
SE (1) | SE505976C2 (sv) |
WO (1) | WO1996000966A1 (sv) |
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP2887357A1 (en) * | 2013-12-17 | 2015-06-24 | Global Nuclear Fuel-Americas, LLC | Nuclear reactor fluence reduction systems and methods |
Citations (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4576785A (en) * | 1983-06-14 | 1986-03-18 | Carolina Power And Light Company | Reduction in rate of radiation exposure to excore nuclear reactor components |
US5271050A (en) * | 1991-05-20 | 1993-12-14 | Kabushiki Kaisha Toshiba | Core construction of a boiling nuclear reaction |
-
1994
- 1994-06-29 SE SE9402293A patent/SE505976C2/sv not_active IP Right Cessation
-
1995
- 1995-06-13 WO PCT/SE1995/000709 patent/WO1996000966A1/en active Application Filing
Patent Citations (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4576785A (en) * | 1983-06-14 | 1986-03-18 | Carolina Power And Light Company | Reduction in rate of radiation exposure to excore nuclear reactor components |
US5271050A (en) * | 1991-05-20 | 1993-12-14 | Kabushiki Kaisha Toshiba | Core construction of a boiling nuclear reaction |
Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP2887357A1 (en) * | 2013-12-17 | 2015-06-24 | Global Nuclear Fuel-Americas, LLC | Nuclear reactor fluence reduction systems and methods |
US9431135B2 (en) | 2013-12-17 | 2016-08-30 | Global Nuclear Fuel—Americas, LLC | Nuclear reactor fluence reduction systems and methods |
Also Published As
Publication number | Publication date |
---|---|
SE505976C2 (sv) | 1997-10-27 |
SE9402293D0 (sv) | 1994-06-29 |
SE9402293L (sv) | 1995-12-30 |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
US7864913B2 (en) | Fast reactor having reflector control system and neutron reflector thereof | |
EP0336203A2 (en) | Two-phase pressure drop reduction BWR assembly design | |
EP0406637B1 (en) | Two-phase pressure drop reduction BWR assembly design | |
US4708845A (en) | BWR fuel assembly with improved spacer and fuel bundle design for enhanced thermal-hydraulic performance | |
US5844957A (en) | Reactor core | |
US6327324B2 (en) | Nuclear fuel assembly | |
EP0094255A2 (en) | Maximum power capability blanket for nuclear reactors | |
JP5878442B2 (ja) | 燃料集合体及び原子炉の炉心 | |
US5949839A (en) | Fuel assembly for a boiling water reactor | |
EP0751527A1 (en) | BWR fuel assembly having fuel rods with variable fuel rod pitches | |
EP0514116B1 (en) | Spacer associated pressure drop in a boiling water reactor bundle having part length rods | |
EP0871960B1 (en) | Fuel assembly for a boiling water reactor | |
EP1149387B1 (en) | Control rod | |
US6298108B1 (en) | Nuclear fuel rod with upward-shifted pellet stack and a device to realize same | |
US5171522A (en) | Fuel design for high power density forced circulation boiling water reactor | |
WO1996000966A1 (en) | Reduction of the neutron dose of a reactor vessel | |
JPS63235891A (ja) | 燃料集合体 | |
US5483565A (en) | Fuel assembly for a boiling water reactor | |
US5422922A (en) | Fuel assembly and reactor core | |
US6181762B1 (en) | Nuclear fuel bundle having different peak power limits | |
EP3573074B1 (en) | An auxiliary device for a fuel assembly, a fuel assembly, and a method of operating a pressurized water reactor | |
EP0897581B1 (en) | Fuel assembly for a boiling water reactor | |
JP2006184174A (ja) | 沸騰水型原子炉の燃料集合体 | |
EP0514215A1 (en) | Part length rod placement in boiling water reactor fuel assembly for reactivity control | |
JPS6110239Y2 (sv) |
Legal Events
Date | Code | Title | Description |
---|---|---|---|
AK | Designated states |
Kind code of ref document: A1 Designated state(s): FI JP US |
|
AL | Designated countries for regional patents |
Kind code of ref document: A1 Designated state(s): AT BE CH DE DK ES FR GB GR IE IT LU MC NL PT SE |
|
DFPE | Request for preliminary examination filed prior to expiration of 19th month from priority date (pct application filed before 20040101) | ||
121 | Ep: the epo has been informed by wipo that ep was designated in this application | ||
122 | Ep: pct application non-entry in european phase |