WO2014088461A1

WO2014088461A1 - Fuel composition for water-cooled thermal neutron nuclear power plant reactors

Info

Publication number: WO2014088461A1
Application number: PCT/RU2013/001046
Authority: WO
Inventors: Борис ЗИЛЬБЕРМАН; Юрий ФЕДОРОВ; Александр РИМСКИЙ-КОРСАКОВ; Борис БИБИЧЕВ; Михаил Николаевич ЧУБАРОВ; Павел Николаевич АЛЕКСЕЕВ
Priority date: 2012-12-07
Filing date: 2013-11-22
Publication date: 2014-06-12
Also published as: RU2012153208A; RU2537013C2

Abstract

The invention relates to the field of nuclear technologies, specifically to fuel for thermal neutron nuclear power plants. Provided is a fuel composition comprising a mixture of recovered plutonium and enriched uranium in the form of oxides, characterized in that the enriched uranium is enriched recovered uranium or a mixture of same with enriched natural uranium, having a ratio of components, determined by energy potential, equal to the potential of freshly prepared enriched natural uranium nuclear power plant fuel, providing a 100% load of the reactor core. Possible variants for mixing said components are claimed. Using the proposed composition allows for maximally utilizing the energy potential of uranium and plutonium, including accumulated SNF, and for greatly reducing the number of storage facilities and even decommissioning same.

Description

Fuel composition for water-cooled thermal neutron reactors

The invention relates to the field of nuclear technology, and in particular to nuclear fuel using thermal neutrons.

At present, water-cooled reactors of nuclear power plants, most of which are pressure reactors (PWR, WWER), are loaded with a uranium dioxide U0 ₂ fuel composition containing 3.5–5% of the ²³⁵ U isotope (30–50 kg / t) for reactors under pressure U). This is necessary to ensure an average burnup of irradiated nuclear fuel (SNF) of 30-50 GW * days / t of heavy metals (heavy metals + fission products - PD) in the charge with a tendency to increase it to 70 GW * days / t of heavy metals. Such high burnup is achieved by the rational movement of spent nuclear fuel through the reactor zones, and the number of such annual overloads during a 1 year reactor campaign increases with burnup.

VVER-1000 SNF with an initial enrichment of 4.33% (43.3 kg / t) ³⁵ U and a burnup of 50 GW * day / t contains 8.6 kg / t ²³⁵ U with 5.7 kg / t ²³⁶ U, which is moderate neutron absorber, as well as 11 kg / t of Pu, including 7.7 kg / t of the sum of the odd (fissile) isotopes ^{239 + 24} 'Pu. Excluding compensation for even isotopes, the energy potential of fissile isotopes for VVER SNFs and PWR-1300 is 40% of the original and can potentially be reused after reprocessing the nuclear fuel. However, for this there are various kinds of limitations both in the design of reactors and in biological protection in the manufacture of regenerated fuel for reactors.

Currently, in Russia, RBMK and VVER-1000 reactors partially use regenerated uranium, and mixed uranium-plutonium regenerated fuel in pressure reactors is partially used only in France, with uranium and plutonium being separated during reprocessing of spent nuclear fuel. Plutonium of the indicated or close isotopic composition with a content of 60 kg / t is used as oxide fuel mixed with depleted uranium (2.5 kg / t ²³⁵ U), which load 30% of the zone of obsolete PWR-900 reactors, which is 40% of the energy capacity of nuclear power plants, that is, using regenerated plutonium, only 12% of the electricity produced at nuclear power plants is produced. The corresponding amount of SNF is processed at the UP-2 plant in France, and the rest of the SNF (~ 40%) is stored. In France, the recovered regenerated uranium is enriched experimentally with the loading of active zones (A3) of two reactors (3% of capacity) with the prospect of increasing to 24% of capacity over 5 years due to the accumulated regenerate of previous years. SNF from reclaimed materials is not serially processed.

Calculations proving the possibility of only partial loading with MOX fuel

The VVER-1 LLC A3 reactors give a similar picture, as a result of which this solution has not yet been applied at Russian nuclear power plants.

A serious additional complication in the implementation of the program for using regenerated materials is the need to produce fuel from them in protective equipment (including the enrichment of regenerated uranium) due to the high toxicity of plutonium and sufficiently strong gamma radiation of daughter actinides as by-products of nuclear reactions.

To overcome the drawback noted above, such as incomplete loading of the A3 reactor with MOX fuel, a MICS fuel composition was proposed, which provides for a reduction in the amount of plutonium in the starting MOX fuel composition (regenerated plutonium with depleted uranium) when it is fed with the estimated amount of natural enriched uranium (Youinou G., Delpech M., Guillet JL, Puil

A., Aniel S. Plutonium Management and Multirecycling in LWRs Using an Enriched Uranium

Support. Proc. Int. Conf. Global'99, (USA, 1999)). Such fuel can load 100% of the core of the PWR-1300 reactor with the usual annual overload circuit, which allows it to be used unlimitedly in the nuclear fuel cycle (NFC) of thermal neutron reactors. Moreover, such fuel can be processed and used in cyclic mode with the corresponding recharge of U between cycles. This composition is chosen by us for the prototype. It should be noted that the use of primarily regenerated uranium was not covered by the prototype.

A similar composition was justified by us for the VVER-1000 reactor

(Pavlovichev A.M., Pavlov V.I., Semchenkov Yu.M., Fedorov Yu.S., Bibichev B.A.,

Zilberman B.Ya. Neutron-physical characteristics of the VVER-reactor core

1000 with 100% fuel loading from a mixture of regenerated uranium, plutonium and enriched uranium. Atomic Energy, 2008, v. 104, N ° 4, p. 196-198) with the difference that the starting mixture is an undivided mixture of uranium and plutonium, recovered during the reprocessing of VVER-1000 spent nuclear fuel, while maintaining the previously separated regenerated plutonium, as well as enriched natural uranium (the latter is similar to the prototype).

The cycling of this composition was not considered, however, in an earlier work

(Fedorov Yu.S., Bibichev B.A., Zilberman B.Ya., Kudryavtsev E.G. Use of regenerated uranium and plutonium in thermal reactors. Atomic energy. 2005. v. 99, issue 2, p. 136-141), multiple cycling of an undivided mixture of regenerated uranium and plutonium was described when replenished with enriched natural uranium. Thus, uranium regenerated from spent nuclear fuel was involved in the nuclear fuel cycle (NFC). Regenerated nuclear fuel, which includes in one form or another a mixture of regenerated uranium and plutonium, was called by us REMIX fuel.

A common drawback of all these compositions is the lack of reduction in the storage facilities of the previously accumulated SNF of the NPP with some “swelling” of its amount during cycling due to the inadmissibility of feeding the composition with enriched natural weapon grade uranium or close to it (enrichment

235

80% U or more) due to restrictions on the non-proliferation of weapons-grade nuclear materials. In the prototype, this is compounded by the fact that excess depleted uranium from the starting MOX fuel is involved in the cycle. The second drawback arising from the first is the ever-expanding production of plutonium-containing regenerated fuel, which requires a protective execution of the production, with a corresponding reduction in the production of the original nuclear fuel from natural materials in the usual version, up to the complete closure of such production or the release of only starter loading kits for new nuclear power plants. Obviously, such a NFC will never reach a stationary state.

The objective of the claimed invention is to develop a fuel composition that allows you to completely and at the same time utilize the recovered uranium and plutonium separated from SNF.

This is achieved by the fact that enriched regenerated uranium or its mixture with enriched natural uranium is introduced into the fuel oxide composition based on regenerated plutonium, with a ratio of components determined by the energy potential equal to the potential of freshly prepared nuclear fuel from enriched natural uranium, providing 100% loading of the reactor core. At the same time, depleted regenerated uranium of low nuclear quality is disposed of as medium-level waste (C AO) for disposal.

Such a result can be achieved in several excellent ways. For example, a composition can be obtained in the form of a mixture of plutonium oxides and a portion of regenerated uranium within the limits of non-proliferation of nuclear materials (less than 19% of the amount of fissile nuclides in the mixture), which is then mixed with enriched regenerated uranium that satisfies the same requirements. At the same time, the regenerated materials can be separated at different times from SNF various batches and burnups, including from different reactors, and they are equipped based on calculations of equipotentiality from SNF of various types of reactors, and they are equipped based on calculations of equipotentiality (approximate equivalence of energy production and characteristics of the formed core) using standard IAEA codes (LA- UR = 03-1987. MCNP - A General Monte Carlo Code, Version 5. License RI C00710MNYCP01 # 7E83-67A4). If necessary, fine adjustment of the composition is achieved by introducing a smaller amount of enriched natural uranium into it.

This composition is obtained, for example, after reprocessing the spent nuclear fuel of the nuclear power plant using the Purex process in the option of producing a re-extract of plutonium mixed with part of the regenerated uranium (patent RU N ° 2 249 267, Bull. 3 »9, 2005) obtained from the subsequent operation re-extract of uranium subjected to evaporation and denitration, uranium oxide is fluorinated and the resulting UF6 is enriched in ²³⁵ U to its content of 5-6%, the product is defluorinated, and the oxide from this or one of the previous batches is dissolved in the above reextract to achieve the calculated isotopic composition, after which the mixture the product is denitrated after or without evaporation; fuel pellets are made from the resulting solid solution of a mixture of U and Pu plutonium oxides, and then fuel assemblies (FA). A small portion of enriched natural uranium or regenerated uranium from spent nuclear fuel with increased starting enrichment can be added to enriched regenerated uranium to adjust the nuclear potential.

It is advisable to irradiate the proposed fuel composition in the maximum burnup mode in specially designed serial reactors with an increased number of overloads, so that the uranium from such SNF (or all SNF) by the amount of isotope U is no longer interesting in terms of cycling in the nuclear fuel cycle the near term. The amount of such spent fuel from a PWR (VVER) reactor is reduced by 3-5 times compared with the primary spent fuel, depending on its burnout. Moreover, when reprocessing old SNF of the PWR type, the fuel composition may contain an additional quantity of Pu taken from the warehouse.

The advantage of this composition is the use of a single regenerated fuel containing both plutonium and uranium, and its quantity, and consequently the number of serial reactors involved under it, in a stationary mode is 4-5 times lower than their number with a standard composition of natural uranium. This creates the prerequisites for using a larger number of reactors for this composition, with the involvement of already accumulated in the processing SNF and / or from foreign nuclear power plants, to which it is forbidden to supply plugonium-containing nuclear fuel to the norms of non-proliferation of weapons-grade nuclear materials.

It should be emphasized that the subject of this invention is a previously unused combination of ingredients of the fuel composition, since its exact composition depends on the type and operating mode of the reactor into which it is loaded, and it is somewhat adjusted as a result of mandatory reactor tests and acquired operating experience, which allows some refinements to working settlement

codes available at each nuclear fuel company.

Example 1

The fuel composition consists of regenerated plutonium dioxide and enriched uranium, incrusted from VVER-1000 spent nuclear fuel with a burnup of 50 GW * day / t (initial amount of actinides in the charge) and aging for 5 years, it contains 5.25% of the mass. Pu (3.41% ^{239 + 241} Pu) and uranium with a composition of 3.45% ²³⁵ U, 2.23% ²³⁶ U and 1.3 * 10 ^_6 % ²³² U (the rest

238

U), and uranium is obtained by enrichment of the initial regenerated uranium with an isotopic composition of 0.91% ²³⁵ U, 0.59% ²³⁶ U and 3 * 10 ^"7 % ²³² U (the rest is ²³⁸ U). The composition has an equal energy potential with standard fresh fuel containing 4.33% ³⁵ U, and is suitable for loading 100% of the zone of the VVER-1000 reactor.

Example 2

The fuel composition consists of regenerated plutonium dioxides and enriched uranium, separated from VVER-1000 spent fuel with a burnup of 50 GW * day / t and a 5-year aging, contains 5.25% of the mass. Pu (3.41% ^{239 + 241} Pu) and final uranium 3.45% ²³⁵ U, 2.23% ³⁶ U and 1.3 * 10 ^{~ 6} % ²³² U (the rest ²³⁸ U), with uranium obtained by enrichment 84 % of the initial regenerated uranium with an isotopic composition of 0.91% ²³⁵ U, 0.59% ²³⁶ U and 3 * 10 ^"7 % ²³² U (the rest ²³⁸ U) up to 1.2 times more enrichment, and the rest is taken as a mixture of regenerated plutonium and uranium obtained directly from the reprocessing of the specified SNF of the NPP The composition has nuclear energy properties as in Example 1.

Example 3

The fuel composition consists of regenerated plutonium dioxides and enriched uranium, incrusted from VVER-1000 spent fuel with a burnup of 50 GW * day / t and a 5-year aging, contains 4.75% of the mass. Pu (3.10% Pu) and uranium with a composition of 3.12% U, 2.0% U and 1.15 * 10 ^" .% U (the rest U), moreover, uranium is obtained by enrichment of the initial regenerated uranium analogously to Example 1. To them 0.50% ²³⁵ U of enriched natural uranium (only 3.62% U) to improve the balance of delayed neutrons. The composition also has an equal energy potential with a standard fresh fuel containing 4.33% ²³⁵ U and is used in a similar manner.

Example 4

The fuel composition consists of a mixture of regenerated plutonium and uranium containing 5.25% Pu and 20% (in balance) of regenerated uranium of the above composition, to which regenerated uranium with an enrichment of 17% ²³⁵ U added during the processing of highly enriched SNF from transport or research reactors is added analogously to example 2. The composition also has an equal energy potential with a standard fresh fuel containing 4.33% U, and is used in a similar manner.

Claims

Claim

1. Fuel composition for water-cooled thermal neutron reactors, comprising a mixture of regenerated plutonium and enriched uranium in the form of oxides, characterized in that enriched regenerated uranium or its mixture with enriched natural uranium is used as enriched uranium, with a ratio of components determined by the energy potential equal to the potential of freshly prepared nuclear fuel from enriched natural uranium, providing 100% loading of the reactor core.

2. The composition according to claim 1, characterized in that it contains regenerated plutonium and part of the uranium regenerated together with it without enrichment.

3. The composition according to claim 1 or 2, characterized in that it contains uranium and plutonium, regenerated at different times, including from spent nuclear fuel of reactors of different types and / or lots, and mixed by calculation in any combination to achieve the required energy potential .

4. The composition according to p. 3, characterized in that the mixture of regenerated plutonium and enriched uranium contains a smaller part of the latter in the form of enriched natural uranium.

5. The composition of p. 3, characterized in that the mixture of regenerated plutonium and enriched uranium contains regenerated uranium with increased starting enrichment.