【０００１】
【発明の属する技術分野】
本発明は、原子炉建屋から原子炉圧力容器を撤去するための工法に関する。
【０００２】
【従来の技術】
原子炉の廃止措置に伴う原子炉圧力容器の安全かつ合理的な解体撤去工法の確立が急務とされている。原子炉圧力容器（以下、圧力容器と略す）を解体撤去するには、圧力容器を細分化して逐次撤去、処分する工法が現実的であると考えられている。
【０００３】
【発明が解決しようとする課題】
しかし、現時点で検討されている工法は、１ｍ３程度の容積の処分容器に収容し得る大きさに圧力容器を細分化するというものであり、したがって膨大な手間を要するばかりでなく、細分化に伴う汚染拡大及び作業者の被ばくを防止するための十分な対策も必要となる。
【０００４】
なお、圧力容器を細分化することなくその全体を一括して原子炉建屋から撤去することも考えられるが、その際には搬出重量が１０００トンを越えるものとなるので、そのような一括搬出を可能とするためには特別かつ巨大な揚重装置の開発が不可欠となり、現時点では非常に困難である。
【０００５】
上記事情に鑑み、本発明は圧力容器を撤去するための有効な工法を提供することを目的とする。
【０００６】
【課題を解決するための手段】
請求項１の発明は、原子炉建屋から圧力容器を撤去するに際し、圧力容器を複数の部分に分割し、各分割体に遮蔽密閉処置を施した後、各分割体を原子炉建屋外へ順次搬出することを特徴とする。
【０００７】
請求項２の発明は、請求項１の発明の原子炉撤去工法において、圧力容器を低放射化部の分割体と高放射化部の分割体とに分割し、少なくとも高放射化部の分割体に対しては、その内部に遮蔽材を充填しかつその外側を遮蔽体により被覆する遮蔽密閉処置を施すことを特徴とする。
【０００８】
請求項３の発明は、請求項１または２の発明の原子炉撤去工法において、各分割体の搬出時の重量がそれを搬出する揚重装置の能力の範囲内となるように圧力容器を分割することを特徴とする。
【０００９】
【発明の実施の形態】
図１〜図３は本発明の実施形態である原子炉撤去工法の概要を示すものである。本実施形態の撤去工法は、原子炉建屋１内の圧力容器２を撤去するに際し、その圧力容器２を分割体３ａ，３ｂ，３ｃに３分割し、それら分割体３ａ，３ｂ，３ｃを順次搬出するようにしたものである。
【００１０】
すなわち、図１に示すように、圧力容器２に接続されている各種配管類４を切断して撤去した後、圧力容器２の上蓋の部分を胴部から分割してその分割体３ａを撤去する。この撤去の際にはジャッキや原子炉建屋１内に設置されている保守用の天井クレーン等の揚重装置を用いれば良い。また、撤去に際しては放射化程度に応じた所定の遮蔽密閉処置を行うこととし、必要に応じて格納容器５の上部に遮蔽バリア６（破線で示す）を設ければ良い。
【００１１】
次に、図２に示すように、圧力容器２の胴部をその上部の低放射化部と、中央部から下部の高放射化部とに２分割する。それらの分割体３ｂ，３ｃのうち、上部側の分割体３ｂは放射化程度が低くかつさして重量も大きくないので、上記の分割体３ａと同様に所定の遮蔽密閉処置、たとえば内部にモルタルを充填し切断面に鋼板で蓋をするといった処置を行った後、適宜搬出すれば良い。
【００１２】
続いて、下部の分割体３ｃを搬出するが、これは放射化程度が高いことから厳重な遮蔽が必要であるので、より高度の遮蔽密閉処置を行う。すなわち、図３に示すように分割体３ｃの外側に鋼板等の遮蔽体７を被覆し、かつ原子炉建屋１内に設けた遮蔽材充填設備８から分割体３ｃ内全体にモルタル等の遮蔽材を充填し、その開口端に鋼板等の遮蔽体９を装着して密封する。そのような遮蔽密閉処置を施した分割体３ｃは搬出重量が数百トン程度となるので、その搬出は原子炉建屋１の外部に設置した大型クレーンあるいは原子炉建屋１内に設けた多数のジャッキにより行えば良い。
【００１３】
本実施形態の撤去工法によれば、圧力容器２を僅かに３分割するにとどめ、各分割体３ａ，３ｂ，３ｃに相応の遮蔽密閉処置を施してそれら分割体３ａ，３ｂ，３ｃを順次搬出するので、圧力容器２を細分化する場合に比べてその作業効率を遙かに改善できるし、汚染拡大の懸念も少なく、したがって大幅な工期短縮と工費削減を実現することができる。また、圧力容器２全体をそのまま一括して搬出することは非現実的であるが、本実施形態のようにそれを３分割することで個々の分割体３ａ，３ｂ，３ｃはそれぞれ搬出可能な重量になり、特に高放射化部の分割体３ｃは厳重な遮蔽密閉処置を施しても汎用の揚重装置のみで搬出が可能な程度の重量に抑制することが可能であり、搬出後の搬送その他の作業も支障なく行うことができ、合理的である。
【００１４】
なお、現在、我が国の放射性廃棄物の処理シナリオでは、上記実施形態において分割した３つの分割体３ａ，３ｂ，３ｃのうち、放射化程度が低い分割体３ａ、３ｂは浅地中処分（深度１０ｍ程度）を行い、放射化程度の比較的高い分割体３ｃはやや深い地中処分（深度５０〜１００ｍ程度）を行うことになるが、本実施形態では圧力容器２の各部を放射化程度に応じて分割してそれぞれを個別に搬出することから、各分割体３ａ，３ｂ，３ｃをそれぞれの放射化程度に応じた最適処分を行うことができ、この点においても合理的である。
【００１５】
なお、圧力容器２は必ずしも３分割することに限らず、圧力容器２の形態や規模、搬出に使用する揚重装置の能力その他の条件を考慮して最適な分割を行えば良く、要は、各分割体をそれぞれの放射化程度に応じた最適かつ確実な遮蔽密閉処置や処分を行い得るように、かつ、汎用の揚重装置により支障なく搬出や搬送を行い得るように、分割数や分割位置を設定すれば良い。ただし、過度に細分化することは本発明の主旨にもとることになるので、諸条件を満たす範囲で分割数は少ない方が好ましいことは言うまでもない。
【００１６】
また、上記実施形態のように、放射化程度の高い分割体３ｃに対する遮蔽密閉処置としては、モルタル等の遮蔽材の充填と鋼板等の遮蔽体の被覆によることが比較的簡便で十分な遮蔽効果が得られるので、本発明においてはそのような遮蔽密閉処置を採用することが好ましく、かつそのような遮蔽密閉処置を行うことを前提として分割の形態を設定することが好ましいが、必ずしもそれに限るものでもなく、それぞれの分割体に対する遮蔽密閉処置はそれぞれの分割体の放射化程度や形態に応じて相応かつ適切に行えば良いことは言うまでもない。
【００１７】
【発明の効果】
請求項１の発明は、圧力容器を複数の部分に分割し、各分割体に遮蔽密閉処置を施した後、各分割体を原子炉建屋外へ順次搬出するものであるから、圧力容器を数分割するにとどめて各分割体に対して相応の遮蔽密閉処置を施すことにより、圧力容器を細分化して搬出する工法に比べてその作業効率を遙かに改善できるし、汚染拡大の懸念も少なく、作業者被ばく低減もでき、圧力容器の撤去工事の大幅な工期短縮と工費削減を実現することができる。
【００１８】
請求項２の発明は、圧力容器を低放射化部の分割体と高放射化部の分割体とに分割するので、各分割体に対してそれぞれ最適な遮蔽密閉処置と処分を行うことが可能であるし、特に高放射化部の分割体に対してはその内部にモルタル等の遮蔽材を充填しかつその外側を鋼板等の遮蔽体により被覆する遮蔽密閉処置を施すことにより、高放射化部に対して確実な遮蔽密閉処置を比較的簡便に行うことができる。
【００１９】
請求項３の発明は、各分割体の搬出時の重量がそれを搬出する揚重装置の能力の範囲内となるように圧力容器を分割するので、特別かつ巨大な揚重装置を必要とせず、各分割体の搬出後における搬送その他の作業も支障なく行うことができる。
【図面の簡単な説明】
【図１】本発明の実施形態である撤去工法の概要を示すもので、圧力容器の頂部からの分割体を撤去している状態を示す図である。
【図２】同、圧力容器の胴部を上下に２分割してその上部側の分割体を撤去している状態を示す図である。
【図３】同、下部側の分割体を撤去するに先立ち遮蔽密閉処置を施している状態を示す図である。
【符号の説明】
１ 原子炉建屋
２ 原子炉圧力容器
３ａ，３ｂ，３ｃ 分割体
４ 各種配管類
５ 格納容器
６ 遮蔽バリア
７ 遮蔽体
８ 遮蔽材充填設備
９ 遮蔽体[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for removing a reactor pressure vessel from a reactor building.
[0002]
[Prior art]
There is an urgent need to establish a safe and rational dismantling and removal method for reactor pressure vessels following the decommissioning of nuclear reactors. In order to dismantle and remove a reactor pressure vessel (hereinafter abbreviated as a pressure vessel), it is considered realistic to construct a method in which the pressure vessel is subdivided and sequentially removed and disposed.
[0003]
[Problems to be solved by the invention]
However, method being considered at present are those that subdivide the pressure vessel to a size that can be accommodated in a disposal container of 1 m 3 of about volume, thus not only it requires enormous effort, the subdivision Sufficient measures are also required to prevent the accompanying spread of contamination and worker exposure.
[0004]
In addition, it is conceivable to remove the entire pressure vessel from the reactor building at once without subdividing it, but in that case, the unloading weight will exceed 1,000 tons, so such Development of a special and huge lifting device is indispensable to make it possible, and it is very difficult at present.
[0005]
In view of the above circumstances, an object of the present invention is to provide an effective construction method for removing a pressure vessel.
[0006]
[Means for Solving the Problems]
According to the invention of claim 1, when the pressure vessel is removed from the reactor building, the pressure vessel is divided into a plurality of parts, and each of the divided bodies is shielded and sealed, and then the divided bodies are sequentially placed outside the reactor building. It is characterized by carrying out.
[0007]
According to a second aspect of the present invention, in the method for removing a nuclear reactor according to the first aspect of the present invention, the pressure vessel is divided into a divided body of a low activation section and a divided body of a high activation section, and at least a divided body of the high activation section. For this purpose, a shielding and sealing treatment is performed in which the inside is filled with a shielding material and the outside is covered with a shielding body.
[0008]
According to a third aspect of the present invention, in the method for removing a nuclear reactor according to the first or second aspect of the present invention, the pressure vessel is divided so that the weight of each divided body at the time of unloading is within the range of the capacity of the lifting device for unloading it. It is characterized by doing.
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
1 to 3 show the outline of a reactor removal method according to an embodiment of the present invention. In the removal method according to the present embodiment, when the pressure vessel 2 in the reactor building 1 is removed, the pressure vessel 2 is divided into three parts 3a, 3b, 3c, and the divided bodies 3a, 3b, 3c are sequentially unloaded. It is intended to be.
[0010]
That is, as shown in FIG. 1, after cutting and removing various pipes 4 connected to the pressure vessel 2, the upper lid portion of the pressure vessel 2 is divided from the body, and the divided body 3 a is removed. . For this removal, a jack or a lifting device such as a maintenance overhead crane installed in the reactor building 1 may be used. Further, upon removal, a predetermined shielding / sealing treatment according to the degree of activation is performed, and a shielding barrier 6 (shown by a broken line) may be provided on the upper part of the storage container 5 as needed.
[0011]
Next, as shown in FIG. 2, the body of the pressure vessel 2 is divided into a lower activation portion at the upper portion and a higher activation portion from the center to the lower activation portion. Of the divided bodies 3b and 3c, the upper divided body 3b has a low degree of activation and is not too heavy. Therefore, similar to the above-described divided body 3a, a predetermined shielding and sealing treatment, for example, filling the interior with mortar Then, after taking measures such as covering the cut surface with a steel plate, it may be carried out as appropriate.
[0012]
Subsequently, the lower divided body 3c is carried out, but since the degree of activation is high and strict shielding is required, a higher shielding / sealing treatment is performed. That is, as shown in FIG. 3, the outside of the divided body 3c is covered with a shielding body 7 such as a steel plate, and the shielding material filling equipment 8 provided in the reactor building 1 is used to entirely cover the inside of the divided body 3c with a shielding material such as mortar. , And a shield 9 such as a steel plate is attached to the open end thereof to seal. Since the weight of the divided body 3c subjected to such shielding and sealing measures is about several hundred tons, the large body crane installed outside the reactor building 1 or the large number of jacks provided inside the reactor building 1 are taken out. It should be done according to.
[0013]
According to the removing method of the present embodiment, the pressure vessel 2 is divided into only three parts, and each of the divided bodies 3a, 3b, 3c is subjected to a corresponding shielding treatment, and the divided bodies 3a, 3b, 3c are sequentially carried out. As a result, the working efficiency can be greatly improved as compared with the case where the pressure vessel 2 is subdivided, and there is less concern about the spread of contamination. Therefore, it is possible to realize a significant reduction in the construction period and the cost. Although it is impractical to carry out the entire pressure vessel 2 at once as it is, it is impractical to divide the pressure vessel 2 into three parts as in the present embodiment, so that each of the divided bodies 3a, 3b, and 3c has a weight that can be carried out. In particular, the divided body 3c of the highly activated portion can be reduced to a weight that can be carried out only by a general-purpose lifting device even if strict shielding and sealing treatment is performed. Can be performed without any trouble, which is reasonable.
[0014]
At present, in the radioactive waste treatment scenario in Japan, of the three divided bodies 3a, 3b, 3c divided in the above embodiment, the divided bodies 3a, 3b having a low degree of activation are disposed in shallow ground (about 10 m depth). ) To perform a relatively deep underground disposal (at a depth of about 50 to 100 m) of the divided body 3 c having a relatively high degree of activation. In the present embodiment, each part of the pressure vessel 2 is changed according to the degree of activation. Since each of the divided bodies 3a, 3b, and 3c can be optimally disposed in accordance with the degree of activation of each of the divided bodies 3a, 3b, and 3c and individually carried out, it is reasonable in this respect.
[0015]
The pressure vessel 2 is not necessarily divided into three parts, but may be divided optimally in consideration of the form and scale of the pressure vessel 2, the capacity of the lifting device used for unloading, and other conditions. The number of divisions and the number of divisions so that each divided body can be optimally and reliably shielded and sealed according to the degree of activation, and can be carried out and transported by a general-purpose lifting device without trouble. Just set the position. However, since excessive segmentation is also included in the gist of the present invention, it is needless to say that it is preferable that the number of divisions is small as long as various conditions are satisfied.
[0016]
Further, as in the above-described embodiment, as a shielding / sealing treatment for the divided body 3c having a high degree of activation, it is relatively simple and sufficient shielding effect by filling a shielding material such as mortar and covering the shielding body such as a steel plate. Therefore, in the present invention, it is preferable to adopt such a shielding and sealing treatment, and it is preferable to set the form of division on the assumption that such a shielding and sealing treatment is performed, but it is not necessarily limited thereto. Not to mention, it goes without saying that the shielding and sealing treatment for each divided body may be appropriately and appropriately performed according to the degree of activation and form of each divided body.
[0017]
【The invention's effect】
According to the first aspect of the present invention, the pressure vessel is divided into a plurality of parts, each divided body is subjected to shielding and sealing treatment, and then each divided body is successively carried out of the reactor building. By performing appropriate shielding and sealing measures for each divided body only by dividing it, the work efficiency can be greatly improved compared to the method of dividing and transporting the pressure vessel into smaller pieces, and there is less concern about the spread of contamination. In addition, it is possible to reduce the worker exposure, and to realize a significant reduction in the construction period and cost of the pressure vessel removal work.
[0018]
According to the second aspect of the present invention, since the pressure vessel is divided into a divided body of the low-activation part and a divided body of the high-activation part, it is possible to perform optimal shielding and sealing treatment and disposal for each divided body. In particular, for the divided body of the highly activated part, the shielding is sealed by filling the inside with a shielding material such as mortar and covering the outside with a shielding body such as a steel plate, thereby increasing the activation. It is possible to relatively easily perform a reliable shielding and sealing procedure for the part.
[0019]
According to the third aspect of the present invention, since the pressure vessel is divided so that the weight of each divided body at the time of unloading is within the range of the capacity of the lifting device for unloading the divided bodies, a special and huge lifting device is not required. In addition, transportation and other operations after carrying out each divided body can be performed without any trouble.
[Brief description of the drawings]
FIG. 1 shows an outline of a removing method according to an embodiment of the present invention, and is a view showing a state in which a divided body from the top of a pressure vessel is being removed.
FIG. 2 is a view showing a state in which the body of the pressure vessel is vertically divided into two parts, and a divided body on an upper side thereof is removed.
FIG. 3 is a diagram showing a state in which a shielding / sealing treatment is being performed prior to removing the lower divided body.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Reactor building 2 Reactor pressure vessel 3a, 3b, 3c Divided body 4 Various pipings 5 Containment vessel 6 Shield barrier 7 Shield 8 Shield material filling equipment 9 Shield