Patent Number: 
Section: claims

1. A construction layout for caverns of an underground nuclear power plant in a mountain having a longitudinal direction, the construction layout comprising: two primary caverns accommodating nuclear reactor powerhouses, combined caverns, electric powerhouse caverns, pressure relief caverns, a first primary traffic tunnel, a second primary traffic tunnel, a third primary traffic tunnel, a top adit system, and a ground adit system;whereina connecting line of medial axes of the two primary caverns accommodating nuclear reactor powerhouses is perpendicular to the longitudinal direction of the mountain;each combined cavern is disposed on one side of each of the two primary caverns along the longitudinal direction of the mountain; each electric powerhouse cavern and each pressure relief cavern are disposed on two sides of each of the two primary caverns perpendicular to the longitudinal direction of the mountain; each electric powerhouse cavern is perpendicular to the longitudinal direction of the mountain;the first primary traffic tunnel and the third primary traffic tunnel are disposed along the longitudinal direction of the mountain on outer sides of the two combined caverns, respectively; the second primary traffic tunnel is disposed along the longitudinal direction of the mountain between the two combined caverns; one end of each of the first primary traffic tunnel, the second primary traffic tunnel, and the third primary traffic tunnel communicates with a ground surface;the two primary caverns, the combined caverns, the electric powerhouse caverns, and the pressure relief caverns form a cavern group of a nuclear island powerhouse of the underground nuclear power plant; anda skewback or an endwall of an arch crown of each cavern of the cavern group communicates with the ground surface via the top adit system; and a bottom of a sidewall or a bottom of an endwall of each cavern of the cavern group communicates with the first primary traffic tunnel, the second primary traffic tunnel, and the third primary traffic tunnel via the ground adit system. 2. The layout of claim 1, whereinthe top adit system comprises: a first primary adit, a first top adit of a first primary cavern, a second top adit of a second primary cavern, a second primary adit, a third primary adit, third top adits of end parts of the combined caverns, fourth top adits of the electric powerhouse caverns; fifth top adits of middle sections of the combined caverns, a sixth top adit of a first pressure relief cavern, and a seventh top adit of a second pressure relief cavern;the first primary adit, the second primary adit, and the third primary adit are arranged along the longitudinal direction of the mountain and communicate with the ground surface; an elevation of the first primary adit is higher than an elevation of the second primary adit and an elevation of the third primary adit;the first primary adit communicates with skewbacks of arch crowns of the two primary caverns via the first top adit and the second top adit, respectively;one end of the second primary adit and one end of the third primary adit communicate with the endwall of the arch crown of one end of a first combined cavern and the endwall of the arch crown of one end of a second combined cavern, respectively; a middle section of the second primary adit communicates with the endwall of the arch crown of the other end of the first combined cavern via one of the third top adits; a middle section of the third primary adit communicates with the endwall of the arch crown of the other end of the second combined cavern via the other of the third top adits;middle sections of the third top adits communicate with endwalls of arch crowns of one ends of the electric powerhouse cavern via the fourth top adits of the electric powerhouse caverns, respectively;the middle section of the second primary adit communicates with the skewback of the arch crown of a middle section of the first combined cavern via one of the fifth top adits;the middle section of the third primary adit communicates with the skewback of the arch crown of a middle section of the second combined cavern via the other of the fifth top adits; andthe sixth top adit and the seventh top adit are disposed on the middle section and the end of the third primary adit to communicate with the skewback of the arch crown of the first pressure relief cavern and the skewback of the arch crown of the second pressure relief cavern, respectively. 3. The layout of claim 2, wherein each top adit of the top adit system has a longitudinal slope smaller than 12%. 4. The layout of claim 2, whereinthe ground adit system comprises: first bottom adits of the two primary caverns, second bottom adits of first end parts of the combined caverns, third bottom adits of the electric powerhouse caverns, fourth bottom adits of second end parts of the combined caverns, and fifth bottom adits of the pressure relief caverns;the second primary traffic tunnel communicates with the bottom of the sidewall of the first primary cavern and a bottom of the first pressure relief cavern via one of the first bottom adits and one of the fifth bottom adits, respectively; the third primary traffic tunnel communicates with the bottom of the sidewall of the second primary cavern and a bottom of the second pressure relief cavern via the other of the first bottom adits and the other of the fifth bottom adit, respectively;the first primary traffic tunnel communicates with the bottom of the endwall of one end of the first combined cavern via one of the second bottom adit; the second primary traffic tunnel communicates with the bottom of the endwall of one end of the second combined cavern via the other of the second bottom adits;each of the second bottom adits communicates with the bottom of the endwall of corresponding electric powerhouse cavern via each third bottom adit connected; andthe other end of the second primary traffic tunnel communicates with the bottom of the endwall of the other end of the first combined cavern via one of the fourth bottom adits; the other end of the third primary traffic tunnel communicates with the bottom of the endwall of the other end of the second combined cavern via the other of the fourth bottom adits. 5. The layout of claim 4, wherein each bottom adit of the ground adit system has a longitudinal slope smaller than 12%. 6. The layout of claim 4, whereineach of the combined caverns comprises: a first safe powerhouse cavern, a nuclear fuel powerhouse cavern, a second safe powerhouse cavern, and a nuclear auxiliary powerhouse cavern longitudinally connected in series;each of the second bottom adits communicates with a bottom of an endwall of the first safe powerhouse cavern;each of the fourth bottom adits communicates with a bottom of an sidewall of the nuclear auxiliary powerhouse cavern;one ends of the second primary adit and the third primary adit communicate with endwalls of arch crowns of outer end faces of corresponding nuclear auxiliary powerhouse cavern;each of the third top adits of the end parts of the combined caverns communicates with an endwall of an arch crown of an outer end face of the first safe powerhouse cavern; andeach of the fifth top adits of the middle sections of the combined caverns communicates with a skewback of an arch crown of the second safe powerhouse cavern. 7. The layout of claim 1, wherein each of the two primary caverns communicates with a corresponding electric powerhouse cavern via a primary steam channel communicating with the ground surface; and the two primary caverns are provided with corresponding apparatus conveying channels communicating with the ground surface. 8. The layout of claim 2, wherein each of the two primary caverns communicates with a corresponding electric powerhouse cavern via a primary steam channel communicating with the ground surface; and the two primary caverns are provided with corresponding apparatus conveying channels communicating with the ground surface. 9. The layout of claim 3, wherein each of the two primary caverns communicates with a corresponding electric powerhouse cavern via a primary steam channel communicating with the ground surface; and the two primary caverns are provided with corresponding apparatus conveying channels communicating with the ground surface. 10. The layout of claim 4, wherein each of the two primary caverns communicates with a corresponding electric powerhouse cavern via a primary steam channel communicating with the ground surface; and the two primary caverns are provided with corresponding apparatus conveying channels communicating with the ground surface. 11. The layout of claim 5, wherein each of the two primary caverns communicates with a corresponding electric powerhouse cavern via a primary steam channel communicating with the ground surface; and the two primary caverns are provided with corresponding apparatus conveying channels communicating with the ground surface. 12. The layout of claim 6, wherein each of the two primary caverns communicates with a corresponding electric powerhouse cavern via a primary steam channel communicating with the ground surface; and the two primary caverns are provided with corresponding apparatus conveying channels communicating with the ground surface.