The invention discloses a
nuclear reactor coolant pump and a passive stopping seal
assembly thereof. The passive stopping seal
assembly comprises a seal ring, a tightening-up ring and a meltable support block. The seal ring is an opening ring. In a normal working condition, a pump shaft is surrounded by the seal ring and a space is kept between the seal ring and the pump shaft. The outer circumferential wall of the seal ring is encircled by the tightening-up ring. In a working condition that power failure happens to a whole
plant, the tightening-up ring provides the seal ring with sufficiently big holding-tightly force to drive the seal ring to close to hold the pump shaft tightly. The meltable support block is inlayed in an opening of the seal ring or of the tightening-up ring. In the normal working condition, the meltable support block prevents the ring where the meltable support block is located from being closed and it is ensured that the seal ring is in an opening state. In addition, in the working condition that power failure happens to the whole
plant, the meltable support block melts and loses
efficacy, so that the seal ring is closed under the action of the tightening-up ring. Compared with the prior art, the passive stopping seal
assembly is only provided with the three elements; not only can the integrity requirement of a shaft seal be met under the condition that an emergency shaft seal injection
system is not relied on in the working condition that power failure happens to the whole
plant, but also the passive stopping seal assembly has the advantages of being simple in structure and firm in seal.