Light Water Reactor category

The remaining 348 issues were considered to be applicable to the design of Advanced Light Water Reactors. Further review was performed by Combustion Engineering, Inc. to determine the subset of issues applicable to the System 80+ Standard Design and the following two categories were established ... 

Since the severe core damage behaviour of PHWRs is somewhat different from that of light water reactors (LWRs), it is worth summarizing the phenomenology here. Analysis of events in category (3) initially started from heat balance calculations (to determine the times to boil off the water in the moderator, and then in the shield tank), followed by calculations of the characteristics of the debris once it collects on the bottom of the calandria vessel. 

The impurities can be grouped into two categories lights (water, cyclohexene, cyclohexadiene) and heavies (phenol, dicyclohexyl-ether, cyclohexenyl- cyclohexanone). To limit their amount, the conversion is kept around 80% with a selectivity of about 98%. The hot reactor effluent is cooled in countercurrent with the feed in FEHE, and finally for phase separation in the heat exchanger (E-2) at 33 °C. The simple flash (S-2) can ensure a sharp split between hydrogen, recycled to hydrogenation reactor, and a liquid phase sent to separation. 

In general, the requirements of this section apply to all large Category A reactors which use a circulating fluid (light water, heavy water, helium, liquid metal, etc.) to cool the reactor core. 

The basic inspection requirements are given in the JEAC-4205, the Japan Electric Association Code for ISI of light water cooled nuclear power plant components [6.29]. The basic examination required by above code is a periodical visual examination of the reactor internal structures (Section 2, Class 1 Components, Examination Category B-N-3). The objective of the visual examination is to discover relevant conditions including distortion, cracking, loose or missing parts, wear or/and corrosion. The examination is performed once every 10 years, using an examination tool coupled with underwater TV camera. The result of this one is recorded on videotape. 

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