Thermal Analysis Of Type 3 Elements In The Sm 1 Sm 1a And Pm 2a Cores

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Download or read book Thermal Analysis of Type 3 Elements in the SM-1, SM-1A and PM-2A Cores written by and published by . This book was released on 1962 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: A steady state and transient thermal analysis was performed on the Type 3 replacement cores for the SM-1, SM-lA, and PM-2A plants. The fundamental criterion for acceptable thermal design is the minimum departure from nucleate boiling ratio (DNBR). The minimum design DNBR at design power conditions and scram power conditions for concurrent transient and steady state analyses is currently specified at 1.5. The steady state thermal analysis indicated that the SM-1 Tyne 3 core will operate safely at design conditions of 10.77 Mw and scram power of 13.45 Mw with minimum DNBR's above 1.5. Stationary elements in some peripheral core positions experience local nucleate boiling. The steady state thermal analysis indicated that the SM-lA Type 3 core will operate safely at design conditions of 20.2 Mw and scram power of 24.2 Mw with minimum DNBR's above 1.5. At scram power conditions a minute amount of local nucleate boiling in the hot channel was evident at the exit end of the most critical control rod and stationary element. Results of the thermal analysis indicated that the PM-2A Type 3 core will operate safely at design conditions of 10.0 Mw and scram power of 12.0 Mw with minimum DNBR's greater than 1.5. The analysis of all Type 3 cores showed they are safe during the early critical period (first 3 sec) of a loss of low transient. The corresponding minimum DNBR produced is 1.96 in the SMlA Tyne 3 core at the peak power level (scram power level) with the scram mechanism inoperative. Since this minimum DNBR occurs under the severest conditions and the minimum DNBR produced is greater than the design criteria of 1.50, all Type 3 cores are considered thermally safe. Under similar conservative conditions the SM-1 Type 3 core has a minimum loss of flow transient DNBR of 4.08 and the PM-2A Type 3 core has a minimum loss of flow transient DNBR of 4.59. At nominal power levels the SM-1 and SMlA Type 3 cores indicated local nucleate boiling in the hot channel while the PM-2A Type 3 core indicated no local nucleate boiling. At the scram power level all Type 3 cores indicate steady state local nucleate boiling in the hot channels. However, only the SM-IA Type 3 core indicated any bulk nucleate boiling in the hot channel during the first 5 sec of the loss of flow accident. In the evaluation of the SM-1 Type 3 core it was determined that increasing the flow coastdown time or scramming the reactor due to reduced flow does not appreciably affect the minimum DNBR but helps to impede the bulk fluid temperature rise during the loss of flow transient. (auth).