Teachin g Notes

Operationa l Reacto r Safet y Course

Lecture : 1 5 –Boilin g Wate r Reactors

Objective :

Since m u ch of the work to th is point focuse d on pressurized water reactors, the aim of this lec t ure is to g ain an a ppreciation of the d i fferences in bo iling water reactors from an operational and saf ety system s point of view. This lectu r e will also b e an im portant prepara tion f o r the sim u lator exe r cis es at th e Pilgrim nuclear plant whic h will occur later in the term .

Ke y Point s t o Brin g Out:

Slid e num be r Point s

2-6 Review the general configurati on of boiling water reactors focusing on the boiling in the core , steam separators, dryer and steam drum in the top of the reactor vessel with steam going direc tly to th e turbin e. Discuss the ro le of the rec i rcula tion pu mps as flow augm entation devices thro ugh the jet pumps. Discuss the layout of the reacto r vessel point ing o u t that control rods are hydraulicly driven in to the core from below the reactor v e ssel.

6-9 Review function and operations of th e recirculation system and jet pum p s.

9 Discuss function and operation of steam separator and dryer to moisture f r o m steam to achieve sa tur ated steam for turb ines.

10-11 Review m a ss flow in a BW R by expl aining chimney effect allowing for m ore m a ss flow with boosts from jet pum p s. W r ite m a ss balance equations to be sure students understand m a ss balance.

12 Discuss boiling regim e in BWRs and heat addition as a function of c o r e he i g ht .

13-15 Introduce th e concepts o f m ain tenance of nucleate boiling an d not

exceeding c r itic al power ratio s (>1.3 ) to avoid tra n sition zone s to f ilm boiling where heat transf er is se verely lim ited leading to overheating of the fuel. Review core boiling regim e s in the core.

16-18 Review key system s of BWRs and their functions – introduce them for future detailed discussion poi nt out the goal to depressurize the System to assure functioning of e m ergency core cooling system s As needed.

19-21 Review function of reactor cont ro l an d trip sy ste m s and the im portance of isolation of the reacto r in a BWR.

MIT OpenCourseWare http://ocw.mit.edu

22.091 / 22.903 Nuclear Reactor Safety

Spring 200 8

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