Teachin g Notes
Operationa l Reacto r Safet y Course
Lecture : 6 – Reacto r En erg y Rem o val
Objective :
The objec tiv es of this le c t ure are to g ain an appre ciation of th e lim its to p o wer gener a tion from nuclear reactors that involve power di stributions, peaking factors and therm a l lim its on fuel and cladding. Im pacts of control r ods on peaking factors are also discussed. Lecture follows Knief Chapter 7.
Ke y Point s t o Brin g Out:
Slid e num be r Point s
2-7 Explain key features of a bo iling water reactor -emphasize boiling is a two phase process with boi ling occurring in the fuel which is why the fuel bundle is in a can so that cooling can be assured.
Describe reactivity control - no boron in coolant with burnable poisons and control rod pattern changes. Explain function of the suppression pool in the containm ent.
8-10 Explain basic features of PW R - no boiling in core - control by soluble boron. Open lattice core since no boiling - single phase coolant at higher pressure.
11-14 Review key characteristics of reacto r types - key on differences in num ber of assem blies in BWR a nd PWRs as well as size of fuel pins. Review pressure diffe rences a nd inlet and outlet tem p eratures. Com p are to other reactor types.
15 Spend som e tim e on this slide by explaining how power is related to neutron flux. Follow Knief text on power distributions and heat generation as a result of fission. Develop concept of peaking factors and how different core shapes have different peaking factors by so lving the d i ffusion equation for each type of shape. Discuss how flux and power distribution lim it the am ount of power produced due to m a terial lim itations.
16-19 Review flux shape effect with bare and unreflected core and resultant peaking factors. Point out the with zoned enrichm e nt one can flatten the power distributi on to reduce the peaking factors enhancing the power capability of the plant - this is what reactor physics designers do.
20-22 Develop heat transfer equations fr om the pellet - to clad to co olant using Kneif outline - but derive equ a tions for better unders tan d ing. Make sure all term s for heat ge neration rates are understood - q''' , q'' , and q' and q. Use basic heat transfer laws - F ourier, Newton and Poisson to link with heat transfer courses.
23 Discuss nuclear lim its in reacto r s and how they affect power capability.
24 Discuss departure from nucleate boi ling and why it is so important to m aintain a 1.3 m argin.
25 Review heat rem oval using this gr ap h which f o llows the axia l tem p erature distribution up the fuel channel. Be sure students understand the differences in the curves.
26-27 Review im pact of control rods on local power distributions and peaking factors. This is especi a lly important in BW Rs which are run rodded. Explain the importa nce of rod "bite" for reactor control.
MIT OpenCourseWare http://ocw.mit.edu
22.091 / 22.903 Nuclear Reactor Safety
Spring 200 8
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