Nuclear Reactor Kinetics

Download Presentation

Comments

Views: 123 | Added: 09-02-2012

Rate Presentation:

Favorites

Feature This

Report This

Description:

Effective Multiplication Factor (keff). . keff determines whether the neutron density within a reactor will remain constant or change.. keff and Power. Power is directly proportional to neutron density keff = 1.0000 ? critical (power constant)keff < 1.0000 ? subcritical (power decreasing)keff > 1.0000 ? supercritical (power increasing).

Nuclear Reactor Kinetics - Transcript

1. Nuclear Reactor Kinetics Craig Marianno NE 113

2. Effective Multiplication Factor (keff)

3. keff and Power Power is directly proportional to neutron density keff = 1.0000 ? critical (power constant) keff < 1.0000 ? subcritical (power decreasing) keff > 1.0000 ? supercritical (power increasing)

4. k Excess Any difference between a given value for keff and 1.0000 is called the �excess� multiplication factor (?k) ?k = keff - 1.0000 = k excess

5. Reactivity When keff is close to 1.0000, ?k and ? and nearly the same. Example: keff = 0.98

6. Delayed Neutrons Single most important characteristic for reactor control Delayed neutrons ? decay of fission products (precursers) Prompt neutrons ? fission Fraction of delayed neutrons = ? Delayed neutrons are more effective than prompt because they are �born� at a somewhat lower energy.

7. Delayed Neutrons

8. Delayed Neutrons

9. Delayed Neutrons While it is true that they are only a small fraction of the total neutron population, they play a vital role in reactor kinetics. Why? They significantly increase the neutron cycle lifetime!

10. Prompt Critical

11. Prompt Critical

12. Reactivity in Dollars From our previous example:

13. Neutron Lifetime For reactor kinetics, it is important to know the average time elapsing between the release of a neutron in a fission reaction and its loss from the system either by absorption of escape. This is typically called the �prompt neutron lifetime�. This time can be divided into: 1) Slowing Down Time 2) Thermal Neutron Lifetime (Diffusion Time)

14. Neutron Lifetime

15. Neutron Lifetime(infinite medium - prompt only) ?a = total thermal macroscopic absorption cross section ?a = absorption mean free path v = mean velocity (2200 m s-1) Note: - finite size reduces average lifetime due to leakage - ?a for a core includes all materials

16. Effective Neutron Lifetime(delayed neutrons included) ?eff = effective fraction of delayed neutrons ?eff = effective decay constant of precursors ? = reactivity

17. Reactor Kinetics We need to construct an expression for the number of neutrons per second in the reactor during a given �neutron cycle�. We could use: n k l

18. Reactor Kinetics Solving:

19. Reactor Period To make the previous equation easier, we can define the reactor period (T) as T = l / ?k. The reactor period represents the length of time required to change the reactor power by a factor of e (2.718). This is why it is sometimes referred to as the �e folding time�.

20. Reactor Kinetics(Prompt Example) Assuming the following, what is the increase in power for a ?k = 0.0025 ($0.357) at the end of 1.0 s? ?a = 13.2 cm v = 2200 m s-1

21. Reactor Kinetics(Delayed Example) Assuming the following, what is the increase in power for a ? = 0.0025 ($0.357) at the end of 1.0 s? ? = 0.0813 s-1 ?eff = 0.007 v = 2200 m s-1 l = 6.0X10-5 s

Nuclear Reactor Kinetics - Effective Multiplication Factor (keff). . keff determines whether the neutron density within a reactor will remain constant or change.. keff and Power. Power is directly proportional to neutron density keff = 1.0000 ? critical (power constant)keff < 1.0000 ? subcritical (power decreasing)keff > 1.0000 ? supercritical (power increasing).
Global Threat Reduction Initiative: U.S. Nuclear Remove Program Foreign Research Reactor Spent Nuclear Fuel FRR SNF Acc - 2. Contents. Program Objective and PolicyProgram implementation statusShipment InformationOperational LogisticsLessons LearnedConclusion. 3. U.S. Nuclear Remove Program Objective. To play a key role in the Global Threat Reduction Remove Program supporting permanent threat reduction by acceptin
Global Threat Reduction Initiative: U.S. Nuclear Remove Program Foreign Research Reactor Spent Nuclear Fuel FRR SNF Acc - 2. Contents. Program Objective and PolicyProgram implementation statusShipment InformationOperational LogisticsLessons LearnedConclusion. 3. U.S. Nuclear Remove Program Objective. To play a key role in the Global Threat Reduction Remove Program supporting permanent threat reduction by acceptin
Chemical Engineering Kinetics and Reactor Design - ????. ??????????????????????????????????????????????? (Chemical Engineering Kinetics and Reactor Design) . ???????????????????? ???? ??????????????????????????? ?????????????????????????????????????????? ?????????????????????????????????????????????????? ????????????????????? ??????????????????
Fixed-Bed Reactor for studying the Kinetics of Methane Oxidation on Supported Palladium Objectives: -
Ch E 441: Chemical Kinetics and Reaction Engineering Mole Balances in Reacting Systems Reactor Design Equations - Learning Objectives. Describe photos of real reactors. Define the rate of chemical reaction. Apply a general mole balance to a batch reactor, a continuous stirred tank reactor (CSTR), a plug flow reactor (PFR), and a packed bed reactor (PBR). . Chemical Identity. A chemical species has reacted w
Cooling a Nuclear Reactor - I -
Cooling a Nuclear Reactor - II - Reactor Coolant Properties. High specific heat capacity, CpThe amount of heat required to heat 1 kg of substance by 1
Natural Nuclear Fission Reactor - Fission. Discovery and implementation of fission is arguably one of the more important and controversial scientific and technological discoveries in physics in the 20th centurySurprisingly this may just been a naturally occurring phenomenonPrecambrian Scientists would have found making a fission r
Nuclear Reactor Power Systems - Overview. IntroductionsCategories of Nuclear ReactorsNuclear Power AccidentsSummary and Nuclear Power Systems Q/AGeneral Q/A. Dwight Williams at a Glance. Education and Registration: Nuclear EngineeringPh.D. -- University of MarylandB.S., M.S. -- North Carolina State UniversityLicensed Professional Engineer, Commonwealth of VirginiaProfessional Experience: Department of DefenseAwards and Activities2005 - 2006 Young Engineer of the Year, NSPE2004 - 2005 Young Engineer of the Year, DC9458