(3/2011) Nuclear Power Plant Contingency Plan

By Dr. Joseph S. Maresca

The Nuclear Power Plant Contingency Plan- A Beginning Conversation

A nuclear reactor is in the nature of a cylindrical  pressure vessel.  The facility contains fuel rods, control rods and a moderator. The fuel rods are comprised of fission materials and release large amounts of energy when bombarded with slow moving neutrons. The moderator consists of graphite rods which surround the fuel rods. The control rods are made of cadmium and these are inserted into the reactor.     1)

The nuclear reactor must have a contingency planning capability to ensure the orderly recovery of nuclear power generating capabilities in case of an exigency like a fire, flood, earthquake, tsunami, primary power failure or other out-of-the norm operating condition or scenario. The contingency plan should outline the methodology to make certain that the needed personnel, facilities, backup, data files, redundant computers and facility supplies/suppliers return to normal operating conditions as soon as possible after an unplanned disaster or major interruption of operations. Automatic shutdown capabilities should be triggered in the event that the exigency consists of external environmental conditions that preclude the return to normal operating conditions.

Cadmium is a robust neutron absorber and thus regulates the supply of neutrons in a fission reaction.

When the control rods are pushed in deep enough, they absorb most of the fission neutrons so that few are available for a chain reaction.  When the control rods are being withdrawn, more and more of these fission neutrons cause a greater chain reaction.     So, the act of pulling out the control rods, increases the power of the nuclear reactor.  Conversely, pushing the control rods back in will reduce the power of the nuclear reactor. When the chain reaction is not controlled, the result will be an explosion due to the uncontrolled increase of energy released.  In practice, a method of cleaning control rods may be employed to enhance operational performance.

At various times during the operational life of a nuclear reactor, there is a need to remove the core and internals from the reactor vessel for maintenance aimed at minimizing contingencies.

For example, graphite seals in the control rod drive mechanism (CRDM) wear gradually, and corrosion products build up inside the drive. The drive must be cleaned to reduce contamination levels and maintain performance.    If regular maintenance of the CRDM is not performed, excessive seal leakage may lead to operational difficulties or inoperative CRDMs.

There is a patented process for cleaning the control rod drive in a nuclear reactor in order to reduce unplanned contingencies.  The process comprises a drive assembly; a cleaning assembly for cleaning the control rod drive mechanism, the cleaning assembly including, a first support ring engaged with the drive assembly, a second support ring, and a plurality of shafts connected between the first support ring and the second support ring, each shaft including a plurality of brushes, the shafts and the first and second support rings configured to rotate about an inserted control rod drive mechanism when driven by the drive assembly; and a reduction gear assembly coupled between the drive assembly and the cleaning assembly, the reduction gear assembly configured to permit different rotation speeds among the drive assembly and the first support ring engaged with the drive assembly.     2)

A typical nuclear power plant should have a documented contingency plan which is updated periodically to reflect changes in the operating conditions which impact plant operations. Copies of the contingency plan should be made available to operations technicians, management at the plant installation and an offsite facility. Prioritization of plant operations should be set forth in understandable language.

The contingency plan should set forth the facility contact persons; such as, operational plant technicians, shift supervisor(s), shift technical advisor, instrument and control technician, electrical maintenance personnel, mechanical maintenance personnel, radiological protection technician,  chemistry technician, engineering support personnel,  computer system maintenance people, security personnel and key supply vendors, as well as backup vendors in an emergency.  A disaster coordination team should be set forth together with alternates and materials/supplies required in an emergency. Mutual assistance agreements with other firms should be set forth , as well as related service bureaus and backups needed in an emergency.

In  practice, the lowering or raising of control rods is accomplished automatically according to the load requirement. The heat produced by the reactor is removed by the coolant, generally a sodium metal.

The coolant brings heat to the heat exchanger. The coolant gives up the heat to the heat exchanger which is used in raising the steam.  After giving up heat, the coolant is again fed to the reactor.   The steam produced in the heat exchanger is led to the steam turbine through a valve after doing  useful work in the turbine. 

The steam is exhausted to the condenser.  The condenser condenses the steam which is fed to the heat exchanger through a feed water pump.  The steam turbine drives the alternator which converts mechanical energy into electrical energy.  The output from the alternator is delivered to the bus bars through transformers, circuit breakers and isolators.

There is a patent for managing the coolant in a power generation system.  This invention has to do with the cooling system for the main steam condenser in the modern-day power plant. The invention replaces the main steam condenser existing once thru the cooling water system with a refrigerant cooling system.

In order for the steam cycle to function properly, the main steam produced by the boiler must have a low-pressure area to discharge into. This area is the main steam condenser. The lower the pressure area -  the more efficient the system is thermodynamically speaking.

When the energy of the steam is spent, after rotating the turbines, it discharges into the main steam condenser. The steam flows around the condenser tubes, as the coolant flows through the tubes the temperature difference causes the steam to condense. The lower the temperature of the coolant flowing thru the tubes the faster the steam is condensed. The condensing of the increased steam flow lowers the main steam condenser internal pressure.

The refrigerant cooling system, improves the efficiency of the system, over the main steam condenser water-cooled system, considerably. The refrigerant has a normal temperature much lower than that of water and a much higher heat transfer rate than water. The main steam condenser refrigerant cooling system is controlled whereas the water-cooled condenser system fluctuates, because of seasonal temperature changes of the river or lake water. For example, the modern day power generating station produces less power in the summer months. The main steam condenser refrigerant cooling system will be much more fuel efficient than, the present once thru cooling water system.      3)

The International Atomic Energy Agency  provides guidance on radioactivity containment. The general requirements should set forth :     4)

o the atmospheric exposure path by which radioactive materials are discharged

o an evaluation of the transport in the atmosphere of radioactive materials discharged under normal operating or accidental condition is in the design and licensing

o contamination in the air, on the ground or in water over short/long periods should be described in the atmospheric dispersion models

The Nuclear Regulatory Commission or NRC prescribes training for key personnel in the nuclear power plant. The training program must be derived from a systems approach to training as defined in 10 CFR 55.4, and must provide for the training and qualification of the following categories of nuclear power plant personnel:

(i) Non-licensed operator.

(ii) Shift supervisor.

(iii) Shift technical advisor.

(iv) Instrument and control technician.

(v) Electrical maintenance personnel.

(vi) Mechanical maintenance personnel.

(vii) Radiological protection technician.

(viii) Chemistry technician.

(ix) Engineering support personnel.     5)

The maintenance and continuing upgrade of fission-based nuclear power plants together with decommissioning existing plants and upgrades to the “Artificial Sun Fusion Plants” will be the work of the 21st century substantially.

References:

1) http://electricalandelectronics.org/2008/10/02/schematic-arrangement-of-nuclear-power-station/

2) Apparatus and Method for Cleaning Control Rod Drive Mechanism-  Patent 7647665 Issued on January 19, 2010.

http://www.patentstorm.us/patents/7647665/claims.html

3) Issued PTO   (No 7,827,792)  by the United States Patent and Trademark Office for the design improvement to the modern day nuclear powered electrical generating station’s Main Steam Condenser Cooling System

4) http://www-pub.iaea.org/MTCD/publications/PDF/Pub1122_scr.pdf

5) http://www.nrc.gov/reading-rm/doc-collections/cfr/part050/part050-0120.html



Joseph S. Maresca Ph.D., CPA, CISA, MBA: His significant writings include over 10 copyrights in the name of the author (Joseph S. Maresca) and a patent in the earthquake sciences. He holds membership in the prestigious Delta Mu Delta National Honor Society and Sigma Beta Delta International Honor Society.  In addition, he blogs and reviews many books for Basil & Spice. Visit the Joseph S. Maresca Writer’s Page.

Copyright © 2006-2011, Basil & Spice. All rights reserved.

Copyright © Basil & Spice. All rights reserved. http://www.basilandspice.com/journal/” target=”_blank”Basil & Spice does not provide professional advice, diagnosis or treatment of any kind — medical, legal, professional, personal. The opinions you read on this site are those of members of the Basil & Spice community, not necessarily those of Basil & Spice.

Read more at Basil & Spice