ML20247F096
| ML20247F096 | |
| Person / Time | |
|---|---|
| Issue date: | 05/16/1989 |
| From: | NRC OFFICE OF GOVERNMENTAL & PUBLIC AFFAIRS (GPA) |
| To: | |
| Shared Package | |
| ML20247F042 | List:
|
| References | |
| FOIA-89-2, FOIA-89-A-7 NUDOCS 8905300003 | |
| Download: ML20247F096 (193) | |
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.... 6L bu U N F~ED STATES NUCLEAR REGULATORY COMMISSION OFFICE OF PUBLIC AFFAIRS,
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C POWER NUCLEAR AND RADIATION O WORKSHOP MANUAL h S;R*388?2
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TABLE OF.CORTENTS-t Nucl ear Power for El ectrical Generation.. . . . . . . . . . . . . . . .'. . . . . . . . . ff The Fis s ion Process and Heat Production.. . . . . . . . . . . . . .. . . . . . . . . . . . 2-1 Ra d i a t i o n Te rm i n ol ogy. . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . ,3,1 .
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Exposure and Dose Measurements.........................'..... 3-I1
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International System of Units............................... 3-23 Radiation Sources................................................. 4-1 Natural Background Radiation Sources. . . . . . . . . . . . . . . . . . . . . . . .. 4-2 Man Made Radiation Sources................................. 4-7 Radiation Sources at Nuclear , Plants............................... 5-1 Biological Effects of Radiation................................... 6-1 C e l l ul a r D ama ge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ... .. . 6-4 R a d i a ti o n Sy n d rome . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6- 10
,,g N R C D o s e L i m i t s . . . . . . . . . . . . . . . . . . . ... . . . . . . . . . . . . . . . . . . . . . . . . 6 - 12 Acu te Radi a ti on Dos e . . . . . . . . . . . . . . . .. . . . . . J J. ; ;i . . . a... .,,ggy. 6-14 .
Cancer Risk Estimates....................................... 6-17 Sensitivity Factors......................................... 6-22 Methods for Protection Against Radiation and - Contamination..............................................t.... 71 M i n i m i z e T i me . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . : . . . . . . . . 7-3 '
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Maximize Distance................. 7 ....... .'............ 7 ,5 . Ma x imi z e Sh i el d i n g . . . . . . . . . . . . . . . . . l. . . . . . . . . . . . . . .' . . ' '. . . . . . 7-7
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Protection Against Contamination... ....................... ** 67-10 *
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BWR Systems......................................sil. 4..'.".'..;;.e'.4.,8 7 1
.5 PWR Systems............................... .. .9-1
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Radioa cti ve Wa s te Di s pos a1. . . . . . . . . . . . . . . . . ...'. . . . .."f,'. a . . . . . . . . . ,J0.1 . \ .. Reacto r Eme rgenci es . . . . . . . . . . . . . . . . . . . . . . . . . . . .' . . . ,... . /,I 2;. 2.: .3.ve:11-1.
. The Three Mil e Isl and Acci dent. . . . . . . . . . . . . . . . . . . . . . . . 4. 4. .. . . . . 12-1 I
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NUCLEAR POWER
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FOR ELECTRICAL GENERATION t l
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The purpose of a Nuclear Power Plant is not to produce or release
" Nuclear Power" but to generate electricity. It should not be surprising then that a nuclear power plant has many similarities to other elec-I trical generating facilities. It should also be obvious that nuclear plants have some significant differences from other plants. Some of these differences could lead to an adverse effect on public health and safety.
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l I r:/// _; l t t v ut ,o-+ Electron j / . I ?*~' low L _ _ _ _ _ _ .J ELECTRICAL GENERATOR Of the several known methods to produce electricity, by far the most prac-tical for large scale production and distribution involves the use of an
" electrical generator." In an electrical generator, a magnet (rotor) revolves inside a coil of wire, creating a flow of electrons inside the wire. This flow of electrons is called electricity. Some mechanical device (wind turbine, water turbine, steam turbine, etc.) must be avail-able to provide rotation.
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4 TURBINE glETAL PLANCE HOUSING ELADE3 i l x l l TURBINE GENERATOR 1 i j When a turbine is attached (flanged) to the electrical generator, the kinetic energy (i.e., motion) of the wind, falling water, or steam pushes against the fan-type blades of the turbine, causing the turbine, and the attached rotor of the electrical generator to spin and produce ! electricity. i l i 1-3 -
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In a hydroelectric power plant, water flowing from a high level to a lower level travels through the metal blades of a water turbine, causing the rotor of the electrical generator to spin and produce electricity. 1-4
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---~~ h C : j) rum, E FOSSIL FUEL STEAM PLANT In a fossil-fueled power plant, heat from the burning of coal, oil or natural gas converts (boils) water into steam (A), which is piped to the turbine (B), where it travels through the blades of the turbine, which spins the electrical generator (C), resulting in a flos of electricity.
After leaving the turbine, the steam is converted back (condensed) into water in the condenser (D). The water is then pumped (E) back to the boiler (F) to be reheated and converted back into steam. f 1-5 -
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FEEDWATER I 4-- T SYSTEM c-PUMP NUCLEAR FUEL STEAM PLANT In a nuclear power plant, many of the components are similar to those in a fossil-fueled plant, except that the steem boiler is replaced by a Nuclear Steam Supply System (P 'S). The NSSS consists of a nuclear reactor and all the components .ecessrij to produce high pressure steam for the production of electricity. 1-6
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9 Fission c 1
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. f Like a fossil-fueled plant, a nuclear power plant boils water to produce electricity. Unlike a fossil-fueled plant, however, the nuclear plant's energy does not come from the combustion of fuel but from the fission (or splitting) of fuel atoms.
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! I l i ENRICHMENT (% U-235)
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Most power reactors (capable of producing electricity) in the United
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5tates use a "slightly enriched" uranium fuel. " Enrichment" refers to the percentage of the easily fissionable U-235 atoms present in the fuel to the less fissionable U-238 atoms (which are far more abundant in nature). " Weapons Grade" Uranium is very highly enriched (greater than 97% U-235). l l l 1-8 ,
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" fuel rod."
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111 11 h 11 I Lower End Fitting i Babcock & Wilcox At the fuel fabrication facility, fuel rods are bundled together into
" fuel assemblies" or " fuel elements." Spacer grids separate the indivi-dual rods to allow for the necessary flow of coolant water between them.
The number of fuel rods per fuel assembly varies, depending on the type and size of the reactor. 1-10 -
REFUELING BRIDGE N N' N N N REFUELING N CANAL N N u
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b0 CORE REACTOR ( VESSEL , At the nuclear power plant, the fuel assemblies are inserted vertically into the reactor vessel (a large steel tank filled with water). The fuel , l is placed in a precise grid pattern known as the reactor " core." l 1-11 . l E_ __ -----___--- --- - 1
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(e a r Pum.P H PUMP PUMP i BOILING WATER REACTOR PLANT (BWR m The Boiling Water Reactor (BWR) operates in essentially the same way as a fossil-fueled generating plant. Inside the reactor vessel (A) heat from the fission of uranium fuel in the reactor core (B) boils coolant water
. into steam. The steam travels through a moisture separator (C) and is piped (D) to the turbine (E), which turns the electrical generator (F).
The steam is condensed back into water in the condenser (G). The water l ) is then pumped (H) back to the reactor vessel to be reboiled. The recir-culation pumps (I) and jet pumps (J) take a portion of the coolant water and reinfect it into the reactor vessel to increase the mixing and flow of reactor coolant. Boiling water reactor systems are manufactured in the U.S. by the General Electric Company, San Jose, CA. BWR's make up about 1/3 of the power reactors in the United States. I 1-12 -
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PLANT 3 Q,~ (PWR) The Pressurized Water Reactor differs from the Boiling Water Reactor in that steam is produced in the steam generator (B) rather than in the reactor vessel (A). The pressurizer (C) keeps the reactor coolant (water) under very high pressure (about 2200 pounds per square inch) to prevent it from boiling, even at operating temperatures of about 600 degrees F. Pressurized water reactors make up about 2/3 of the Power Reactors in the U.S. PWR's are manufactured by the Westinghouse Electric Company, Pittsburgh, PA; Babcock & Wilcox Company, Lynchburg, VA; and the Combustion Engineering Company, Windsor, CN. 1-13
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REACTOR i VESSEL FEEDWATER I T C: PUMP HIGH TEMPERATURE GAS-COOLED REACTOR PLANT ( HTGR ) Another type of reactor uses helium gas instead of water as its coolant. The only High Temperature Gas Cooled Reactor (HTGR) in the U.S. is the Fort St. Vrain plant in Colorado. The plant was manufactured by General Atomic Company of La Jolla, CA. HTGRs are widely used in other i countries. l l 1 1-14 - 4 l
l 1 Fission )
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e-RADIATION i DECAY HEAT ( Since nuclear power plants produce electricity by fission r,ther than combustion their byproducts are very different than those associated with fossil-fueled plants. " Fission products" are highly radioactive atoms produced by the splitting of the larger uranium atoms. Because of the intense radiation associated with fission products a system of " barriers" has been developed to prevent these atoms from escaping into the j environment. The rapid rate of decay of most fission products causes a significant amount of energy to be generated inside the fuel pellets. This energy is called " Decay (Residual) Heat" and unless removed could result i'n damage to portions of the barrier system, or even to the fuel j pellets themselves. " Radiation," " Decay Heat" and " Fission Product Barriers" are all discussed further in subsequent sections of this l manual. O
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-- 6 CIRCULATING WATER SYSTEM To operate properly all steam plants whether nuclear or fossil fueled, need a circulating water system to remove excess (waste) heat from the steam system and transfer that heat to the environment. The circulating water system pumps water (A) from the environment (river, lake, ocean) through thousands of thin metal tubes in the plant's condensor (B).
Steam exiting the plant's turbines (C) rapidly cools and condenses into Since the water when it comes in with contact the much cooler tubes. tubes provide a barrier there should be no physical contact between the steam and the environmental circulating water. Because the condenser's operation produces a vacuum, any tube leakage in this system will produce an " inflow" of water to the condenser rather than an " outflow" to the environment.
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C l ,f.....,[ Intake Cire. Water Pump - 1 Power plants located on the ocean (or other large bodies of water) will often discharge their circulating water directly back to the ocean under strict environmental protection regulations. Water is taken from the ocean, pumped through the thousands of small tubes in the condenser to remove the plant's waste heat and is then discharged back into the ocean. The expected . temperature increase from circulating water inlet to outlet is about 5-10 degrees F. 1-17 -
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( l =^ Cire. Water Pump s Most nuclear power plants not located on the ocean need cooling towers to remove waste heat from the circulating water system. One type is the forced draft cooling tower, in which circulating water from the condensor is permitted to splash downward through the cooling tower transferrireg some of its heat into air. Several large electrical fans located at the top of the cooling tower provide forced air circulation for more effi-cient cooling. t 1-18 _
e 4 Turbine Generator (J1-\(l/) () Jl y s Natural
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r ( } k' ' Cire. Water Pump The taller, hourglass shaped natural convection cooling towers do not require fans to exhaust waste heat from the circulating water system into the air. Rather, the natural tendency of hot air to rise removes the waste heat as the circulating water splashes down inside the cooling tower. 1-19 _
COLD-DRY RELATIVE air HUMIDITY (M T {j 35- j ,
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0' 34 gms 25- # WARM
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15' AIR METER , AIR 1a , 30 50 70 90 ggg F
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The " steam" vented from the top of a cooling tower is really luke warm water vapor -- and it's not radioactive. As the warm, wet air from inside the cooling tower contacts the cooler, dryer air above the cooling
- tower, its ability to hold moisture is reduced. The released cloud of water vapor is visible only until it can be dispersed and absorbed by the air. The graph above shows air's ability to hold water as air temper-ature changes, l
1-20 _
I . TYPICAL REACTOR PLANT LAYOUT i ( PRESSURIZED WATER REACTOR ) l I75 . 5/G S/G w un k - li U Get It: m- =I e dlolhCll,ul;,' w.,
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' lccoreg Tour Audery C.w% Turbine Buksng Bulding Buading The major structures at a pressurized water nuclear plant are the containment building, which houses the reactor and its high pressure steam generating equipment; the turbine building, which houses steam turbines, condensers and the electrical generator; the auxiliary building, which houses normal and emergency support systems (such as the Residual Heat Removal System, fuel handling and storage equipment, laboratories, maintenance areas and the control room. Depending on the plant location, there may or may not be a coolina tower to remove waste heat from the f acility. !
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1-21 __m_______ __ _ _ _ - _ _ _ _ _ _ _ _ _ _ . _ _ _ _ _ . _ _ _ _ - . _ . _ _
TYPICAL REACTOR PLANT LAYOUT (Boiling. Water Reactor) 1 t RX Primary Containment . (DWI) MSR
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Circ. Pump Tower Reactor Building Turbine (Secondary Containment) Building The major structures at a Boiling Water Nuclear Plant are the Primary Containment (Drywell), which houses the reactor and recirculation pumps, the Reactor Building (Secondary Containment) which surrounds the Primary Containment and serves many of the functions of a PWR's Auxiliary Building and the Turbine Building. Depending on the plant location there may or may not be a coolina tower to remove waste heat from the facility. l 1-22 -
4 THE FISSION PROCESS AND l-EAT PRODUCTION A nuclear power plant converts the energy within atomic nuclei into elec-trical energy. This section discusses the release of nuclear energy by the fission of uranium atoms and the methods used to control the rate at which energy is released and power is produced. I 2 -_--__ _ _ - - - - . __.--_m-_..m --___. -- .- . _ . . - - -
Electron Proton .
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i Atoms are composed of positively charged protons in the nucleus and nega-tively charged electrons orbiting the nucleus. The simplest atom is Its atomic number, hydrogen, composed of one proton and one electron. derived from the number of protons, is 1. _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ . _ _ _ _ _ _ _ _ _ _ _ _ _ - . _ _ _ _ _ _ A A
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+ ,+ l 2He Helium
( 1 More complex atoms have more protons and electrons, but each unique com-bination of protons and electrons represents a different chemical element. Helium, for example, with two protons has an atomic number of two. 2-3 ______--___--___m-____._____-____m- _ . _ _ _ _ _ _ _
PERIODIC TABLE OF THE ELEMENTS H He LiBe B C N O F Ne NaMg Al Si P S Cl Ar Gage K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn As Se Br Kr Rb Sr Y -Zr NbMo Tc RuRh Pt Ag Cd in Sn .Sb Te I Xe . ChBa la Hf Ta W Re Os ir Pt Au Hg Tl Pb Bi Ib At Rn Fr Ra,Ac Lu Ce Pr No RnSn Eu Gc Tb Dy Ho ..Er TmYb .. ,. Th Pd,U Np,Pu, Aron BkCf Es;FmMc NoLw , Each element has been assigned a chemical symbol. Elements are listed by increasing atomic number and grouped by similar chemical characteristics on the Periodic Table of Elements. O
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Like Charges _ Repel Opposites Attract n l > ; g ( Electrostatic Force ' Since all protons are positively charged, and since like charges repel, electrostatic force tends to push protons away from each other. . I e 2-5 .
e I Neutrons Provide l g Nuclear-Attractive Force No Electrostatic , 4 Repulsion i Hold Larger Atoms < Together 4 Neutrons, with no electrical charge, provide the attractive nuclear force to offset electrostatic repulsive forces and hold atoms together. All atoms found in nature (except the the basic hydrogen atom) have one or more neutrons in their nuclei. 4
Hydrogen isotopes - TRITIUM DEUTERIUM
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( rH HYDROGEN A chemical element can have several different combinations of protons and neutrons in its nuclei. Hydrogen, above, has three naturally occurring combinations (known as " isotopes"); Basic hydrogen (one proton, no neutrons); deuterium (one proton, one neutron) and tritium (one proton, two neutrons). l _ __ p g
AT@MIC NUMDERO - l I I o % @ @ i tH 2 He 3 Li sQ t 27 CO 99 7sAU s2 U l J 1 l 1 1 The number of protons an element has (atomic number) determines its chemical characteristics. Atomic numbers are always related to the same element (hydrogen-1, cobalt-27, gold-79, uranium-92). When used in technical literature, the atomic number is usually written to the lower left of the chemical symbol (as shown above). Often the atomic number for an element will be omitted from technical writings since this number will never change for the element under discussion. 2-8 -
I 4 Naturally Occurring ~ Carbon
'sC ': C ':C 6 Protons 6 Protons 6 Protons ;
6 Neutrons 7 Neutrons 8 Neutrons C l 1 Since chemical elements can have different numbers of neutrons,the use of isotopic numbers (or mass numbers) is necessary to distinguish one iso-tope from another. Naturally occurring isotopes of the element carbon are shown above. The isotopic number (shown to the upper left of the chemical symbol) is the sum of the number of protons and the number of neutrons in the nucleus of an atom.
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_ _ _ _ _ _ - _ __ _ _ _ _ _ _ -______ _ _ _ _ _ nx
Naturally Occurring Copper ..
- Cu :: Cu 29 Protons 29 Protons 34 Neutrons 36 Neutrons The commonly found isotopes of copper are shown above. Although the placement of the isotopic number in the upper left is technically correct, many variations are encountered. For example:
63 63 hCU, CU, CU , CU-63, copper-63 All refer to the same isotope of copper. 2-10 -
e Naturally Occurring . Uranium 234 235 238 92 92 92 92 Protons 92 Protons 92 Protons 142 Neutrons 143 Neutrons 146 Neutrons l Power reactors in the United States use uranium as fuel. The naturally occurring isotopes of uranium are shown above. About 99.3% of all uranium atoms are the isotope U-238. About .7% are U-235. Trace amounts (f ar less than 1%) of U-234 can be found. Another isotope, U-233 does , not exist naturally but can be manufactured and used to fuel some types of reactors. I
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ENRICHMENT i'% U-235} - Uranium-235 (enriched from .7% abundance to about 3.5%) is the fuel for most power reactors in the United States. I b__-__________________.___ _ _ _ _ _ _ _ _ _ ____ _ 2-12
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e FeISSIOn Absoration g.*. 9 b Uranium-235 is uset ul as a reactor fuel because: (1) it will readily absorb a neutron to become the highly unstable isotope U-236. (2) U-236 has a high probability of fission (about 80% of all U-236 atoms will undergo fission) (3) The fission of U-236 releases energy (in tte form of heat)
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which is used to produce high pressure steam and ultimately electricity. (4) The fission of U-236 releases two or three additional neutrons which can be used to cause other fissions and establish a
" chain reaction."
Fissions > Heat _ . Rate of Rate of > Heat Fission Production l ( l l Every fission releases a tiny amount of heat. Trillions of fissions per second are necessary to produce high temperature, high pressure steam for electrical power production. The rate at which uranium atoms are fissioned determines the rate at which heat (and power) is produced. ) 2-14 -
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I Since neutrons are necessary to cause the fission reaction and since each fission releases neutrons, there is the potential to set up a self-sustaining chain reaction (if there is a sufficient quantity of fis-sionable material and the material is shaped to decrease the chance of neutrons escaping).
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2-15
Criticality
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Steacy Rate o" Power Generation Criticality is the term used to describe the condition of " balance" in a j reactor. When the number of neutrons being produced by fission exactly l equals the number of neutrons being absorbed by all materials (uranium, structural components, shielding, etc.) the reactor is said to be
" critical." In a critical reactor the number of neutrons present, the number of fissions occurring and the heat being produced are all steady over time.
1 s 2-16 _
For Criticality: 1 1
- 1. Neutrons Must Leak Out of the Core
- 2. Neutrons Must be Absorbed by Poisons C
Because more neutrons are released by fission than are needed to produce a steady rate of fission, there is always a surplus of neutrons whenever the reactor is operating. To maintain the " critical" balance needed for a constant reactor power level, some of these excess neutrons must be allowed to " leak out" or escape the fuel area where they cannot cause further fission. The remaining surplus must be absorbed by non-fissionable materials in the reactor core. These neutron absorbers are called neutron " poisons." t
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/ !~. - / '.Y:4 ? % y l. / -
Water
/ / v. -
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.- Moderator
/ .. . . ' .
p >%
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n .
/ %
Reactor
/ ... . /
Vessel Wall y
/ -
l Some of the neutrons released by fission will " leak" out of the reactor core area to be absorbed by dense concrete shielding around the reactor vessel. All the remaining neutrons in the reactor core area will be absorbed by some . material (U-235, U-238, water, steel, control rods, etc.) E 2-18
NEUTRON POISONS
~~
CONTROL RODS SOLUBLE BORON FISSION PRODUCTS URANIUM-238 STRUCTURAL COMPONENTS Any material that absorbs neutrons and dcas not fission is a " poison" to the fission process. The reactor vessel, structural components and the reactor coolant all absorb neutrons. Several fission products absorb neutrons (especially xenon-135 and samarium-149). Uranium-238 sometimes fissions, but when it does not, it acts as a poison. Reactor operators
~
can manipulate the total amount of pois>ns in the reactor by moving control rods and (in PWR's) changing the concentration of boron in the reactor coolant water.
e e CONTROL RODS
~~
IN - FEWER NEUTRONS POWER DOWN OUT - MORE NEUTRONS POWER UP Control Rods are concentrated neutron absorbers (poisons) which can be moved into or out of the core to change the rate of fission in the reactor. Rod insertion adds neutron poison, thus fewer neutrons are
~
available to cause fission, fission rate decreases, heat production decreases and reactor power goes down. Pulling control rods out of the core removes poison, thus more neutrons are available for fission and reactor power goes 'sp. - _ _ _ _ _ _ _ _ - _ _ _ _ _ _ _ . _ _ _ _ _ _ _ . . _ . . - _ _ - - - - - _ _ _ _m--_--- - - - -
~
Reactor Scram 1 BWR s bhY ] If1rify s _ - PWR ( Rapid insertion of Control Rods to Shutdown the Fission C1ain Reaction A reactor " scram" (or " trip") is the rapid (two-four seconds) insertion of control rods to stop the fission chain reaction. In a boiling water reactor, control rods are inserted from below the core. In a pressurized water reactor, control rods are inserted from above the core. Although a reactor scram does not stop all fission in the core, the " chain reaction" is immediately broken causing a significant decrease in reactor power in a few seconds. l l
~
_ _ _ _ _ _ _ _ _ _ _ 2-21
. 1 l
i Thermalization Birth ' )f. ~ Rg / . y~ Q Absorption mo
#5 Neutron Life Cycle Fuel Pellet Fuel Rod Moderator The wate.* used in a BWR or PWR reactor coolant system has two important functions. As a coolant, water carries away heat from the reactor fuel rods (maintaining temperatures in the core within 'specified limits).
l Water's other major function is to control the fission process by slowing down and reflecting back high energy neutrons so that more fissions can occur. This " slowing down" process is called "thermalization" or
" moderation."
l 2-22 -
~
~
l t TEVIPERATURE-DE\ SITY RELATIONSHIP OF WATER Water w j
..,- Tempt -
. . De~nsityl-s > .
..- Neutron Leakagel-Power Output!
- ~
Moderator
~ '
. Temperature
% 2 .
The use of water as a neutron moderator helps produce a steady rate of reactor power. If the reactor coolant temperature increases, the water becomes less dense and less effective as a neutron moderator. This tends to reduce the power level of the reactor. Conversely, if the reactor coolant temperature decreases, it becomes a better moderator, thus tending to increase the numoer of fissions that occur in the fuel. This temperature - density relationship is a major factor in controlling the fission process and heat production of the reactor.
~
2-23
i j 0o g o00 0 ' > 0 0 Voids 0 ~ 0 0 LSteam BubblesD 09
@o go w s a)g o
f Very (Low Densitys 3 p of {go f, w , jo More Voids-
- c. & .
More Leakage-Power , et to lk > I s. Moderator density changes are important factors in controlling the fission rate and power production of a reactor. In boiling water reactors, the conversion of water into steam produces a dramatic change in moderator density from the bottom to the top of the core. Water at i the bottom of the core is far more dense (and moderates neutrons far better) than does the water-steam mixture at the top. l l
~
2-24
l
- '! 1700 F
- A a" 3e '
1400 F , b
- f,' :! 750 F w 3 -
l
!: ,f 650 F
- s : 600 F
- :l l5 !l TYPICAL FUEL ROD
~
i
;" ,e ' .
- AND C O O L A NT . TEM PER ATUR E S C
When a power reactor is operating, these are the approximate normal temperatures in the reactor core and reactor coolant system: 1700 degrees F in the center of the fuel pellets where many of the fissions
. occur, 750 degrees F at the outer surface of the fuel pellets, 650 degrees F at the cladding tube and 600 degrees F in the coolant water.
The average fuel pellet temperature under normal operating conditions is L about 1400 degrees F. Melt temperature for the ceramic fuel pellet material is about 5200 degrees F. Fuel clad damage will start to occur above about 1800 degrees F. Significant fuel damage can be expected at sustained temperatures above 2200 degrees F. Reactor emergencies and their consequences are discussed in section eleven of this manual.
~
2-25
G e e 6 43 N v' f
- s
'hr J
S 0
.m
___m_--m_____um-_._____m___.. _ _ _ . _ . _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ . _ _ _ _ _ _ . - - _ . . _ _ _ _ _ _ _ _ _ _ _ _ _ . - _ - _ _ _ _ _ _ _ _ _ _ . . . _ _ _ - _ _ _ _ _ _ _ __--_______._-__________..___m.__._-____.____._.-_____._________m_______ _ _ . - _ _ _ _ _ _ _ _ . _ _ _ _ _ _ - _ . _ _ _ _ _ - _ _ _-, _ . _ _ - _ _ _ _ . _ . . - - - - -
R ADIATION - TERMINOLOGY l a This section discusses the terms and concepts which are necessary for any meaningful discussion of radiation, its sources and its risks. 3-1 ;
e
. l GrY Radioactive Atom o
PARTICLE A " radioactive material" contains atoms which are unstable due to some excess of energy in their nuclei. In an attempt to become more stable,a radioactive atom disintegrates (or decays) by ejecting particles or elec-tromagnetic energy (photons). 3-2 _
1 Energy { m/ .. . Radioac:ive Radiation A:om O Particle (. l Radioactive material ejects particles and/or photon energy as it decays. The particles and/or energy emitted are " radiation."
1 CURIE:
)
( 1400 lbs 1gm 238U 92 1/1000 gm ECO TRa s-3.7 x 1010 Disintegrations per seconc Radioactivity is measured in " curies." One curie is defined as the amount of any radioactive material (radioisotope) that will decay at a rate of 37 billion disintegrations per second (the rate of 1 gram of Radium-226). ii 3-4 - l
7-200 s W E
\ .
\.*
HALF LIFE 3 . O 'g
. ~~lN THALFLl!E PERIODS y
p
's p ygy THERACl0ACTIVITYo/*
., THE MATER /AL HA$
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1 1 , I l
~ - ,. ,._ ,. , ,
3 1 2 3 4 g i TlME (. . The rate of nuclear decay is measured in " half lives." The half life of any radioactive material is the length of time necessary for one half of the atoms of that material to decay to some other material. Half lives range from millionths of a second (for highly radioactive fission products) to millions of years (for long lived materials such as _j naturally occurring uranium). { I i i 3-5 -
l T
,-~,\ ~~_ /
,i
,/ - s i'
u . l
'l IONIZATION l 1
l Nuclear power plants produce ionizing radiations. " Ionization" is the process of stripping or knocking electrons away from their orbital paths creating chemically active ions. This process can cause chemical changes in the material where it occurs. If chemical changes occur in the cells of our bodies some cellular damage may result. The biological effects of radiation exposure are discussed in section six of this manual. 3-6 - - _ - _ - _ - _ - - - _ - _ _ _ _ _ ___ \
i l
]
[ C ALPHA Alpha radiation is a particle made up of two protons and two neutrons. Alphas are low speed, low penetrating particles which can only travel one or two inches in air. Alphas are easily shielded (stopped) by thin sheets of paper or the body's outer layer of skin. Alphas are considered to be an " internal hazard" due to their ability to cause a large number of ionizations in a small area if the radioactive atom can get inside the
~
body. Outside the body, alphas present little or no hazard. I 3-7 -
l l BETA l
\
l
)
\
Betas are high speed, high penetrating particles which are usually nega-tively charged. About 1/1800 the mass of a proton or neutron, the beta I can easily penetrate the skin and is considered both an " internal" and an
" external" hazard. Betas are best shielded by thick metals and plastics.
3-8 _
\
l h GAMMA Gamma radiation is electromagnetic energy (no mass, no charge) similar in many respects to visable light (but far more energetic). Gammas can travel thousands of feet in air and can easily pass through the human body. Gammas are best shielded by very dense materials such as lead, concrete, and uranium. Note: X-rays are similar to gammas but are produced by changes in electron position rather than nuclear decay or fission. 3-9
- NEUTRON Neutron radiation is the high speed, high energy neutrons emitted by nuclear fission and by the decay of some radioactive atoms. Neutrons can travel hundreds of feet in the air, can easily penetrate the human body and are best shielded by materials such as water, polyethylene and concrete.
J 3-10 -
7____________-__ d EXPOSURE AND DOSE l l MEASUREMENTS ROENTGEN
~
RAD ! REM C When radiation interacts with a material it causes ionizations. These ionizations can be measured and their effects estimated. The commonly used units for radiation exposure and dose measurements in the U.S. are the roentgen, the rad and the rem. l t 3-11 -
ROENTGEN
,_______n
,/ .,____,/__,, -________.__
, n-e i Gamma !_"- ~ ~ ~ ~T,
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- s. _ _ _ _ _ _ _ ,e s 1 Esu/Cm3 Dn/ Air v
The roentgen is a measure of exposure to X or gamma radiation. One roentgen will deposit enough energy to strip about two billion electrons out of their orbits in a cubic centimeter of dry air. I i J t
~
3-12 _ _________-___ - __ -
1 RAD 4 4s 4m, -- i 1 d_b 100 Ergs / gram (Any Material) ( The rad is a measure of absorbed dose (the energy deposited in a material). One rad is the deposition of one hundred ergs of energy in one gram of any material due to ionization from any type of radiation. (One erg is about one ten billionth of a btu). Rad is an acronym for
" Radiation Absorbed Dose."
~
---------._---------_-------------3-13--
l Rem Damage Equal . 4 To 1 Rad of Gamma ; Radiation i in Body Tissue . The rem is a measure of biological damage caused by ionization in human tissue. One rem equals the biological damage that would be caused by one rad of exposure to gamma radiation in the body. Rem is an acronym for
" Roentgen Equivalent Man."
3-14 _
FOR GAMMA ( AND X-RAYS ) -- Roentgen
~
1 - 1 Rad - 1 Rem. c For gamma and X radiations, one roentgen of exposure is (about) equal to one rad of absorced energy which equals one rem of biological damage in humans. l
~
__________________________________________.____CL,Gl4_____
]
. 3 .
s G.h
..g_
d R-
. j.g. '
S. s ge. _ 1 Rad Alpha 1 Rad Gamma Particulate radiations such as alphas and neutrons have been found to cause more biological damage than do gamma or X-rays for the same energy deposited. For example,100 ergs deposited by alpha can be expected to cause about twenty times the damage caused by 100 ergs deposited by gamma. This difference in ability to cause damage is called the
" Relative Biological Effectiveness" (RBE).
3-16
DOSE Energy vs. Damage -- - 1 Rad Gamma = 1 Rem 1 Rad Beta = 1 Rem 1 Rad Neutron = 10 Rem 1 Rad Alpha = 20 Rem REM = Rad x Quality Factor l To account for Relative Biological Effectiveness, a group of " Quality Factors" has been developed which convert the energy deposited (rads) into an equivalent biological damage in rems. l 3-17
4 REM VS. MILLIREM ! MW s, s s :s:~s's_Mh s s s .
- s : s
- s: s .
s ss s s
~
s ' N % g g s k g s % g g%; s es:
%; s 1 Rem = 1000 m Rem 1 m Rem = 1/1000 Rem All the units used in a discussion of radiation and radioactivity may be prefixed to indicate fractions (or multiples) of the standard unit. The table below lists the most common prefixes for scientific use.
PREFIXES d deci (= 10 1) da deka (= 10) e centi (= 10 2) h kecto (= 102 ) m milli (= 10 3) k kilo (= 103 ) p micro (= 10 s) M mega (= 10s) n nano (= 10 8) G giga (= 108 ) p pico (= 10 12) T tera (= 1012) f femto (= 10 15) a atto (= 10 18) 3-18 _
DOSE RATE
=
p XMeasure of the , g Strength of 5 i Na Radiation s F.ld ie
% U 8
C The dose rate is the amount of radiation exposure (or equivelent biologi-cal damage) that a person would receive in a particular length of time. It is a measure of radiation intensity (or field strength). Commonly used dose rates are: mrem /hr, rem /hr, mrem /wk, rem /wk, rem / quarter, rem /yr
- I 3-19
J 1 1 Dose = Dose Rate x Time 1 25 m Rem =50 mrem x1/2 Hour HR { w The dose is equal to the strength of the radiation field (dose rate) multiplied by the length of time spent in that field. The example above indicates a person could expect to receive a dose of 25 mrems by staying in a 50 mrem /hr field for thirty minutes. L
~
3-20
STAY TIME Dose
~ --
Limit / Dose Rate 100 m Rem / 50 m Rem / H r= 2 Hour C. Stay Time The " stay time" is the length of time a person can remain in a radiation field before exceeding some " dose limit." In the example above, a dose limit of 100 mrems has been established. The dose rate is 50 mrem /hr. The stay time is calculated by dividing the dose limit by the dose rate.
Contamination
== QA&
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4 ___ __ M.-. Radiation Contaminai. ion is generally referred to as some aaterial in a location where it is not intended or desired to be. Radioactive contamination is radioactive atoms that have escaped the systems t.r structures thet nor-mally would contain them. Additionally, if a worker must enter a " container" (for example, to per-form steam generator repair on a PWR or turbine repair on a BWR) we say that worker will enter a " contaminated area." Methods of protection against radiation and contamination are discussed in section seven of j this manual. t 3-22 -
ILNTERN ATON AL SYSTEV 0: UN TS
\
SI UNIT OLD UNIT - CURIE BECQUEREL COULOMB ROENTGEN KILOGRAM RAD GRAY SIEVERT REM The United States has yet to fully implement the use of the internation-ally accepted system of units and measures (SI). The SI units shown above are expected to gradually replace the curie, roentgen, rad and rem in technical lit'erature. f 3-23
1 CURIE : SEC. 1 Bq. : SEC. !
~
1 Bq. 2.7 x 10 ' 'Ci. One curie is defined as the amount of any radioactive material that decays at the rate of 37 billion disintegrations vr second. One bec-querel equals one reciprocal second (sec~1). Therefore, we can s:Jy that one curie equals 37 billion becquerel. l l l 3-24 -
COULOMB
- 2.58 x 10 , _
1 ROENTGEN KILOGRAN 1 COULOMB _ GEN KILOGRAM (. The roentgen will not have a designated SI equivalent unit, but the force produced by a roentgen can still be expressed. The correct representa-
-1 tion of coulomb / kilogram is coulomb kilogram ,
1 RAD =
/ -GRAY 7
1 GRAY = 100 RAD i The gray will replace the rad as the unit of absorced dose. One rad equals 1/100 of a gray. One gray equals 100 rad. 3-26 -
1 1 REM : SIEVERT 1 SIEVERT : 100 REM ( 1 The sievert will replace the tem as the unit of biological damage to human tissue. One tem equals 1/100 sievert. One sievert equals 100 rem. l 3-27 -
d Radiation . Sources 9-m_- I This section discusses the sources of radiation exposure to the general U.S. population. Both naturally occurring and man made radiation sources are discussed. 4-1
- j I
NATURAL BACKGROUND RADIATION SOURCES l OUTER SPACE . AIR WATER GROUND MINERALS FOOD / TOBACCO' PRODUCTS BODY TISSUES l ; 1 l i l Our bodies are penetrated thousands of t'imes each second by naturally occurring radiations. Natural Background Radiation comes from the Sun and other stars and the decay of naturally occurring radioactive elements in the ground, air, water, plants, and animals and inside our own bodies. 4-2 -
BACKGROUND SOURCES COSMIC RADIATION l PROTONS -- ( l NEUTRONS BETAS GAMMAS I X - RAYS 38 - 75 m REM / YEAR ( l j Activity on our Sun (and other stars) and the Earth's magnetic fields l cause the upper etmosphere to be bombarded with high speed particles and photons. While the EartA's atmosphere shields us from much of this direct radiation, we are still exposed to some of this " primary" l l radiation. Interactions in the upper atmosphere release " secondary radiations" which are the source of most of the cosmic radiation which reaches the earth. 1
~
4-3
e e TERRESTRIAL RADIATION , Granite, Soil, Minera s, -- Ground Water, Etc. E , " C s *19 K , 222 86 R n 1 22eR a , 232 Th s 88 90 2*U 92 1 6 15-120 mrem / Year i i l l 1 l Terrestrial radiation comes from the decay of naturally occurring radio-active materials which can be found in varied amounts throughout the worl d. Some of the most abundant natural radioisotopes are listed above. i 4-4
1 f INTERNAL SOURCES 6 C i
*K 19 i 88"Ra 1
15-20 m Rem / Year ' C i All of us have some radioactive material inside our bodies. Three of the most abundant internal radiation sources are listed above.
NATURAL BACKGROUND RADIATION l COSMIC 38 - 75 m REM / YEAR TER.RESTRIAL 15 - 140 m REM / YEAR INTERNAL 15 -20 m REM / YEAR AVERAGE : 100 m REM / YEAR The average American receives a dose of about 100 m Rem each year due to background radiation. 4-6 -
MAN MADE RADIATION SOURCES MEDICAL EXPOSURES 90 m REM / YEAR BUILDING MATERIALS & l CONSUMER PRODUCTS 5 m REM / YEAR 1 WEAPONS FALLOUT 5 m REM / YEAR 1 AVERAGE : 100 m REM / YEAR l I ) < 4-Medical procedures (both diagnostic and therapeutic) are the largest source of man made radiation exposure to the general public. The use of building materials containing trace amounts of natural radioactivity, some consumer products, and fallout from nuclear weapons add slightly to the total man made radiation dose.
~
__ Aav
CONSUMER PRODUCTS - TV SETS LUMINOUS WATCHES ._ SMOKE DETECTORS AIRPORT X-RAYS NATUR AL GAS INCANDESCENT MANTLES FOOD / TOBACCO PRODUCTS s The consumer products listed above either contain small amounss of radio-active materials or generate high speed particles or photons in the course of their operation. 4-8 _
GENERAL U.S. POPULATION : NATURAL BACKGROUND 100 m REM / YEAR ' MAN MADE SOURCES 100 m REM / YEAR AVERAGE = 200 m REM / YEAF ( t The average U. S. citizen receives a total annual dose of about 200 m Rem as a result of naturally occurring and man made radiations. 1 l 4-9
COMPUTE YOUR OWN RADIATION DOSE Your Annual Common Source of Radiation inventory Location: Cosmic radiation at sea level ................................ 26 For your elevation (in feet) - add this number of mrem . . . . . . . . . . . . . . . . . Devation - mrem 1000 2 4000 15 7000-40 2000 5 5000 21 8000 53 WHERE 30.00 9 6000-29 9000 70 . YOU Devation of some U.S. crties (in feet): Attanta 1050. Chicago 595. Dallas
!.IVE 435. Denver 5280. Las Vegas 2000. Minneapolis 815. Prttsburgh 1200.
St. Louis 455. Salt Lake City 4400. Spokane 1890. (Coastal crties are assumed to be zero. or at sea level) Cround: Vi awrage ............................................... 26 House Construction - For stone, concrete or rnasonry building. add 7 .. ... I' d WHAT YOU Water US. awrage 24 EAT DRINK. AND BREATHE We a pons test fallout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 X ray and radio pharmaceutical diagnosis Number of chest x rays x10.............................. HOW Number of lower gastrointestinal tract x rays x 500 . . . . . . . . . . Number of radiopharmaceutical examinations x 300 . . . . . . . . . . YOU g (Anrage dose to total Ui population s 92 rnrem) 9 Jet plane travet: For each 2500 miles add 1 mrem . . . . . . . . . . . . . . . . . . . . . . TV viewing: For each hour per day x 0.15 . . . . . . . . . . . . . . . . . . . . . My total annual dose in mrem = \ V
, $r)
L. @ o b ... . . ,
~ One mrem per year is equal to: Moving to an elevation 100 feet higher.
Increasing your diet by 4L Taking a 4 to 5. day vacation in the Merra Nevada Mountains. l 4-10 -- u _-- -- _ - . - - - - - - - - - - - - - - -
RADIATION SOURCES ! AT NUCLEAR PLANTS - i Nuclear Fue Decay a
~
Fission Process Fission Product Decay Activation Products Calibration Sources This section discusses the sources of radiation found at power reactors. 5-1 _ _ _ _ _ _ ,
Nuclear 0-Poel Natural Decay 238 235 l l 92 i 92 V G Uranium-238 (about 96% of the fuel) and uranium-235 (4%) are naturally radioactive and decay by the emission of alpha particles and gamma rays. Beta particles are released by the fuel as uranium's daughter products r.ontinue the natural decay process toward a stable form (lead). Since the fuel is sealed inside airtight fuel rods, there should be little or no alpha radiation problem at the nuclear plant unless there is some fuel rod damage. 5-2 -
l 4 1 l e n - I Fission Process 4
-? '
I
/l l
/
i l l 9, ' ( . fl . l l During the fission process uranium atoms split into two or three smaller atoms (called fission products). Powerful gamma rays and high speed neutrons are released during (and immediately following) the fission process. ) 5-3
1 l Fission Product
-= Decay l
/
/ .
The new atoms produced by fission (fission products) are intensely radioactive. Most will decay rapidly but several decay very slowly. Fission products generally decay by beta and gamma emission. 5-4 _
FISSION PRODUCT BARRIERS CERAMIC PELLET
~
FUEL ROD y N REACTOR VESSEL ( CONTAINMENT Since a significant fission product release could seriously jeopardize public health and safety (and the environment) a system of fission pro-duct barriers is a part of every power reactor design.
~
5-5
Q, . - - w j .. . g
~
Activation of Water
~~
w j
.- . and Corrosion Products
, .Y , -y/- }
- ( *,
(CRUD) l
. e /o. .
.. Contam.inat. ion nw A .
i r & a During the fission process, some of the .~ "p g' g materials in the vicinity of the reactor a _ core will absorb neutrons and be changed from a stable form to e non-stable (radio-
]) .
\
b active) form. These materials (called a,ctivation products or " crud") are not ' contained inside. tt.e fuel rods (as are u most fission products) and are eas ly , transported by the reactor coolant system. ) i i O Crud is the source of most radioactive contamination at nuclear power plants. d, m fr CN , 3
, ___.- g i
O 5-6 -
MATERIAL RADIATION HALF LIFE Krypton-85 Beta 10 years Gamma l Strontium-90 Beta 28 years lodine-131 Beta 8 days Gamma . C,c::ium-137 Beta 30 years I Gamma Carbon-14 Beta 5770 years Zinc 45 Beta 245 days Gamma Cobalt 40 Beta 5 years Gamma fron-59 Beta 45 days Gamma Tritium Beta 12 years (Hydrogen-3) C Above is a partial list of radioactive materials produced either by fis-sion (fission products) or neutron absorption (activation products). These materials are of particular interest because of:
- 1. Their relatively long half-lives
- 2. Their relative abundance in the reactor (or)
- 3. Their ability to chemically interact in biological systems ,
5-7
4 INSTRUMENT CALIBRATION r h ' ' I q M
! 8 1
ne SOURCES . e Small quantities of radioactive material (sources) are stored on the plant site to allow instrument technicians to properly test and calibrate radiation detection devices. These sources are completely sealed and are stored in isolated areas when not in use. 5-8
El BEliological Effects -- , of Radiation
't
. . . . . . ./
~
. / - ?;;:*::.**..H s
-------- Z.T.~.~.~.T___j' _
This section discusses the expected short term \ and long term effects of radiation exposure on Y
'N biological systems.
- 6-1
~
Radiation Causes O lonization
'/.m*N .
k ' 'j h . Decomposition Of H2O j In Cell O 1 Radiations such as alpha, beta, gamma, x-ray and neutron can deposit enough energy inside human tissue to knock or strip electrons away from their nuclei. Since a large percentage of the body is water, most of the Some of radiation induced ionizations will involve water molecules. The these molecules may be decomposed (hydrogen separated from oxygen). If a large water molecules involved may or may not recombine into H 20. number of water molecules are ionized, a certain number can be expected to form into other combinations. (Example: 2H 20*H2 + N22 0 )" 6-2 -
. T Damage To DNA From lonization
/
Inside the cell nucleus, the DNA moleu;les represent a relatively small (but very important) percentage of the whole body. Ionizations occurring in these molecules may result in the transfer of incomplete (or in-correct) genetic information to the cell's offspring during reproduction, l
- ~ - - - . _ _ _ _ _ ~ ~ ' ' ' ' _ , _ _ _
6-3
~
CELLULAR DAMAGE: 1m lon.izat. ion \_qq . 7 .. 2m Chemical J ' [- Recombination L 1ON J - Radiation can cause cellular damage by ionization and by the potentially harmful effects of forming new chemical compounds as a result of the ionization process. 6-4 -
POSSIBLE CELLULAR PROCESSES
- 1. Normal Repair of Damage (Normal Reproduction .
F3 a d.1 3 3
@w L a
<a g d
( At low levels' of radiation (such as normal background) the affected cell can usually repair (overcome) any damage resulting from the exposure. 6-5 -
POSSIBLE CELLULAR PROCESSES
~
- 1. Normal Repair of Dambge
- 2. Cell Dies From Damage 4
e n Y
\
-i4 f
I l At high levels .of radiation, cellular damage may ultimately result in the death of the af fected cell or in the inability of the cell to reproduce. I i I 6-6 _ i
POSSIBLE CELLULAR PROCESSES
- 1. Normal Repair of Damage
- 2. Cell Dies From Damage
- 3. Daughter Cells Die I
L i
%) w3
-- v l
'f genetic damage occurs, the cell may reproduce, but the resultant
<bughter cells may not live (or may if ve but be incapable of further reproduction).
4 5 0 6-7 --
~
.POSSIBLE CELLULAR PROCESSES
- 1. l\ormal Repair of Damage
- 2. Cell Dies From Damage--
- 3. Daughter Cells Die
- 4. No Repair or Non-Identical Repair Before Reproduction i
G m lw)
.- =
g ,l wJ A small portion of DNA changes are reproducible. The resultant changes, (or mutations) may range from non-detectable to life threatening. 6-8 _
I I RADIATION EFFECTS i ACUTE CHRONIC , l RISK IS LOW UNDETECTABLE I ^ AT DOSES BELOW I H EACH ADDITIONAL 5 - 50 REMS EXPOSURE b The effects of radiation exposure on living tissue can be short term (acute) and long term (chronic). Acute radiation exposures can cause sickness and even death at doses of 300 - 1000 Rems. Acute exposures below 5 - 50 Re.ns should cause no short term ill effects.' l The chronic effects of radiation exposure are considered to have no thres-hold for risk. Although very small (compared to the total cancer risk, a person faces) the risk of a radiation induced cancer increases with each i additional exposure. t L e-o - 3
~
RAD ATION
~
SYNDROME Nausea Fatigue Loss of Appetite Vomiting l
~l l
Acute radiation sickness (the radiation syndrome) can be expected if a person receives a dose of 50 - 200 Rems or more over a short period of time. The onset of symptoms and the severity of the illness are related I to the total dose received, the duration of the exposure and several other factors. Most people exposed to radiation doses below about 300 Rems can be expected to ultimately recover from these short term effects. t 6-10 _
RADIATION SYNDROME Ultimate Effeet Can - Be
~
c Death The ultimate effect of any exposure to a hazardous material can be death. The likelihood (risk) of death increases 'as the dose increases. E 6-11
~
NRC DOSE - LIMITS 10 CFR 20 . DOSE STANDARDS IN RESTRICTED AREAS: QUAR'itRLY YEARLY WHOLE BODY (REM) 125 5 HANDS & FEET (REM) 18.75 75 SKIN OF WHOLE BODY (REM) 7.5 30 3 REM /OUARTER IF EXPOSURE HISTORY iS KNOWN (NRC FORM 4) AND LIFETIME EXPOSURE DOES NOT EXCEED 5(N.18) N= AGE IN YEARS The NRC radiation exposure limits shown above are designed such that no worker at a nuclear facility will receive an acute whole body radiation exposure sufficient to trigger the radiation syndrome. The risk of cancer (although not zero) should be no higher than the risk of cancer from other occupations. , 6-12 -
NRC DOSh t LIMITS . i 10 CFR 20 UNRESTRICTED AREA:
~
2 m Rem /HR ( 100 m Rem /7 Days
- The NRC limits all licensees in the handling and use of radioactive materials such that no member of the public (or worker outside the re-
- stricted area) will receive a radiation dose of 2 millirems in any hour, or 100 millirems in any seven consecutive days. Additionally, the NRC has provided design objectives for power reactor licensees to keep off-site releases as far below the 10 CFR 20 limits as is reasonably achievable. These guidelines can be found in 10 CFR Part 50. See page 10-7 of this manual for more information on design objectives.
l 6-13
~
ACUTE RADIATION DOSE . O-5 Rem No Detectable Effect 5-50 Rem Slight Blood Changes __ 50-100 Rem Blood Changes, Nausea, Fatigue 100-200 Rem Above Plus Vomiting,1% LED 200-450 Rem Hair Loss, Severe Blood Changes, Some Deaths in 2-6 Weeks 450-700 Rem Lethal to 50% of Those Exposed Within 1 Month 700-1000 Rem Probable Death For 100% of Those Exposed in 1 Month 5000 Rem immediate Incapacitation Death Within 1 Week The table above lists the expected effects from an acute whole body radiation exposure. The duration of the exposure is assumed to be short 1% LED is the lethal effective dose for one percent ] (24 hours or less). l of a group of individuals exposed to a dose of 100 - 200 Rems. 1 a 6-14
. 1 l
99.99 - 99.3 . 99 . PERCENT 98 = 95 . MORTALITY 90 . -- 80 . A WITHIN 70 . E I 60 DAYS 40 . 30 C 20 , 10 - 5 .
'2 ,
1 . 0.5 . 0.2 ( 0.05 . 0 200 400 600 800 1000 1200 DOSE (REM) Curve A - Minimal Medical Treatment Curve B - Supportive Medical Treatment Curve C - Heroic Medical Treatment The grafts above indicate how supportive and heroic medical assistance can significantly reduce the effects of the acute radiation syndrome. The 50% mortality line lies at about 300 Rems for minimal assistance, about 450 Rems for supportive (normal) assistance and about 1000 Rems for heroic / extensive) assistance. _ _ __ 6 __ _- 1 5
1 4 9 AS DOSE INCREASES: Risk of Cancer Increases The chronic effects of radiation exposure are considered to have no threshold for risk. In other words, there is no level of exposure which
~
is completely safe. The risk of a radiation induced cancer is considered to be very low (but not zero) compared to the normal incidence of cancer in the population (one person in four). 1 I i 6-16 - I . - . ..
l l l CANCER RISK ESTIMATES
- 1. ADDITIONAL CANCERS
- 2. REDUCED LIFE EXPECTANCY
( Two commonly used methods to evaluate risks are decreased life expectancy
. and increased probability of cancer related to certain activities. The National Academy of Sciences' Advisory Committee on the Biological Effects of Radiation (BEIR), the International Commission on Radiation Protection (ICRP), the National Council on Radiological Protection (NCRP), the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR), and many other national and international scientific bodies have studied and continue to study the risks of radiation exposure.
I 6-17 -
~
RADIATION INDUCED - CANCERS 1 I + RISK INCREASES ABOUT .03 % j FOR EACH REM l l
.016 .045 % BEIR , 1980
.02 % ICRP, 1977
.015 .035 % UNSCEAR, 1977 s ;
The normal incidence of cancer in the U. 5. i s about 25% (one person in four). Out of 10,000 people, 2500 can be expected to develop a cancer, j If all these people were to receive a dose of one additional rem we can estimate between 1 and 4 additional persons will develop a cancer.
)
f 6-18 _
RADIATION INDUCED CANCERS DECREASED LIFE EXPECTANCY SUBTRACT ONE DAY FOR EACH REM Estimated Loss of Life Expectancy from Health Risks
- Estimates of Days of Several studies have compared the projected Life Expectancy Lost.
" ' ^ '"' 8 '
decrease in life expectancy resulting from exposure to radiation and other health risks. Smoking 20 cigarettes / day 2370 (6.5 years) Overweight (by 20fe) 985 (2.7 years) The additional risk associated with radiation A11 accidents combined 435 (1.2 years) exposure has been calculated to be a reduction [c*ohoen mption (U.S. average) 3 of life expectancy by about one day for each rem. Home accidents 95 l Drowning 41 Natural background radiation, 8 l calculated { Medical diagnostic x rays (U.S. 6 i average), calculated All catastrophes (earthquake, etc.) 3.5 i I tem occupational radiation dose, , I calculated (industry average for the higher dose job categories is l 0.65 rem /yr) I I rem /yr for 30 years, calculated 30 1
)
n bi'W l0.? \%'" "* ~^ c*'"' t 6-19 - _ _ _ _ _ _ _ _ _ - _ _ _ - _ _ _ _ _ . -_ 1
~
RISK OF CANCER A RADIATION EXPOSURE IS NOT l A GUARANTY OF CANCER MOST PERSONS EXPOSED WILL NOT DEVELOP A CANCER BUT EVERY EXPOSURE' SLIGHTLY INCREASES THE RISK OF A CANCER The risk of cancer related to radiation exposure is under continuing study. The statements above can be used to summarize the results of most of the scientific findings in this area, j
)
6-20 _
NATIONAL CANCER INSTITUTE'S SEVEN STEPS TO AVOID CANCER
- 1. DON'T SMOKE OR USE TOBACCO AT ALL
- 2. EAT LESS FAT
- 3. DRINK LESS ALCOHOL
- 4. FOLLOW INDUSTRIAL SAFETY RULES
- 5. AVOID UNNECESSARY X-RAYS
- 6. PROTECT YOUR SKIN FROM THE SUN
( 7. AVOID UNNECESSARY ESTROGEN TREATMENTS. The National Cancer Institute recommends the above precautions to markedly reduce the risk of cancer. f
- 1. Type of Radiation
- 2. Amount of Radiation
- 3. Type of Cell Involved ._
- 4. Stage of Cell Division
- 5. Age of Individual
- 6. General State of Health
- 7. Part of Body Exposed
- 8. Percentage of Body Exposed
- 9. Duration of Exposure Different individuals exhibit different sensitivity to radiation. Some of the factors affecting radiosensitivity are listed above.
6-22 _
MOST LEAST SENSITIVE SENSITIVE B.ood Cel's . Bone Cel s Bone Marrow Muscl'e Ce'Is Eye Lens Nerve CeLis Reproductive Ce'Is 1 The different cells of the body exhibit a wide range of sensitivity to radiation. Some of the most and least sensitive cells are listed above. i f 6-23 -
~
Methods
~
For Protection ~ Against Radiation and Contamination t A.A a CAUTION RADIOACTIVE MATERIAL This section discusses the methods used to protect individuals from the harmful effects of radiation and contamination. 7-1 _
~
PROTECTION - AGAINST RADIATION
~
- 1. Time
- 2. Distance
- 3. Shielding
~ Reducing the dose from any external source of radiation involves the use of three protective measures: Reduced time Increased distance Use of shielding 8 7-2 .
MINIMlZE TIME DOSE RATE x TIME = DOSE MINIMlZE DOSE The length of time spent in a radiation field is directly related to the I dose received. 7-3. . . . . . . . . . . . .
~
MINIMlZE TIME l
/
% ~
__ l 1
\
s 5 Rem /HR s x Field I rea r 5,
.57,j-s In a five Rem /Hr field an individual would receive a dose of:
100 mRems in 1.2 min. 1.25 Rems in 15 min. 3 Rems in 36 min. 5 Rems in 60 min. l 7-4 -
~
MAXIMlZE DISTANICE u e Y E
- =
l 100 m Rem / Hr. ~ b at 1 foot
~~
$f r
b1 m Rem / Hrc 6.25 m Rem / Hr. at 10 feet at 4 feet MINIVilZE DOSE ( Many radiation sources are " point sources" (appear to come from one spot some distance away). The radiation dose from these sources can be signi- ; ficantly reduced by applying the protective measure of " distance" as ) demotistrated above. l 4 7-5 1
.J
MAXIMlZE DISTANCE f I Is
/ '
. x SRem h ) 'm HR
)/ 's %%N 1 Rem i x
) ~i l
Moving a few feet further away from a source of radiation can signi-ficantly reduce the dose rate and significantly increase an individual's l stay time in a radiation area. l l t
e MAXIMlZE SHIELDING e i (,,,,,,,,,,, 400 m REM
%# ; 1/2 Thickness
[ Shield hi HALF E VALUE SHIELD LAYER (,,,,,,,,,,, 5 0 m R EM HR MINIMlZE DOSE Shielding is another effective way to reduce radiation exposure. The example above shows that the installation of a one half-value layer (half-thickness) of shielding will reduce the dose rate by a factor of two at a set distance from the source of radiation. l 7-7 _
MAXIMlZE USE OF SHIELDING y -- I
\
x .3 REM
' HR s
)/ s ,' gh kN .06 REM X HR
* ~.
Installing several half-value layers of shielding can significantly lower radiation dose rates and allow much longer stay times than could other-wise be possible.
. \
{ 7-8 _
O Relative Efficiency Of Various Shiefding Raterials l CONCRETE WATER
. . . . x:W
. . . h .. _= W -
m
= "!
J_ ~
}!p!.'.,$h.Y ih.%!? 0.~ .. . .q. W$Wj
~ ~
ex
- ?.~:9. ..?.%).1:$:...:1l*:,-
. :. . . . : . . . ~ - n.: j
-4 ;
' '%. .: ... . . : . : ::.=:.. ?.;;:
-} i. f
/MJ ,
;it..::.1...,2-r y- . ,/ /
[W,- - _/ + 5 7 .. IRON LEAD Materials differ greatly in their cbili*,y to shield (absorb radiation). The example above shows the relative efficiency of four common shield materials for gamma radiation. yg -
PROTECTION
~
AGAINST CONTAMINATION
- 1. Minimize Leakage I
- 2. Frequent Surveys ..
]
- 3. Good Housekeeping
- 4. Access Control 3
- 5. Protective Clothing
- 6. Respiratory Protection
- 7. Bioassays N ~ ~~C 01
- I LJ jp The protective measures listed
{ _.
\ W - above are used to prevent, detect
; j hj j1 or contain radioactive contamination,
}
}
^
f,' fl A '
/ j ^1 li t
t 7-10 - L
. l I
CAUTION CAUTION bob bob HIGH l RADIATION AREA RADIATION AREA i i RWP REQUIRED FOR RWP REQLilRED FOR ENTRY. ENTRY. DOSE RATE AT THIS PolNT IS DOSE RATE AT THIS PolNT IS MR/HR DATE POSTED BY MR/HR DATE POSTED BY CAUTION HOT 8,A SPOT
'f CONTAMINATED AREA FULL ANTI-CONTAMINATION g CLOTHING REQUIRED CAUTlON EATING, DRINKING AND RADIOACTIVE SMOKING PROHIBITED MATERIAL Some commonly used radiation / contamination warning signs and labels are shown above. The international symbol for radioactive material is a magenta or purple three bladed design on a yellow background.
~
7-11
o BWR . l SYSTEMS ( This section discusses the purposes of the major systems and components of Boiling Water Reactors. 8-1
e o I hAVS(EL
~~
THROTTLE VALVE STEAM LINE , l
; E; ------>-
NQ;i . - ,, WOISTURE SEPARATOR [::
. ;.g.g.g:.t E g ......: :.~ ayn
- pi:
TURBINE ::' '^ :- / / I. .:. .I*..,
/ / J !
, , . . .. F
- :: .: ** * /w vj nEACTOR ;. - -
4
** o
/
- Nj CCRE
- f. .
- O Nf,i'.: . :l[.
* * [,3 .
n G ELEcTmicAL j j' JET jl CONDENSER GENERATOR j
- PUMP i
-M M-h FEEDWATEM p mEcine I l ~ T p p nEcine ( _
m r PUMP
\ 0 PUMP ruur H l 1
~
BOILING WATER REACTOR PLANT (BWR) Inside the Boiling Water Reactor Vessel (A) a steam water mixture is pro-duced as coolant water removes heat from the reactor core (B). The steam-water mixtures moves upward and into the moisture separator (C), where water droplets are removed before the steam is allowed to enter the steam line (D). The steam turns the turbine (E), which turns the electrical generator (F). The steam than enters the condenser (G), where it is condensed into water. The water is pumped by the feedwater pump (H) from the condenser back into the reactor vessel. The recirculation pump (I) and jet pump (J) allow the operator to vary the coolant flow rate (and thus change reactor power). , 8-2 _
l 4 REACTOR BUILDING TURBINE BUILDING U"J VALVE WO.STURE SS,AAATOR / =MSAftR if> STEA. motArew vuvat taaortte v"v' " j g 4 onyw Lt .,
\ fff"n"no~cuacs ne l j --
d t, -. . vuves 6,
- -N .. .
~ ~ = "* l: : 1 !l l:.! pf#b
'/ - . . . . .
-c-3"u. ;;;;;; ;;;;;; Cm j MEA R CONOGNSER ELECTADCR j
- /w .I N eananAton s
f i VU j 1
,asowArea
~
d nueton YESSEt 4 t OW ee f WATER j l e ,e WATSR nsAnn l j f . j d e.E.."., . "- wA.ren
. t / 1
( 1 l A boiling water reactor's coolant system consists of the reactor vessel, steam turbines, condensers, condensate and feedwater pumps, the reactor's recirc system and the pipes linking these components. I 8-3 _ - - - _ __ _u. _ _ _ _ _ _ - - _ _ - _ - _ _ _ _ - _ _ _ _ _ _ _ _ - _ _ _ - _ _ _ _ _ _ _ _ - _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
BWR REACTOR WATER CLEAN UP SYSTEM , REACTOR CONTAINMENT VESSEL /
/
-. - -- -* STEAM --
.---- ,.s:-- FEEDWATER s %
I
\.... ..) F G v f REGENERATIVE HEAT EXCHANGER HON. REGENERATIVE
/ HEAT EXCHANGER RECIRC PUMP : '
/ ~ "
[ -. -- - 4
+
rn.TER/ REACTOR WATER DEMINERALIZED CLEAN UP PUMP - - n ir REACTOR BUILDING CLOSED COOLING WATER
. The reactor water cleanup system provides a means for the removal of corrosion and wear products and chemical impurities from the recirc system and the bottom of the BWR vessel.
I 8-4 -
-_- -_-__. -__ - ---- _ _----- __ --_____----_-_-__J
.g BWR RESIDUAL HEAT REMOVAL SYSTEM (SHUTDOWN COOLING) l REACTOR VESSEL
-+ e STEAM
.---- - . FEEDWATER
\.. . .ti
~
l RECIRC 9 PUMP o CONTAINMENT o b ' MESIDUAL HEAT REMOVAL HEAT RESIDUAL HEAT EXCHANGER REMOVAL PUMP .
} SERVICE o WATER The BWR's Residual Heat Removal System is used during reactor shutdown to transfer the core's decay heat away from the fuel to the environment.
t 8-5 i
[ d . BW.R REACTOR CORE ISOLATION
. COOLING 4 l
l
- TO --
' MAIN TURBINE l
q Ihf 1' -5 r o
% ISOLATION VALVES l I .. . ,,
= = = =
I -- JI u CONDENSATE STORAGE TANK
-FEEDWATER LINE CST h I
= -
au'#RCIC
/
YCX9 PU P j " ' CONTAINMENT i' s e The BWR's Reactor Core Isolation Cooling System is used to supply water for decay heat removal when the normal source of coolant (feedwater) is not available. r 8-6 ,
t BWR EMERGENCY-COOLING SYSTEMS CONTAINMENT SPRAY A .. e
*'amo .
HPCI < STEAM LINE TURSINE CONDENSATE. f m STORAGE sO --
~ ~
_ TANK Pu
. \ ,
\ t
~
i........'I f1 RHR I OU U;Q ) - 1 1 t CONTAINMENT M' SERVICE f PRAY WAygg (, I^<^>^>^er*- DRYWELL
^^"^ ----
^ ^ ^^" -
" RHR WATER v
I PUMPS \hSPRAY -PUMP POOL b d 3 LPCI The BWR Emergency Cooling Systems are designed to supply water to cool the reactor core end the containment in the event of a loss of coolant accident (LOCA). t 8-7 - w__--___=________ _ _ _ _ _ _
BWR STANDBY. LIQUID CONTROL SYSTEM O ;! , CORE >NN ' N '
- (
d I. ... . . .f m POISON h TANK h - i lQ[ EXPLOSIVE b (BORON) VALVE PUMP CONTAINMENT The BWR's Standby Liquid Control System provides a method to stop the fis-sion process and maintain the reactor in a shutdown condition even if there is no control rod movement. 8-8 _
- l HAnors 4 k y - aoLLs as
*)/ FAT,'
d - ' _. - i c ;- ,. ,
. . .u s. ,
l o ,
- I #
.6
%*_ ~ swi cuno.
, 'l e ma -l ,
neurao p \g ,=aana Nh'l[ i l , .... - }. # I "A"3 i sv .s ca.w6 , t t
' # g i i 8 Laos ! F -
<W 6 . ... .uv.
% l r g )
cerac. . . ;I l
- g l
- a ~.u j 'C ')
/ -
"' 4]L
' EEIT f h MANDLt
. m
- ;i i i
i
.. i
.v i l
GENER AL h ELECTRIC i4 ..l > U.'ii'a"
" soc'UI AOLLsas l
These cutaway drawings show the major components of a BWR fuel assembly and control blade (rod). 8-9
T N6 l
< i .ww. y ==- BWR 6 REACTOR ASSEMBLY c;
h $^" T*"'M"
.. 1 .- sani m $ nrcriac g e se6g, b p f (
l r , , 1' . . . . _ . . i l === p , . 3; w.6a
.qr b5
~"
1. y* -_
"J
$N ,,- -
, , .- - .-- ,,,, T l l1
'==
g g%sp ' _ . , . , -. N ma.aa.6s yp.. ~ , p/ . N .- - w.s Ctus asunvo. 7, _...-. h
- ~ -
1 i p These cutaway drawings show the asei ca.n;;%g,,,,,; ;; , t major components of a BWR's reactor I . - s ,
,,,,,,,,,,, l j . . , l vessel and recirculation system. .
e{ g '- I
'~s':
t_ _
~
gt- l
,,,:5 .
/ . . . . . . !
8-10 -
e I I v m *J Y lf ~
~
h.
~.- 't b,
,4 .,
- i. -
'%, 2 g i I
s
.- I
.k h k ory wea -' p-g
, /
DRYWELL TORUS [,/'% $- S E N E R AL $ ILECTRIC , { , 8g h 1~ These drawings show the layout and major components of a Mark I (Drywell - Torus) Containment. 8-11 .
_ai
~
l / .% h h_ l
=
H Ii j l w
,~ w n.
j
.J= =
l I q .,
, d ., ,
? ..
'j BWR CONCRETE CONTAINMENT
, GENER AL $ ELECTRIC These drawings show the layout and major components of a Mark II Containment.
8-12 _
4
\ .
Ue' e
,' 3 ,_
. . 6, : , , f=r; O
{ I usi . . l/ e::, ., r ""* 66 1[y
%. w 4 ; ,M/
I
~
? j gl.O i
([ t ... I i I;f a1 semang s ! [- =:- -
.I $
in (
,i ( " L ji
- i ,3 _
u
!b-MARKlli CONTAINMENT REACTOR BUILDING
[ (**s sw et SENERAL $ ELECTRIC 1 Polar Crane
- 4. Refwhng Pistform tor Water Cleanup
- 7. Reactor Vessel 9 Shed Wa
- 10. Foodwater une FCutaton Loop Vent
- 15. Suppressen Pool AUXtUARY BUILDING These drawings show the layout
,'I, $*'o*, $t[cee,, and major components of a Mark III
& RHR Spte Containment.
FUEL BUILDtNG
- 19. Fuel Transfer Bndge
- 21. hng usi u
- 24. Cask Loadng Pool
- 25. Spent Fuel SNpping Cask
- 26. Fuel Cask Skd
~
_ ___ _ _ __ _ fil- 9 El
1 PWR .- SYSTEMS i c l 9 This section discusses the purposes of the major systems and components of Pressurized Water Reactors. l P 9-1 - c_--_______________-_____
L. . Turbine
.. ~ <- :- ;.,
t
!::l
.iyl:L aaa steam C : !!El / / .' I Generator f y' v'j
/
2
= : .: .
2 0 . Eseth - Pressurizer by hi:i f ii:@l 'l:l[ Generator e\. d a .- s a _. ' Condenser o o Feed
}} L
}
,g A
J $-- 6 ( p - % Purnp l Reactor vessel o PRESSURIZED WATER bh REACTOR 3 PLANT O~ Reactor Coolant Purnp The pressurized water nuclear steam supply system consists of two ' closed f loop water systems. The primary system transfers heated water from the
)
reactor vessel through the steam generator tubes (where heat is removed) to the reactor coolant pump, which forces the water back into the reactor The secondary system is the steam that exits vessel to remove more heat. the steam generator, turns the turbine and electrical generator, and The secondary system also includes the condensed enters the condenser. water pumped by the feedwater pump back to the steam generator. 9-2 _ i
4
. / ~.
Moss,u,. sep., ,or. ReheatIt
/
/
/ u.
v,
/ =txter r ,.
v
=
n
~
/ .
f _ X_ y W_, , . .,
/p ,= - . < <.
s i... .. .. .. .., . l c ....,
/ 1.,,,,, ... .., ... ., ,,..,
d llllll IIIO I Eiect,ic
- gl# $ * ='
7' 9""'.~ l r
- /
/ 1 '? a u .n -
l 3: . ~. .- i
- s. .
1.- /
/ e s i
co,ad.n. ,.
*( _%' 'f / He.t.'
; Ch,c.*
W8 V g,, ,. W.i., /
/k g
/ a = k' , 5 p %, ,) ,
f 7 a T co u', i f
/ y t, . s..
f , _% ..., U _c__, 3 PWR SECONDARY SYSTEM ~ l (STEAM / CONDENSATE /FEEDWATER) A pressurized water reactor's secondary system consists of the steam, condensate and feedwater systems. Since physically separate from the contaminated primary system (by the steam generator tubes) the secondary system water should contain little or no radioactive material.
- l i
l 9-3 -
PWR CVCS SYSTEM . Co .,, Reacio, Water Cooknt Ii -
"1. ,
.Lf
~ = 5- o '"** -
+ t- Tanks
- : - ""i"d'""n#* 6 B @4p a
Resenersi~e Heat Eachanger o 1 ;w.;-... .a E:3, goric I$Y ltk?il Pure Water Acid d
-.< PZR SS G :.*/-
% Q M. , ' 4
% ;9 Volume Controe ;;ld&l& .'
" % , f' Tank Chemical - .E..+.
Addition # ~7 ' ~
-% r ( Tank v a RX T T Pues Water ACP w Pump y
c Charging Pump Bonc Acid Reactor Coolant System Pump The Chemical and Volume Control System provides filtration, chemical cleanup, chemical addition and waste removal for the PWR's reactor coolant system. The CVC5 also responds to demands for volume changes in the reactor coolant system due to temperature changes and minor leakage. 9-4 -
/
TO ENVIRONMENT SERVICE CCW Heat Enchanger WATER _ , SYSTEM : {~ 8 W Pump l
= - ._ !
CCW Pump COMPONENT
,'Z"
*' g:" so / '
, i -
COOLING !
;- I ;
" - '*Qm
.. t vf g WATER j W97 SYSTEM g.
3 u -
-% f ([ _.
nHn H :
< ~
RESIDUAL HEAT , Eschenger RHR Pump i Rx o REMOVAL l V aca SYSTEM ;
^ i g -
_= 1
..... c M###x24 -
..,s ..-
PWR RESIDUAL HEAT REMOVAL l ( .. l 1 l i The Residual Heat Removal System (RHR) provides a heat exchange method for the transfer of decay heat from the reactor core to the environment. RHR is only operated after the reactor fission process has been stopped and the reactor coolant system has been partially cooled end ) depressurized. e .l 9-5
w i PWR AUXILIARY FEEDWATER ' SYSTEM ,
)
. I am T _
l d ,
? PZR
' F'#*
~
^
h h? s O s d.: i
, a Water m
f., Storage
- % f, r
& M ~
}
y7-IIIII RX g ; V ! T k.i
= ,
L '
- x.,
Meector Cooient System fs///////////////////////5Yl/////8VM -- . y " The Auxilicry Feedwater System provides feedwater from a storage tank to the steam generators during reactor startup and shutdown. Aux Feed can remove the reactor's decay heat and (as steam) transfer that energy to the main condenser or out steam relief valves to the environment. 9-6 - Kw___.,-----_.----a --n.-.----- - - - - . _ - - - - - _ - - - - - - - - - - - - - - - - - - - - - _ - - - - . - - _ - - - - - - - - - - . - - - - - - - - - . . - -
c. e PWR EMERGENCY CORE COOLING SYSTEMS
= ,
n J_ ~~
.. Core Floodme enk BIT invec$.on Tank Tank age L
~
\ T Id
*T - _
t" - u.e..d _ Safety inpoeten
? pyg Q* '.:sa;'t System IChargingl g
~
< y $$At " T' W meermodore Head Safety
% , p Irwecten p
8 - - Syssom "
-i (swe;,T -
Eschenger Low Heed 1 IIlli ax S.<ety i e inpoctum System (RHR) a RCP 1 : T Reactor cooient System sN~'
= =
(- In an emergency, a PWR might need additional neutron poisons (to insure a safe reactor shutdown) or additional water (to makeup for rapid changes in volume due to leaks and decreasing reactor coolant temperature). The PWR's emergency safety systems must be capable of injecting Boric Acid and' a large quantity of water to the reactor under a wide variety of emergency conditions. t 9-7 _ l'
L pgsr////>//,,,, PWR
/ / CONTAINMENT SPRAY
/ Spray R.ing SYSTEM i
'. D 1,
l ' +e$. $ .$ $.. e- __ .
.g l n Water, 'I
'2
- P2R nk -
t":SG;'t ... 9 3. g
/
E
@ - o
_ p (j Containment Spray Pump T F RCP
- T n
Reactor Coolant System l l
' w Containment "
Sump lI __ The PWR Containment must be able to withstand the stress of a complete depressurization (leak) of the reactor coolant system. One system in-stalled to reduce containment pressure is the Containment Spray System which pumps water to the top of the building and sprays the water over the steam which would result from a large Reactor Coolant System leak. I G-8 -
I'-- .. d Y Babcock &Wilcox
=m )R ;
~
p ;. :
%1 * ,S:#
i l
$$Ns J
' ~
These drawings show the basic layout of , components for the three PWR vendors in the ( . United States. b>; y I
. Westinghouse e-o
e . l
-' l "i COesTROt, ROO D8tiVE MECMAhlW4 18eETRUMENTATION
, I PORTS
' I UPPER SUPPORT l ruts ,
- THERMAL SLEEVE
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a POWER ewwa.SYSTEMS v -.. ,,a This cutaway drawing shows the major components involved in fueling /re-fueling a pressurized water reactor. t
; 9-16 _
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l RADIOACTIVE WASTE
._ )
I g GASEOUS EFFLUENT i NUCLEAR POWER PLANT Q
&\ LIQUID q EFFLUENT '
W Iu g ; $2q sig 1 1 i 1 TRANSFORT C l' DISPOSAL This section discusses the sources, handling and ultimate disposal of radioactive wastes generated by Nuclear Power Plant operations. 10-1 _ L-__- _ _ _ _ - _ _ - _ - _ _ _ _ _ _ _ _ _ _ - _ _ _ _ _ _ _ _
)
HIGH-LEVEL - R ADIO ACTIVE WASTE
~
FUEL HANDLING BRIDGE l l i h
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( FISSION PRODUCTS ) High Level Radwaste (fission products) are sealed inside the spent fuel rods. They are presently being stored in spent fuel pools at nuclear plants and at some off site temporary storage facilities. 10-2 ~ l l _ _ _ _ _ _ _ _ _ . . _ _ _ _ _ _ _ _ _ _ _ _ . . _ _ _ _ _ _ _ _ _ )
LOW LEVEL WASTE SOURCES L I O U I D: 1 EOUIPMENT LEAKOFF POlNTS
- 2. EOUIPMENT VENTS AND DRAINS
- 3. FLOOR DRAIN SYSTEM --
- 4. RELIEF VALVE DlSCHARGES
- 5. SOLID WASTE SYSTEM ( DE-WATER )
S O Li D:
- 1. CONTAMINATED AAGS. TOOLS, CLOTHING. ETC.
- 2. SPENT FILTER CARTRIDGES
- 3. SPENT DEMINERALIZED RESINS G A S E O U S:
- 1. EQUIPMENT VENTS
- 2. LI0U10 WASTE SYSTEM
( EVAPORATOR GAS STRIPPER ) The principal sources of low level radwaste are the reactor coolant (water) and the compor1ents and equipment which come in contact with the coolant. The major constituents of radwaste are activation products (crud) with a very small percentage of fission products. 10-3 -
- - - - - _ - - - - - - - - - - - - - - - - _ - - _ - - - - - - - - - - - - 4
1 l i WASTE , FROM CVCS cooling no ciar : SOLIO RADWASTE 7~,
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T IIIII ax T Pure Water RCP - Pump b ne etor cooieni system cherging Pump oric Acid The drawing above shows some of the sources of low level radwaste from a pressurized water reactor. In the Chemical and Volume Control System solid particles (some of which are radioactive) are removed by the Reactor Coolant Filter and Demineralizers. Gases are removed in the Volume Control Tank. Liquids can be pumped to storage tanks for sampling and reprocessing as necessary. 10-4 _
- LjQUID' ;
loN ( CAY)
,, FILTER 4 % ANo % ANo RADWASTE ,og,, --* ExCNANoER SAMPLE g TANK d'
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- DRUM eacCE. __. SYSTEM maan. voets. etotass. oe. opp.ssTE SOLID M AD WASTE ( sumiAL )
c a n vaios e s canvascos. STORAGE olluTioN GASEOUS ( oECAy )
=> d FILTER -* CoWPRESSOR -* ANo -e FILTER ==$ ANo RADWASTg s TA u,pgE o sCNanct The block diagram above shows the _ layout for a simple radwaste handling system. Solids, . liquids and gases are first separated from one another and then processed individually. All solid low level wastes will be shipped to licensed burial sites. Liquids and gases will be held up to allow most of the short-lived radioactivity to decay off and then will be diluted and released into the river / lake / ocean (for liquids) or the atmosphere (for gases).
I i E-10-5 i
GASEOUS EFFLUENT NUCLEAR POWER PLANT bi I
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1 The drawing above shows many of the possible pathways for radiation k j exposure to a member of the general public. i l 1 10-6 _
10 CFR 20 DOSE STANDARDS 2 m REM IN ANY HOUR 100 m REM IN ANY 7 DAYS e 10 CFR 50 DESIGN OBJECTIVES LIQUIDS 10 m REM / YR TO ANY ORGAN (, GASES 15 m REM / YR TO SKIN SOLIDS & 15 m REM / YR TO ANY ORGAN IODINE The licensee must not release radioactive material so that any member of the public receives a dose of 2 m Rem in any hour or 100 m Rem in any seven consecutive days. Additionally, the NRC has issued numerical design limits for each reactor unit for exposure to releases into water and air which are considerably lower than the limits published in 10 CFR 20. t 10-7 -
l e l l I l REACTOR j {
)
I EMERGENCIES i l l l This section discusses some of the possible events which could lead to a significant releast of fission products from the reactor core and the emergency systems, strectures and components designed to prevent these accidents or mitigate their consequences to protect public health and I safety. )
~
i- - - . .
.. __J
REACTOR EM E9GENCIES . OVERHEATING FUEL RODS MECHANICAL DAMAGE TO RODS GAP
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Fission product release can be a result of overheating or mechanical shock to the fuel rods. An abnormally high rate of fission or lack of decay heat removal can result in overheated fuel. Mechanical damage could be caused by a fuel handling accident, spent fuel pool damage or industrial sabotage. 1 l l 11-2 _
4 E V ERGE N CY SAFETY SYSTEM S
= PROTECT FUEL RODS -
=
PROTECT RCS
=
PROTECT CONTAINMENT ( = PROTECT THE PUBLIC All power reactors must have specially designed safety systems to insure the reactor can be shutdown and the fuel cooled under a wide variety of emergencies. The reactor safety systems are designed to protect or miti-gate the consequences of damage to the fuel rods, the reactor coolant system and the containment structure. The overall goal is to protect l public health and safety from the consequences of an accident. I 11-3 -
REACTOR EN ERGENCIES . 1 REACTOR RADIATION SCR AM / TRIP EXPOSURE SIGNAL TO PUBLIC IF \ l [ CORE COOLINGIF NORMAL \ l EMERGE'NCY PREPARE 0 NESS l [ MODERATING SYSTEMS Fall SYSTEMS Fall E QY RELEASE TO START ENVIRONMENT IF IF EMERGENCY \ [ IF REACTOR \ [ CONTAINMENT CORE COOLING ( I COOLANT SYSTEM l l I" SYS ""] M A! INTEGRITY FAILSj pg
\ \ /
RELEASE FUEL FR M DAMAG.E pCS : A combination of several low probability failures must occur for a signi-ficant amount of fission products to be released from reactor fuel into the environment. If these failures combine with an inadequate emergency preparedness system the released radioactive materials can cause an ex-posure to the public. I 1 i 11-4 _
STEAM GENERATOR TUBE RUPTURE i Moisture Separator / Reheater A ":Ek ~ l j[/ ,e%, VMv's Ta,.iiie Vd y n y o f/ x-isoiesion HP v yM LP LP volve -- steam oe .a, ,
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w, ; /; - Reactor Coolant Pump l l In a PWR, a steam generator tube rupture could lead to releases of radio-
. cative material due to increased steam line pressure. The operator's l main goal in this situation is to provide an orderly shutdown and cool-l down of the reactor coolant system so that the leaking steam generator can be completely isolated and the steam relief valves will not open.
t l 11-5 _
/ .
1 . CONTROL ROJ MALFUNCTION
- m OR ROJ --
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'i EJECTIOh h
v SAFETY
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elt SYSTEM
.. _ c. - - (BORON) i A control rod malfunction or control rod ejection may require the inser-tion of additional neutron poisons. Both PWR's and BWR's have systems which can pump a boron solution into the reactor to provide the necessary neutron poisons for reactor shutdown.
11-6 _
-STE AM LINE BREAK-SAFETY INJECTION SYSTEM l
- Moisture S,,eparator/Aenester
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Reactor Coolant Pump In a PWR, a steam line break can cause a rapid temperature drop in the reactor's coolant system. As coolant temperature decreases, more neu-trons are moderated and reflected back into the reactor core causing more fissions and higher fuel rod temperatures. This situation requires a rapid reactor shutdown which may include the injection of boric acid solution to ensure the reactor remains shutdown. 11-7 .
LOSS OF . COOLANT i , ACCIDENT l PZR y , 9 1 l 5.. _m e L EMERGENCY ; w !
- ax v CORE COO _lh G RCP
*=
c' - SYSTEMS, b8.-,o, c .. so,.'" CONTAINMENT SYSTEMS l I A loss of coolant accident decreases the reactor coolant system's ability to transfer decay heat away from the reactor core. The plant's emergency core cooling systems iust be able to provide the necessary volume of water to prevent fuel damage. l 11-8 . l _ _ -------_ -- - - - - - i
PWR EMERGENCY CORE COOLING SYSTEMS
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Reactor Coolant System Containment Sump I 7 The above drawing shows a simplified version of a PWR Emergency Core l Cooling System which can inject borated water into the primary system under a variety of accident conditions.
--------u-----_-- - - - - - - - - - - .- - , - _ _ _ . - . - _ _ _ _ _ _ _ _ _
3 BWR EMERGENCY COOLING SYSTEMS CoNTAiHuENT SPRAY p l sieAu Line Esius cowogusare el l O~
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The above drawing shows a simplified ve-sion of a BWR's Emergency Cooling Systems. These systems can inject pure water into the reactor vessel (and provide containment cooling) under a variety of accident conditions. 11-10 _
CONTATVEhE~ BULJING l l I l i
= ISOLATION SYSTEM i
= SPRAY SYSTEM
= AIR COOLING SY' STEMS
= AIR PURIFICATION SYSTEMS k
Thould serious fuel damage occur, fission products will be released from the fuel rods into the reactor coolant system. The primary function of the containment structure is to block the escape of this highly contami-nated fluid. The containment must be properly isolated, cooled and de-contaminated in order to minimize fission product release to the environment. 11-11 -
exaco
,j , CONTAINMENT SPRAY Spray Ring SYSTEM m
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Reactor Coolant System Containment Sump The drawing above shows a simplified version of a PWR's Containment Spray System. Containment Spray is one method available to cool and depres-surize the PWR containment in the event of a loss of coolant accident, t 11-12 --
1 l - EMERGENCY ACTION LEVELS l UNUSUAL EVENT ALERT INCREASING SEVERITY SITE EMERGENCY GEhERAL EMERGENCY ( , I The Emergency Action Levels (shown above) have been established to pro-vide prompt notification of minor events which could lead to more serious consequences or which may indicate more serious conditions which have not yet been fully realized. ~ _ - _ _ . _ . - . - - - - _ _ - - - _ _ - - - - _ _ - - . _ _ - - _ _ _ - - _ _ _ _ - _ _ _ _ _ _ . . . . . .. . .- _
1 EVENT UNUSUAL , ECCS ACTUATION l i 1 HIGH COOLANT ACTIVITY SAMPLES -- I ABNORMAL COOLANT / FUEL TEMPERATURES VALVE / PIPE FAILURES POWER FAILURES (OFF SITE) FIRE OR DEGRADATION OF FIRE PROTECTION LOSS OF MONITORING / COMMUNICATION SYSTEMS SECURITY THREAT ABNORMAL NATURAL PHENOMENON AIRCRAFT / TRAIN ACCIDENT ON SITE The Notification of Unusual Event indicates that there is a potential degradation in the level of plant safety. The notification:
- 1. Provides current plant status information.
- 2. Assures that the first step in any later response found to be necessary has been carried out.
- 3. Provides a test of emergency communication systems.
11-14
f
. )
l ALERT I I SEVERE CLAD DAMAGE l 1 RELEASE 10 TIMES GREATER THAN TECH SPECS { i i SIGNIFICANT PRIMARY COOLANT LEAKAGE LOSS OF AC OR DC POWER SUPPLIES INABILITY TO COMPLETELY SHUTDOWN /C00LDOWN FUEL HANDLING ACCIDENT
/ IRE POTENTIALLY INVOLVING SAFETY SYSTEMS LOSS OF ALARM / ANNUNCIATOR SYSTEMS SEVERE NATURAL PHENOMENA AIRCRAFT / EXPLOSION DAMAGE TO FACILITY ANTICIPATED OR ACTUAL EVACUATION OF THE CONTROL ON G0ING SECURITY COMPROMISE The Alert classification indicates that events have occurred (or are occurring) which involve an actual or potentially substantial degradation of plant safety. This notification:
- 1. Assures emergency response personnel will be available if needed.
- 2. Provides an updated plant status report.
- 3. Provides a test of emergency response centers and personnel. !
~
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ . _ _ _ _ _ _ _ _ _ _ _11-_15
a SITE EMERGENCY l SIGNIFICANT CORE DAMAGE _ i LOSS OF COOLANT (BEYOND MAKEUP CAPACITY) LOSS OF AC OR DC POWER FOR 15 MINUTES MAJOR DAMAGE TO SPENT FUEL FACILITIES NATURAL PHENOMENA BEYOND DESIGN LEVELS DAMAGE TO SAFETY EQUIPMENT BY FIRE / IMPACT / EXPLOSION s EVACUATION OF CONTROL ROOM WITH NO LOCAL CONTROL ESTABLISHED IMMINENT LOSS OF PHYSICAL SECURITY The Site Emergency classification indicates that events are occurring (or have occurred) which involve actual or likely failure of major plant functions necessary to insure public health and safety. This notification:
- 1. Assures response centers are staffed.
- 2. Assures response teams are dispatched.
- 3. Provides all response organizations with current plant status information.
- 4. Provides a test for local, state and national response organizations. '
11-16 - l
GENERAL EMERGENCY MAJOR INTERNAL / EXTERNAL EVENT (OR COMBINATION OF EVENTS) WHICH WOULD CAUSE: LOSS OF 2 0F 3 FISSION PRODUCT BARRIERS FAILURE OF ECCS TO SHUTDOWN AND C00LDOWN REACTO OFF SITE DOSE RATES: 1 REM / HOUR WHOLE BODY k 5 REM / HOUR THYROID The General Emergency classification indicates that events are occurring (or have occurred) which involve actual or imminent substantial core
, damage with the potential loss of containment integrity. This notification- '
i
- 1. Provides current and continucus plant status information to all response organizations.
- 2. Initiates predetermined actions for the protection of the public.
- 3. Initiates other protective measures as indicated by the situation.
11-17 .
^
THE THREE MILE ISLAND ACCIDENT CONTROL RQD l " Drives u I V' d 80 $7005 AND NUTS (20 TONS), REACTCR MEAD I
$ERviCE STRUCTURE ]
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~
.dj j t This section discusses the core damage and the release of radioactive material resulting from the Three Mile Island accident.
12-1 _
THREE MILE ISLAND REACTOR BUILDIRG (C0f(TAINMWT) AUXIUAP.Y BUILDING [ F
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TMI REACTOR BUILDING ( CONTAINMENT ) This cutaway drawing shows the leyout of components inside the TMI Reactor I Building. ! I 12-4
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( (p *] (t i / CONTAINMENT A U XILI A R Y BUILDING BUILDING i 1 Fission products (mostly gases) ascaped from the damaged reactor core into the reactor coolant. Reactor coolant was moving through the Auxi-liary Building and through the pressurizer. Leakage from the pressurizer relief tank severely contaminated the Reactor Building. The concen-tration of fission products in the Auxiliary Building piping caused that building to be evacuated. Some of the fission product gases leaked from the Auxiliary Building piping and were picked up by the Auxiliary Building Ventilation System and blown out the plant vent stack. 12-7 _
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\ Television cameras lowered into the TMI core indicate a large void area at the top half of the core and a bed of rubble (fuel pellets, fuel rod debris, etc. ) on top of the remainin9 lower half. - The exact condition of the lower portion of the core has not been determined. i 12-8 t L____________________________________________ _ _ _ _ _ _ l
O l i TMI PRESSURE CONTROL, ) VOLUME CONTROL AND WASTE SYSTEMS mD v 4 sA tfY y yg PLANT j PON sLOCM VENT STACK r% _..._ ..s - .n OENERA OR SIIAM LINE lL
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N neACTOR suu, V vesset ,,oy } 9 ""' enAmosso puu, x suu, _ J- A l C k ., m S C O NT AINMENT A U XILI A R Y BUILDING BUILDING The major systems involved in the TMI radiation release are the Reactor Coolant System, the Pressurizer and its's relief valves, the Chemical and Volume Control System, the Waste Gas Handling System and the Auxiliary Build 4ng Ventilation System. t 12-5 _
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t K -) Q -. COLD LEG Following a relatively common reactor scram, a pressurizer relief valve stuck open causing a gradual loss of coolant pressure. Automatic safety equipment started as designed but was stopped in order to prevent the pressurizer from overfilling with water. (The rate of water pumped into the Chemical and Volume Control System was increased for this same reason). The resulting low pressure and high temperature caused the coolant water to boil. The low coolant pressure also caused the reactor coolant pumps to be shutdown. With little or no cooling available to remove decay heat, . the reactor f uel rods started to crack and breakdown. Some radioactive fission products (mostly gases such as Xenon and Krypton) were released into the reactor coolant. Later, when the stuck open relief valve was isolated, the reactor coolant pumps were restarted. This caused cold
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TMI CONSEQUENCES MAXIMU\4 PROJECTED OFF-SlfE DOSE: LESS TH AN 100 m REM AVERAGE DOSE TO POPULATION: s== 1.4 m REM / P E RSON PROJ ECTED ADDITIONAL CANCERS: 0-1 . ! 1 Fortunately the environmental and public health consequences of the TMI accident were very small (compared to other industrial accidents) but the psychological effects and the impact on the nuclear industry were (and continue to be) enormous. e a _ _ _ _ _ . _ _ _ _ _ _ _ _ _ . _ _ . _ _ _ _ _ _ _ _ _ _ _ _ . _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ . _ _ . _ . _ _ _ _ _}}