- WELCOME TO NUCLEAR CHEMISTRY PART FOUR.
HERE, WE WILL LOOK AT THE DIFFERENT UNIT SYSTEMS
THAT ARE USED TO DESCRIBE NUCLEAR DECAY.
LET'S GET STARTED. ALL RIGHT.
SO THE BIOLOGICAL AFFECTS OF IONIZING RADIATION
CAN LEAD TO DAMAGE OF OUR DNA CAUSING GENETIC MUTATIONS
BY BREAKING THE PHOSPHOESTER BONDS
CLOSE TO EACH OTHER ON OPPOSING STRANDS OF DNA.
AND SO BECAUSE OF THESE BIOLOGICAL EFFECTS,
ALPHA, BETA, POSITRON,
GAMMA AND X-RAYS INTERACT WITH MATTER CAUSING ION FORMATION
AND SO THAT'S WHY THEY'RE DESCRIBED AS IONIZING RADIATION.
OKAY. AND SO WE HAVE TO LOOK,
WE'VE NOTICED THAT THERE'S DIFFERENT TYPES OF ENERGY,
DIFFERENT PENETRATIONS AND THINGS
AND SO THESE DIFFERENT FORMS OF RADIATION
WILL HAVE DIFFERENT BIOLOGICAL EFFECTS
AND THIS IS GOING TO LEAD TO A VARIETY OF UNIT SYSTEMS
AND MEASUREMENT TECHNIQUES FOR MONITORING
WHAT KIND OF RADIATION DOSE WERE BEING EXPOSED TO.
SO THE FIRST THING
TO KEEP IN MIND IS THAT THERE'S TWO PRIMARY CONSIDERATIONS,
ONE IS THE TYPE OF RADIATION
AND THEN WE HAVE THE PENETRATING POWER.
SO, LET'S LOOK HERE.
SO, AS WE'VE LEARNED, SO NOW, ALPHA,
THIS IS AN INTERESTING PARADOX,
THEY HAVE, RIGHT, MEGAELECTRON-VOLTS.
SO ELECTRON VOLTS IS JUST ANOTHER ENERGY UNIT.
SO WE SEE THAT ALPHAS ACTUALLY HAVE THE HIGHEST ENERGY.
HOWEVER, AT THE SAME TIME,
THEY HAVE THE WEAKEST PENETRATION.
AND THEN AS WE LOOK AT BETAS,
THEY HAVE A SLIGHTLY LOWER ENERGY CAPACITY AND--
EXCUSE ME, HIGHER PENETRATION.
AND THEN WHEN WE GET TO GAMMA RAYS,
OR-- EXCUSE ME,
X-RAYS, NOTICE THAT X-RAYS CAN BE STOPPED IN LEAD.
WE NEED AT LEAST A HALF OF CENTIMETER.
AND THEY HAVE--
BECAUSE THEY DO HAVE LOWER ENERGY
AND THEN THERE'S THEIR PENETRATION
AND THEN LAST BUT NOT LEAST,
THE GAMMAS MID TO HIGH ENERGY WITH DEEPER PENETRATION, RIGHT?
AND SO THEN THERE ARE THE GAMMAS RIGHT THERE,
NOTICE THAT WE WOULD TAKE 10 CENTIMETERS
OF LEAD TO STOP, OKAY?
SO THE GAMMAS HAVE, RIGHT,
THE GREATEST PENETRATION.
SO, IT'S IMPORTANT TO RECOGNIZE THE AMOUNT OF ENERGY.
AND THE PENETRATION ARE NOT NECESSARILY CORRELATED
WITH EACH OTHER AND YOU WANT TO KNOW
THE RELATIVE PENETRATION ABILITY OF EACH ONE.
NOW, LET'S LOOK AT HOW WE MEASURE RADIATION, SO,
AND I THINK WE'VE ALL HEARD OF THE GEIGER COUNTER,
OFFICIALLY CALLED THE GEIGER-MULLER COUNTER
AND BASICALLY THIS IS SIMILAR TO SOLUTION CHEMISTRY,
EXCEPT NOW OUR SOLVENT IS THE AIR
INSTEAD OF WATER OR A LIQUID.
ELECTRICITY IS CONDUCTED THROUGH GAS
THAT CONTAINS CHARGE PARTICLES.
SO REMEMBER THAT WE CALL THIS IONIZING RADIATION.
SO THE BETA, X-RAY,
AND GAMMA RAYS, RIGHT,
THEY CAN PENETRATE THIS WINDOW, OKAY.
AND REMEMBER, SO ALPHAS CAN'T, RIGHT,
SO A GEIGER IS NOT A GOOD WAY TO MEASURE ALPHAS
BECAUSE THE ALPHA PARTICLES WILL GET STOPPED IN THE WINDOW.
BUT THE BETA PARTICLES AND THE X-RAY AND THE GAMMA RAYS
WILL BE ABLE TO PENETRATE THROUGH THE WINDOW, RIGHT?
AND THEY'RE CALLED THE IONIZING RADIATION AND IONIZE THE GAS,
RIGHT, INSIDE THE METER
OR COUNTER, OKAY, CREATING AN ELECTRICAL CURRENT
OR-- SO CREATING IONS,
RIGHT, TO CARRY THE ELECTRICAL CURRENT.
SO INSIDE, RIGHT,
THERE'S THE GAS AND THEN THERE'S THE WIRE AND WE HAVE,
RIGHT, WE HAVE THE POSITIVELY CHARGED AND THEN
WE HAVE NEGATIVELY CHARGED AND SO,
AS THE IONIZING RADIATION COMES IN AND IONIZES THE GAS MOLECULES
AND THEN THESE MOVING IONS CAN CARRY ELECTRICAL CURRENT,
RIGHT, WHICH CREATES A SIGNAL ON OUR METER, RIGHT?
BECAUSE REMEMBER, MOVING IONS CARRY ELECTRICAL CURRENT.
AND WE SAW THIS IDEA RIGHT
WHEN WE LOOKED AT IONIC AND COVALENT COMPOUNDS THEN
WHEN WE DISSOLVE IONIC COMPOUNDS AND WATER,
WE CALL THEM ELECTROLYTES BECAUSE THEY CAN CARRY,
CONDUCT ELECTRICITY.
SO IT'S THE SAME IDEA
IN REMEMBERING THAT ALPHA PARTICLES,
RIGHT, NO ALPHA DETECTION, OKAY.
NOW, WE'LL LOOK AT ANOTHER FORM,
ANOTHER WAY TO MEASURE RADIATION EXPOSURE
AND THAT'S WHAT THE FILM BADGE OR A DOSIMETER
AND SO BASICALLY WHAT HAPPENS IS THE FILM BADGE,
THE FILM IS IN A CASE RIGHT?
SO THERE'S THE FILM AND THEN IT HAS A PROTECTIVE CASE,
OKAY, TO AVOID IT FROM LIGHT, ALL RIGHT?
BUT, RIGHT, THE EXPOSURE,
RIGHT, SO THE BETAS, THE X-RAYS,
AND THE GAMMA RAYS, RIGHT,
THEY CAN PENETRATE THROUGH THE PROTECTIVE CASE,
RIGHT, TO EXPOSE THE FILM.
SO WHAT HAPPENS WHEN PEOPLE WERE FILM BADGES IS LIKE ONCE A MONTH
YOU TRADE YOUR FILM BADGE OUT AND YOU GET A NEW FILM BADGE
AND SO THE DEGREE OF EXPOSURE
IS PROPORTIONAL TO THE AMOUNT OF RADIATION, OKAY.
AND THE SYMBOL HERE, RIGHT, PROPORTIONAL.
AND SO THEY'VE DEVELOPED A PROCEDURE
FOR CORRELATING THE AMOUNT OF EXPOSURE
TO THE AMOUNT OF RADIATION AND.
SO IF SOMEBODY'S EXPOSURE IS ABOVE THE RECOMMENDED LIMIT
THEN STEPS ARE TAKEN TO FIND OUT
WHERE THE EXPOSURE IS COMING FROM,
SOMETIMES IT JUST MEANS A SAMPLE HAS BEEN MISPLACED
OR SOME SHIELDING HAS BEEN LOST.
SO GET THAT TAKEN CARED OF.
NOW, LET'S LOOK AT THIS IN TERMS
OF HOW WE MEASURE IT WITH UNITS, RIGHT?
SO THERE ARE THREE MAIN THINGS TO CONSIDER,
ONE IS HOW MANY RADIOACTIVE EMISSIONS ARE OCCURRING?
DECAYS PER SECOND, ALSO CALLED DPS
AND A COMMON UNIT HERE IS CALLED THE CURIE, SYMBOLIZED, CI.
SO WE CAN DO A VERY LITERAL DEFINITION,
DECAYS PER SECOND OR WE'LL SEE BELOW,
WE HAVE THE UNIT CALLED THE CURIE
AND THAT'S RELATED TO HOW MANY RADIOACTIVE DECAYS ARE
OCCURRING PER UNIT TIME.
AND THEN WE COULD LOOK AT THE ABSORBED DOSE.
SO THAT'S THE ENERGY IN RADS ABSORBED
AND THEN OVER THE MASS OF TISSUE,
OKAY, AND SO THIS IS WE'RE WE'LL USE THE UNIT,
OOPS, RAD. OKAY.
NOW, RADS ARE VERY COMMON,
MAKE SURE THAT EVERYONE SEES THAT'S AN A,
RIGHT, SO THERE'S RAD.
THE THING ABOUT RADS THOUGH IS THEY DO NOT CONSIDER PENETRATION
AND SO WE'VE SEEN ON THE PREVIOUS PAGE,
RIGHT, THAT PENETRATION IS A BIG DEAL.
AND SO THEN THAT LED TO THIS LAST UNIT CALLED THE REM.
NOW, WE SAW THAT BEFORE, WE SAW THAT IN AN EARLIER TUTORIAL
WHEN WE WERE LOOKING AT OUR EXPOSURES
AND SO THIS WILL BE THE ABSORBED DOSE
BUT WE'RE GOING TO ADD A SECOND TERM,
RIGHT, PER MASSIVE TISSUE,
BECAUSE THIS IS A-- OKAY.
AND WHAT THIS IS FOR, THIS ALLOWS, RIGHT,
THIS IS THE ADJUSTMENT FOR PENETRATION. RIGHT.
SO BEING EXPOSED TO AN ALPHA EMITTER THAT'S FAR AWAY,
RIGHT, THERE IS VERSUS A GAMMA EMITTER.
SO THIS IS--
WE HAVE THIS Q FACTOR, ALL RIGHT.
SO, THE ABSORBED DOSE VERSUS THE EFFECTIVE DOSE.
SO REALLY, IF YOU WANT TO,
YOU COULD THINK OF IT AS THE EFFECTIVE DOSE
IS SIMPLY THE ABSORBED DOSE TIMES Q, RIGHT?
AND THIS ADJUST FOR PENETRATION, RIGHT,
THAT VARIES WITH RADIATION SOURCE PER RADIATION TYPE, OKAY.
SO, NOW LET'S DO AN EXAMPLE HERE
TO HELP YOU APPRECIATE THIS, ALL RIGHTY.
SO ONE RAD OF ALPHA, RIGHT,
CAUSES TWENTY TIMES THE DAMAGE OF ONE RAD OF GAMMA RAYS, RIGHT?
BECAUSE THEY HAVE--
IF WE WERE ACTUALLY TO INGEST A GAMMA SOURCE,
IT WOULD CAUSE A LOT MORE DAMAGE THAN-- EXCUSE ME,
IF WE WERE TO ABSORB AN ALPHA SOURCE INGESTED INTO OUR BODY,
IT WILL CAUSE US A LOT OF DAMAGE.
HOWEVER, A GAMMA SOURCE,
THAT BECAUSE IT CAN PENETRATE, IT CAN GO,
PENETRATE IN BUT IT COULD ALSO PENETRATE OUT,
SO WE WOULD ACTUALLY HAVE LESS DAMAGE INSIDE US.
WE WOULD BE CAUSING MORE DAMAGE
TO THE WORLD AROUND US BUT WE WOULD HAVE LESS DAMAGE.
WITH AN ALPHA SOURCE INSIDE US,
WE WOULD ABSORB ALL THE DAMAGE.
THAT'S THE PROBLEM WITH RADS COMPARING ALPHAS TO GAMMAS.
HOWEVER REM TAKES THAT INTO ACCOUNT.
SO ONE REM OF ALPHA CAUSES THE SAME DAMAGE
AS ONE REM OF GAMMA
AND THERE ARE A VARIETY OF UNITS OUT THERE,
SO I'VE GIVEN YOU A FEW BUT I
JUST LIKE FOR YOU TO BE EXPOSED TO ALL OF THEM.
SO THE AMOUNT OF RADIOACTIVE DECAY, RIGHT,
THAT'S THE DECAYS PER SECOND,
IT COULD ALSO BE A BECQUEREL
OR THE CURIE THAT WE'VE TALKED ABOUT,
SO ONE CURIE IS 3.7 TIMES 10 TO THE 10TH DECAYS PER SECOND.
THE ABSORBED DOSE, RIGHT,
REMEMBER THAT DOES NOT ALLOWED FOR PENETRATION DIFFERENCES
IS THE GRAY OR THE RAD RADIATION ABSORBED DOSE.
AND THEN THE LAST ONE IS THE EFFECTIVE DOSE WHERE WE DO
ALLOW FOR THE DIFFERENT PENETRATION CAPACITIES.
AND THERE'S THE SIEVERT OR THE REM
THE ROENTGEN EQUIVALENT TO MAN, ALL RIGHT.
AND SO, NOW TO PUT THIS ALL INTO CONTEXT,
LET'S LOOK AT THE HEALTH EFFECTS OF IONIZING RADIATION
AND WHAT WE CAN SEE IS THAT IT'S GOING TO DEPEND ON THE INTENSITY
OF ENERGY AND THE LENGTH OF EXPOSURE AND THEN OF COURSE
WHETHER THE RADIATION SOURCE IS INSIDE OR OUTSIDE OUR BODY.
SO TO MEASURE THESE KIND OF EFFECTS,
WE USE SOMETHING CALLED THE LD
AND THEN WE PUT A PERCENT HERE, RIGHT?
SO THE LD IS THE LETHAL DOSE, RIGHT, TO KILL,
RIGHT, THIS X PERCENT OF POPULATION, ALL RIGHT.
SO, OKAY.
LET'S LOOK AT WHAT HAPPENS WITH RADIATION,
THE FIRST THING--
SO WHAT WE'RE GOING TO DO
IS WE'RE GOING TO LOOK AT ACUTE, RIGHT?
SO THIS IS A ONE-TIME HIGH EXPOSURE VERSUS CHRONIC
WHERE WE HAVE A MANY SMALL EXPOSURES OVER TIME, OKAY.
SO, WE CAN SEE IF WE HAVE AN ACUTE EXPOSURE AND THE .05
TO 0.2 EFFECTIVE DOSE OF SIEVERTS, NO PROBLEM.
IF THAT RISES UP,
WE SEE THAT WE START TO GET US A DECREASE
IN OUR WHITE BLOOD CELL COUNT AND WE MAY GET A HEADACHE
OR BE MORE SUSCEPTIBLE TO INFECTION.
AS THE DOSAGE STARTS TO GO UP ABOVE ONE SIEVERT,
WE SEE THAT PEOPLE OR INDIVIDUALS
IN THE POPULATION WILL START TO DIE 10%.
THERE'LL BE NAUSEA, HAIR LOSS, FATIGUE,
CONTINUED WHITE BLOOD CELL LOSS
AND FROM THEN TEMPORARY STERILITY.
AS THE DOSE GOES HIGHER AND HIGHER,
WE CAN SEE THAT THE AMOUNT OF MEMBERS OF THE POPULATION,
A HIGHER AND HIGHER GROUP DIES,
PERCENTAGE DIES AND THE SYMPTOMS BECOME MUCH MORE SEVERE.
IF WE GET ABOVE ON EFFECTIVE DOSE OF 10 SIEVERTS,
THEN BASICALLY THE ENTIRE POPULATION IS DEAD IN 14 DAYS,
DEFINITELY SOMETHING TO RESPECT ABOUT RADIATION.
WITH THE CHRONIC EXPOSURE,
BASICALLY WHAT HAPPENS IS WE END UP
WITH GENETIC MUTATIONS THAT CAN LEAD TO CANCER.
ALL RIGHTY.
AND THEN SO WHAT DO WE DO TO MINIMIZE OUR EXPOSURE,
SHIELDING, RIGHT?
NOTICE LEAD APRONS
WHEN WE GO TO GET A DENTAL X-RAY OR THINGS, RIGHT?
LEAD IS A GREAT STOPPER.
IT CAN STOP X-RAYS
WE WOULD NEED 10 CENTIMETERS TO STOP GAMMA BUT,
SHIELDING IS AN IMPORTANT WAY AND THEN DISTANCE,
THE INTENSITY IS INVERSELY PROPORTIONAL
TO THE SQUARE OF THE DISTANCE.
SO WHAT DOES THAT MEAN?
THAT MEANS, RIGHT,
THAT IF WE DOUBLE OUR DISTANCE AWAY FROM A SOURCE,
RIGHT, FROM A RADIOACTIVE SOURCE,
THEN OUR EXPOSURE IS ONE-FOURTH, RIGHT?
THEN WHAT HAPPENS?
THEN WE DECREASE OUR EXPOSURE, RIGHT?
SO IT'S A SQUARE
BY ONE OVER TWO SQUARED OR ONE-FOURTH, RIGHT?
SO EACH TIME WE DOUBLE OUR DISTANCE,
WE REDUCED THE DOSAGE
THAT WE ARE EXPOSED TO BY ONE QUARTER, RIGHT?
SO, ANYTIME WE'RE IN A PRESENCE OF A RADIOACTIVE SUBSTANCE,
WE CAN USE LEAD APRONS AND DISTANCE TO PROTECT US.
ALL RIGHTY.
SO, THAT CONCLUDES OUR TUTORIAL ON THE BIOLOGICAL EFFECTS
OF IONIZING RADIATION AND HOW WE ENDED UP
WITH SO MANY DIFFERENT TYPES OF UNITS TO DESCRIBE THE RADIATION,
WHETHER IT'S SIMPLY HOW MANY DECAYS ARE OCCURRING,
WHAT THE OVERALL ENERGY IS OR THE REM,
WHAT'S THE ACTUAL HEALTH CONSEQUENCE
SO WE CAN COMPARE ALPHAS TO GAMMAS AND THAT SORT OF THING.
PLEASE TAKE SOME TIME NOW TO REINFORCE YOUR UNDERSTANDING
WITH SOME HOMEWORK QUESTIONS.