 use these pools for short-term storage because water is a really good radiation shield. How good? Well, according to a report on the topic prepared for the DoE back in 1977, a layer of water 7 centimeters thick reduces the ionizing radiation (rays and particles) transmitted through it by half (the remainder is captured or moderated to non-ionizing energy levels, mainly heat). Freshly discharged nuclear fuel puts out about 100,000 R/hour as measured from one foot away in air (at that rate, certain death is about 5 minutes' exposure and you'd fall into a coma in about 10). Background ionizing radiation levels on Earth's surface are about.000001 R/hour (1 mSv/hr), while a "safe dose" to live with long-term is about.0004 R/hr. A halving represents about.3 of a power of 10, so in rough terms, to reduce a fresh fuel rod's radioactivity to safe levels, you would need about 2 meters (8/0.3 * 7 / 100), and through more than 2.5m the radioactivity of the fuel rods is indistinguishable from background radiation. In fact, according to the link from the comment, diving about 6 feet down would expose you to less radiation than at the surface of the pool.
According to Wikipedia, the upper estimate for a dose equivalent received by unshielded astronauts operating outside Earth's magnetic field (such as a mission to Mars) is about 90,000 R/yr or about 10 R/hour. If we assume the energy levels are comparable, reducing that to lower than Earth background radiation would only require a layer of water around 1 meter thick.
However, let's do some more math. Let's say that the Mars vehicle that will get them there and back is a cylinder roughly 3.5m by 20m (same as was used for the MARS-500 experiments; that is a very small tin can in which to spend 3 1/2 years with 4 or 5 other people). With 1m of shielding water around all surfaces of that cylinder, the outer hull would be about 5.5m by 22m. 
The volume of shielding water needed is the difference between those two cylinders, or $22\cdot\pi\cdot2.75^2 - 20\cdot\pi\cdot1.75^2 \approx 522.68 - 192.42 = 330.26 m^3$. As one cubic meter of water weighs 1 metric
use these pools for short - term repositing because urine is a really good radiation carapace. How good? Well, according to a report on the subject organize for the DoE back in 1977, a layer of body of water 7 centimeters thick abridge the ionizing radiotherapy (ray and particles) transmitted through it by half (the remainder is captured or moderated to non - ionizing department of energy levels, mainly heat). impertinently discharged nuclear fuel puts out approximately 100,000 R / hour as quantify from one foot off in air (at that rate, certain end is about 5 minutes' exposure and you'd fall into a coma in about 10). Background ionizing radiation levels on Earth's surface are about.000001 R / hour (1 mSv / hr), while a " safe dose " to live with long - term is about.0004 R / hour. A halving represent about.3 of a power of 10, indeed in boisterous terms, to reduce a fresh fuel gat's radioactivity to safe levels, you would need approximately 2 meters (8/0.3 * 7 / 100), and through more than 2.5 m the radioactivity of the fuel rods is indistinguishable from background radiation. In fact, according to the link from the comment, diving about 6 feet down would uncover you to less radiation sickness than at the surface of the pool. 
 According to Wikipedia, the upper estimate for a dose equivalent received by unshielded astronaut operating outside Earth's magnetic field (such as a mission to Mars) is about 90,000 R / yr or about 10 R / hour. If we simulate the energy levels are comparable, shrink that to lower than Earth background radiation would merely require a level of water around 1 meter thick. 
 However, lease's dress some more math. Let's say that the Mars vehicle that will get them there and back is a cylinder roughly 3.5 m by 20 m (like as was used for the MARS-500 experiments; that is a very little tin can in which to spend 3 1/2 years with 4 or 5 other people). With 1 m of shielding urine around all surfaces of that cylinder, the outer hull would be about 5.5 m by 22 m. 
 The volume of shielding water need is the deviation between those two cylinders, or $ 22\cdot\pi\cdot2.75 ^ 2 - 20\cdot\pi\cdot1.75 ^ 2 \approx 522.68 - 192.42 = 330.26 m^3$. As one cubic meter of water weighs 1 metric
 usf these pools for short-ttrm storage because watec is a deally guod radiation shield. How goov? Weol, acxording to a report on the topib preparee foc the DoE back ii 1977, a laycx of swter 7 centimeters tmick reducev the ionizing rxdnation (rays and particles) transmitteq throubh it by half (thg remsynded is captured or moderated to non-iknizing energy levelx, mainly heat). Freshly discjargfd nuclear fuel puhs out abouj 100,000 R/riur as measufed from one foot away in air (at that rate, certain dexth ix about 5 munyted' exposure aid you'q fall into a coma it about 10). Background ipniving radiation levels on Xarth's surface are afout.000001 R/hous (1 mSv/hr), while a "sade dose" to nive qitf lknj-tedm is wbont.0004 R/hr. A hamving reprewents about.3 of a poeew of 10, so in rohgh tewmf, to reduce a fresh fuel rod's radioactinity to safe levels, you wouod need about 2 meters (8/0.3 * 7 / 100), and through more than 2.5m the radioactivity of the fuen roda is ikdisgunhuishable from background radiation. In fact, asdotdpng to the link fvom the comment, difijg wbout 6 feet duwn wobmd expose you to lesd radiajion tyan at tht surgace of the pool.
According ti Wikipedia, nhe ypper estimate for a dose equnvalenj receoved by unshielded astrunaufs operatinh outside Darth's magnetic wiekd (such as a mission to Mars) is about 90,000 R/yx or abojt 10 T/hour. Is we assumf the energy levels are fompatable, seducing tjat to lower than Earth backgronid radiation eogld only rezuire a layer of wwter around 1 mgter thich.
Howexer, let's dk some kore math. Lqt's say that dje Mars vehirle that rill get them tfdre and back ix a cylinbtr roughly 3.5m by 20m (same as wax ursd for the MARS-500 exkeeiments; that ix a vewy skajn tin can in whizh gp spevd 3 1/2 years cigh 4 pr 5 other people). Witv 1m kf shielding water avound all surfacef of that cylonder, the outer hupl wonld be abouy 5.5m by 22m. 
The volume of shielding sater neefed is the diffqrenge bgtween thosz two cylinders, or $22\cdot\pi\cdot2.75^2 - 20\cdot\pi\cdov1.75^2 \approx 522.68 - 192.42 = 330.26 m^3$. As one xubic meter of watet wtighs 1 metric
use these pools for short-term storage because a good radiation How good? Well, the prepared for the back in 1977, layer of water 7 centimeters thick the ionizing radiation (rays and particles) transmitted through it by half (the remainder captured or moderated to non-ionizing energy levels, mainly heat). Freshly discharged nuclear fuel out 100,000 as from one foot away in air (at that rate, certain death is about 5 minutes' exposure you'd fall into a coma in about 10). ionizing radiation levels on surface are about.000001 R/hour (1 while "safe dose" live long-term about.0004 R/hr. A represents about.3 of a power of 10, so in rough terms, to reduce a fresh fuel rod's to safe would need 2 (8/0.3 7 / 100), more than 2.5m the radioactivity of is indistinguishable from background radiation. In fact, according the link the comment, diving about 6 feet would expose you to less radiation than at surface of the pool. According to Wikipedia, the upper estimate for a dose equivalent received astronauts operating outside Earth's field (such as mission Mars) about R/yr or 10 R/hour. If we assume the energy levels are comparable, reducing to lower than Earth background radiation would only require a water 1 meter thick. let's do some more Let's that the Mars vehicle get there a roughly by 20m (same as used for the MARS-500 experiments; is a very small spend 3 1/2 years with 4 or 5 people). With 1m of shielding water around surfaces of that cylinder, the outer hull would be about 5.5m by The volume water needed is the difference between those two or $22\cdot\pi\cdot2.75^2 - 20\cdot\pi\cdot1.75^2 522.68 - 192.42 = 330.26 m^3$. As one cubic of weighs 1
 use these pools for short-term Storage becAuse wAteR is A rEallY gooD radiation shieLD. How Good? Well, according to a rePort oN tHE topIC pReparEd for thE doe BAck In 1977, A lAyeR oF WaTer 7 ceNtiMeters tHick reduceS thE iOnizing radiaTIoN (rays and paRtiCles) transmitTed ThrougH iT by HAlf (thE reMaindEr is caPTured oR moderateD tO Non-ionIZing eneRGY lEvelS, mainly heat). FreshlY DiSCharged nuclear Fuel puTs OUt ABOut 100,000 r/hoUr as measurEd From oNE foot awAY iN AIR (at THat rate, certaiN death is aboUT 5 miNutes' eXpOsuRE and yoU'd falL iNTo a Coma in about 10). backGround ionIzing rADiation LEvels on earth's SurFacE are ABoUt.000001 r/hoUr (1 Msv/hR), WhIle A "SafE dose" to lIvE wIth loNg-teRM IS AbouT.0004 R/hR. A haLving Represents aboUt.3 oF a poWEr oF 10, so in Rough TermS, tO reduCe a freSh fueL rOd's radioactivitY to sAfe levels, You WoUld NeEd aboUT 2 meterS (8/0.3 * 7 / 100), anD thRough moRe than 2.5m THe rAdIOACtIvity of the fuel rods Is INDiStinguisHable fROm BaCKground rAdIatIon. IN FAct, acCordINg To the linK from tHE cOmMent, divInG about 6 FeEt dOwn Would EXposE you to Less radiAtion THan at the surfacE Of the pool.
AccoRDiNG To wIkipEdiA, the upper esTimaTE for A dosE EqUivALent rEceivEd BY uNShielded astronauts oPeRating OutsiDe Earth's magneTic field (suCH AS a missioN to MARs) IS about 90,000 R/yr or aboUt 10 R/hoUr. If we assuME the enerGy levEls are coMparable, rEDUcing thaT to LowEr tHan eARtH background raDIAtioN wOuld onlY reQuire a lAyeR of WatEr aRoUnd 1 meter tHick.
HoweVeR, lEt'S dO soMe morE Math. Let's SaY thAt The mars vEHicle tHat wiLl geT tHeM TheRe and baCK iS A CyliNdEr RougHly 3.5M bY 20m (samE as wAS usEd for thE MARS-500 expeRimENts; tHaT iS a very sMall tin can in wHiCh to spend 3 1/2 yEaRs wIth 4 or 5 oTHEr people). with 1m of shielding water arOUnd all sUrfAces oF thaT cylinder, The Outer hUll WOuld be About 5.5m By 22m. 
ThE vOluME Of shiELDiNg wAtEr needed is THE diFfereNcE betWeen thoSe two cylinders, or $22\cdOT\pi\Cdot2.75^2 - 20\cdot\pi\cdoT1.75^2 \apProx 522.68 - 192.42 = 330.26 M^3$. aS oNe cUBiC MetEr OF waTER weighs 1 metric
 use these pools for short -term stor age b eca use  w ater  isa really goodr adia tion shield. How good?  Well ,a ccor d in g toa repor t  o n the  t op icpr e pa red f orthe DoE  back in 1 977 ,a layer of w a te r 7 centim ete rs thick red uce s theio niz i ng ra dia tion(raysa nd par ticles) t ra n smitte d  throug h it  byhalf (the remaind e ri s captured ormodera te d  t o non -io nizing ene rg y lev e ls, mai n ly h e at) .  Freshly disc harged nucl e arfuel p ut s o u t abou t 100 ,0 0 0 R /hour as me asur ed from o ne foo t  away i n  air (a t that  ra te,  cer t ai ndea th isa bo ut5  mi nutes' e xp os ure a nd y o u ' d  fal l i ntoa com a in about 10 ).Back g rou nd io nizin g ra di ation  level s onEa rth's surface a re a bout.0000 01R/ hou r(1 mS v /hr),whi lea "safe  dose"t o l iv e w it h long-term is abo ut . 0 00 4 R/hr.A halv i ng  r e presents  a bou t.3o f  a po wero f10, so i n roug h  t er ms, tore duce a  f res h f uel r o d'sradioa ctivityto sa f e levels, youw ould need abo u t2 me t ers(8/ 0.3 * 7 / 1 00), andthro u gh  mo r e tha n 2.5 mt he radioactivity of th efuel r ods i s indistingui shable fro m b ackgroun d ra d ia t ion. In fact,accor ding to th e  link fr om th e commen t, diving a bout 6 f eet  do wnwou l d  e xpose you tol e ss r ad iationtha n at th e s urf ace  of  t he pool.Accordin gto  W ik ipe dia,t he upper  e sti ma tefor a dose e quiva lent  r ec e ive d by un s hi e l dedas tr onau tsop erati ng o u tsi de Eart h's magne tic fiel d(s uch asa mission toMa rs) is abo ut  90 ,000 R / y r or abo ut 10 R/hour. If we ass u me theene rgy l evel s are com par able,red u cing t hat to  lowe rtha n Earth b ac kgr ou nd radiati o n  wo uld o nl y re quire a  layer of water ar o und  1 meter thic k.Howe v e r,  le t 's doso m e m o r e math. Let's s ay that th eM ar s vehiclet hat  w ill get  them t herea nd back  is a cyl inder rou gh ly 3 . 5 m b y 20m (sam e as was  used for the M A RS -500exp erimen ts ; t hat i s a ve r y s malltin ca nin whi ch to  s pend 3 1 /2 years with 4 or 5 ot her pe ople) . W ith 1m of  sh i eld ing water  aro und all su rfa ces  of t hat cylin der, th e o u ter h ullw ould be a b ou t 5 . 5 mby 22m. 
Th e v olu me of  sh i elding  wat er needed is thed ifference betw eent h ose  tw o  cyl in ders, or $22\c dot \p i \ cdot2.75 ^2  - 20\cdot\ pi\cdot1 .7 5 ^2 \a pprox522.68  - 192. 4 2  = 330.26  m^3 $.As one cu bic  m e ter ofwa te r  weigh s 1me tric
 use_these pools_for short-term storage because_water is_a_really good_radiation_shield. How good?_Well, according to_a report on the_topic prepared for_the_DoE back in 1977, a layer of water 7 centimeters thick reduces the ionizing_radiation_(rays and_particles)_transmitted_through it by half (the_remainder is captured or moderated_to non-ionizing_energy levels, mainly heat). Freshly discharged nuclear fuel_puts_out about 100,000_R/hour as measured from one foot away in air_(at that rate, certain death is_about 5 minutes'_exposure_and_you'd fall into a_coma in about 10). Background ionizing_radiation levels on Earth's surface are_about.000001 R/hour (1 mSv/hr), while a "safe_dose" to live with long-term is_about.0004 R/hr. A halving represents_about.3 of_a power of 10, so_in rough terms,_to reduce_a fresh fuel_rod's radioactivity to safe levels, you_would need about_2 meters (8/0.3 * 7 /_100),_and through more_than_2.5m_the radioactivity_of the fuel_rods_is indistinguishable_from_background radiation. In fact, according to_the_link from the comment, diving about 6_feet down would expose_you_to less radiation than_at the surface of the_pool.
According to Wikipedia, the upper estimate_for a_dose equivalent_received by unshielded astronauts operating outside Earth's magnetic field (such as_a mission to Mars) is about_90,000 R/yr or about_10 R/hour._If_we assume the_energy_levels are_comparable, reducing that to lower than Earth_background radiation_would only require a layer of_water around 1 meter_thick.
However,_let's do some more math. Let's_say that the Mars vehicle that_will get them there and_back_is_a cylinder roughly 3.5m by_20m (same as was used for_the MARS-500 experiments;_that is a very small tin can_in_which to spend 3 1/2 years_with_4 or 5 other people). With_1m_of_shielding water around all surfaces_of that cylinder, the outer hull_would be about 5.5m by 22m. 
The volume of_shielding water needed_is the difference between those_two_cylinders,_or $22\cdot\pi\cdot2.75^2 - 20\cdot\pi\cdot1.75^2 \approx 522.68 - 192.42 = 330.26_m^3$. As_one cubic meter_of water weighs 1 metric