orum discussions<\/a> have been going on about it. The other peculiar thing is the activity levels, the activity per cm\u00b3 is just crazily high. I suspect they are really measuring activity per liter and mistakenly report it as cubic centimeter and I will give 2 arguments for that.<\/p>\n1. The activity of the water<\/strong>
\nThey reported that 3 workers had been working in the water for more than an hour, their dosimeters showed a dosage close to 200 mSv and two of the workers didn’t wear rubber boots so they got a large surface dose on their ankles and feet from beta radiation(some reports say up to 6 gray). But this does not match with the activity levels seen in the table I pasted above. If one multiplies the activity in Bq\/cm\u00b3 with the Q value, i.e the energy released in the decay of one atom, and massage the numbers a bit to get the numbers in joules instead of keV and in cubic meters instead of cubic centimeters. Then one finds that the water is putting out 1.68 Watts per cubic meter of water. Something like 20% of that energy is from gamma rays, the rest is beta rays and recoil energy in the decaying nuclei.<\/p>\n1.68 Watts doesn’t sound like a lot given that a normal water kettle can have a power of 1000 W. But in terms of ionizing radiation 1.68 W is just crazy. Radiation dose is measured in Grays, one Gray is equal to one joule absorbed by one kg of tissue and a Watt is as we know one Joule per second. A one Gray whole body dosage is enough to get radiation sickness, 10 Grays will kill you slowly(over a few days) and 100 Grays kills you instantly.<\/p>\n
These workers where working in water that is putting out watts of radiation, that means they should have gotten hundreds of Grays in an hour. It was stated they where knee deep in this water! Now if we instead consider that perhaps they mean activity per liter, misstakenly reported as cubic centimeters, then everything goes down by a factor of 1000(there are one thousand cubic centimeters in a liter). Instead of hundreds of Gray the workers would have gotten hundres of milligray, that is consistent with their dosimeter readings.<\/p>\n
2. The neutron flux needed to create Cl-38<\/strong>
\nThe probability that a Cl-37 atom will absorb a neutron and turn into Cl-38 is quite low, 1 barn(this probability is measured in a unit called barns, one barn=10^-24 cm\u00b2, uranium has as comparison a fission probability of \u00a0about 600 barns). So one needs a lot of neutrons to create any significant quantity of Cl-38. If one assumes the water concentration of Cl-38 has dropped by a factor 1000 when traveling from the reactor vessel to the water in the turbine hall basement(dilution, decay etc). \u00a0Then one can make a rough approximation of the neutron flux needed in the core in order to create the Cl-38 concentration seen in the turbine hall(technically solving the Bateman equation for a equilibrium case with one group cross sections).<\/p>\nNeutron flux ends up being around 10\u00b9\u00b2\u00a0\u00a0neutrons per square centimeter and second. A reactor running at full power produces on the order of 10^14 n\/cm\u00b2*s. The core would have to be running at about 1% of its full power(10-20 MW thermal) to produce that flux, but I might as well be off by a factor of 10 in my estimate of dilution, which would put the power in the rage from 1-100 MW. We can exclude 100 MW since we have not seen a pressure and temperature spike that high in reactor number 1. We can not exclude 1-10 MW power levels because it is on the same order as the decay energy. But if we also again here assume they mean Bq\/liter instead of Bq\/cm\u00b3 then the needed flux to produce the Cl-38 goes down to something around 1*10^9 neutrons\/cm\u00b2*s. That kind of neutron flux could plausibly be around from radioactive decay or a very very low power level.<\/p>\n
Those 2 factors\u00a0together\u00a0makes me believe they are reporting activity levels wrongly. Lets see if I will have to change my opinion when new information arrives.<\/p>\n
Notes for the interested.<\/strong><\/p>\nTo convert from the unit eV(electron volt) to joule one multiplies 1 eV with 1.602*10^-19 <\/em><\/p>\nThe Bateman equation describes the time dependent concentration of radionuclides. For the case of a nuclide created by a neutron flux and destroyed by decay one gets this equation<\/em><\/p>\ndN\/dT= N_37*sigma_37*flux – N_38*lambda_38<\/em>
\nWhere: <\/em>
\nN_37=number of Cl37 atoms per cubic centimeter(I assumed saturated salt water at 100 degres, which gives 0.39 grams of salt per cm\u00b2 which gives 9,74*10^20 Cl37 atoms per cm\u00b3)<\/em>
\nsigma_37=neutron capture cross section, around 1*10^-24 cm\u00b2<\/em>
\nflux=neutron flux in neutrons per cm\u00b2 and second<\/em>
\nN_38= Number of Cl-38 atoms per cm\u00b3. <\/em>
\nlambda_38 = decay constant for Cl-38(equals to Ln(2)\/half life)<\/em><\/p>\nIf one assumes equilibrium then dN\/dT=0 and one gets that<\/em><\/p>\nflux=N_38*lambda_38\/(N_37*sigma_37)<\/em><\/p>\nOne get N_38 from dividing activity with decay constant and then multiplying by a dilution factor.
\nHere are all the numbers I plugged in in case someone can spot an error.<\/em><\/p>\n\n\n\n\n\n\n\n<\/colgroup>\n\n\nFind flux<\/span><\/strong><\/td>\n<\/tr>\n\n| \u00a0<\/td>\n | \u00a0<\/td>\n | \u00a0<\/td>\n | \u00a0<\/td>\n | \u00a0<\/td>\n | \u00a0<\/td>\n<\/tr>\n | \n| Avogadros number<\/td>\n | 6,02E+023<\/td>\n | \u00a0<\/td>\n | \u00a0<\/td>\n | \u00a0<\/td>\n | \u00a0<\/td>\n<\/tr>\n | \n| Salt density(gram per cm3)<\/td>\n | 3,90E-001<\/td>\n | \u00a0<\/td>\n | \u00a0<\/td>\n | Dilution factor(from vessel to puddle)<\/td>\n | 1000<\/td>\n<\/tr>\n | \n| Molar mass sodium<\/td>\n | 2,30E+001<\/td>\n | \u00a0<\/td>\n | \u00a0<\/td>\n | Cl37 capture cross section<\/td>\n | 1,00E-024<\/td>\n<\/tr>\n | \n| Molar mass chlorine<\/td>\n | 3,55E+001<\/td>\n | \u00a0<\/td>\n | \u00a0<\/td>\n | Cl37 number density (per cm\u00b3)<\/td>\n | 9,74E+020<\/td>\n<\/tr>\n | \n| Moles of NaCl<\/td>\n | 6,67E-003<\/td>\n | \u00a0<\/td>\n | \u00a0<\/td>\n | Cl38 lambda<\/td>\n | 3,10E-004<\/td>\n<\/tr>\n | \n| Fraction Cl-37<\/td>\n | 2,42E-001<\/td>\n | \u00a0<\/td>\n | \u00a0<\/td>\n | Cl38 number density (per cm\u00b3)<\/td>\n | 5,16E+009<\/td>\n<\/tr>\n | \n| Moles Cl-37<\/td>\n | 1,62E-003<\/td>\n | \u00a0<\/td>\n | \u00a0<\/td>\n | \u00a0<\/td>\n | \u00a0<\/td>\n<\/tr>\n | \n| Number of Cl-37 per cm\u00b3<\/td>\n | 9,74E+020<\/td>\n | \u00a0<\/td>\n | \u00a0<\/td>\n | Flux<\/strong><\/td>\n| 1,64E+012<\/strong><\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n \u00a0<\/p>\n Links(english)<\/p>\n Kyodo News\u00a0Woes deepen over radioactive waters at nuke plant, sea contamination<\/a>
\nReuters\u00a0Soaring radioactivity deals blow to Japan\u2019s plant<\/a>
\nBBC\u00a0Radiation soars at japan reactor<\/a>
\nNHK\u00a0extreme radiation detected at number 2 reactor<\/a><\/p>\nLinks(swedish):
\nDN\u00a0Arbetare evakueras efter akut str\u00e5lning<\/a>
\nSvD\u00a0Fler svenskar misstror k\u00e4rnkraft<\/a>
\nSVD\u00a0Nya bakslag vid Fukushima<\/a>
\nAftonbladet\u00a0tio miljoner g\u00e5nger h\u00f6gre str\u00e5lning<\/a>
\nR\u00f6da berget<\/a>
\nJinge<\/a>
\nIn your face<\/a>
\nKunskapssamh\u00e4llet<\/a>
\nSvensson<\/a><\/p>\n","protected":false},"excerpt":{"rendered":"Two days ago we first got the report that there is highly radioactive water in the turbine building basement of reactor 1. NISA released this…<\/p>\n Continue readingRegarding the contaminated water in turbine buildings<\/span><\/a><\/div>\n","protected":false},"author":2,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[433,1],"tags":[484,690,434,487,246,486,435],"_links":{"self":[{"href":"https:\/\/nuclearpoweryesplease.org\/blog\/wp-json\/wp\/v2\/posts\/2130"}],"collection":[{"href":"https:\/\/nuclearpoweryesplease.org\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/nuclearpoweryesplease.org\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/nuclearpoweryesplease.org\/blog\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/nuclearpoweryesplease.org\/blog\/wp-json\/wp\/v2\/comments?post=2130"}],"version-history":[{"count":12,"href":"https:\/\/nuclearpoweryesplease.org\/blog\/wp-json\/wp\/v2\/posts\/2130\/revisions"}],"predecessor-version":[{"id":2135,"href":"https:\/\/nuclearpoweryesplease.org\/blog\/wp-json\/wp\/v2\/posts\/2130\/revisions\/2135"}],"wp:attachment":[{"href":"https:\/\/nuclearpoweryesplease.org\/blog\/wp-json\/wp\/v2\/media?parent=2130"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/nuclearpoweryesplease.org\/blog\/wp-json\/wp\/v2\/categories?post=2130"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/nuclearpoweryesplease.org\/blog\/wp-json\/wp\/v2\/tags?post=2130"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}} | | |