֩σʔλχϡʔεɼNo.126 (2020)ʮ৽ത࢜஀ੜʯࢲͷֶҐ࿦จͱӃੜੜ‫ײࡶ׆‬
North Carolina State Univ.ʢ‫۝ݩ‬େʣ
Postdoctoral Researcher, Nuclear Reactor Program
Department of Nuclear EngineeringཥɹԸஐelee23@ncsu.edu

1. ͸͡Ίʹࢲ͸ɺ2014 ೥ 4 ݄ΑΓ‫۝‬भେֶେֶӃ޻ֶ෎ΤωϧΪʔྔࢠ޻ֶઐ߈ʹॴଐ͠ɺ2019 ೥9 ݄ʹ޻ֶതֶ࢜ҐΛऔಘ͠·ͨ͠ɻ‫ࡏݱ‬͸ɺϙευΫ‫ڀݚ‬һͱͯ͠ North Carolina State େֶʹ‫ۈ‬຿͍ͯ͠·͢ɻֶ෦࣌୅ΑΓ‫ͳʹऀڀݚ‬Δ͜ͱΛ໨ࢦ͠ɺਂֶ͘ͼ͍ͨͱߟ͑ɺେ‫౓ڧ‬ɾߴΤωϧΪʔՃ଎‫ڀݚث‬ͷઌਐࠃͰ͋Δ೔ຊͷେֶ΁ਐֶ͢ΔࣄΛܾஅ͠·ͨ͠ɻ͜ͷ 5 ೥൒ͷཹֶͰɺ஌‫͕޿͕ݟ‬ΓɺࢲͷເʹҰา͍ۙͮͨͱࢥ͍·͢ɻੴ‫( ࣨڀݚڮ‬2014∼2016 ೥) ΍લാ‫ࣨڀݚ‬(2016∼2019 ೥) ʹॴଐ͍ͯͨ͠ 5 ೥൒͸‫ڀݚ‬΍࣮‫ݧ‬ͷΈͳΒͣɺ೔ຊͰͷָ͍͠೔ৗੜ‫׆‬ͷ‫ݧܦ‬Λ͢Δ͜ͱ͕ग़དྷ·ͨ͠ɻࠓճ͸ɺ೤৺ʹऔΓ૊Μͩ‫ڀݚ‬΍Ӄੜੜ‫Ͳͳ׆‬Λ·ͱΊΔͱͱ΋ʹɺΞϝϦΧͷ฻Β͠Λ‫ؚ‬Ίͯ‫ࡏݱ‬ͷ‫׆ڀݚ‬ಈͷ֓ཁΛ঺հͯ͠Έ͍ͨͱࢥ͍·͢ɻ·ͣ࠷ॳʹɺ1. തֶ࢜Ґ࿦จͷτϐοΫʹ͍͓ͭͯ࿩͍ͨ͠ͱࢥ͍·͢ɻത࿦͸ɺ์ࣹઢ෺ཧ‫ܭ‬ଌͷཱ৔͔ΒߴΤωϧΪʔதੑࢠͷ҆શར༻Λ֬อ͢Δ‫ڀݚ‬ͷҰ‫ͯ͠ͱ؀‬ɺߴΤωϧΪʔதੑࢠͷःณઃ‫͓ܭ‬ΑͼධՁͷߴ౓ԽΛ໨ࢦ͠·ͨ͠ɻա‫ൃʹڈ‬ද͞Εͨؔ࿈࿦จͷௐࠪΛߦ͍ɺղܾ͢΂͖໰୊Λநग़͢Δͱͱ΋ʹɺःณମதͷதੑࢠͷ‫ڍ‬ಈΛ࠶‫͢ݱ‬ΔͨΊͷ์ࣹઢղੳγϛϡϨʔγϣϯͷਫ਼౓‫ؔ͢ʹ্޲ূݕ‬Δ‫ڀݚ‬੒ՌΛऔΓవΊͨ΋ͷͰ͢ɻଓ͍ͯɺ2. Ӄੜੜ‫׆‬ͷதͰ‫ͨ͡ײ‬ʮ͋Ε͜ΕʯΛड़΂·͢ɻ࠷‫ʹޙ‬͸ɺ3. ‫ࡏݱ‬ͷ‫׆ڀݚ‬ಈͷ֓ཁͱ 4. ऴΘΓΛ‫͢·͍ࢥͱ͍ͨ͠ه‬ɻ

2. തֶ࢜Ґ࿦จͷτϐοΫ
2.1 ߴΤωϧΪʔՃ଎‫ث‬ͷःณઃ‫ܭ‬ͷͨΊͷίϯΫϦʔτͱ߯మͷதੑࢠ‫ݮ‬ਰʹؔ͢Δ‫ڀݚ‬ߴΤωϧΪʔ์ࣹઢরࣹ৔Ͱ͸ҟͳΔΤωϧΪʔͷ༷ʑͳछྨͷ์ࣹઢ͕ଘࡏ͢ΔɻಛʹɺߴΤωϧΪʔͷඇՙిཻࢠ (E ʼ 20 MeV ͷதੑࢠ) ͸ःณମΛ௨ա͠΍͍ͨ͢Ί [1]ɺதੑ

– 25 –ࢠͷःณઃ‫ͼٴܭ‬ઢྔධՁ͕ॏཁͰ͋ΔɻߴΤωϧΪʔՃ଎‫ࢪث‬ઃͷ҆શઃ‫ܭ‬ͷͨΊʹ͸ɺϏʔϜͷিಥ఺෇ۙͰ֩൓ԠʹΑͬͯੜ੒͞ΕͨߴΤωϧΪʔதੑࢠͷΤωϧΪʔεϖΫτϧ΍શதੑࢠൃੜྔͷσʔλ͕ඞਢͱͳΔɻੈքͰ͸‫ʹط‬ɺ์ࣹઢͷੜ੒ɺ૬‫༻࡞ޓ‬ͷ෺ཧϞσϧͱཻࢠ༌ૹΛѻ͏ͨΊͷ༷ʑͳγϛϡϨʔγϣϯ͕࢖༻͞Ε͍ͯΔɻ͔͠͠ɺγϛϡϨʔγϣϯʹΑͬͯதੑࢠൃੜྔ΍์ࣹઢྔ͕ҟͳΔͨΊʹγϛϡϨʔγϣϯͷ༧ଌਫ਼౓‫ݕ‬ূ͕ඞཁͰ͋ΔɻGeV Λ௒͑ΔΤωϧΪʔྖҬͰͷߴΤωϧΪʔཻࢠϏʔϜͱͷ֩൓ԠͰੜ੒͞ΕΔ਺े MeV Ҏ্ͷதੑࢠΤωϧΪʔεϖΫτϧͷར༻Մೳͳσʔλ͸ඇৗʹগͳ͘ɺΤωϧΪʔ͕ߴ͘ͳΔ΄ͲγϛϡϨʔγϣϯͷਫ਼౓͕Լ͕Γɺྫ͑͹ःณମް͞ͷධՁͷ‫ޡ‬͕ࠩ૿Ճ͢Δ܏޲ʹ͋Δɻ[2] ͜ΕʹͰ͖Δ͚͍ͩۙΤωϧΪʔྖҬͷཻࢠϏʔϜΛ༻͍࣮ͯ‫ݧ‬஋Λऩू͠ɺ‫ࢉܭ‬γϛϡϨʔγϣϯͷ‫ূݕ‬Λߦ͍ͬͯ͘ඞཁ͕͋ΔɻεΠεͷԤभ‫( ߏػڀݚ֩ࢠݪ‬CERN) ͷ CERN High energy AcceleRator Mixed ﬁeld facility(CHARM) ࢪઃ͸ɺ24 GeV/c ཅࢠͱ‫ݻ‬ମඪతΛ༻͍ͯߴΤωϧΪʔࠞ߹์ࣹઢ৔Λ‫ܗ‬੒͠ɺ์ࣹઢ๷‫ؔ͢ʹޢ‬Δ‫ثػͼٴڀݚ‬ͷ์ࣹઢ଱ੑͳͲΛධՁ͢ΔࢪઃͰ͋ΔɻϏʔϜϥΠϯͱःณߏ଄͕ൺֱత୯७ͰɺःณϒϩοΫͷް͞ʹΑͬͯΤωϧΪʔͱ‫౓ڧ‬෼෍Λௐઅ͕ग़དྷΔͨΊɺ༷ʑͳ৚݅ͰͷߴΤωϧΪʔதੑࢠͷःณ΍໎࿏ʹ͓͚ΔதੑࢠΤωϧΪʔεϖΫτϧ͕ಘΒΕΔɻຊ‫Ͱڀݚ‬͸ɺ༗‫ػ‬ӷମγϯνϨʔλ NE213 ͷΞϯϑΥʔϧσΟϯά๏Ͱղੳͯ͠தੑࢠΤωϧΪʔεϖΫτϧ‫ܭ‬ଌ๏ͱେ‫ن‬໛ःณ࣮‫ݧ‬ମ‫ʹܥ‬ஔ͚Δதੑࢠ༌ૹγϛϡϨʔγϣϯख๏Λߏங͠ɺίϯΫϦʔτͱ߯మΛ௨աͨ͠தੑࢠͷΤωϧΪʔεϖΫτϧͱ‫ݮ‬ਰ௕ͷ࣮‫ݧ‬஋Λ੔උͨ͠ɻ͜ΕΒͷ࣮‫ݧ‬஋͸ɺߴΤωϧΪʔՃ଎‫ࢪث‬ઃʹ͓͚Δ์ࣹઢ҆શઃ‫ؔ͢ʹܭ‬Δ‫ૅج‬σʔλͱͯ͠ɺՃ଎‫ࢪث‬ઃͷ์ࣹઢ҆શઃ‫ܭ‬΍௕ण໋์ࣹੑഇ‫غ‬෺ͷ௿‫ݮ‬Խٕज़։ൃʹར༻͞ΕΔཻࢠ༌ૹγϛϡϨʔγϣϯͷਫ਼౓ධՁʹ༻͍ΒΕΔɻߋʹɺೋཻ࣍ࢠੜ੒֩Ϟσϧͷਫ਼౓‫ʹূݕ‬΋ॏཁͳ໾ׂΛՌͨͤΔɻ
Removable shield blocks
Concrete

Liquid organic scintillator
Veto detectors
Cast iron support plateCGE

SteelBariteConc.

Shield material
test locationNHAConcreteshield block

Marble slab

24 GeV/c Proton BeamIrradiation room

Iron Beam
Dump

Cu target

Unit : mm

ਤ 1 CHARM ϏʔϜϥΠϯͷॎஅ໘ਤਤ 1 ʹຊ‫͢ࢪ࣮Ͱڀݚ‬ΔϏʔϜϥΠϯͷॎஅ໘ਤΛࣔ͢ɻCERN ͷ East Hall ʹ͋Δ CHARMϏʔϜϥΠϯͰ਺ճͷ༧උ࣮‫ݧ‬Λߦ͍ɺσʔλͷऔಘͷͨ ΊͷϏʔϜ৚݅ɺःณͷมߋͳͲ– 26 –Λߦ͍ɺ࣮‫ڥ؀ݧ‬Λ੔͑ͨɻՃ଎‫͔ث‬Βͷ 24 GeV/c ͷཅࢠϏʔϜ͕ਤࠨΑΓೖࣹ͠ɺরࣹࣨ಺ͷП 8 cmɺ50 cm ௕ͷಔλʔήοτΛরࣹ͢ΔɻλʔήοτͰͷ֩൓ԠʹΑΓੜ੒ͨ͠ೋཻ࣍ࢠɺಛʹதੑࢠ͸রࣹࣨ಺ʹ์ग़͞ΕɺΤωϧΪʔͷߴ͍΋ͷ͸पลͷίϯΫϦʔτΛಁա͢Δɻλʔήοτͷ্෦͸ 10 cm ͷେཧੴɺ40 cm ͷ߯੡ͷ൘͕͋Γɺͦͷ্͸ഩ์ࣹԽ࣮‫༻ݧ‬ίϯΫϦʔτϒϩοΫɺಁա࣮‫༻ݧ‬ίϯΫϦʔτɾ߯మϒϩοΫʹͳ͍ͬͯΔɻ͜ΕΒͷϒϩοΫ͸ΫϨʔϯͰ༰қʹҠಈͰ͖ΔΑ͏ʹͳ͓ͬͯΓɺ಺෦ʹઃஔͨ͠์ࣹԽࢼྉΛ୹࣌ؒͰऔΓग़͠ଌఆʹ‫͢ڙ‬Δ͜ͱ͕Ͱ͖ͨɻಁա࣮‫Ͱݧ‬͸ɺλʔήοτ্෦ 6.8 m Ґஔʹ༗‫ػ‬ӷମγϯνϨʔλ NE213 Λઃஔ͠ɺಁա࣮‫༻ݧ‬ͷίϯΫϦʔτͱ߯మΛೖΕସ͑ɺ
మ 40 cm ްΈʹՃ͑ɺίϯΫϦʔτ 0 cm ͔Β 360 cm (˞ 80 cm ͸ 2 ͭͷέʔεͰଌఆΛߦͬͨ)ɺ߯మ 0 cm ͔Β 80 cm ͷް͞·ͰͷଌఆΛߦͬͨɻಔλʔήοτͰੜ੒͞ΕͨதੑࢠΛϏʔϜ͔࣠Β 90 ౓্ํ޲ʹ͓͍ͯɺλʔήοτ͔Β௚઀౸ୡ͢ΔதੑࢠΛଌఆ͢Δͱͱ΋ʹɺ෦෼తʹίϯΫϦʔτϒϩοΫΛೖΕͯɺಁաް͞͝ͱͷதੑࢠͷΤωϧΪʔεϖΫτϧΛ eV ͔Β GeV ·ͰͷൣғͰଌఆͨ͠ɻ͜ΕΒͷଌఆ஋ΛΞϯϑΥʔϧσΟϯά๏ʹΑΔதੑࢠͷΤωϧΪʔεϖΫτϧΛಘΒΕͨɻ
ਤ 2 ʹଌఆͰಘΒΕͨதੑࢠͷΤωϧΪʔεϖΫτϧͷ࣮‫ݧ‬஋ͱ‫ࢉܭ‬஋ͷൺֱ݁ՌΛࣔ͢ɻਤΛ‫ݟ‬ΔͱްΈʹΑΓதੑࢠͷྔ͕‫͍ͯͬݮ‬Δ͜ͱͱɺεϖΫτϧͷ‫ܗ‬ঢ়͕มԽ͍ͯ͠Δ͜ͱ͕Α͘Θ͔Δɻਤதͷઢ͸ࢀߟͷͨΊͷ؆қମ‫Ͱܥ‬ͷγϛϡϨʔγϣϯͷ݁ՌͰ͋Δ͕ɺ࣮‫ݧ‬ͷ܏޲͸࠶‫͍ͯ͠ݱ‬Δ΋ͷͷࠩҟ͕‫ݟ‬ΒΕΔ͜ͱ͕Θ͔Δɻ͜ͷ͜ͱ͔ΒγϛϡϨʔγϣϯΛվળ͢Δඞཁ͕͋Δ͜ͱ͕Θ͔Δɻ͜ͷ࣮‫ݧ‬σʔλ͸ɺߴΤωϧΪʔதੑࢠͷ෺࣭಺Ͱͷ‫ڍ‬ಈΛ‫ه‬ड़͠ɺͦͷӨ‫ڹ‬ΛධՁ͢ΔͨΊͷ‫ج‬൫ σʔλͱͳΓ͏Δ΋ͷͰɺ์ࣹઢ޻্ֶ༗༻Ͱ͋Δɻࠓ‫ޙ‬ͷ์ࣹઢ๷‫ͱޢ‬ःณͷ෼໺ʹͱͬͯҙ͕ٛ͋ΓɺిྗɺΤωϧΪʔؔ܎෼໺΁ͷ೾‫ޮٴ‬Ռ͕େ͖͘‫ظ‬଴͞ΕΔɻ

3. Ӄੜੜ‫ײࡶ׆‬Ӄੜੜ‫׆‬ͷ࿩Λ͍ͨ͠·͢ͱ·ͣ࠷ॳʹ͜Ε·Ͱ͓ੈ࿩ʹͳͬͨଟ͘ͷઌੜํɺ‫ࣨڀݚ‬ͷઌഐɾ‫ޙ‬ഐͷօ༷ʹਂ͘‫͢·͍ͨ͠ँײ‬ɻ࣌ʹ͸ਏ͍‫ڀݚ‬ੜ‫׆‬Λ࠷‫Ͱ·ޙ‬΍Γ਱͛Δ͜ͱ͕ग़དྷͨͷ͸ɺօ༷ͷ͓͔͛Ͱ͢ɻ͜ͷ 5 ೥൒ΛৼΓฦΔͱɺຊ౰ʹ৭ʑͳ‫ݧܦ‬Λ͢Δ͜ͱ͕ग़དྷͨɻ‫ڀݚ‬ੜɺTAɾRAɺֶձ‫׆‬ಈɺ‫׆ڀݚ‬ಈɺҿΈձͱͦΕͧΕ಺༰͸ҟͳΔ͕ɺऔΓ૊ΜͰ͍Δࡍ͸େมͩͬͨ෼ɺॆ࣮ͨ͠‫ͨ͠Ͱؒظ‬ɻͲΕ΋ࢲͳΓʹखΛൈ͘͜ͱͳ͘શྗͰऔΓ૊Μͩͱ͍͏‫ͪ࣋ؾ‬͸͋Δɻ
‫ʹࣨڀݚ‬഑ଐʹͳͬͨӃੜͱͯ͠Ұ൪ҹ৅ʹ࢒ͬͨ͜ͱ͸ɺΘ͔Βͳ͍͜ͱ͸पΓͷਓʹฉ͖ɺपΓͷਓ΋౴͑Δ͜ͱͰߟ͕͑੔ཧ͞Ε͍ͯ͘͜ͱͰ͋Δɻ͓‫͜͏߹͖ڹ͘ྑʹ͍ޓ‬ͱ͕ՄೳͰ͋Δ͜ͱΛ࣮‫͖ͨͰײ‬ɻ͏ͪͷ‫Ͱࣨڀݚ‬͸ɺ௨ৗि 3 ճ (2 ճͷεϙϨʔγϣϯάϧʔϓͷθϛͱ̍ճͷ‫ࣨڀݚ‬શһͷθϛ) ͷθϛΛ௨͡ɺ࣮‫݁ݧ‬Ռͷ෺ཧ‫ݱ‬৅ͷղੳ͸໪࿦ɺա‫ൃʹڈ‬ද͞Εͨؔ࿈࿦จͷௐࠪΛߦ͍ɺ৽ͨͳΞΠσΟΞΛ࢈Έग़͢͜ͱ͕ग़དྷͨɻࢥ͍ग़ͷதͰಛච͢΂͖͜ͱʹɺੈքͷ༷ʑͳਓͱ‫ݧܦڀݚ‬Λ‫ڞ‬༗͢ΔͨΊΠλϦΞͷࠃࡍ֩σʔλεΫʔϧʹࢀՃ͠ɺϙελʔൃදΛͨ͜͠ͱ͕͋Δɻ͜ͷ‫ूڀݚ‬ձͷൃද͸Ұͭͷձ৔ͰߦΘΕɺଟ਺ͷ‫ֶͱऀڀݚ‬ੜͷલͰൃදͰ͖ΔνϟϯεͰ͋ͬͨɻॳࠃࡍूձΛߦ͑ͨͷ͸‫Ͱͱ͍͜͠خ‬͸͕͋ͬͨɺෛ୲΋େ͖͘‫͡ײ‬ΒΕͨɻ͜ͷෛ୲Λ৐Γӽ͑ɺແࣄʹ– 27 –

10-4

Void40cm × 1010Void-120cm × 10-6-180cmA × 10-2

Neutron fluence [#/sr/MeV/proton]

40cm × 10-280cm × 10-2120cm × 10-310-860cm × 10-3160cm × 10
10-480cm × 10-4-10200cm × 10-5

10240cm × 10-6-12360cm × 10-7
10-14

10-16

10Concrete

Steel

Exp.
Calc.

Exp.
Calc.
100

10100

Neutron energy [MeV]ਤ 2 ଌఆͰಘΒΕͨதੑࢠͷΤωϧΪʔεϖΫτϧͷ࣮‫ݧ‬஋ͱ‫ࢉܭ‬஋ͷൺֱ݁Ռ– 28 –ൃදΛऴ͔͑ͯΒ͸ࣗ෼ͷϓϨθϯςʔγϣϯʹࣗ৴Λ࣋ͭΑ͏ʹͳͬͨɻͦΕ͔Βൃදʹ௅Ήͱ͖ɺৗʹࣗ৴Λ࣋ͬͯಊʑͱൃදͰ͖ΔΑ͏ʹͳΓɺ‫ͯ͠ͱऀڀݚ‬ͷେࣄͳҰาΛ౿Έग़͢͜ͱ͕ग़དྷͨɻࠃ΋‫ڀݚ‬෼໺΋ҟͳΔਓୡͱҙ‫ݟ‬ΛަΘ͢͜ͱͰେ͖ͳϞνϕʔγϣϯΛಘΔ͜ͱ͕Ͱ͖ɺ֤ࠃͷօ༷ͷඇৗʹ‫ڀݚ‬೤৺ͳ࢟੎ͱ஌త޷‫ح‬৺͸ࢲͷ‫ڀݚ‬ҙཉΛ͔͖ͨͯͯ͘Εͨɻ͜ͷ‫ݧܦ‬͸֩σʔλχϡʔε No.113 (2016) ʹใࠂͨ͠ɻࠃࡍަྲྀͱͯ͠͸ɺεΠεͷԤभ‫( ߏػڀݚ֩ࢠݪ‬CERN) ͱͷ‫ڞ‬ಉ‫ࢀʹݧ࣮ڀݚ‬Ճ͢Δ͜
ͱ͕ग़དྷͨɻʮࣸਅ 1ʯ(‫ڀݚ‬୅දऀɿߴΤωϧΪʔՃ଎‫ࠤ ߏػڀݚث‬೾ढ़࠸ ‫ڭ‬त) ւ֎ͷํͱ΋ੵ‫ۃ‬తʹަྲྀ͠ɺଟ͘ͷ࣌ؒΛ‫ڞ‬༗͠େّͳ࣮‫ʹݧ‬औΓ૊Μͩ͜ͱ͸๨Εͳ͍ͱࢥ͏ɻ 

ʮࣸਅ 1ʯ৯ಊͷఉ͔Β‫͑ݟ‬ΔϞϯϒϥϯ (ࠨ) FY16 ʹࢀՃͨ͠ϝϯόʔͱͷϞϯϑϥϯͷల๬୆Ͱͷू߹ࣸਅ (ӈ)Ұਓͷੜెʹରͯ͠ɺ͔͍͋ͨͨ͝ࢦಋΛ௖͍ͨߴΤωϧΪʔՃ଎‫ߏػڀݚث‬ͷࠤ೾ढ़࠸‫ڭ‬तɺഡ‫ݪ‬խ೭।‫ڭ‬तɺେࢁོ߂ٕࢣɺ௕൞੣ٕ࢘ࢣɺਗ਼ਫ‫ݐ‬ઃͷதඌಙথത࢜ɺ޿ౡେֶͷֿຊ߶ॿ‫ڭ‬ɺ‫౎ژ‬େֶͷീౡߒॿ‫ڭ‬ɺ࢈‫ۀ‬૯߹‫ॴڀݚ‬ͷদຊ఩࿠ओ೚‫ڀݚ‬һɺ૿ా໌඙ओ೚‫ڀݚ‬һʹ৺͔Β‫͢ँײ‬Δɻ‫ڀݚ‬໘͚ͩͰͳ͘೔ৗੜ‫͍͓ͯʹ׆‬΋ଟ͘ͷ‫ྗॿޚ‬Λ௖͍ͨɻ೔ʑͷָ͠͞͸ɺCERN ৯ಊͷ֎ͷςʔϒϧʹਞऔͬͯ೔ຊ͔Βͷ‫ͱํऀڀݚ‬ਅͬനͳϞϯϒϥϯࢁ (4807 m) ΛோΊͳ͕ΒϏʔϧΛ܏͚ͨ͜ͱͩͬͨɻࠓͰ΋·Ϳͨʹු͔Ϳɻ

ʮࣸਅ 2ʯ೔‫֩ؖ‬σʔλαϚʔεΫʔϧͰͷ‫ه‬೦ࣸਅ·ͨɺ4 ճͷ೔‫֩ؖ‬σʔλαϚʔεΫʔϧࢀՃͨ͠ɻʮࣸਅ 2ʯϙελʔൃදΛߦͬͯ༏– 29 –लϙελʔ৆Λड৆͓ͯ͠Γɺ‫ֶྗࢠݪ‬ձͷଞֶੜ΍‫ࠃؖ‬ͷֶੜͱަྲྀ͢Δྑ͍‫ػ‬ձΛ࣋ͬͨɻަྲྀʹ͸ɺҿΈձ͕΍͸Γ໾ʹཱͭ΋ͷͰɺօ͞Μେ͍ʹ੝Γ্ָ͕͍͓ͬͯ࣌ؒ͠ʹͳͬͨɻʮࣸਅ 3ʯHIMAC Ͱͷ‫ڞ‬ಉར༻࣮‫ݧ‬ͷू߹ࣸਅ (ࠨ) εϙϨʔγϣϯάϧʔϓͷ‫ޙ‬ഐͨͪͱͷҿΈձ (ӈ)ଞͷ࣮‫Ͱݧ‬͸ɺ‫ࠃؖ‬ͷ੒‫ؗۉ‬େֶͱ໌஌େֶ͔Β࣮‫ݧ‬ґཔΛड͚ͯ์ࣹઢҩֶ૯߹‫ॴڀݚ‬(HIMAC) Ͱͷ‫ڞ‬ಉར༻࣮‫ݧ‬ΛࢀՃͨ͠Γʮࣸਅ 3 (ࠨ)ʯɺ‫ޙ‬ഐͷख఻͍ͰཧԽֶ‫Ͱॴڀݚ‬ͷ࣮‫ࢀʹݧ‬Ճ࣮ͯ͠‫ݧ‬΍ղੳํ๏ͳͲͷ‫ࢦڀݚ‬ಋΛ೚͞Εͨ͜ͱ΋͋Δɻಛʹ࣮‫ͯؔ͠ʹݧ‬͸ɺ‫۝‬େͷࣥߦઌੜ͔Βଟେͳ‫ࢦޚ‬ಋΛ௖͍ͨɻ์ࣹઢɾ‫ʹֶ޻ྗࢠݪ‬ରͯ͠୯ͳΔ஌ࣝͰ͸ͳ͘ɺઌੜຊਓͷ๛෋ͳ‫ͯ͠ͱऀڀݚͮ͘جʹݧܦڀݚ‬ͷ࢟੎ɺಛʹͲ͜·Ͱ΋୳‫͢ٻ‬Δ࢟੎ʹ͸‫ײ‬୰ͨ͠ɻ‫ڀݚʹڞ‬Λߦ͍ɺ༷ʑͳ͜ͱʹ͝‫ྗڠ‬௖͍ͨεϙϨʔγϣϯάϧʔϓͷօ༷ʹ‫͢ँײ‬ΔɻҰॹʹҿΈձ΋ग़དྷͯɺ‫ڀݚ‬ͷ࿮Λ௒͍͑ͯΖ͍Ζͱ࿩͕Ͱ͖ͨ͜ͱ΋͋Γɺຊ౰ʹָ͔ͬͨ͠ɻʮࣸਅ 3 (ӈ)ʯͦͷଞʹ΋ɺ‫ֶྗࢠݪ‬ձʹࢀՃͯ͠‫ޱ‬಄ൃදΛߦ͏͜ͱͰ‫ऀڀݚ‬ͷํʑ͔Βଟ͘ͷࢦఠΛ௖͖ɺඇৗʹษ‫ͨͬͳʹڧ‬ɻࢦಋ‫ڭ‬һͷख఻͍ͰΦʔϓϯΩϟϯύεʮࣸਅ 4 (ࠨ)ʯ΍ɹ LTDɹࠃࡍֶձͰͷ௨༁ͷΞϧόΠτʮࣸਅ 4 (ӈ)ʯͷ‫ݧܦ‬΋͋Γɺຊ౰ʹָ͍͠Ӄੜੜ‫׆‬Λա͢͜͝ͱ͕ग़དྷͨɻ

ʮࣸਅ 4ʯΦʔϓϯΩϟϯύεͰͷࢦಋ‫ڭ‬һͷख఻͍ (ࠨ) LTD ࠃࡍֶձͰͷ௨༁ͷΞϧόΠτͰͷ‫ه‬೦ࣸਅ (ӈ)– 30 –

4. ‫ࡏݱ‬ͷ‫׆ڀݚ‬ಈͷ֓ཁࠓॅΜͰ͍Δ North Carolina ͷ Raleighʮࣸਅ 5ʯ͸ΞϝϦΧͰ೐΍͔ͳ౎ࢢͰ͸ͳ͘ాࣷͷงғ‫ؾ‬ͷ੩͔ͳ౎ࢢͰ͋Δ͕ɺ෺Ձ͸࣏҆ͯ҆͘΋ྑ͍ͱ͜ΖͰॅΈ΍͍͢౎ࢢͰ͋Δɻ౉ถ‫ʹ͙͢ޙ‬ɺ৽‫ܕ‬ίϩφ΢Πϧε͕ੈքͰ໠ҖΛৼΔͬͯΞϝϦΧ͸େมͳ࣌‫͕ظ‬ଓ͍͍ͯΔɻࡏ୐‫ۈ‬຿Λ࣮ࢪ͔ͯ͠Βɺ͍ͭͷؒʹ͔ 2ϱ݄ۙ͘ʹͳΔɻ1 ೔΋ૣ͘ී௨ͷ೔ৗ͕໭ΕΔΑ͏ʹ‫ف‬Δɻ

ʮࣸਅ 5ʯNCSU ͷ ໊෺ Bell tower (ࠨ) NCSU ͷֶੜձ‫ ؗ‬talley union (ӈ)‫ࢠݪ‬࿍ͷ֩෼྾தੑࢠ͸ɺ‫ࢠݪ‬࿍಺ʹ͓͍ͯ֩෼྾ʹΑͬͯ์ग़͞ΕΔதੑࢠͱͯ͠ɺฏ
‫ ۉ‬2 MeV ఔ౓ͷߴ͍ΤωϧΪʔΛ΋͕ͭɺ͜ͷߴ଎தੑࢠ͸‫ݮ‬଎ࡐͱͷ஄ੑࢄཚ͋Δ͍͸‫֩ࢠݪ‬తͳඇ஄ੑࢄཚʹΑΓ࣍ୈʹΤωϧΪʔΛࣦ͍ɺ೤ΤωϧΪʔʹ·Ͱ‫ݮ‬଎͞ΕΔɻ΋͠೤ΤωϧΪʔྖҬʹ͓͍ͯதੑࢠͷ‫ٵ‬ऩ͕ͳ͚Ε͹ɺͦͷྖҬʹ·Ͱ‫ݮ‬଎͞Εͨதੑࢠ͸ઈରԹ౓ T Ͱ‫ن‬ఆ͞ΕΔ Maxwell ෼෍Λ΋ͭ‫ݮ‬଎ࡐͱͷিಥʹΑΔΤωϧΪʔʹΑͬͯ೤ฏߧʹ౸ୡ͠ɺಉ͡Թ౓Ͱͷ Maxwell ෼෍Λࣔ͢ɻैͬͯɺ‫ࢠݪ‬࿍‫ݮ‬଎ࡐʹ͓͚Δதੑࢠͷ‫ݮ‬଎ͱ೤ฏߧ΁ͷ౸ୡΛਖ਼͘͠‫ٻ‬ΊΔ͜ͱ͕‫ۃ‬Ίͯॏཁͳ՝୊Ͱ͋Δɻ[3][4]தੑࢠͷ଎౓Λ஗͘͢Δ‫ݮ‬଎ࡐͱͯ͠ࠇԖ (Graphite) ͸ɺੈքͰॳΊͯͷ‫ࢠݪ‬࿍ Chicago

Pile-1 [5] Ͱ༻͍ΒΕͨ෺࣭Ͱ͋Δɻ͜ͷͨΊɺେྔͷ७ਮࠇԖϒϩοΫ͕੡଄͞Εͨɻ७౓ΛߴΊΔͷ͸ɺதੑࢠͷ‫ٵ‬ऩʢଛࣦʣΛগͳ͘͢ΔͨΊͰ͋ΔɻࠇԖ͸தੑࢠͷ‫ٵ‬ऩஅ໘ੵ͕গͳ͘ɺ์ࣹઢʹ‫͘ڧ‬ɺ଱೤ੑʹ༏Εɺ೤Λྑ͘఻͑ΔͳͲ࿍৺ߏ଄ࡐͱͯ͠΋‫ۃ‬Ίͯ༏Εͨੑ࣭Λ͍࣋ͬͯΔɻैͬͯɺࠇԖ͸ Generation IV; Very High Temperature Reactor(VHTR)ɺAdvanced High Temperature Reactor (AHTR) [6][7][8] Λ‫ؚ‬Ή༷ʑͳ‫ࢠݪ‬࿍ͷ֓೦ʹద͍ͯ͠Δɻલड़ͷͱ͓Γɺ‫ݮ‬଎ࡐʹ͓͚Δதੑࢠͷ‫ݮ‬଎ͱ೤ฏߧΛਖ਼֬ͳཧղ͸ɺকདྷͷ೤࿍γεςϜͷ҆શར༻ʹॏཁͳ໾ׂΛՌͨ͢ɻ͜ͷաఔΛɺ‫ݮ‬଎ࡐͰதੑࢠ‫ݮ‬଎࣌ؒ๏ (Neutron slowing

down time technique) ΑΓଌఆ͠ɺཧ࿦σʔλͱൺֱ͢Δɻ͜ͷํ๏͸ɺ೤Խ‫ڍ‬ಈΛ‫ؚ‬Ή‫ݮ‬଎ࡐ಺ͷதੑࢠͷ૬‫༻࡞ޓ‬Λཧղ͢ΔͨΊʹෆՄܽͳϕϯνϚʔΫٕज़ͱͯ͠ɺ‫ݮ‬଎ࡐͰ‫ݮ‬଎͢ΔதੑࢠͷΤωϧΪʔͱɺͦͷΤωϧΪʔʹ౸ୡ͢Δͷʹཁ͢Δ࣌ؒͱͷ‫ج‬ຊతͳ݁߹ʹ– 31 –‫͍ͮج‬Δɻதੑࢠ͕Ұ୴೤ΤωϧΪʔʹ౸ୡ͢Δͱɺ‫ݮ‬଎ࡐͱதੑࢠͷ૬‫༻࡞ޓ‬͸೤தੑࢠࢄཚ๏ (Thermal neutron scattering law, TSL) ʹΑͬͯ‫ه‬ड़͞ΕΔɻ͜Ε͸ɺ‫ݮ‬଎ࡐͷߏ଄త͓Αͼྗֶత৘ใΛ‫ؚ‬Ήɻ‫ࢉܭ‬γϛϡϨʔγϣϯͰ͸ɺ‫ݮ‬଎աఔʹ͓͚Δதੑࢠͷฏ‫ۉ‬ΤωϧΪʔ E(t) ͕ಘΒΕΔɻதੑࢠͷฏ‫ۉ‬ΤωϧΪʔ E(t) ͸ɺE(t) =EE · ψ(E, t)dE ,(1)͜͜Ͱɺψ(E, t) ͸࣌ؒʹґଘ͢ΔதੑࢠΤωϧΪʔεϖΫτϧͰ͋Γɺਖ਼‫ن‬Խ͞ΕΔɻࣜ(1) ʹΑΓɺ࣌ؒʵΤωϧΪʔͷ૬ؔؔ܎Λ਺஋తʹཱ֬͠ɺϕϯνϚʔΫͷࢦ਑ͱͯ͠༻͍Δ͜ͱ͕Ͱ͖Δɻ[9] ࠓ·ͰҰൠతͳ‫ݮ‬଎ࡐͰͷ༷ʑͳ࣮‫ߦ͕ݧ‬ΘΕ͖ͯͨɻ͔͠͠ɺ͜ΕΒͷ݁Ռ͸ɺ‫ࡏݱ‬ͷதੑࢠ‫ݮ‬଎࣌ؒ๏ͷͱେ͖͘ҟͳΔ͜ͱ͕Θ͔ͬͨɻ[6][10] ͜ͷํ๏Λద༻ͨ͠ࢼΈ͸ɺA.I.Hawari [6] ʹΑͬͯ‫͞ٴݴ‬Εͨɻຊ‫ڀݚ‬ͷ໨త͸ɺ্‫ه‬Λ౿·͑ͯɺࠇԖͷதੑࢠ‫ݮ‬଎ͱ೤ฏߧʹؔ͢ΔཧղΛਂΊɺ೤தੑࢠࢄཚϥΠϒϥϦΛϕϯνϚʔΫ͢Δ͜ͱͰ͋Δɻ5.

͓ΘΓʹ‫۝‬େͰͷ‫ڀݚ‬ΛਐΊΔʹ͋ͨΓɺଟ͘ͷํ͔Β‫͓ྗॿޚ‬Αͼ‫ࢦޚ‬ಋΛ௖͖·ͨ͠ɻதͰ΋ɺ‫ڀݚ‬ͷ‫ػ‬ձΛ༩͑ͯͩ͘͞Γɺͦͷ਱ߦʹ͋ͨͬͯଟେͳ‫ࢦޚ‬ಋΛ௖͖·ͨ͠‫۝‬भେֶେֶӃ޻ֶ‫ڀݚ‬ӃΤωϧΪʔྔࢠ޻ֶ෦໳ ੴ‫݈ڮ‬ೋ ‫ڭ‬तɺࣥߦ৴‫ڭॿ ׮‬तɺલാ‫ژ‬հ ।‫ڭ‬तɺҏဇຊ௚ࢠ ।‫ڭ‬तɺߴΤωϧΪʔՃ଎‫ࠤ ߏػڀݚث‬೾ढ़࠸ ‫ڭ‬तʹਂ͘‫͢·͠ँײ‬ɻۙ͘Ͱ‫ʹڀݚ‬औΓ૊Ή࢟ΛΈͳ͕Βɺ‫ͯ͠ͱऀڀݚ‬େ੾ͳࣄฑΛଟֶ͘͹ͤͯ௖͖·ͨ͠ɻ͜ΕΒͷ͜ͱΛࠓ‫ޙ‬ͷ‫ڀݚ‬ੜ‫ʹ׆‬΋‫͢·͍ࢥͱ͍͖͍͔ͨͯ͠׆‬ɻӃੜੜ‫׆‬Λ࠷‫Ͱ·ޙ‬΍Γ਱͛Δ͜ͱ͕ग़དྷͨͷ͸पғͷେ੎ͷํୡͷଘࡏ΍ྑԑʹ‫·ܙ‬Ε͔ͨΒʹଞͳΓ·ͤΜɻ‫ࣨڀݚ‬ͷੜ‫ࢲͰ׆‬͸ɺଞਓʹ഑ྀ͠ଞਓͷҙ‫ݟ‬Λड͚ೖΕΒΕΔΦʔϓϯϚΠϯυΛֶͼ·ͨ͠ɻਖ਼௚ͳͱ͜Ζɺ‫ڀݚ‬Λ͚ͭͮΔ͏ͪʹɺࢲ͚ͩͷͩ͜ΘΓ͕Ͱ͖ͯɺଞͷਓͷҙ‫ݟ‬Λड͚ೖΕͳ͍ଶ౓Λগ͠͸͍࣋ͬͯ·ͨ͠ɻ֤ࣗʹ༩͑ΒΕͨྗྔ͸͢΂ͯҧ͍·͕͢ɺ໌Β͔ͳ͜ͱ͸ஂ݁͢Ε͹΋ͬͱҒେʹͳΔͱ͍͏͜ͱͰ͢ɻࢲ΋ΑΓओಋతɾੵ‫ۃ‬తͳ৺Ͱଞਓʹ഑ྀ͠ɺଞਓͷҙ‫ݟ‬Λड͚ೖΕΒΕΔΦʔϓϯϚΠϯυΛҡ࣋͢ΔΑ͏ʹৗʹࣗ෼ࣗ਎Λ࣏ΊΔͭ΋ΓͰ͢ɻͦΖͦΖకΊ·͕͢ɺ͜ͷ 5 ೥൒ͰಘΒΕͨ༗‫ܗ‬ແ‫ܗ‬ͷࡒ࢈Λ༗ޮʹ࢖͍ɺ͞Βʹ্Λ໨ࢦ͍͖͍ͯͨ͠ͱࢥ͍·͢ɻࠓΛ౿Έ୆ͱ͠ɺδϟϯϓͰ͖ͨΒΑ͍ͱࢥ͍·͢ɻ஍ಓʹ‫ؤ‬ுΓ͍ͨͱࢥ͍·͢ɻʮ‫ʹڏݠ‬ɺͻͨΉ͖ʹɺ‫ँײ‬ͷ‫Ͱͪ࣋ؾ‬ʯΛ๨Εͳ͍Α͏ʹ͠·͢ɻࠓ·Ͱࢧ͑ͯͩͬͨ͘͞େ੎ͷઌੜํ΍͓ੈ࿩ʹͳͬͨ‫ࣨڀݚ‬ͷϝϯόʔʹԸฦ͠Λ͢ΔͨΊʹ΋ࠓ‫ޙ‬΋ਫ਼ਐΛଓ͚͍ͨͱܾҙΛ৽ͨʹ͠·ͨ͠ɻօ༷ͱ‫͓ͼ࠶ʹؾݩ‬ձ͍ग़དྷ·͢Α͏ʹɻࢀߟจ‫ݙ‬[1] N. Nakao et al.: Nucl. Instrum. Meth., B266, 93 (2008).
[2] H. Hirayama et al.: Proc. SATIF-13, NEA/NSC/R2, 274 (2018).

– 32 –[3] Lamarsh, John R. Introduction to nuclear reactor theory, Addison-Wesley, 1966.
[4] Sébastien P. Chabod, Neutron slowing-down in matter, Nucl. Instrum. Meth. Res. A669, 32(2012).
[5] E. Fermi, The Development of the ﬁrst chain reaction pile, Proceedings of the American Philosophy Society 90, 20 (1946).
[6] A. I. Hawari, B. W. Wehring, Observation of neutron thermalization in graphite using theslowing-down-time technique, No. JAEA-CONF-2014-003, 2015.
[7] A. I. Hawari, J. L. Wormald, C. A. Manring, Testing of Graphite Thermal Neutron Scattering
Law Data in Support of TREAT Neutronic Analysis, Transactions 115 (1), 1401 (2016).
[8] T. Zhou, Benchmarking Thermal Neutron Scattering in Graphite, Ph.D. dissertation, North
Carolina State University 2006.
[9] A. I. Hawari, et al, Monte Carlo Assessment of Time Dependent Spectral Indexes for Benchmarking Neutron Transport in Iron, Proc. of ISRD, Brussals Belgium, 2002.
[10] Y. Kaneko, R. Kurokawa, F. Akino, et al., Journal of Nuclear Science and Technology, 4 (4),177 (1967).

– 33 –