2011 03 22 Japan Nuclear Crisis

2011 03 22 Japan Nuclear Crisis - The Japanese Nuclear ...

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: The Japanese Nuclear Reactor Situa4on Nuclear Engineering & Radiological Sciences Dept. The University of Michigan Unit 1 Six BWR units at the Fukushima Nuclear Sta4on: –  Unit 1: 439 MWe BWR, 1971 (unit was in opera4on prior to event) –  Unit 2: 760 MWe BWR, 1974 (unit was in opera4on prior to event) –  Unit 3: 760 MWe BWR, 1976 (unit was in opera4on prior to event) –  Unit 4: 760 MWe BWR, 1978 (unit was in outage prior to event) –  Unit 5: 760 MWe BWR, 1978 (unit was in outage prior to event) –  Unit 6: 1067 MWe BWR, 1979 (unit was in outage prior to event) Hydrogen Detona4on at Unit 1 Refuel Floor Reactor Building Hydrogen Produc5on from the Zirc ­Water reac5on Zr + 2 H2O → Zr02 + 2 H2(∼1204 deg Cent) Detona4on Deflagra4on inert •  H2 Detona4on preven4on mechanisms •  Iner4za4on by N2 •  Controlled combus4on •  Cataly4c recombiners •  Spark igniters •  Fukishima Unit I •  Primary containment iner4zed •  Secondary containment had igniters … but apparently didn’t work? REACTOR REACTOR BUILDING PRIMARY CONTAINMENT NITROGEN INERTIZATION PRESSURE SUPPRESSION CHAMBER (TORUS) Normal opera5on of the Emergency cooling The subsequent required cooling of the Torus The probable path of the H2 out of the Torus was through the safety valve of the primary containment as a consequence of the increased pressuriza5on H2 Explosion Cooler ceiling allowed for condensa4on of steam and contributed to the increased concentra4on of H2 Significant damage of the secondary containment (reactor building) as a consequence of the explosion TMI ­2 Accident •  Small LOCA that uncovered the core and led to substan4al fuel mel4ng, ~2/3 of the fuel. •  Radia4on release was rela4vely small, perhaps equivalent to a few chest xrays to people in the area of TMI ­2. The reason for this is that the primary containment remained intact. Sufficient cooling water was forced into the core to keep the fuel cool. •  The challenge for TMI ­2 and the Fukushima reactors was removing the decay heat power. •  TMI ­2 is classified as an INES Level 5 accident (accident with wider consequences). Chernobyl •  Prompt supercri4cal power excursion (~1000x) of the reactor while it was at power. This heat boiled away the water coolant and the resultant steam explosion blew a 1000 ton reactor cover off the reactor. •  The 2000 tons of graphite moderator caught on fire and lasted 10 days. The fire provided the mo4ve force to vaporize solid fission products and send them 40k feet into the atmosphere, where it could be readily distributed to Europe and the world. •  Chernobyl had no containment. It was an ideal mechanism to transport fission products from the core to the atmosphere. The radia4on releases were huge. There was substan4al loss of life. This was truly a worst case accident. •  Chernobyl is classified as an INES Level 7 accident (major accident), a factor of ~100 more severe than TMI ­2. Severity of the Fukushima accident •  The spent fuel pools are open to the atmosphere. While there isnt a mo4ve force like 2000 tons of burning graphite, the fuel could fail. •  Fukushima may be moving away from a TMI ­scale accident towards (but s4ll distant from) a Chernobyl event. •  Gelng the pools in a stable configura4on would help to keep this in the direc4on of TMI ­2 severity. High Level Radia4on Health Effects Skin burns Central nervous system Gastrointestinal tract Male sterility (temporary) Cataracts Blood Emergency worker limit 5-y limit (international) Worker limit (U.S.) Public limit rad 3,000 1,000 500 400 200 100 Gy 30 10 5 4 2 1 rad/y 25 10.6 10 5 0.1 Gy/y 0.25 0.106 0.1 0.05 0.001 <= contamination <= serious <= One worker (3/13) Higher Level Dose Rates 10x Background Kitaibaraki (3/15) Perimeter (<3/14) Unit 1 Building (<3/14) Main Gate (Block 4 explosion) Outside Unit 3 (3/15) rad/h 0.00003 0.0004 0.13 0.67 1.2 40 mGy/h 0.0003 0.004 1.3 6.7 12 400 <= no impact <= no impact <= no impact <= no impact <= 5 h: 6 rad (60 mGy) <= 40 min for 25 rad (250 mGy) ...
View Full Document

This note was uploaded on 11/15/2011 for the course PUBPOL 481 taught by Professor Duderstadt during the Winter '11 term at University of Michigan.

Ask a homework question - tutors are online