Wednesday, March 30, 2011

Fukushima reactor status update for 2011 03 30

NucNet reports on the latest developments in Japan’s nuclear crisis

(Note to readers: Today’s status reports are courtesy of NucNet a service of the World Nuclear Association.  Regular blog posts about nuclear energy will resume later this week.

You can follow breaking news about Fukushima via the American Nuclear Society (ANS) Twitter feed @ans_org which I am helping run.  Also, see twice daily news updates at the ANS blogANS Nuclear Cafe  provided by Rich Michal, an editor at ANS Nuclear News.  Laura Scheele, ANS Outreach Office, and Joe Koblich, IT Director at ANS, and his staff, make this work possible.

Please see the special Fukushima tab at the top of this blog for additional sources of information.

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Work Continues To Remove Contaminated Water At Fukushima-Daiichi

30 Mar 2011 (NucNet): Work is continuing to remove contaminated water from the basement of the turbine hall at unit 1 of the Fukushima-Daiichi nuclear plant by pumping spilled water into the condenser.

But at units 2 and 3 there is not enough free capacity in the condensers and work is taking longer than expected, plant operator Tokyo Electric Power Company (Tepco) said.

The condensers are heat exchangers below the turbines, where low-pressure vapor from the turbines is condensed by removing residual or waste heat to the main heat sink.

The Japan Atomic Industrial Forum (JAIF) said “no major progress” has been reported in efforts to drain the basement water.

The delay is hampering work to cool down and stabilize the plant, JAIF said.

According to the International Atomic Energy Agency (IAEA), the Nuclear Safety Commission of Japan has suggested that higher activity in the water discovered in the unit 2 turbine building is caused by water which has been in contact with molten fuel rods and directly released into the turbine building via some, as yet unidentified path.

JAIF confirmed today that damage and leakage is suspected to the primary containment vessel (PCV) structural integrity at unit 2. JAIF had previously said the PCV’s status was “unknown”.

Removal of water from the turbine building basements is an important step before workers can continue efforts to fully restore power to the plant.

Meanwhile, Japan’s Nuclear and Industrial Safety Agency (NISA) said it has ordered Tepco to solve the problem of heavily contaminated water that has leaked into trenches outside the controlled zones of units 1 to 3 at the plant.

The IAEA said today that dose rates at the surface of accumulated water found in trenches close to the turbine buildings were 0.4 mSv/hr for unit 1 and more than 1,000 mSv/hr for unit 2.

An investigation is under way to discover how the water accumulated in the trenches.

Fresh water is being continuously injected into the reactor pressure vessels (RPVs) of units 1, 2 and 3 in an effort to cool the nuclear fuel. At unit 1, the temperature at the RPV’s feedwater nozzle – normally the coldest point of the RPV – has increased from 273.8 degrees Celsius to 299 degrees Celsius. The temperature at the bottom of the RPV remained stable at 135 degrees Celsius.

Temperatures at unit 2 appear relatively stable at the same measurement points. At unit 3, the temperature at the RPV feedwater nozzle is about 61.5 degrees Celsius and 120.9 degrees Celsius at the bottom of the RPV. However, Tepco said the validity of the RPV measurements is still being checked.

Tepco also said that periodical spraying of water onto the spent fuel pools of units 1 to 4 is continuing. Since yesterday Tepco has been spraying fresh water instead of seawater. The pool temperature is known only for unit 2 and was at 46 degrees Celsius this morning (30 March).

In unit 4, lighting was re-established in the control room yesterday. This means all control rooms now have light.

Fukushima-Daiichi Nuclear Plant Status Update

30 Mar (NucNet): The following is a summary of the status of all six reactor units and the spent fuel pools (SFPs) at the Fukushima-Daiichi nuclear plant. The main change since yesterday is that damage is now suspected to the reactor pressure vessel integrity of unit 2.

Unit Status Summary At Fukushima-Daiichi, 29 March 2011 at 12:00 Japan time:

  • Unit 1

Core and fuel integrity: damaged. Reactor pressure vessel integrity: unknown. Core cooling requiring AC power: not functional. Building integrity: severely damaged by hydrogen explosion. Water level in the rector pressure vessel (RPV): fuel partially or fully exposed. Pressure of the RPV: now decreasing after initial increase (5–6 bar). Temperature of the RPV: slight increase (310 degrees Celsius at feedwater nozzle; 138 degrees Celsius at bottom head). Water injection to core: continuing. Now using fresh water instead of seawater. Water injection to containment vessel: to be confirmed. Containment venting: temporarily stopped.

  • Unit 2

Core and fuel integrity: severely damaged. Reactor pressure vessel integrity: damage suspected (suppression chamber).

Core cooling requiring AC power: not functional. Building integrity: slightly damaged. Water level in the rector pressure vessel: fuel partially or fully exposed. Pressure of the RPV: stable (0.7–0.8 bar). Temperature of the RPV: slight increase (158 degrees Celsius at feedwater nozzle; 120 degrees Celsius at bottom of head). Water injection to core: continuing. Now using fresh water instead of seawater. Water injection to containment vessel: to be confirmed. Containment venting: temporarily stopped.

  • Unit 3

Core and fuel integrity: damaged. Reactor pressure vessel integrity: unknown. Core cooling requiring AC power: not functional. Building integrity: severely damaged by hydrogen explosion. Pressure of the RPV: now stable (1.3 bar). Temperature of the RPV: slight increase (62 degrees Celsius at feedwater nozzle; 121 degrees Celsius at bottom of head). Water injection to core: continuing. Use of fresh water under consideration. Water injection to containment vessel: to be confirmed. Containment venting: temporarily stopped.

  • Unit 4

Shut down at the time of the earthquake, no damage to fuel (which had already been removed from the reactor and transferred to the pool), core or containment. Building integrity severely damaged by hydrogen explosion.

  • Unit 5

Shut down at the time of the earthquake, no damage to fuel, core or containment. Vent hole opened in roof as precaution against hydrogen explosion. Unit in cold shutdown.

  • Unit 6

Shut down at the time of the earthquake, no damage to fuel, core or containment. Vent hole opened in roof as precaution against hydrogen explosion. Unit in cold shutdown.

Spent Fuel Pool Status At Fukushima-Daiichi 30 March 2011:

Fuel integrity: unknown at units 1 and 2; possibly damaged at units 3 and 4; safe at units 5 and 6, and in the common spent fuel pool.

  • Unit 1

Water injection being considered.

  • Unit 2

Water injection carried out periodically since 20 March; switch from seawater to fresh water on 29 March; water temperature 46 degrees Celsius.

  • Unit 3

Water level low, water injection continues; switch from seawater to fresh water on 29 March.

  • Unit 4

Water level low, water injection continues; switch from seawater to fresh water on 29 March. Reactor building damaged by explosion and fire on 15 March.

  • Units 5 & 6

Pool cooling capability recovered.

Common Spent Fuel Pool

Seawater was sprayed over this pool on 21 March. Pool cooling was restarted after successful installation of an external power supply line on 24 March.

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