Recriticality or nuclear fission could be occurring in Unit 2 if Xenon is being generated - Fukushika Daichi

Tepco Handout: Xenon detected in Reactor No. 2 containment vessel — 9 hour half-life

Title: Primary Containment Vessel of Unit 2 of Fukushima Daiichi Nuclear Power Station, Sampling Result by the Gas Control System
Date: February 14, 2012
By: Tokyo Electric Power Company

Sampling time: February 13, 2012, 16:24-16:54 (charcoal filter)

• Xe-133 @ 0.016 Bq/cm3 (5 day half-life) or 16,000 Bq/m3
• Xe-135 @ 0.023 Bq/cm3 (9 hour half-life) or 23,000 Bq/m3

Recent Tepco press handouts

Title: Fukushima No. 2 reactor’s thermometer likely faulty: TEPCO – The Mainichi Daily News
Source: Kyodo
Date: February 14, 2012

[...] The utility said it believes sustained nuclear reactions were not taking place in the reactor as no radioactive xenon has been detected inside the containment vessel. To prevent the possibility of the reactor going critical, it increased on Sunday the amount of water injected as coolant by 3 tons per hour and poured in 1 ton of boric acid. [...]

or this the case .... with Tepco , you also wonder which way is up ? 

http://enenews.com/tepco-told-find-ways-measuring-temperature-reactor-2-claimed-xenon-detected

NHK: Tepco told to find ways of measuring temperature at Reactor No. 2 and report by tomorrow — Still claimed no xenon detected

Title: TEPCO: No.2 reactor thermometer likely brokenSource: NHK
Date: Tuesday, February 14, 2012 15:32 +0900 (JST)

[...] The operator denied the possibility of the reactor heading toward criticality again, as it has not detected any radioactive xenon, which would be generated from continuous nuclear fission.

It says it will continue to circulate water through the reactor and carefully monitor the situation.

The Nuclear and Industrial Safety Agency has instructed TEPCO to measure the temperature in different ways and submit a report by Wednesday. [...]

Read the report here

“It has not detected any radioactive xenon, which would be generated from continuous nuclear fission”? See: Tepco Handout: Xenon detected in Reactor No. 2 containment vessel -- 9 hour half-life