Subject: Nuclear Power Update 5-26

From: Chris in Delaware

Date: Thu, 26 May 2011 14:38:18 -0400

Some Fukushima News - Crediting Team Member Joe for coming up with his special insights:

TEPCO NEVER USED/INSTALLED HARDENED VENT

* Concerning TEPCOs Wetwell (Torus) Venting Systems that were supposed to be upgraded:

ο Attached is a Piping and Instrumentation Diagram of what a Hardened Vent looks like at a United States Plant.

ο The same Vent that TEPCO claims that they didn't need (or even worse, that they installed but apparently didn't use!)

o This vent was constructed of Durable Piping, instead of the Flimsy Ductwork that is originally supplied with the Standby Gas Treatment System at the plant

o It's purpose is to VENT steam from the Torus (Wetwell) portion of the Containment in order to keep the Fuel inside the Reactor Vessel from being Damaged

o A combination of POOR Decisions and Design prevented them from Venting hydrogen off Units 1, 2, and 3. The Fukushima Story may have been much better had they Installed this Simple Modification.

As stated in the GL 89-016, this design change provides the ability for direct venting of the torus' to the main 'stack'. Containment venting is one core damage prevention strategy utilized in the BWR Owners Group Emergency Procedure Guidelines (EPGs) as previously approved by the NRC and is required in plant-specific Emergency Operating Procedures (EOPs). The torus vent line connecting the torus to the main stack will provide an alternate vent path for implementing EOP requirements and represents a significant improvement relative to existing plant vent capability. For 56 psi saturated steam conditions in the torus, approximately 1% decay heat can be vented.

This design change (Figure 1b) provides a direct vent path from the torus to the main stack bypassing the Standby Gas Treatment System (SBGTS). The bypass is an 8" line whose upstream end is connected to the pipe between primary containment isolation valves AO-5042 A & B. The downstream end of the bypass is connected to the 20" main stack line downstream of SBGTS valves AON-108 and AON-112. An 8" butterfly valve (A0-5025), which can be remotely operated from the main control room, is added downstream of 8" valve AO-5042B. This valve acts as the primary containment outboard isolation valve for the direct torus vent line and will conform to NRC requirements for sealed closed isolation valves as defined in NUREG 0800 SRP 6.2.4. The new pipe is ASME III Class 2 up to and inclusive of valve AO-5025. Test connections are provided upstream and downstream of AO-5025.

Figure 1b Direct Torus Vent System (DTVS)

In GL 89-016, the NRC basically adopted the Boston Edison Company (BECo) installation of A Direct Torus Vent System DTVS as the reference system for venting Mark I containments. GL 89-016 provided details of that design for use by the Nuclear Industry.

The design change replaces the existing AC solenoid valve for AO-5042B with a DC solenoid valve (powered from essential 125 volt DC), to ensure operability without dependence on AC power. The new isolation valve, AO-5025, is also provided with a DC solenoid powered from the redundant 125 volt DC source. Both of these valves are normally closed and fail closed on loss of electrical and pneumatic power. One inch nitrogen lines are added to provide nitrogen to valves AO-5042B and AO-5025. New valve AO-5025 will be controlled by a remote manual key-locked control switch. During normal operation power to the AO-5025 DC solenoid will also be disabled by removal of fuses in the wiring to the solenoid valve. This satisfies NUREG 0800 SRP 6.2.4, Containment Isolation System acceptance criteria for a sealed closed barrier. An additional fuse will be installed and remain in place to power valve status indication for AO-5025 in the main control room.

A 20" pipe will replace the existing 20" diameter duct between SBGTS valves AON-108, AON-112 and the existing 20" pipe to the main stack. The existing 20" diameter duct downstream of AO-5042A is shortened to allow fitup of the new vent line branch connection.

A rupture disk will be included in the 8" piping downstream of valve AO-5025. The rupture disk will provide a second leakage barrier. The rupture disk is designed to open below containment design pressure, but will be intact up to pressures equal to or greater than those which cause an automatic containment isolation during any accident conditions.

New 8" vent pipe (8"-HBS-44), including valve AO-5025 is safety related. Vent piping downstream of AO-5025, including SBGTS discharge piping to main stack, is also safety related. All safety related piping will be supported as Class I. Nitrogen piping is non-safety related and will be supported as Class II/I.

If Fukushima had this design installed with the ability to open the Air Operated Valves (AOVs) to the hardened vent with DC power, then I suggest that they chose not to do this and tried to vent through the SBGT system which has low pressure duct work that failed because of the high pressure from containment venting. This would explain why the hydrogen was released into the reactor building.

Thanks Joe!

UPDATE with Commentary (mostly commentary)

ο WHERE DID THE HYDROGEN THAT EXPLODED UNIT 4 COME FROM?

o This is almost as perplexing a mystery as some WTC 7. TEPCO tenders up a hypothesis that the Hydrogen came from UNIT 3's Reactor Vessel Venting.

o TEPCO maintains that Unit 4 Spent Fuel Pool shows NO Damaged Fuel

o While it is true that Unit 3 and Unit 4 SHARE a Vent Stack, and therefore some of the Ductwork, how plausible is it that?

§ Unit 4 exploded almost 24 Hours AFTER Unit 3!

§ Iodine 131 was detected at Unit 4 Spent Fuel Pool!

§ Pictures of Unit 4 Spent Fuel Pool CLEARLY show damaged Fuel Assemblies!

ο What does this mean?

o All the Fuel at Unit 4 was in the Spent Fuel Pool due to a plant Outage

§ This "Fresh" fuel required much Decay Heat Removal in order to prevent Boiling in the Pool - Perhaps 600,000 WATTS of Energy to Remove

§ They Lost that ability When the Station Blackout (due to Tsunami) occurred

§ The Pool Heated up and Boiled or Evaporated enough Water off to EXPOSE even a portion of Fuel Assemblies

§ Once the Zirconium Fuel Cladding Reached 2200F, it underwent the infamous Zirc-Water Reaction - Liberating Huge amounts of Hydrogen which detonated.

§ This also means that Spent Fuel Pools need to kept from boiling dry

· Even here in the U.S. there is a Strategy to SPRAY Fuel in order to keep it cool - I have Doubts about the effectiveness of this Strategy

ο What Events Could Lead to a Fukushima?

o Let's realize that Fukushima was absolutely the Perfect One-Two Punch that any power plant ever endured

o So lets Boil it down to see what it really takes for ANY Nuclear Power Plant to "Fukushima"

§ Simple Answer - A Station Blackout of sufficient Duration (Total Loss of ALL Alternating Current Sources - and eventual DC Sources)

· Fukushima Lost Offsite Power due to the Earthquake, Then the Tsunami killed the Emergency Diesels. The Batteries ran down on other safety systems within a few hours

· Therefore, it took two Severe Events in a close time frame (OR one event of Long Duration WITH another Severe Event)

§ Let's examine Parallels to Other Events to another plant

· A Flood is a Severe Event of Long Duration

· IF another Severe Event occurs within the Recovery Duration - It may "Fukushima"

· How about a Flood Induced Earthquake concurrent with a Flood?

· Maybe Tornado/Hurricane Disabling the Power Grid (long duration) Concurrent with Something Else?

§ What else?

· In our Probabalistic Risk Assessments (PRA's) One of the MOST important Failures is Human Related

· Human Error/Design Error/Maintenance Error all are a huge Contributor

· We saw some of this just 3 weeks ago when on April 27, Browns Ferry was attacked by Tornados

o There was a Long Duration Loss of Offsite Power AND

o Some mechanical problems with Emergency Diesel Generators

· Fortunately, all went well because of Training, Procedures, and No Radiological Fields to contend with (but what if there was a fire too? We must always consider that an environment adverse to life could spring up

o While a Flood and a subsequent Earthquake are not the ONLY events that could lead to a Fukushima, I am attaching a Map of the New Madrid Fault and a link to some historical data (I try to use the government's own words, that way it minimizes the "kook factor" Also attached is a Map (courtesy Greenpeace) of locations of plants on fault lines.

http://earthquake.usgs.gov/earthquakes/world/historical.php/

http://earthquake.usgs.gov/earthquakes/states/events/1811-1812.php#february_7

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ο Why is Nuclear Power Plant Safety IMPORTANT

o Simple Answer - Ramifications of allowing Fission Products and Radioactive Particles to escape freely to the Environment

§ The unborn are at risk and so are their offspring

§ A tornado or hurricane will destroy homes, communities, and lives – but as we are seeing at Fukushima - the entire world will be affected. (One of my Co-Workers LOST his home during the April 27 Swarm of Tornados that took out the power from Browns Ferry, so my heart goes out to the people suffering such loss)

o Simple Answers - People!

o People who are responsible for maintaining a Questioning Attitude and Relentlessly seeking Improvement - but don't

§ Plant People who accept Good Enough, when Excellence is just a hurdle away (Homer Simpson)

§ Utility Management who place the Bottom Line ahead of achieving nuclear safety (Mr. Burns)

o Can People operate nuclear power plants safely?

§ I believe so. We need to stop dwelling in what "used" to be good enough and face reality that antiquated seismic evaluations, procedures, training, etc.

ο Where are we in Nuclear Power safety?

o My current assessment of Nuclear Power Plant Safety is as follows:

§ We in the United States and perhaps several other nations are about 12 Laps behind where we should be in the race to Nuclear Safety under all conditions, but we have lots of ground to cover. We are also way ahead of those emerging nuclear nations who desire to operate their first plants. Why do I think this?

§ The first reason is the same answer for both, why we are ahead, and why we are not winning - Maturity

§ Thanks to the time-honored teachings of Experience from the industry, nuclear navy, etc., we have Maturity to at least understand what "Good" looks like.

§ Unfortunately, due to a downturn in recruiting and training bright youths for this career, we have become Lazy and Complacent when it comes to tirelessly pursuing "Good." Due to the same Maturity issue, we have allowed ourselves to condone, "Acceptable," and "Marginal," and perhaps worse, because we desperately need the questioning minds of a fresh set of eyes on the problem.

§ This is especially true in a Dynamic Environment, where "what used to be OK, is no longer the case."

This is my shameless commercial for the industry where you can provide over a GigaWatt of electrical energy, Operate, Maintain, Manage, and Engineer a MILLION Horsepower Steam Engine - ALL WITHOUT Burning a molecule of Oxygen.

ο What do we need to do?

o See my Nuclear Safety Wish List

o Restore Safety Culture and Objectivity by getting Fresh Eyeballs on the problems

* Lots mre but for now. .. Chris in Delaware Senior Reactor Operator