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Japan Earthquake: nuclear plants

by gmax137
Tags: earthquake, japan, nuclear
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wizwom
#12475
Mar3-12, 10:01 AM
P: 71
Quote Quote by duccio View Post
Are you sure about the 1MW? They're keeping the reactors cool with 6 or 9 t/hour of water, I don't believe that would be enough if the core was still emitting that much energy...
Well, 7.2t/hr would be 500J/gram for 1MW, which is a low heat rate, easily handled. Since they are not seeing temperature rises, but staying about 45C (so, 15-25C above ambient), they have it at a steady state.

But even 0.6 MW is WAY too high for purely decay product radiation. Full power was only 1.2GWth for reactor 1, and 1.8GWth for 2 & 3, we'd expect purely decay heats in the hundreds of watts range after almost a full year shutdown. The fact that they have to continue pumped active cooling is a tacit statement that there is still significant fission occurring in the reactors, that is, the debris at the bottom is basically an almost uncontrollable reactor.
CaptD
#12476
Mar3-12, 10:26 AM
P: 20
Quote Quote by wizwom View Post
Well, 7.2t/hr would be 500J/gram for 1MW, which is a low heat rate, easily handled. Since they are not seeing temperature rises, but staying about 45C (so, 15-25C above ambient), they have it at a steady state.

But even 0.6 MW is WAY too high for purely decay product radiation. Full power was only 1.2GWth for reactor 1, and 1.8GWth for 2 & 3, we'd expect purely decay heats in the hundreds of watts range after almost a full year shutdown. The fact that they have to continue pumped active cooling is a tacit statement that there is still significant fission occurring in the reactors, that is, the debris at the bottom is basically an almost uncontrollable reactor.
I agree with your reasoning; there is "much" more going on below reactors 1-3
... than anyone would describe as acceptable in a "cold shutdown"...
zapperzero
#12477
Mar3-12, 10:31 AM
P: 1,042
Quote Quote by wizwom View Post
Full power was only 1.2GWth for reactor 1, and 1.8GWth for 2 & 3, we'd expect purely decay heats in the hundreds of watts range after almost a full year shutdown.
We would? Care to share your calculation?
etudiant
#12478
Mar3-12, 10:38 AM
PF Gold
P: 858
Quote Quote by wizwom View Post
Well, 7.2t/hr would be 500J/gram for 1MW, which is a low heat rate, easily handled. Since they are not seeing temperature rises, but staying about 45C (so, 15-25C above ambient), they have it at a steady state.

But even 0.6 MW is WAY too high for purely decay product radiation. Full power was only 1.2GWth for reactor 1, and 1.8GWth for 2 & 3, we'd expect purely decay heats in the hundreds of watts range after almost a full year shutdown. The fact that they have to continue pumped active cooling is a tacit statement that there is still significant fission occurring in the reactors, that is, the debris at the bottom is basically an almost uncontrollable reactor.
Not sure that is correct.
According to Wikipedia here: https://en.wikipedia.org/wiki/Decay_heat
spent fuel has a decay heat of about 10 kW/ton after one year.
The indicated values would be about in line with the reactor fuel loadings.
CaptD
#12479
Mar3-12, 10:41 AM
P: 20
Quote Quote by wizwom View Post
Well, 7.2t/hr would be 500J/gram for 1MW, which is a low heat rate, easily handled. Since they are not seeing temperature rises, but staying about 45C (so, 15-25C above ambient), they have it at a steady state.

But even 0.6 MW is WAY too high for purely decay product radiation. Full power was only 1.2GWth for reactor 1, and 1.8GWth for 2 & 3, we'd expect purely decay heats in the hundreds of watts range after almost a full year shutdown. The fact that they have to continue pumped active cooling is a tacit statement that there is still significant fission occurring in the reactors, that is, the debris at the bottom is basically an almost uncontrollable reactor.
I agree with your reasoning; there is "much" more going on below reactors 1-3
... than anyone would describe as acceptable in a "cold shutdown"...
Rive
#12480
Mar3-12, 10:42 AM
P: 355
Quote Quote by wizwom View Post
The fact that they have to continue pumped active cooling is a tacit statement that there is still significant fission occurring in the reactors, that is, the debris at the bottom is basically an almost uncontrollable reactor.
Nope. That almost MW scale heat production comes from decay, not fission. There is no sign of ongoing chain reaction in any of the damaged reactors and without chain reaction the heat from spontaneous fissions in nuclear fuel is practically negligible.
rmattila
#12481
Mar3-12, 10:50 AM
P: 242
My sketches from spring ( http://www.physicsforums.com/showpos...postcount=5788 ) give around 400 - 600 kW, so it seems we're on the same map.
tsutsuji
#12482
Mar3-12, 04:50 PM
PF Gold
P: 1,220
Continuation of the translation started on http://www.physicsforums.com/showpos...ostcount=12465

1 March report http://www.tepco.co.jp/cc/press/betu...es/120302a.pdf attachments 7-1 and 7-2 p. 40/91-41/91 :

Attachment 7-1 Jet pump instrumentation work: implementation plan and problems (work preparation)

1. Work flow

①decontamination⇒②bring machinery and materials, prepare the area (temporary lighting, etc.)⇒③remove obstacles ⇒④installation of working floor (temporary scaffolding)⇒⑤bring in and install shielding material (in the vicinity of the penetration)⇒⑥final clean up

2. Problems (constraints as regards application methods and feasibility) and solutions

①decontamination

Constraints as regards application methods and feasibility
* radiation decrease obtained from decontamination
* radiations in penetration parts are unknown
* decontamination domain/method are undecided
* If the PCV outer wall is to be decontaminated, the installation of a working floor is necessary

Solutions
* radiation measurements. perform assessment before starting the work.
* perform radiation measurements in penetration parts
* study decontamination domain/method. Develop equipments.
* before starting work, perform onsite inspection for the installation of working floor

②bring machinery and materials, prepare the area (temporary lighting, etc.)

Constraints as regards application methods and feasibility
* need of detailed estimate of quantities of each material and machinery needed for the work
* need to study methods to lift machinery and materials up to the penetration level.
* ensure that obstacles are absent on the transportation route

Solutions
* detailed listing and study of quantities of each material and machinery needed for the work
* perform onsite survey
* perform onsite survey as regards transportation route. Also, adjust interferences with the working spaces of other works

③remove obstacles
Constraints as regards application methods and feasibility
* the presence of obstacles, interfering objects is unknown

Solutions
* perform onsite survey

④installation of working floor (temporary scaffolding)

Constraints as regards application methods and feasibility
* need to study if we decide to use a scaffolding or a lifter
* the working floor must secure a 2 m x 2 m area

Solutions
* study after performing onsite survey
* perform onsite survey and check the presence of obstacles.

⑤bring in and install shielding material (in the vicinity of the penetration)

Constraints as regards application methods and feasibility
* in function of the radiation around the penetration, shield installation can be necessary
* we plan to perform the time consuming thermometer insertion work in a shielded area installed on the floor level

Solutions
* planning of shielding after onsite survey and radiation measurements
* onsite survey of the floor. Study of the shield's location and shape.

⑥final clean up

Constraints as regards application methods and feasibility
* the piping work and the insertion work's clean-up materials and machinery, and the final situation are unknown

Solutions
* list up the the piping work and the insertion work's clean-up materials and machinery and check the final situation

Attachment 7-2 Jet pump instrumentation work: implementation plan and problems (piping work)

1. Work flow

①check onsite working area (presence or absence of obstacles, etc.)⇒②preparation work (temporary electric power source, covering, etc.)⇒③fill water into the pipe (near the PCV penetration)(fill water from the instrumentation line, etc.)⇒④install the tool needed for pipe freezing and fill dry ice (or liquid nitrogen) into the tool⇒⑤check that the pipe is frozen⇒⑥install pipe cutting tool(omitted if cutting by hand is possible)⇒⑦pipe cutting⇒⑧globe valve body removal {case of alternative plan}⇒⑨machining of groove⇒⑩pipe welding (to attach stop valve)⇒⑪additional piping installation and pipe binding

2. Problems (constraints as regards application methods and feasibility) and solutions

Common problems and solutions for ③⇒④⇒⑤⇒⑥⇒⑦⇒⑧⇒⑨⇒⑩⇒⑪

[Problems of the pipe freezing and cutting method]

Method by filling water between the stop valve and the PCV penetration end plate, freezing the pipe to obstruct it, and cutting the pipe right before the valve.

1) Since the distance between the PCV penetration end plate and the stop valve is short (expected to be 300 mm or less), it is thought that stoppage by freezing the pipe is difficult.
2) As mentioned above, it is thought that creating enough space to cut the pipe between the PCV penetration end plate and the pipe [???] is difficult.
3) Even if stoppage by freezing is achieved, the frozen plug is formed in the short space of the straight part of the pipe, and there is a risk that the frozen plug gets removed. (in the normal pipe freezing method, the ice plug is formed in a discontinuous part such as an elbow, so that it does not get removed)
4) When freezing is performed, it is necessary to build a temporary box where dry ice, alcohol, etc. is injected, but as this interferes with other instrumentation lines, it is thought that such a construction is difficult.
5) It is necessary to secure a method to confirm freezing.
6) It is necessary to maintain freezing under high radiations.

[Solutions to the problems of the pipe freezing and cutting method]

1), 3), 5) The freezing method is confirmed by a mock-up test.
2) As mentioned below, an alternative plan is studied where the pipe is cut downstream the valve
4) Study of the pipe freezing tool where dry ice or alcohol is injected
6) Study of a method to maintain freezing and to survey freezing during the work. Study of freezing substance replenishment method.

[Problems of the alternative method]

Method: the frozen area is extended to the valve entrance, and the pipe is cut downstream the valve. After cutting downstream the valve, a tool is inserted through the cut opening. Then the valve body, etc. is removed as it would be an obstacle when the thermometer is inserted.

1) It is necessary to study and develop a valve body removal device.

[Solutions to the problems of the alternative method]

1) The valve body removal tool is checked with a mock-up test.

[Other problems]

1) The working location is in high elevation (about 5 m) and high radiation. If the radiation is not lowered, the workers can merely go to the working location and cannot work. Also, remote surveillance, remote controlled operations and shielding, etc. must be studied.
2) In order to measure the dimensions regarding the distance between the PCV penetration end plate and the stop valve, an onsite check must be done.
3) As the working location is a narrow space, it is possible that obstacles interfere.
4) As it is necessary to fill water into the pipe before freezing, it is necessary to study the water filling method and the way to confirm water seal.
5) As the working environment is with high radiations, as an access to an elevated place must be provided, and as the method is not certain, it is not possible to estimate how many workers are needed.

[Solutions to the other problems]

1) before the work in the high radiation area, workers perform training drills, and the work must be done after the working efficiency has been improved.
2) before the work, an onsite survey is performed to measure the dimensions.
3) before the work, an onsite survey is performed to check the presence of obstacles, and countermeasures are studied.
4) the water filling method is studied after inspecting the injection line for example on the side of the instrumentation rack
5) after performing mock-up tests and taking the final decision about the working method, an evaluation of which workers are needed is performed.
duccio
#12483
Mar3-12, 06:17 PM
P: 21
Quote Quote by wizwom View Post
Well, 7.2t/hr would be 500J/gram for 1MW, which is a low heat rate, easily handled. Since they are not seeing temperature rises, but staying about 45C (so, 15-25C above ambient), they have it at a steady state.
Maybe I'm getting it completely wrong, but 500 Joules/gr should be around 120 calories... or +120 degrees C. At atmospheric pressure, water would evaporate well before taking away all the heat. Besides, if water would evaporate at such high rate, where does the water accumulating in the basement come from?
etudiant
#12484
Mar3-12, 07:26 PM
PF Gold
P: 858
Quote Quote by duccio View Post
Maybe I'm getting it completely wrong, but 500 Joules/gr should be around 120 calories... or +120 degrees C. At atmospheric pressure, water would evaporate well before taking away all the heat. Besides, if water would evaporate at such high rate, where does the water accumulating in the basement come from?
Apparently TEPCO estimates inflows from ground water through the cracked walls of the plant at around 500 tons/day. To stop that, TEPCO would need to build a barrier all around the plant, a non trivial task given continuing aftershocks in the area. Moreover, inflows are a lot less problematical than outflows which could contaminate the groundwater.

Re the decay heat absorption by the water injection, it seems plausible that the heat is boiling some of the water, as the fuel is probably concentrated in some piles that are getting sprinkled, rather than held in rods bathed in coolant.
Rive
#12485
Mar4-12, 02:38 AM
P: 355
http://www.tepco.co.jp/en/nu/fukushi...20302_05-e.pdf

My question is: will they continue to operate the radioactive filtering, or they will just switch to the desalinating facility?

As I understand, damaged spent fuel under water releases the fission products continuously: so if they cease filtering for radioactive materials then the radioactivity of the water in the pool will start increase again (if the pool contains damaged fuel: I think it likely does in case of U3 and U1).

For the SFP of U1 they had stopped the filtering for radioactive materials. Do we know anything about the concentrations afterward?

Ps.: about the decay heat of the cores: maybe we can put together a rough estimation about the 'power' already removed from the cores by the cooling water. How much is the heat production of an used, 'spent' filtering tower used for the decontamination of water from the basements? How many towers were used up till now? Any information, anybody?
zapperzero
#12486
Mar4-12, 04:05 AM
P: 1,042
Quote Quote by Rive View Post
http://www.tepco.co.jp/en/nu/fukushi...20302_05-e.pdf

Ps.: about the decay heat of the cores: maybe we can put together a rough estimation about the 'power' already removed from the cores by the cooling water. How much is the heat production of an used, 'spent' filtering tower used for the decontamination of water from the basements? How many towers were used up till now? Any information, anybody?
I wonder if it's worth it. I think it's bound to be only a couple of percent of the total and we have much larger sources of uncertainty still - such as exactly for how long the fuel had been used before scram.
SteveElbows
#12487
Mar4-12, 07:13 AM
P: 630
Quote Quote by Rive View Post
http://www.tepco.co.jp/en/nu/fukushi...20302_05-e.pdf

My question is: will they continue to operate the radioactive filtering, or they will just switch to the desalinating facility?

As I understand, damaged spent fuel under water releases the fission products continuously: so if they cease filtering for radioactive materials then the radioactivity of the water in the pool will start increase again (if the pool contains damaged fuel: I think it likely does in case of U3 and U1).

For the SFP of U1 they had stopped the filtering for radioactive materials. Do we know anything about the concentrations afterward?
It sounds like they just did it in order to get ready for desalination, although I suppose they could restart filtering again later if they needed to.

Did they even filter unit 1's pool? I don't remember, I know they did reactor 2's pool because here are the results:

http://www.tepco.co.jp/en/nu/fukushi...11206_01-e.pdf

For reference, here are initial evaluations of fuel pool contamination:

http://www.tepco.co.jp/en/nu/fukushi...10825_02-e.pdf

Also http://www.tepco.co.jp/en/nu/fukushi...10906_03-e.pdf and http://www.tepco.co.jp/en/nu/fukushi...10624_02-e.pdf and http://www.tepco.co.jp/en/nu/fukushi...10708_02-e.pdf
SteveElbows
#12488
Mar4-12, 07:31 AM
P: 630
Quote Quote by etudiant View Post
Thank you, SteveElbows.
That is exactly the kind of info that would help, if it is available for prior dates as well, ideally at least monthly since the accident.
November: http://www.tepco.co.jp/en/nu/fukushi...11118_01-e.pdf

December: http://www.tepco.co.jp/en/nu/fukushi...11212_01-e.pdf

Before then it looks like the published data was not in such a comprehensive format, e.g.:

October: http://www.tepco.co.jp/en/nu/fukushi...11021_02-e.pdf

September: http://www.tepco.co.jp/en/nu/fukushi...10909_02-e.pdf

Also a document from late October that contains a load of detail about the facilities, and some charts towards the end:

http://www.tepco.co.jp/en/nu/fukushi...11029_03-e.pdf
etudiant
#12489
Mar4-12, 07:45 AM
PF Gold
P: 858
Quote Quote by SteveElbows View Post
It sounds like they just did it in order to get ready for desalination, although I suppose they could restart filtering again later if they needed to.

Did they even filter unit 1's pool? I don't remember, I know they did reactor 2's pool because here are the results:

http://www.tepco.co.jp/en/nu/fukushi...11206_01-e.pdf

For reference, here are initial evaluations of fuel pool contamination:

http://www.tepco.co.jp/en/nu/fukushi...10825_02-e.pdf

Also http://www.tepco.co.jp/en/nu/fukushi...10906_03-e.pdf and http://www.tepco.co.jp/en/nu/fukushi...10624_02-e.pdf and http://www.tepco.co.jp/en/nu/fukushi...10708_02-e.pdf
Thank you, SteveElbows, for this very helpful data.
Does not the relatively low radioactivity in SPF 4 invalidate the hypothesis that the explosions in reactor 4 arose out of a fuel cladding failure after the SPF ran dry?
Surely SPF4 would be much more contaminated if unclad, partially used fuel pellets were in the water.

Separately, I'm puzzled by the reference to Iodine 131 levels on P13 of your previous linked document here:
http://www.tepco.co.jp/en/nu/fukushi...11029_03-e.pdf

That shows I 131 levels at about 10**4 Bq/cc pretty steadily from June to late Oct. As this is about 20 half lives, something does not jibe.
SteveElbows
#12490
Mar4-12, 08:22 PM
P: 630
Quote Quote by etudiant View Post
Thank you, SteveElbows, for this very helpful data.
Does not the relatively low radioactivity in SPF 4 invalidate the hypothesis that the explosions in reactor 4 arose out of a fuel cladding failure after the SPF ran dry?
Surely SPF4 would be much more contaminated if unclad, partially used fuel pellets were in the water.

Separately, I'm puzzled by the reference to Iodine 131 levels on P13 of your previous linked document here:
http://www.tepco.co.jp/en/nu/fukushi...11029_03-e.pdf

That shows I 131 levels at about 10**4 Bq/cc pretty steadily from June to late Oct. As this is about 20 half lives, something does not jibe.
I think much interest was lost in SFP 4 explosion hypothesis after such data came out, especially when combined with videos of the pool contents, and alternative explanation for building 4 exploding. Especially when combined with the info about the reactor well & d/s pit water flowing into the fuel pool due to gate losing its seal. Japan realised that reactor 3 pool was more of a concern than reactor 4 pool as early as the day they tried to drop water from the helicopter, but it took others much longer to accept that unit 4 fuel pool was not the nightmare that had been assumed. This was one of the most striking things about the transcripts of the US NRC that were released a little while ago, the guy they sent to Japan had trouble accepting that the pool still existed or had water in it, even after he had seen the first helicopter video. This is very understandable given the decay heat in that pool and the explosion, and we kept talking about unit 4 pool in a scary manner for a lot longer, but eventually it became clear that the reactor 3 pool was probably worthy of more attention than reactor 4's.

As for the I131 stuff in that chart, I spent a while staring at the underlying data and decided that its the same as is available in the other relevant press release handouts that I linked to (e.g. September and October links in my last post).

But what they have done is to plot on the graph the I131 levels even when the raw data shows that I131 was N.D (below detection limit). They have plotted the detection limit that is shown under the N.D, and failed to make any mention of this on that chart, so it causes confusion. Some of the very first entries from June were not below the detection limit.

e.g. this one (of quite a few others that I won't post now) from June:

http://www.tepco.co.jp/en/nu/fukushi...10624_04-e.pdf

By August its gone N.D as we can see from these handout for August which I just located:

http://www.tepco.co.jp/en/nu/fukushi...10812_01-e.pdf

http://www.tepco.co.jp/en/nu/fukushi...10820_02-e.pdf

As usual their detection limits fluctuate a bit, and thats whats ended up being plotted on that chart.

For comparison the last page of this document shows us JAEA analysis of water from turbine buildings of all 4 of the reactors, sampled in the latter part of march and analysed in mid april.

http://www.tepco.co.jp/en/nu/fukushi...10522_04-e.pdf

As usual, reactor 2 gives us some rather large numbers as a starting point.
etudiant
#12491
Mar4-12, 10:45 PM
PF Gold
P: 858
Quote Quote by SteveElbows View Post
I think much interest was lost in SFP 4 explosion hypothesis after such data came out, especially when combined with videos of the pool contents, and alternative explanation for building 4 exploding.

As for the I131 stuff in that chart, what they have done is to plot on the graph the I131 levels even when the raw data shows that I131 was N.D (below detection limit). They have plotted the detection limit that is shown under the N.D, and failed to make any mention of this on that chart, so it causes confusion. Some of the very first entries from June were not below the detection limit.

.
Thank you, very helpful again.
You have more dedication that I do, to pore over the TEPCO releases that carefully.

Am still a little surprised by SPF 4, as the sharp decline in emissions was pretty exactly coincident with the spraying of water onto it, around Mar 19 if memory serves. There must have been something else happening concurrently that was not adequately appreciated.
tsutsuji
#12492
Mar5-12, 07:40 AM
PF Gold
P: 1,220
Continuation of the 1 March report translation (part 3)
http://www.physicsforums.com/showpos...ostcount=12465 part 1
http://www.physicsforums.com/showpos...ostcount=12485 part 2

1 March report http://www.tepco.co.jp/cc/press/betu...es/120302a.pdf attachment 7-3 p. 42/91 :

Attachment 7-3 Jet pump instrumentation work: implementation plan and problems (insertion work)

1. Work flow

①transportation of machinery and materials⇒②installation of machinery and materials⇒③work preparation⇒④thermocouple insertion⇒⑤final check of work execution

2. Problems (constraints as regards application methods and feasibility) and solutions


①transportation of machinery and materials

Constraints as regards application methods and feasability
* Tool and equipment design taking into consideration transportability by human force in narrow space and under high radiation, is needed.
* If the installation is on an elevated floor, there is a need to think of the method to lift machinery and materials up to the elevated place.

Solutions
* Study of most suitable design based on study of method

②installation of machinery and materials

Constraints as regards application methods and feasability
* Tool and equipment design taking into consideration workability in narrow space and under high radiation, is needed.
* If the installation is on an elevated floor, there is a need to think of the workability in such elevated place.

Solutions
* Study of most suitable design based on study of method

③work preparation

Constraints as regards application methods and feasability

[securing boundary after the pipe and the equipment have been connected]

* After the new stop valve on the pipe side, etc. is turned to "open", the following risks have to be thought :
⇒The injected water leaks (in case the water level is higher than the pipe)
⇒The reactor gasses leak (especially hydrogen, radioactive gasses)

* It is necessary to think of an equipment function that stops or lowers the leaks by purge gas supply
development of purge/seal function

* It is necessary to design a seal function using O-rings, etc.
(the perfect sealing of a cable devoid of rigidity is difficult ⇒ the design must probably be based on a leaking allowance)
* low resistance, high durability sealing function
* the sealing function must allow sealing diameter differences (sensor and cable)

Solutions
* testing of the characteristics of materials and machinery ; suitability checking with mock-up
* If suitable materials and machinery don't exist, it is necessary to develop new ones

④thermocouple insertion

Constraints as regards application methods and feasability

(1) reactor gasses and injected water leaks during work execution : see work preparation

(2) materials and machinery such as the inserted thermocouple (whether universal products are suitable)
selection of a thermocouple that responds to the insertability, measured temperature range, radiation conditions.

constraints regarding cable thickness
* it must be both flexible enough to pass elbows and rigid enough to be insertable
* it must be able to pass the orifice (about 6 mm)
* selection of material with concern for degradation (a periodical replacement is also an option)

protection of the extremity during insertion
* If the thermocouple is not protected, it will be hurt during insertion, so that a protection is necessary, which does not prevent temperature measurement.
* In function of the chosen protection method, the temperature sensing responsiveness can be reduced

study of accompanying material
* In order to confirm arrival at destination, etc. an accompanying camera is desirable.
(regarding size, passing the orifice is a problem)

Solutions to (1),(2)
* testing of the characteristics of materials and machinery ; suitability checking with mock-up
* If suitable materials and machinery don't exist, it is necessary to develop new ones

(3) mechanism for the inserted thermocouple, etc. (features to be developped)
* As the stroke is long, insertion might not be possible by pushing force only

Study of insertion mechanism
* Reducing the candidates to a short list, the features are checked in mock-up tests (it is possible that universal products won't pass the tests)
* Insertion resistance control method when insertion is performed in accordance with the pipe (it is necessary to feel elbows, orifices)

Solutions to (3)
* testing of the characteristics of materials and machinery ; suitability checking with mock-up
* If suitable materials and machinery don't exist, it is necessary to develop new ones as follows:
⇒self propusion of the extremity (a new development is necessary, but as the diameter is small, it is difficult)
⇒self adjustment of the extremity (development of a mechanism to change the direction of the extremity so that the insertion is performed in accordance with an elbow, etc.)
⇒auxiliary mechanisms (study of insertion auxiliary methods using compressed gas, compressed water, etc.)

(4) In relation with the insertion device (important elements to be developped)
As the necessary equipments related to insertion power, insertion mechanism are not available on the market, new specialized equipments have to be designed and developped.
If the sealing function is necessary, the insertion device itself will become a boundary, and the soundness as boundary is necessary.

Development ES uncertainties
Compared to the first entry equipments, the stroke is long and it is necessary to pass through narrow and complicated routes (it is necessary to meet the conditions mentioned in (3)), so that it is difficult to respond within a normal development duration.

Solutions to (4)
* With the shortest ES duration in mind, it is necessary to develop a new insertion equipment combining parts available on the market.
* Check suitability with mock-up

⑤final check of work execution

Constraints as regards application methods and feasability

(1) Arrival criteria : arrival at the tip of nozzle N8 "Jet pump instrumentation line penetration seal (reactor outside)" is a prerequisite (no insertion into reactor inside)
* In case the thermocouple is inserted alone, stroke management is a prerequisite.
* In order to check arrival with certainty, simultaneous insertion of camera, etc. is desirable (whether the size allows the passing of orifices is a problem)

Solutions to (1)
* testing of the characteristics of materials and machinery ; suitability checking with mock-up
* If arrival cannot be confirmed, a new development is necessary

(2) Check of measurement object (check of contact / verification of measured temperature)
When it is judged that insertion and arrival have been completed, is the measured temperature that of the nozzle metal ? Or is it that of the nozzle atmosphere ? It is necessary to make that clear.

* With machinery and materials in mind : check of arrival and contact (if the tip of the thermocouple is protected by a protective part, there is no direct contact)
There is a risk that if the arrival is checked with the stroke alone, it will be difficult to reach a conclusion on the sensor position.

Solutions to (2)
* adopt clear criteria
* analysis-oriented study
⇒making assumptions on reactor interior status, execute heat transmission analyis, etc. of reactor lower part, nozzle, nozzle interior atmosphere, etc.
⇒study of responsiveness against temperature variations.


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