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 Ø 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.