BWR Incore Instrumentation

[wlrun3@aol.com]

   LPRMs are changed out from the refuel floor...SRMs and IRMs are changed out from under vessel...

   Do the TIPs penetrate the vessel from below or from the side?

   Are there any significant variations from this general scheme, especially in the BWR 6s?

[refuelflunkie]

In a BWR 6, LPRM's are changed out from under vessel.  TIPs also enter the core via under vessel through an indexer located in the drywell.  The drive box is located in the Reactor Building just above the supression pool.

[RAD-GHOST]

All the TIP systems I have seen, "Transversing Incore Probes", have entered through the under vessel instrumentation paths. 

The system is typically configured as such:

Drive Box/Position Indicator, I/S the TIP room, O/S the TIP room, or on the TIP room roof.
Tip Shield, always in the TIP room.
Ball type indication, again in the TIP room, (tells operations when the little bugger has left Containment).
Outboard Isolation valve, last, but not least in the TIP room.
Inboard Isolation valve, immediately I/S containment.
Five Path, I/S Containment.
Ten Path, I/S Containment.
Dry Tubes, Under vessel and inserted about twelve feet into the core. (Path that the TIP follows).

They have variable speeds, normal and get the hell out of here when necessary!

TIP detectors are fission chambers, (Special Nuclear Material....U-235), and normally leave containment well in access of the VHR range.  Although the majority of the detectors fission products decay rather quickly, the cable and detector casing does not, especially the transition point of the drive cable to detector!  I'm not sure what material they used to fuse that transition, but it gives a new meaning to the theory of point source!  400 mr/hr @ 12" can easly equate to 400 R/hr @ contact, after a ten year decay!

Where's the Seal Table..........Don't Ask!

Systems 101.............RG!     

[wlrun3@aol.com]

   ...thankyou...

[RRhoads]

All the TIP systems I have seen, "Transversing Incore Probes", have entered through the under vessel instrumentation paths. 

Correct in a General Electric Type 5...you have to duck under/crawl over the damn things in the drywell.

[azkidd]

In a BWR 6, the Drive Boxes are in Containment.  They drive the TIPs into an indexer, inside the Drywell, the Indexer directs it under vessel, and up into the vessell.  RAD GHOST is right; a BWR 6 has 5 drive boxes.  The TIPs are pulled inside the Bioshield wall between Containment and the Drywell for storage/decay.  LPRM's, IRM's, and SRm"s are all pulled from under vessel, of course unless you have a "stuck" LPRM.  It is then pulled with the drytube from the refuel floor.  Seal table??  I believe the seal table serves as the indexer?? in a PWR.  You can find them located in the Rx Cavity itself in some PWR's, and outside the bioshield, in Containment in others.  That is where the probes are pulled, and inserted in a PWR.

[wlrun3@aol.com]

   ...thankyou Azkidd...

   ...is Palo Verde the only PWR with seal table in the cavity?...

[azkidd]

CORRECTION!!  The LPRM's are inserted into the table and pulled from the reactor in a PWR.  Sorry 

I cannot answer that question.  I haven't been to ALL the PWR's in the country.  However, another acronym in a BWR 6 is an "APRM".  An APRM consists of a number of LPRM's, a number of IRM's and a number of SRM's...together this is an APRM.  I have forwarded this topic to a "Resident Expert" of undervessel activities in a BWR 6.  He is considered a Man of Men??  One who is feared due to his in depth knowledge of the different arrays of .....PRM's??  Look for his answer.  I think his Nukeworker handle is "Nedstrodamous" 

BTW..you are welcome.

[wlrun3@aol.com]

   ..."Five Path, I/S Containment.
Ten Path, I/S Containment."

   ...do all the bwr's have this?...thankyou radghost.

[refuelflunkie]

   ..."Five Path, I/S Containment.
Ten Path, I/S Containment."

   ...do all the bwr's have this?...thankyou radghost.

No.  Speaking for how River Bend  (BWR 6) is set up, we have four drives that each feed into a ten path indexer.  The drives are located in the RX bldg. on a platform above the suppression pool. The indexers are located in the DW outside of the bioshield.  When not in use the detectors are stored in the DW wall.

[RRhoads]

CORRECTION!!  The LPRM's are inserted into the table and pulled from the reactor in a PWR.  Sorry 

I cannot answer that question.  I haven't been to ALL the PWR's in the country.  However, another acronym in a BWR 6 is an "APRM".  An APRM consists of a number of LPRM's, a number of IRM's and a number of SRM's...together this is an APRM.  I have forwarded this topic to a "Resident Expert" of undervessel activities in a BWR 6.  He is considered a Man of Men??  One who is feared due to his in depth knowledge of the different arrays of .....PRM's??  Look for his answer.  I think his Nukeworker handle is "Nedstrodamous" 

BTW..you are welcome.

APRM=average power range monitor
not just in Mark 6's..5's as well

[tr]

The earlier statement that "An APRM consists of a number of LPRM's, a number of IRM's and a number of SRM's...together this is an APRM." is incorrect.  The APRM is designed for power operation (something like 0-125%), and uses LPRMs as input.  The LPRMs that input to a given APRM are scattered enough throughout the core that the APRM reads an average power.  The IRMs and SRMs are independent instruments that do not feed into the APRMs at all.  All 3 (APRM, IRM, SRM) feed into the reactor trip system.

[wlrun3@aol.com]

   ...people that actually know...how inspiring...again...thankyou...

[Motown homey]

The earlier statement that "An APRM consists of a number of LPRM's, a number of IRM's and a number of SRM's...together this is an APRM." is incorrect.  The APRM is designed for power operation (something like 0-125%), and uses LPRMs as input.  The LPRMs that input to a given APRM are scattered enough throughout the core that the APRM reads an average power.  The IRMs and SRMs are independent instruments that do not feed into the APRMs at all.  All 3 (APRM, IRM, SRM) feed into the reactor trip system.

Also, the IRMs (Intermediate Range Monitors) and the SRMs (Source Range Monitors) are at the end of rods that drive them into the vessel when they are needed and retract them from the vessel when they aren't needed.   This keeps the U235 that's used as the target media from depleting faster than necessary.

[Fermi2]

The earlier statement that "An APRM consists of a number of LPRM's, a number of IRM's and a number of SRM's...together this is an APRM." is incorrect.  The APRM is designed for power operation (something like 0-125%), and uses LPRMs as input.  The LPRMs that input to a given APRM are scattered enough throughout the core that the APRM reads an average power.  The IRMs and SRMs are independent instruments that do not feed into the APRMs at all.  All 3 (APRM, IRM, SRM) feed into the reactor trip system.

Only 95% Correct. While the SRM feed into RPS (BWR do not have a Reactor Trip System, they have a Reactor Protection System, RTS is a PWR term) they do not provide Reactor Scram Capability under normal operations. Normally they are jumped out with Shorting Links. The only time you remove the shorting links is during strongest rod out testing which is the BWR Kindergarten form of Physics Testing.

Also, SRM and IRM do not retract from the Reactor Vessel. IIRC during Start Up both are inserted to about 3 feet above core centerline. As Neutron Counts increase you withdraw the SRM in order to keep them onscale. By the time the IRMs are at a certain scale you expect the SRM to be in their Withdrawn condition. After you enter Mode 1 which is somewhere on IRM Range 10 you place the Mode Switch into Power Operation Mode 1 and withdraw the IRM. The fully withdrawn IRM and SRM Position is about 3 feet below the bottom of the core which is well inside the vessel. 100% on IRM range 10 is 30% power, and each range below that is 3.16 times below that so every other range is about a decade. Range 8 would be 3 % power. I might have one number off, and that might be the position of the IRM and SRM when fully inserted. It might be 1.5 feet above core centerline with the fully out position about 4.5 feet below the bottom of the core. IIRC they moved at 3.33 Feet per minute. I know it sucked having to withdraw all 8 IRM because Fermi did not have Seal in for Withdraw. Ranging IRM until the POAH literally SUCKED especially if someone cowboyed a low reactor peiod.

As I was leaving the BWR World they were coming out with the NUMAC Wide Range Monitor system where all APRM, IRM and SRM signals were routed through a NUMAC Computer. The signals came from the same places as usual but were no longer routed through huge cabinets. Fermi had NUMAC APRMs when I left, everything that took a cabinet that was 12 feet high was being done in a tiny box. Don't confuse Wide Range Power Monitor with APRM. WRPM process IRM, SRM and APRM Signals but they are still different instrumentation systems.

Mike

[Len61]

Yep,
At BFN it's 18" above C/L when full in.
We have the NUMAC's, but the IRM's & SRM's do not input to them.
Len

[flamatrix99]

CORRECTION!!  The LPRM's are inserted into the table and pulled from the reactor in a PWR.  Sorry 

I cannot answer that question.  I haven't been to ALL the PWR's in the country.  However, another acronym in a BWR 6 is an "APRM".  An APRM consists of a number of LPRM's, a number of IRM's and a number of SRM's...together this is an APRM.  I have forwarded this topic to a "Resident Expert" of undervessel activities in a BWR 6.  He is considered a Man of Men??  One who is feared due to his in depth knowledge of the different arrays of .....PRM's??  Look for his answer.  I think his Nukeworker handle is "Nedstrodamous" 

BTW..you are welcome.

As far as a BWR 6 goes (specifically River Bend) there are 8 APRM channels. Four in Div I and four in Div 2. Each Div 1 APRM has 17 LPRM inputs and each Div 2 has 16 LPRM inputs. If there are less then 11 LPRMs inputs you will get an APRM Inop.

There are no SRMs or IRMs in the APRM circuitry.

[wlrun3@aol.com]

   ...are the low range power monitors, source range monitors, intermediate range monitors and traversing incore probes all uranium fission chambers...