NuMI Target Pile Shielding Review July 27, 2001

Response to comments from previous (Sept 2000) Review

Subject: Comments on Minos target pile

Date: Fri, 29 Sep 2000 15:07:40 -0500

From: Jim Kilmer \<kilmer@fnal.gov\>

To: Greg Bock \<Bock@fnal.gov\>, Jim Hylen \<hylen@fnal.gov\>,

Dave Pushka \<pushka@fnal.gov\>

CC: Craig Moore \<cmoore@fnal.gov\>, \"David B. Augustine\"
\<augustine@fnal.gov\>,

Ernie Villegas \<villegas@fnal.gov\>, Jim Kilmer \<Kilmer@fnal.gov\>,

Pat Hurh \<hurh@fnal.gov\>, Paul Czarapata \<PCCEED@fnal.gov\>

Gentlemen,

Here are my comments on the review. I\'ve also appended all of the
comments

from the other members of the team.

Jim Kilmer\'s list:

1\. How do you grab a T block remotely with the crane? Needs to be done

in a radiation field later.

Each T-block will have a handle welded on top. A special hook has been
designed which attaches to the crane and can slip under the handle
remotely. A prototype T-block has been constructed, and a test of the
remote pickup will happen in the near future. A set of cameras will be
set up so that the crane operator can move T-block without being close
to the radioactivated components

2\. I don\'t understand how T blocks are installed under transverse
beams.

Write-up stated they were installed before carriage went in. Then how
does

the horn get past them?

The crane lowers the horn module nearly all the way into the chase, then
moves the module upstream before letting it rest on the carriage. Not a
particularly attractive operation, but one motivated by having to get
the target and horn together. One could put all of this burden on the
target module, which is a change still relatively easy to make; the
target module would need to extend further under the carriage beams, but
since that module is not designed yet it would involve almost no
re-work.

3\. Should green and blue blocks standing on edge be tack welded
together

to ensure stability of the structure?

A prototype stackup of a section of the target pile was done. Based on
this test, and the siesmic analysis from ANL, we do not plan to tie the
blocks together. Both because the composition varies widely, and because
the blocks are mildly radioactivated, welding of blocks is not thought
to be an option.

4\. What supports the helium tubes? Do they have to be removed (or

moved) to get out a horn?

The helium pipes have been removed from the design. They would not have
needed to be moved for a simple horn replacement, but would have
severely constrained future flexibility in beamline reconfiguration.

5\. I\'m worried about the air cooling flow rate in the chase too. Note

that from Dave\'s talk if you consider the clear flow area cross-section
you

get 71 mph and not 30 mph.

The final sizing of the air flow will be done over the next two months,
but the current range under consideration is 10,000 cfm to 30,000 cfm,
which corresponds to 12 mph to 36 mph by horn 2 (which is the largest
obstruction in the chase).

6\. A concern was raised in the meeting about methods required to keep

crane controls functioning in the high radiation field. Think NM2.

The current estimate is that the crane controls will get 60 Rad/yr. The
controls will be removed during beam on conditions; the crane bridge is
estimated to receive 10,000 Rad/yr. We thus believe that radiation
damage will not be a problem.

7\. It was mentioned that H blocks might have to be purchased. Two items

are noted. a) If blocks are purchased try to get low sodium concrete

blocks. b) We used a large number of H blocks in HIL for E-872.

Noted. We do expect to purchase H blocks.

8\. There was discussion about whether the present location of the

prototype horn would be available for future horn work. This should be

sorted out quickly by Beams Division and for the life of the experiment.

We agree this should be done, but has not.

Paul Czarapata\'s list:

Actually I think you had them in your comments. i.e. An
instrumentation/electrical engineer should be brought into the game now
so that any instrumentation that is desired can be incorporated now and
not have to be \"kludged\" on to the final product. Issues such as cable
routing, sensor etc. should be handled up front.

This also has not been done. A review of this issue is scheduled for
Aug. 20.

Paul

Dave Augustine\'s list:

My main concern was the tunnel temp, humidity ,and wet floors. At that
elevation water will slowly leach into the tunnel. Air flow must be
enough to evaporate it. De-humidifiers must be enough to dry the air to
a reasonable level, 50%. Hugh amounts of new air is introduced into the
tunnel to cool the shield steel. A paddle wheel type de-humidified is
planned. I am assuming that the 100 degree waste heat is being dumped
into the tunnel for heat as well.

The airflow which cools the steel is in a closed loop within the target
pile, and should provide any dehumidification necessary for that region.
The air through the target hall above the target pile enters very dry,
and we hope will maintain a reasonable humidity level in the target
pile. The target hall is shotcreted to reduce water inflow, as a
mitigation for just the point of keeping it reasonably dry. Do we have
any further mitigation if conditions turn out to be damper than desired?
If the closed loop cooling is fairly tight, keeping the radioactived air
contained, then the air flow rate above the pile (which was limited to
about 1000 cfm in initial designs during beam-on operations to limit
exhaust of radioactived air) can be increased substantially. The higher
flow rate capacity is being built in any case for beam-off conditions.
The waste heat is not kept in the target hall, but must be extracted in
water.

Ernie Villegas\' list:

Just a few notes concerning the Numi target pile review.

1\) From the point of view of a first time observer, the design

seems well beyond the conceptual stage. Still,there is a great

deal of engineering/design/fabrication work that has to be completed

within the next two years. I would question whether enough manpower

allocations have been made to this area. In particular I was surprised

to hear that electrical engineering has not been involved to date.

We certainly did not have enough engineering manpower, but have acquired
mechanical engineering from PPD as CDF/D0 have rolled in. Need for
understanding electrical is again noted.

2\) Power connections to the horns(striplines?) do not seem to be well

define.

Two engineers are now working on this part of the design.

3\) The work required to finalize the controls for the modules is just

begging for engineering support.

Have an engineer assigned as contact to controls group, and have
received estimates for various components from them.

4\) Given the lack of dimensional precision and weight (10 tons) for the

shielding steel blocks, has Enough manpower been devoted to this task?

Five per day seems fine at first glance, but maybe a closer look would

indicate a slower rate of progress.

The prototype stackup has given us confidence that five blocks per shift
is reasonable.

Pat Hurh\'s list

Here\'s a summary of my comments from the review:

General:

Overall, I see no major holes or \'show-stoppers\' in the plans

presented. It should be noted that the plans presented were conceptual

designs with only portions of detailed design complete. There are

several issues that require detailed engineering and designing, but

overall the concepts presented seem sound. I think the only general

concern that I have is the amount of manpower and other resources that

are required to complete the Target Hall on schedule. It is clear that

additional engineering, drafting, and technician support is needed to

complete the detailed work successfully on schedule.

The delay in the civil construction completion has so far covered the
engineer-shortage related slippage in target pile design, and we now
have engineers, so our schedule now looks reasonable.

Specific:

Some details that need significant attention:

1\) Chase Shielding Installation - The geometrical tolerances of the
Duratek steel blocks are large enough to require individual shimming,
fitting, and grouting of each block. Because of the weight and numbers
of blocks required and the deep locale of the target hall, installation
will be a major project by itself. Blocks should probably be measured
and classified into tolerance groups ahead of installation to ease
selection and fitting. Blocks can also be classified according to
chemical content so that blocks undesirable for radiological reasons can
be placed in locations of least impact. Mechanisms and devices to tow
the blocks from the shaft to the chase must also be carefully developed.

The block tolerances were what motivated the prototype stackup. Blocks
equivalent to about 10% of the total target pile were stacked, including
blocks in all designed configurations. A satisfactory result was
obtained with no shimming or grouting. Block tolerance did not end up to
be a problem, and although we had started to measure and classify blocks
we have halted that effort as unnecessary. Although it is a reasonable
thing to imagine, we are not looking at chemical content of blocks. The
design for the carts to tow blocks from the shaft to the chase is still
yet to be done.

2\) Target Hall Access Procedures - Although detailed procedures cannot

readily be produced for Target Hall accesses (i.e. to change a horn

location), general procedures which outline the steps involved for

major accesses should be developed now. These procedures will help

engineers and designers visualize how their designs will be utilized

in practice and ensure that enough flexibility in the Target Hall

design is provided to accommodate needed tasks. Special attention

should be paid to the musical chairs game that will be played with

filler tee-blocks and modules.

Although this exercise is not completed, we do now have reasonably
detailed procedures for changing out a broken horn, including radiation
doses from each step, and have drawings showing the T-block stackup
area. This will be the subject of a review on Aug. 3.

3\) Alignment of Target Hall components - Although absolute placement

of the components can be done to the given tolerances (.020\" )

initially, over time the alignment may shift out of tolerance due to

thermal expansion/contraction and mechanical backlash/hysteresis. The

thermally hot areas (especially at Horn 1 module) should be looked at

carefully to see how they affect alignment of the components. Cooling

and/or thermally isolating the Horn 1 support shafts should be

considered to minimize vertical thermal motion of the Horn. A strung

wire system with capacitive pick-ups looks like a promising idea to

provide absolute referencing of the components over time (esp.

horizontally).

Studies of the thermal shifts of the horn and its support mechanisms are
ongoing, and will be presented at the Aug 10 Horn review. Whether the
\"short circuit\" air flow along the support shaft from the general
target pile forced air cooling is sufficient or some extra measure is
needed to cool the shaft is not known yet. Physics studies done with the
\"low energy beam\" configuration indicate that tolerances may be
modestly loosened, compared to the \"medium energy beam\" configuration
which was the original baseline. This lessens the motivation for adding
systems like capacitive pickup.

4\) HVAC - The plan presented seemed feasible to cool the shielding

blocks and keep the poured concrete thermally stable. The high air

velocities in the chase seem surprising, but theoretically doable. In

practice, engineers and designers must be careful to make sure that

additional loadings on all components in the Target Chase are taken

into account. Small instrumentation wires and other non-rigid

structures could see extreme buffeting from the 32 mph winds

predicted. Installation workers also must be careful to ensure that

all air leaks are minimized (ensure flow through chase) and that

channels between concrete and steel (especially at the bottom) remain

clear and free. During operation failure of the sump system may mean

that the lower air passages could be blocked with water (?) this

should probably be looked at.

Noted. As for the water flow, it is below the concrete that forms the
air seal, to a sump at the downstream shaft. So sump failure impacts the
MINOS experiment long before the target pile.

The actual ducting and HVAC equipment has not yet been finalized.

Obviously care must be taken in order to make sure the resulting

system is easily configured and balanced for the as built geometries.

In addition, a system to collect and test condensate for irradiation

must be developed and implemented.

Noted, and engineering is just beginning on HVAC equipment. Our \"plan\"
is to just let condensate run into the sump water, but the NuMI
Radiation Safety committee should take a look at this.

5\) Hot Work Cell Equipment - Lift tables, shielding issues and remote

manipulation issues must be addressed for this area. It is important

to predict what operations can be done and can\'t be done using this

facility so that engineers and designers don\'t just assume that some

task can be done in the Hot Work Cell.

This design has progressed, and a pretty short list of tasks are assumed
to be doable in the work cell. Horn or traget change-over is done
entirely from the top of the cell. Penetrations are planned for one side
and one end of the work cell, imagining a repair of a water connection
before the horn is too severely irradiated, and the ability to unbolt
the stripline from the horn if the remote stripline clamp fails to
release.

6\) Flexible Stripline Joint - Although this probably isn\'t technically

part of the review panel\'s charge, it looks like the biggest technical

unknown at this time. Engineering resources should be brought to bear

as soon as possible on this problem. A possible \'plan B\' described

during the review was to move the entire stripline module with the

horn. I don\'t think that is a particularly attractive idea because of

the loads placed on the horn support. I think a possible back-up plan

would be to automate the stripline hard connection at the bottom of

the module so that when the horn is moved the joint is loose. However,

welding of the connection under many high current pulses could

complicate that mechanism.

Flexible stripline design is now actively progressing, but is not a
solved problem yet. Your suggestion of essentially a remote clamp is
still a fall-back option.

7\) Instrumentation and Controls - There seemed to be a lack of

information about sensing devices and control systems for the various

motion devices. Electrical Engineering support should be added to

address these issues at this time. It is preferable to have these

issues settled early so that accommodation of the needed devices can

be made by the mechanical designers.

An update will be presented at the Aug 10 Horn review.

Craig Moore\'s list:

,

These are some of the concerns/issues that I have from the review:

The question of the relative alignment of the devices once they are out

of sight. If a beam based alignment scheme can be used in a relatively

straightforward way without a great deal of time, then a lot of my

concern is obviated, and there is probably enough steering to hit the

center line of the elements if they are on a line. However being able

to remotely monitor the relative motion of the objects while the

temperature us changing could be very useful (and reassuring). It is

clear that the horizontal motion is of the most concern. At the least,

being able to check the elements by using removable plugs in the

shielding seems a good idea; and at the most, having a remote readout

system based on stretched wire techniques, laser techniques, or other

techniques would be ideal.

The design includes removable plugs to be able to check horn position.
We do not feel we can justify the cost of a remote position sensing
system, although we considered it.

I understand that the force of the 30 m.p.h. air flowing down the chase

is not much but I would still worry about turbulence and the inducement

of normal mode oscillation of the hanging elements.

The target is the only delicate item in the chase. There is a good
chance that when the thermal design is finished, the air velocity at the
target will only be about 10 mph. If something in the range of 30 mph
ends up being required, then we could implement either a wind test of
the target or a baffling arrangement to slow down air flow in that
region.

The question of neutron leakage through the uneven blue/green blocks

needs to be looked at.

The radiation flow through cracks between T-blocks is currently being
modeled with MARS Monte Carlo, and studies aimed at understanding cracks
in general are planned. In addition, a benchmarking of MARS with data
taken at AP0 is under way. The initial results from the T-block study
are encouraging.

If additional concrete shielding blocks need to be purchased then

finding out how much extra it would cost for low sodium concrete would

be useful.

Noted.