Comments from a Review of Shielding of Target Hall Area

**July 27, 2001**

## Radiation protection requirement/calculation update

## Presenter: N. Grossman

1.  ([Reviewer: M. Gerardi]{.underline}) Equipment placed upstream of
    the target pile that could eventually become a limiting aperature to
    complicate the residual dose rates at the upstream face of the pile.

2.  ([Reviewer: M. Gerardi]{.underline}) Was there any mention of how
    water leakage into the target hall area on the floor, that could be
    activated, is either contained or routed ?

3.  ([Reviewer: N. Grossman]{.underline}) It seems NuMI may need re-do
    the air and prompt rates in the Target Hall based on the present
    design, or write a document that justifies why it is not necessary.
    It may be easier to simply get the numbers from already existing
    MARS runs.

4.  ([Reviewer: N. Grossman]{.underline}) NuMI needs a MARS run with the
    baffle just upstream of the target in as presently it is envisioned
    to look at backsplash and beam and residual dose rates. Perhaps we
    can have Igor Tropin do this next.

5.  ([Reviewer: N. Grossman]{.underline}) What does NuMI envision the
    contamination issues to be in changing out a hot component? Will
    activated rust particles and dust etc. get dispersed in the Target
    Hall during a change-out? Clearly the possibility of the spread of
    contamination during change out needs to be minimized and I am not
    sure that this has been addressed at all. Perhaps it came up in the
    hot horn handling review.

6.  ([Reviewer: N. Grossman]{.underline}) I thought I heard that the
    chase air-cooling was based on MARS results and a 10% safety factor.
    Is there a good basis for the 10%? My concern is that perhaps that
    is not enough of a safety factor.

7.  ([Reviewer: T. Leveling]{.underline}) Consideration of the shielding
    design for prompt and residual ionizing radiation appears to be
    comprehensive. The MARS calculations developed to understand
    residual dose rates in the NUMI target hall appear to work well for
    times greater than about an hour. Since it is improbable that target
    vault components can be removed within an hour of beam going off,
    the calculations should also be sufficient for purposes of this
    review. A waiting period of at least one hour should be imposed when
    the target hall be comes operational to preclude personnel access
    when dose rates are very high and not well understood.

8.  ([Reviewer: T. Leveling]{.underline}) The shielding calculation
    process is reasonably well understood and is fairly reliable at
    predicting actual conditions. However, a comprehensive measurement
    plan should be developed to check and confirm calculations when
    target hall operation begins.

9.  ([Reviewer: T. Leveling]{.underline}) Groundwater calculations and
    groundwater protection has been considered extensively. The RAW
    systems associated with the target hall will be a significant source
    of activated water. It would be more complete to include, at least
    peripherally, some mention of engineering controls to be used to
    preclude RAW system water from entering groundwater.

10. ([Reviewer: T. Leveling]{.underline}) The Access portion of Grossman
    slides, includes the statement \"RAW Room may have a locked door.\"
    The RAW Room appears in the list of NUMI spaces where beam on access
    is permitted. This is a little surprising. Even though the NUMI RAW
    room does not contain a beam dump cooling system, it seems probable
    that dose rates due to activated horn water would prohibit personnel
    access. Perhaps this room should be listed under \"NO ACCESS\" and
    should have a delay time after beam goes off before personnel access
    should be permitted. In addition, a remote monitoring system (e.g.,
    chipmunk on MUX) should be used to determine radiation dose rates
    before permitting personnel access.

11. ([Reviewer: T. Leveling]{.underline}) The shielding of the RAW room
    is not addressed in the target hall shielding presentation except
    for mention of a penetration. If not already done, the RAW room
    shielding needs to be addressed somewhere.

12. ([Reviewer: T. Leveling]{.underline}) Comment on crane dose rates:
    mentioned 10 krad/year to crane bridge. Does this include any
    electronics, for example radio receiver, controls circuits? Upper
    limit for solid state components is about 10 krad. While not a
    concern for structural or electrical systems, electronic stuff
    begins to break down at this level. If gamma only, electronic stuff
    may be good for a factor of 10 higher integrated dose.

13. ([Reviewer: T. Leveling]{.underline}) Operational aspects of target
    hall are not presented. It will be a major concern what modules will
    require removal and replacement and how all that is too be done.
    Facility design vv. ALARA and personnel exposure control needs to be
    addressed.

14. ([Reviewer: T. Leveling]{.underline}) Personnel radiation exposure
    resulting from operation of this facility needs to be estimated and
    reviewed in context of annual exposure limits, ALARA, and DOE
    performance criteria.

15. ([Reviewer: P. Martin]{.underline}) The NuMI Radiation Safety
    Advisory Committee review of 7/99 and the Preliminary Radiation
    Shielding Assessment of 10/99 were both based upon the construction
    drawings as they went out for bid. The change to the Tunnel Boring
    Machine was proposed by Healy and accepted by the lab subsequent to
    these reviews. The NuMI project should verify that the changes from
    the use of the TBM do not alter the conclusions of those reviews.

## Thermal Model Update

[Presenter: J. Hylen]{.underline}

1.  ([Reviewer: N. Grossman]{.underline}) Does horn 2 module costs
    include allowances for movement? If so then perhaps we should remove
    them. If the movement allowances have already been removed, that
    means we do not plan to do a horn 2 flexible joint even if we end up
    having \$ for it, correct?

[Description of shielding block layout, tests, air handling]{.underline}

[Presenter: Andy Stefanik]{.underline}

1.  ([Reviewer: D. Cossairt]{.underline}) The cracks between the Duratek
    steel blocks remain a concern. How these will work out when the
    blocks are stacked on the floor of the target enclosure remains to
    be seen. These cracks should perhaps not be filled. Past experience
    with materials used to fill cracks is not encouraging. The shielding
    calculations, hopefully, allow for the cracks by, perhaps, using a
    reduced density. This should be good enough provided the blocks are
    laid with good masonry practices of well-developed overlaps.

2.  ([Reviewer: D. Cossairt]{.underline}) Reference was made to HEPA
    filters. Perhaps the word \"HEPA\" should not be used to designate
    this equipment. This conjures up \"nuclear facility\" type air
    systems, which are costly, or impossible, to maintain in accordance
    with strict ANSI standards applicable to such systems as commonly
    used to directly protect personnel in other kinds of installations.
    If one simply calls them \"high efficiency\" filters without the use
    of the acronym, this potential compliance issue may well be averted.
    The other review panel members are welcome to create a better name.

3.  ([Reviewer: D. Cossairt]{.underline}) The material of choice for the
    windows (Be or Ti) was going to be checked as an action item. Ti may
    be preferred.

4.  ([Reviewer: D. Cossairt]{.underline}) Be careful in deleting the top
    row of blocks over the target station. It appears from the drawing
    shown that this could leave cracks of unacceptable orientation,
    number, and/or size.

5.  ([Reviewer: D. Cossairt]{.underline}) A final check of airflows and
    their directions will be needed after construction/installation. The
    air flow pattern is a complicated one and may not be completely
    predictable given other uncertainties related to cracks, etc.

6.  ([Reviewer: M. Gerardi]{.underline}) The use of titanium windows in
    lieu of berrylium windows is highly encouraged. The failure of a Be
    window iinvolves significant down time, cost, and IH (industrial
    hygene)requirements.

7.  ([Reviewer: M. Gerardi]{.underline}) It is not a good idea to
    consider removing the top row of concrete blocks. There are always
    cracks and gaps associated with this type of installation of which
    there are few effective solutions.

8.  ([Reviewer: M. Gerardi]{.underline}) I was able to view the Blue
    Blocks assembled at MDB and had some concerns with the arrangement
    that provided several aligned cracks which will surely cause
    operational problems. Some of the cracks amy be large and require
    some type of fill. However, the choices are limited and many times
    cause more problems. It is best to minimize all cracks rather than
    look for cosmetic fill later.

9.  ([Reviewer: M. Gerardi]{.underline}) Replacement of too many
    T-Blocks with Blue Blocks may cause considerable additional cracks
    and gaps that must be dealt with, which could in turn ultimately
    cost more.

10. ([Reviewer: M. Gerardi]{.underline}) The ability to monitor airflow
    and the desired path is important from the radiological discharge
    standpoint. Decay time is necessary since a significant part of the
    labs permit will be eaten up by NuMI operation.

11. ([Reviewer: N. Grossman]{.underline}) NuMI needs to figure out how
    to seal around the transmission line as it goes through the target
    pile. Does it need to be "sealed" only at the top, and not worry
    about air going in one direction at the bottom of the TL and in the
    other direction at the top and thus some leakage? And NuMI needs to
    make sure that under whatever sealing conditions are determined that
    the TL is kept sufficiently cooled.

12. ([Reviewer: N. Grossman]{.underline}) Along the same lines, is there
    a rough estimate as to how much will leak out of the whole target
    pile to ensure that a limit of 1500-cfm leakage is well above what
    we expect and thus air activation is not a concern?

13. ([Reviewer: N. Grossman]{.underline}) Is moisture in the pseudo-HEPA
    filters a problem? An observer suggested that it might be a problem
    for the filter. Do we expect them to get damp? Where the filters are
    located the dose rates should be reasonable so that personnel
    changing them do not incur too much dose. Do we have estimates as to
    what these dose rates are and how often the filters will need to be
    accessed?

14. ([Reviewer: T. Leveling]{.underline}) Target hall ventilation does
    not appear to be fully designed at this point. It would be prudent
    for NUMI to review air sample results of pbar vault air UPSTREAM of
    the HEPA filtered target vault exhaust. My recollection is that
    fairly significant airborne contamination (above and beyond PET
    isotopes C11, N13, etc.) exists in the vault upstream of the HEPA
    filter during beam operation due to activation of airborne dust,
    rust, etc. This source of contamination could be spread throughout
    the air cooling system resulting in contamination control
    requirements for the air cooling system maintenance. In addition,
    condensate drains in the system could become radioactive due to
    deposition of same materials on cooling system coils. Recent samples
    with beam off and beam on have been collected by the BD ES&H
    Department at pbar vault. If this is found to be a problem, NUMI
    should strongly consider the use of HEPA filters to remove
    particulates from the vault return air prior to cooling.

15. ([Reviewer: T. Leveling]{.underline}) Removable radioactive
    contamination may be more of a concern at NUMI than at previous
    facilities due to intended beam power. Care needs to be taken in the
    facility design to provide for this (e.g., handling and storage of T
    blocks in manner that lower surfaces of blocks don\'t come in
    contact with uncontrolled surfaces.)

16. ([Reviewer: P. Martin]{.underline}) The Alignment and Metrology
    Group should be consulted about the wall that is proposed just
    upstream of the target hall. Placing this wall during the present
    excavation contract or the follow-on outfitting contract will make
    their life more difficult. It wasn't fully clear whether this wall
    was just for air-containment, but if so, it can be a simple concrete
    masonry unit wall, erected near the end of the installation.

17. ([Reviewer: P. Martin]{.underline}) The target hall shielding
    installation schedule takes the better part of a year, working two
    shifts. This will require at least three task managers.
    Identification of these people ought to be a fairly high priority.

18. ([Reviewer: P. Martin]{.underline}) The air cooling relies upon
    control of cracks that can short-circuit the intended path of flow.
    Once installed, the proposed aluminum sheets will be inaccessible.
    This whole problem should be given more thought. How do you verify
    the desired flow once the installation is complete? Are there any
    intermediate measurements that can be done during the installation
    phase, while it is still possible to correct things? Is it worth
    developing a prototype, as was done for seeing how the blocks would
    stack?