Comments for Review of NuMI Target Hall shielding

                           July 27, 2001

                   from T. Leveling
                       ------------------------

1. Overall Remarks
I was away from the laboratory during the formal presentation on July
27th, so my review is based on materials found at
http://www-numi.fnal.gov:8875/numwork/reviews/july_27.html. Materials
presented by Hylen and Stefanik were received through the mail on 8/17.
Slides 15 - 21 in Grossman PP file were received 8/14.

2. Itemized suggestions, questions and concerns

(1)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.

(2)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.

(3)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.

(4)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.

(5)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.

(6)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.

(7)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.)

(8)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.

(9)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.

(10)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.