ML20056B636
| ML20056B636 | |
| Person / Time | |
|---|---|
| Site: | Monticello  |
| Issue date: | 12/14/1977 |
| From: | Mayer L NORTHERN STATES POWER CO. |
| To: | Stello V Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 9102070646 | |
| Download: ML20056B636 (6) | |
Text
Mg NSF I
NORTHERN GTATES POWER COMPANY i
t M I N N E A PO U S. M I N N E S OTA 55409 I
4 December 14, 1977 TO{
g
//
8 Mr Victor Stello, Director
~
~8 d,
Division of Operating Reactors
- [ 4, g!82 4
i c/o Distribution Services Branch, DDC, AIM
/g ~
1 U S Nuclear Regulatory Commission l
Washington, DC 20555 g#
g 4
N
Dear Mr Stello:
=
MONTICELLO NUCLEAR GENERATING PLANI Docket No. 50-263 License No. DPR-22 Response to 11/23/77 Request for Infomation on HDFSS i
On November 23, 1977 the NRC Project Manager for Monticello verbally r2 quested additional infomation related to the proposed High Density l
Fuel Storage System (HDFSS). The questions are repeated belcw along I
with their respective responses.
Q.1.
In your report, entitled, " Replacement of Spent Fuel Pool Storage Racks", dated August 17, 1977, on Page 29, you refer to operating both trains of the spent fuel pool cleanup system "during re-fueling outages". How long are refueling outages?
A.1.
The reference to refueling outages was used to differentiate, in a general way, that period of time when both trains of the spent fuel pool cleanup system are in service, rather than only one. Annual refueling and maintenance outages characteristically range from four to eight
]
veeks. The period of time when both trains are kept in service is determined on the basis of water quality (conductivity, turbidity and disolved solids.) For the calculation of the annual volume of solid wastes generated in the form of spent resins, it was conservatively assumed that two cleanup trains were operated eight weeks out of each year with weekly back-washes and one train was operated the remainder j
of the year with monthly backwashes, y a, og6
)
go 913 l
9102070646 771214 CF ADOCK 05000263f P
CF j;
NORTHE STATE 3 POWER COMPA Mr Victor Stello Page 2 December 14, 1977 Q.2 The Licensee estimates 22 man-rem as the occupa-tional exposure for removal and disposal of
<?
the old racks and installation of the new ones.
M-%
You should demonstrate that the methods he will MP use for this operation will provide ALARA exposures w
fm -
to the personnel performing it.
Relevant experi-
,'. yi ence may be used as necessary.
In response to
.lR this question, the Licensee should address dose eMQY rates, occupancy factors, and man hours expanded q
%e&
for each phase of the operation.
A.2 H
The estimated 22-man-rem for the spent fuel pool i
st orage modification was conservatively cal-ct. lated and is therefore much higher than would actuelly be anticipated during the project.
The methods employed in estimating the Monticello fuel rack replacement occupational exposure were similar to those used in estimating the occupa-tional exposure for the Prairie Island spent fuel rack replacement. The Prairie Island occupational exposure estimate was 28 man-rem.
Actual project occupational exposure, as measured by thermoluminescent dosimeters (TLD),
was less than 5 man-rem.
The occupational exposure for the Monticello spent fuel rack replacement program was derived
'i by breaking the job down into its component I
activities, estimating man-hours for each i
activity and estimating a conservative dose level for each activity.
The estimated man-hours during which signifi-cant exposure would be received, the average dose rates and the resulting exposures are given in Table I below for each activity.
i TABLE I - ESTIMATED MODIFICATION EXPOSURES Dose Rate Manhours Exposure Activity (mrem /hr)
(hrs)
(man-rem) i:
0 I Rack removal and dis-65 300 19.5
[
posal II New rack installation 4
425 1.7 III Fuel Handling 2
200 0.4
'TOIAL 925 21.6 y
l t,i jj; i
= _ _
NORTHER CTATES POWER COMP e
Mr Victor Stello Page 3 December 14, 1977 I
Activity I i
T Man-hours for removal and disposal of existing
^
l spent fuel racks were estimated from Monticello i j plant experience with removal and disposal of f
l twelve control-blade storage racks. Dose during removal and disposal of spent fuel racks was assumed to come from two sources; the pool and the contaminsred racks. Dose from the i
pool was based on typical radiation levels above the pool. Spent fuel rack radiation levels were estimated based on radiation levels
{
of the Monticello control blade racks which 4
were removed. The exposure received by the plant personnel who removed and disposed of the racks was very low and was not r,eadily distinguish-able from their nomal daily exposure.
1 Activity II l
Workers who will be installing new spent fuel racks (modules) are assumed to receive exposure only from the pool. The dose rate is based on typical radiation levels in the pool area.
Man-hours of activity in the pool area are estimated for each phase of the installation.
Activity III Fuel handling durations were estimated based on plant experience. The only significant source of personnel exposure is from the pool. The dose rate for fuel handling is based on typical spent fuel pool radiation levels.
Occupational radiation exposure AIARA considera-tions were included in planning the pool prepara-tion and construction sequence for the modification.
Installation methods for the new racks and disposal methods for the old racks were discussed with the plant radiation protection personnel to assure that the selection of methods for per-forming the work were consistent with good radio-logical health and safety practices.
The new spent fuel racks (modules) and their installation tools are designed to simplify installation and shorten the constmetion time to the extent practical. This will reduce the exposure by reducing the occupancy factor. The 4
tool and rack design also facilitate our intent to perform the modification fr;m thc= tht pool.
Therefore, it is not anticipated that the modi-fication will require use of a diver, k
i NORTHER STATES POWER COMPA e
=.
Mr Victor Stallo
~
~
i Page 4 i
December 14, 1977 The pool radioactivity, the primary source of exposure for many of the modification activities, t
will be kept as low as practical by optimum use of the pool cleanup systems.
4 Most of the calculated exposure for replacf ng the spent fuel racks is received from handting the ccntaminated racks. To minimize the exposure from this source, the racks will be flushed
~
down with water as they are pulled from the spent
{
fuel pool. The old spent fuel racks will be j
handled using techniques similar to those used j
when handling the control blade racks sich resulted in low exposures.
);
The Monticello spent fuel racka vill be boxed i
for disposal using essentially the same method that was used for disposal of the Monticello control I
blade racks and the Prairie Island spent fuel racks. A comparison was made between boxing racks and cutting up racks for the Prairie Island spent fuel pool modification. Based on the evaluation for Prairie Island, it was con-cluded that boxing spent fuel racks at Monticello I
would res alt in the least exposure.
4 All provisions of 10 CFR Part 20, Standards for j
Protection Against Radiation will be enforced during this modification just as they are for z
all plant operations. Routine plant radiation protection measures d ich are described below, will help to assure that the exposures are kept i
AIARA. Workers will wear anti-contamination protective clothing during the work near the spent fuel pool and during disposal of the old j
racks. Control points will also be established to contain radioactive contamination 4 thin the work area. All personnel will wear personnel monitoring equipment. In addition, radiation surveys will be conducted to monitor area radiation levels. All phases of the rack replace-l ment and disposal will be performed using written I
procedures sich will be reviewed by the radiation protection personnel for AIARA considerations.
l All workers, as a minimum,must wear a pocket dosimeter and a thermoluminescent dosimeter (TLD) een working in radiation areas. The l
pocket dosimeter'can be read anytime and as a minimum is read when the worker leaves the plant I
i, I
i
l t
NORTHERN STATES POWER COMPANY j
Mr Victor Stello Page 5 December 14, 1977 for the day. So~rmallytheTLDisreadmonthly, but it may be checked any time there is a reason to believe a worker is approaching a radiation limit. Also the plant has administrative 1y set a radiation exposure limit below Part 20 standards to provide a margin which includes dosimeter inaccuracy. In accordance with NRC regulations, all personnel working in radiation areas receive instruction on radiation, use of protective clothing, and methods of minimizing exposure.
As a further check on occupational exposure, plant radiation protection personnel are present when first-time activities occur, such as re-moval of a contaminated spent fuel rack from the pool.
If the plant radiation protection supervisor determines that any of the activities have potential significant radiological con-
- iderations, radiation protection personnel would be present for all of those activities.
Other activities will be monitored on a periodic basis.
Yours very truly, cd'd.
v L 0 Mayer, PE Manager of Nuclear Support Services LOM/MHV/deh cc: J G Keppler G Charnoff MPCA Attn: J W Ferman
.NG LICENSE l
N /EIER. ISSUANCE OF OF 4,n;KET NUM DED UA NUcLEAD CEOULATo3Y CoMMts58-1 h]l ' "5" Zdr $
. as
~
&[
N5C DISTRIBUTION ren PART 50 DOCKET MATERIAL cAra or occuutNT t
12/14/77 FROM:
Northern States Power Company S
., Hro Victor Stellof "
Minneapolis, Minnesota care muctivso 12/19/77 L. O. Mayer NUusan or cortes acceivso i
- y*y7 :
iwrvt eom
- 0*
..QwoTomizmo I GCETTa1.;y. b:; yfMN f.EGwcLAssireao
- ice, Qi c r:- -
. -wr vr$2v ENCLosuPE i DIPTl08t4_'uth.g l,;
q%?s@[fg.3
.W:W?!yev:
11/23/77 request
, Consists (ofj~responseto by1MRCJfor.information on the proposed lj Righ M usity Fdel S,torage System........
4 i
l.
I (5-P)
(
'o' FLANT NAME: Monticello s
f
~ itJL 12/20/77 40 NGL-5
~
t I
FOR ACTION /INFORMATION i SAFETT i l BRANCH CHIEF: (7) l 3Af) ti I
1 i
i i
l 1
LNTERNAL DISTRIBUTION l
-- ~ r i
f fvTr: TTt] 3 i
her vrm i i IT rr tv I i hnn l
bANAti1:9
~
r I
j j j V n ry t
{
l kTerNum
)
I ;
(
' 12.a o i
i F
I l
MAFT l
I
' 'ntm 70 l
' tmTvrs i
i lf. COLLINS i 17 "c rr';7" t
I i i l
l i I l
't I
l
,t t
i l
)
CONTROL NUMBER 1
0 EXTERNAL OtSTRIBUTION l TLC l {
l p
} - {[j 1
L?DR: 117tdAJPA/MJf5 MA/
4 1
l 773540086
/
- - ~I i
1 NSIC
! FM 10 CYS SENT CATEG3R1 ff j
,y.
, i l
e i i