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ATOM CS INTERNATIONAL A Division of North American Aviation, Inc.

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730-V-33 ( R E V 1-62) C L A S S I F I C A T I O N LEVEL 6, C, OR U)

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YRItTEW 5ElmiK- By A * &Oadea &k ATOMICS INTERNATIONAL

A Division of North American Aviation, Inc.

3p tM1 YO.

MB 7508 3621 L944

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LEDGER ACCI.

SUB-ACCT . TWR 8200

1 OF a PACE

=PIES TO: R. L. A E U ~ it 14. P. a i shr * W. P. Kmlcel" J . E. Mahh&ster P. J . #ellon

W. T. Horgan C. J. Brow re W. B. Hols 8. A. Ross-Clunis 0. J. Fowt R. C . Gerber J. Po Hale "

Include f i g u r e s 6 and 7 with all copies

~~

corrtErr s : I STATEMENT OF PRSBLEM ...................... PAGE 1

I1

1 1 1

I V REFERENCES AM@ APPENDICES . . . . . . . . . . . . . . . . . . . PACE

S W A R Y OF '?E';uL'S CiNC Q E C U H N D A T I O N S . . . . . . . . . . . . . PACE

ETHOD U S E D , CESG?!PTIO)( OF EQUIPMENT, SAMPLE CALCUUTIolls . . . PACE

I STATEMENT OF PROBLEM

Deterndne the expected maximum contamination of the cold traps and primary sodium pumps. removal and shipping. removal operation and for shipping these components may from the reactor site .

Deterndns the maxim dose rates from these components during Specify suitable shielding for casks to be used in the

If S W Y OF aEsULTS AND RECowlgsIoDATICRIS

A. Cold Trap

Access to an nnshielded cold trap is limited by high dwe rates, i .e . , 100 m/hr a t Ix, Ft, after 180 dqya decay t h . depend upon the length of tim the cold trap has been in use.) A hand3ing cask providing a radial shield o f personnel protection for the removal operation, if 180 days decay time is aUored before the trap is removed. the cask body, before it is lifted from the floor, would be 10 mr/hr a t 20 ft.

( m e dose rate does not

of lead will provide adequate

As shown by Figure 7, dose rates from

An additional 2.4" of lead 5s required for off-s i te shipment of the cask. This additional shielding can be added after the trap has been removed from the reactor building.

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- ATOMICS INTERNATIONAL A Division of North American Aviation, Inc.

NO. 4757 DATE December 15, 1959 PAGE 2 O F

Dose ra tes from the cold t r ap a f t e r the shield plug has been removed from the access hole are shown i n Figure 6. If d i r ec t line-of-sight exposure is avoided, dose r a t e s t o personnel will be belaw 100 mr/hr a t any position, and below 10 mr/hr a t distances greater than 20 f t from the access hole.

Dose r a t e s from the cask during i t s t rave l away from the hole, sham i n Figure 7, w i l l be bebw 100 m/hr a t distances from the cask greater than 10 f t and be law 10 m/hr a t 35 f t , i f the cask i s raised no more than 3" from the f loor during i ts travel.

B, Prlmary Sodium Pump

Remote, unshielded handling of a primary sodium pump i s feasible, since dose ra tes would be 100 m/hr a t 28 f t and 10 w/hr a t 90 f t , a f t e r ten years of operation, and providing j&at 4 days decay t i m e i s allowed t o eliminate ac t iv i ty from the Na film clingin@; t o the pump. Dose ra tes after oQy one year of operation would be a fac tor of 4 lower than those quoted above . The cold t r ap handling cask, described i n par t A, can a l so be used fo r sodium pump removal. required f o r off-si te shipIRent of the pump.

Additional shielding of 1" of lead is

Dose r a t e s from the cask during pump handling w i l l be well below those during handling of the cold trap, and thus w i l l present no serious d i f f icu l ty .

j 111 METHOD USED

I A. Dose Rate Calculations t

I

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Calculations of handling and shipping cask requirements were made, using the methods and equations developed i n Reference 1. methods and equations f o r calculating dose r a t e s from the cold t rap a f t e r the shield plug is removed, and d&ing the t r ave l of the cask over the floor, are developed i n Reference 2.

The

B. Cold Trag

1. Contamination :

Th dominant contamination of the cold t r ap after the decay of Idah, is expgcted t o result from fission products which have been released from the core In to the sodium coolant and deposited i n the cold trap. Based on Reference 10, the amount of f i ss ion products released from the core is estimated as O.Ol$ of the t o t a l core f i ss ion product inventory a f t e r 1 year of operation a t 254 &(ti).

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- -. 730-V-45 (REV 5-59]

ATOMICS INTERNATIONAL A Division of North Americon Aviotion. Inc.

A f t e r 60 Days 2,616 Decay Time

~ . . - _ _ . - . - . - __ - .

NO. 4757 DATE December 15, 1959 PAGE 3 O F a

2,534 72

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I The activity of this quantity of f i s s ion products was calculated from Reference 4. follows :

The resul tant values are as

TABLE I t f i s s ion Product Contamination of Cold Trap (Gamma Curies?

i I Total 1 @ - 0.8 E3ev 1 1.k - 1.6 Mev I 2.0 - 2.2 Mev -

A f t e r 180 Days I 605 Decay Time 1 799 I 6.2

The above values include the vola t i le components which may and may not deposit i n the cold trap. comprise no more than about 2s of the t o t a l a t the decay times indicated. essent ia l ly independent of the operating lifetime of the cold t r ap . The deposits i n the cold t rap locallzed i n the top portion. (97 For dose r a t e calculations, two assumptions are made; f irst , t h a t the ac t iv i ty is localized i n the top 2 f t of the active length of the trap, and second, t ha t the ac t iv i ty is unf9rmly dis t r ibuted along the 6 f t of active length. between these extremes.) higher dose r a t e i n a par t icular s i tuat ion is used.

kmever, the volat i les

It is assuned that this maximum contamination i s

e expected t o be somewhat

(The true s i tua t ion will, of course, l i e The assumption which gives the

2. Unshielded Access:

Using the methods of Beference 1, and a s s d n g a 4" steel s h e l l fo r the cold trap, and t density about 24 lb/ f t 3)tI the dose ra tes from an unshielded cold t r ap were calculated and presented i n Figure 1.

it is f i l l ed with &eel wool of

Using the same method a8 above, and assuming a 3" lead r ad ia l shield t o be provided by the handling cask, the dose r a t e s a t the cask surface are presented in Figure 2, fo r the cam of 180 days decay. factor of 6 higher. Therefore, a decay time of 180 days is preferable .

Dose r a t e s a t 60 days decay would be a

* 1 G 'anima Curie = 3.7 x lo1* photons/sec

. - .. 730-V-45 (REV 5-59)

NO. 4757

ATOM ICs INTERNATIONAL DATE December 15, 1959 PAGELOF a

A Division of North Amerrcon Avmtion, Inc

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4.

5.

6.

Shipping Caskt

The additional shield required t o reduce the dose r a t e t o 10 mr/hr a t 1 meter is shown i n Figure 3 t o be 2.4" of lead. Figure 4 shows, as a matter of i n t e re s t , dose r a t e s from the top and bottom ends of the cask as a function of shield thickness. Figure 5 e v e s a mans of estimzting the amount of lead shield fo r which 1" of several d i f fe ren t materials can be substi tuted. Figure 5 is not exact, but provides a convenient estimate . Dose Hates from Open Access Hole:

Dose r a t e s i n the reactor room, a f t e r the shield plug is re- moved from the access h o b , arise from d i r ec t radiation, scat ter ing from the side of the access hole, and from sca t te r - ing from the roof. (The last contribution is r e l a t ive ly insignificant.) msthods developed i n Reference 2, and are shown i n Figure 6.

Dose Rates Near the Handling Cask D u r i n g Travel Across Floor:

These dose ra tes are calculated by the

By adding the dose ra tes from photons penetrating the handling cask t o those from photons scat tered from the floor, Figure 7 was prepared, showing t o t a l dose r a t e s near the handling cask during i ts t r ave l across the floor. high enough t o present any serious d i f f icu l ty .

The dose r a t e s are not

c . Primary sodium pump

1. Contamination:

Contamination due t o retention of so l id sodium, in the freeze seal design pump, is t reated thoroughly i n Reference 6. present free surface design essent ia l ly free of sodium. tamination must be Investigated. taroination, after 34 days decay time t o eliminate 2t ac t iv i ty , w i l l be from m s s transfer activity on the lower surfaces which are i n contact with the primary coolant.

2 The contaminated surface area is estimated as 65,000 cm . extent of contamination is extrapolated from the data of References 8 and 9, which is given i n terms of dose rate a t the surface of 8 16" pipe;

The will, however, drain Thus, other sources of con-

of con- (6tY"p

The principal so

The

1 --- 730-V-45 (REV 5-59]

Total Contamination

of a Sodium Pump

. . ..-.

10 46 uc/cm2 100 uc/cm2

1 - 3.9 curies

10 3 curies 6.5 curies

ATOMICS INTERNATlONAl A Division of North Americon Aviation, Inc.

The pump, i tself , will absorb about half of the radiation, giving a sui table safe ty factor t o calculations using this data. The ac t iv i ty is appraximately u n i f o d y dis t r ibuted along the lower 63" of the pump.

2. Unshielded Access :

From the contamination values of Table 11, dose ra tes from an unshielded sodium pump w e r e computed and shown in Figure 1.

3. Handling and Shipping Casks:

Using the methods of Reference 1, Figure 8 was prepared. From this, the dose r a t e s f o r the handling cask with a 3" lead wall are shuwn t o be 85 mr/hr a t the surface and 42 m/hr a t 1 mster. A n a d d i t i o n a l l " of lead is required for off-s i te shipment

Since the pump contamination is considerably lower than the cold t r ap contamination, dose rates from scat tered radiation wi l l be considerably lower, as can be seen from Figure 1. Thus, scat tered radiation will not present any serious exposure problems during handling of the sodium pump.

ATOM ICs INTERNATIONAL A Division of North Americon Awiotion, Inc.

NO. 4757 DATE December 15. 1959 PAGE 6 O F A

IV HEFERENCES

1.

2.

3.

4.

5.

6.

7.

8.

9.

10 .

W. A. Rhoades, llShielding Requirements fo r HNPF Shipping Casks", TDR 4473, October 16, 1959.

G. L. Wegmann, "Remote Removal of HNPF Moderator Cans", TDR 4487, October 20, 1959.

IOL, J. P. Hale t o J. E'. Stolz, "Design Cr i t e r i a f o r Removal of a Primary Cold Trap - HNPFII, November 22, 1958.

P. Spiegler, "Energy Release from the Decay of Fission Products11, TDR 4128, July 31, 1959.

Personal C o d c a t i o n , W . N, Hoschouer, Design Engineering Group, Atomics International.

W. P. K u r ~ k e l , nRadiologfcal Hazards Associated with Removal of the Primary Sodium Pumpn, TDR 2640, April 3, 1958.

Personal Communication, L. € . Manners, Design Engineering Group, Atomics International,

Personal Communication, F. D. Anderson, Component P a r e r Plant Group, Atomics International . F. D. Anderson, "Summary of Accessibil i ty Studies f o r the b l l a m Nuclear Parer Faci l i tyn, (Secret R.D.), MU-SR-3389, December 1958.

Theodore L. Gershun, ed., nPreliminary Safeguards Report Based on U-Mo Fusl f o r the HNPF", NAA-SR-3379.

-- 130-V-45 (REV 5-59)

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