ML19276E785
| ML19276E785 | |
| Person / Time | |
|---|---|
| Site: | 07109098 |
| Issue date: | 01/16/1979 |
| From: | Voth M UNION CARBIDE CORP. |
| To: | Macdonald C NRC OFFICE OF NUCLEAR MATERIAL SAFETY & SAFEGUARDS (NMSS) |
| References | |
| 12132, NUDOCS 7903210071 | |
| Download: ML19276E785 (6) | |
Text
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h UNION CARBIDE CORPORATION p.o. sox 324. ruxtoo. nco vo u mm TELED,
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Charles E. MacDonald, Chief k
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Nuclear Regulatory Commission S
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Dear Sir:
O cn on October 11, 1978 we requested that the limit for radioactive material shipped in Model No. UCC-20WC-2 packaging be increased from 600 to 1000 Curies.
This container has been issued Certificate of Compliance No. 9098.
Your November 17, 1978 letter requested information regarding our leak testing and maintenance program which is presented below.
The UCC-20WC-2 container consists of five containments, the three inner-most being designed as barriers for the escape of the liquid contents.
The inner-most container is a 200 ml poly-ethylene bottle which will contain the 1000 Curie tolution of Mo-99.
Next is a gasketed 2R container which is sucjected to the leak testing and maintenance program discussed be. low.
Around the 2R is a gasketed specification 55 depleted uranium pig.
The pig and its contents are enclosed in shock abscrbent material.
The outer-most shipping container is of a steel drum type of construction.
The leak testing and maintenance program includes initial leak testing, periodic maintenance and pre-shipment assembly verifi-cation leak testing.
Before using a 2R container for radioactive material shipments in the range of 600 to 1000 Curies of Mo-99, it will be subjected to a helium leak test which is calibrated at 1.0-8 atm cms /sec.
The acceptance leakage criteria will be 10-6 atm cm3/sec or less.
Within 12 months of the pre-use test the 2R may be decontaminated and re-tested to the same acceptance criteria or be retired f rom service for that level of shipment.
Shipment of less than c00 Curies of Mo-99 per container are not subjected to the initial
- td periodic checks but must pass the stringent pre-shipment assembly verificatio., test.
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USNRC Transportation Branch January 16, 1979 Pre-shipment assembly verification inspections and leak tests are done for all UCC-20WC-2 shipments irregardless of the radioactive material content of the shipment.
Prior to shipping the entire package is visually inspected.
The assembled 2R container is leak checked in the hot cell with a test sensitivity approximately 10-5 atm cm3. sec, two orders of magnitude more sensitive than required.
Any 2R container which does not pass the leak test is either rejected or regasketed and retested prior to shipment.
To expedite our review we have attached for your information a detailed evaluation of the current procedures developed to im-pliment the above leak testing program.
If you wish to discuss this matter by phone please feel free to call me at (914) 351-2131 extension 345.
Yours very truly, Marcus H.
Voth 1 > Y" Manager Nuclear Operations MHV:js Attachment
EVALUATION OF UCC-20NC-2 LEAK TESTING PROCEDURES (Attachment to January 16, 1979 4etter from M.H.Voth, UCC, to C.E.MacDonald', USNRC) 1 INITIAL USE AND PERIODIC LEAKAGE TESTS ANSI-N14.5-1977 states that leak tests for reuseable containment packaging systems shall be done prior to first use, after the third use and at no longer than 12 month intervals thereafter.
The maximum permisslbe leakage rate is the greater of the two values determined by Criteria I and II below:
Criteria I-ANSI-N14.5-1977 Section 5.32 R/C L
=
where permissible leakage rate for the medium L
=
package containment requirements R
=
-10
~1 2.78x10 X A2 sec (limit per table 1 of N14.5)
=
A2 IAEA quantity referenced = 80 Curies
=
specific activity of the contents C
=
The A2 value used is the most conservative in the Mo-99 + Tc-99m + Tc-99 decay chain.
The specific activity, C, is 20 Curies per cm3 This is the result of two conser-vative assumptions.
The activity of both Mo-99 and Tc-99m is included, each being 1000 Curies.
The solution contain-ing 1000 Curies of Mo-99 occupies approximately 180 ml; it was assumed to contain only 100 ml.
The calculated maxium leakage is therefore
-10
-1)
(80 Curies) 2.78x10 sec L
=
(2000 Curies) / (100 cm3)
-9 3
1.11x10 cm /sec (liquid)
L
=
1/16/79 e +
Criteria II - ANSI-N14.5-1977 Section 3.7 A leakage rate of 10-atm cm /sec or less based on air at 250C is considered to represent leaktightness.
When the calculated maximum leakage rate is 10-7 or less, it need only be demonstrated that the leakage rate does not 3
exceed 10-7 atm cm /sec.
It is recoginized that leakage rates of this order of magnitude are small and clog easily with liquids or minute carticles.
Criteria II is the governing criteria, at 10-7 3
atm cm /sec air at 250C.
Test Method The acceptance criteria for tg/sec for a helium gas fill test e pre-use test of the 2R container is selected to be 10-6 atm em The equivalent liquid leak is calculated by ANSI-N14.5-1977 equation B9, 2L q
L (Pu - Pd)lig
=
lig gas gas lig (Pu2 - Pd ) gas 2
n where L11q an equivalent leakage rate of liquid
=
L a measured leakage rate of gas
=
as fluid viscosity n
=
F., Pd upstream and downstream fluid pressure in
=
atmospheres absolute
-6 3
The liquid leakage rate equivalent to the 10 atm cm /sec helium test, for the 0.2N solution of NaOH, across the standard pressure differencial, is calculated to be 3
2 (10-6 atm cm /sec)
(.017 Cn)
(1 -.01)
L
=
lig 2
7 (1.05 C )
{ l
.01")
p 3.21 x 10-8 atm em /sec 3
L
=
lig The helium gas fill test is done using a Model 925-40 Varian Porta-Test Mass Soectrometer Leak Detector.
The device is calibrated to a calibr'ated leak of 10-8 atm cm3/9ec.
It is not feasible to contaminate the leak checking device, restricting helium leaking casting to either new or decontaminated containers.
Decontamination generates an additional volume of radioactive was tes, increases personnel exposure, and increases the likelihood of inadvertently spreading contamination.
The benefits of periodic helium leak 1/16/79 checking have been evaluated.
Since the 2R container is so well protected from physical damage, the need for periodic testing is age-related rather than use-related. hie have concluded that it is better to focus on a sensitive, 100%, pre-shipment assembly verification leakage test than on periodic helium leak tests.
For the larger shipments requested in our October 11, 1978 letter, (600 to 1000 Curies Mo-99 per container) the pre-use leak test procedure will be initiated.
New 2R containers will be subjected to a helium leak test with an accentance criteria of 10-6 atm 3
em /sec.
Those containers will be'used for no more than 12 months and retired to lower level shipments; an acceptable alternative is that prior to 12 months of service the containers be decon-taminated, subjected to helium leak testing, and reused.
For shipment containing less than 600 Curies per container the pre-shipment assembly verification leak test will supplant the periodic leak test.
PRE-SHIPMENT ASSEMBLY VERIFICATION LEAKAGE TESTS The November 17, 1978 letter from Mr. Charles E.
MacDonald (USNRC) states two criteria for the leakage test acceptance.
The maximum permissible leakage rate is the greater of the two values de-termined by Criteria I and II below:
Criteria I - Less than a type A quantity in 10 days.
The type A quantity for Mo-99, Tc-99m, Tc-99 is 20 Curies.
As above, assuming a concentration of 2000 Curies in 100 ml gives a leakage rate of
-6 3
L 1.16 x 10 cm /sec (liquid)
=
Criteria II - Absolute Sensitivity.
The alternate criteria is an air test at 25 C having a sensitivity of L=
1 x 10~
atm em /sec (air) across a boundary of 1 atm leaking into 10~
atm.
A liquid leak of this magnitude, determined using the pre-vious equation, is 2 (10~ ) (.017) (1 -.01)
L
=
1.05 (1
-.01 )
3.21 x 10~
atm cm /sec (liquid)
L
=
The governing criteria is therefore Criteria II.
1/16/79
. Test Method All 2R containers are leak tested in the hot cell for pre-shipment assembly verification.
The test is similar to the air bubble, vacuum, and glycol leakage test described in ANSI-N14.5-1977 Section A3.6 except that water is used in place of glycol.
The nominal test sensitivity stated for normal field conditions is 1 x 10~
atm cm /sec (air).
L
=
After the vial of radioisotope product is sealed in the 2R con-tainer, the package is placed in a clear container of water.
The water level is just enough to cover the 2R container.
A plate with a wetted rubber surface is placed over the container of water.
A vacuum of one half atmosphere is drawn and held for 30 seconds while the technician checks for air bubbles escaping through the water.
Water is used in place of glycol because it generates much less waste and contamination than glycol while giving a very satisfactory leak test under these conditions.
Converting the test sensitivity to a liquid leak under the condition of the test, using the same equation as before, gives 2 (10-atm em /sec) (.017 Co) (1 -.01)
L
=
11q 2
2 (1.05 C )
(1
- 0.5 )
p
-7 3
L 4.27 x 10 atm em /sec
=
ygq The sensitivity of this test exceeds that determined by the more restrictive Criteria I; it exceeds by two orders of magnitude the governing sensitivity requirement, Criteria II.
1/16/79