ML20116G613

Intervenor Exhibit I-GANE-71,consisting of 891026 Memo Re Leak of Coolant,Light Water,Used to Remove Heat Deposited by Gammas,Neutrons & Activation Products in Inner Bismuth Block on 890918

ML20116G613
Person / Time
Site:	Neely Research Reactor
Issue date:	06/28/1996
From:	Karam R Neely Research Reactor, ATLANTA, GA
To:
References
REN-I-GANE-071, REN-I-GANE-71, NUDOCS 9608080219
Download: ML20116G613 (10)

Text

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US L,7(C NEELY NUCLEAR RESEARCH CENTER f,

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ATLANTA GEORGIA 30332-o425

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v5 J1 18 R2 32 October 26, 1989 g((l[{ ri: c r ; p r T,' q y CC[(Qlb b r C[ Docket No. NUCLEAR REGULATORY COkAMISSION rp;;q'ff,~

In the rnatter d~M of -/(e s u- 4 F A) __ EXHIBIT NO._N _

O p UM O Stati D Applicant Of6ervenor O Other i Gidentiied G Recewed O Rejected Dateh / h O/ 4 /, Reporter /x1/ cd Witness [M __

TO: Nuclear Safeguards Committee FROM: R. A. Karam [8

SUBJECT:

Bismuth Block Leak and What To Do About It Dr. Bernd Kahn was kept informed about the leak of the coolant, light water, used to remove the heat deposited by gammas, neutrons and activation products in the block of the Georgia Tech Research Reactor (GTRR). inner Dr.

bismuth Kahn was briefed on 9/18/89 with regard to the leak location and what is being done to fix it.* Also a subcommittee composed of Dr. Kahn, Dr. Desai, and Dr. Mahaffey, of the Nuclear Safeguards Committee met October 19, 1989 with Dr. Revsin and Dr. Karam to consider possible solutions to the problem of the bismuth block leak. ,

The subcommittee was presented with a plan for a temporary solution. The solution consists of installation of a system which would collect the leaking water and channel it catch to a condensate pump. The pump could circulate this water through a 5 y filter and return it to the cooling water storage tank (see attached blue print). Additionally the cooling water system for the bismuth block will be deionized by an ion exchange column.

The temporary solution is recommended for the following reasons:

1

1. Attempts at repair by application of epoxy to the block did not work.

2. Dose rates at the leaking block surface were =5 R/ hour.

This level of radiation limits the amount of time a person can spend in the vicinity of the block.

• The fix attempted was to use epoxy in combination with glass fiber. Once the epoxy hardened, a stop leak compound was added to the circulating water. This recipe for fixing the leak was used effectively the last time the bismuth block leaked, August 12, 1983. This time however the leak was not stopped.

9608080219 960628 l PDR ADOCK 05000160 0 PDR TeiE: 542507 GTRIOCAATL Fax: 404 894 3120 (Venfy 404-8944951)

A Urut of the Urwersty Systern of Georgia An Ecual Education and Emp:oyrnent opportunity insttuton

3. The leaking water does not present a health hazard.  !

Activity in the water is limited to 1.8 x 10-' pCi/cc l

'H and 2.2 x 10-* pCi/cc ' ' Zn. I I

4. A class in reactor laboratory (the course is designed to measure reactor parameters) comprised of 16 N.E.

students needs the reactor to finish the course.

5.- The Center has several contractual obligations to run the reactor. One includes a contract with Savannah River for $75K.

6. The Center is negotiating with DOE for a short duration l contract with large amount of dollars contract is essential for the Center's continued

(=$300K). This l

existence.

i

! Questions raised by. the subcommittee concerning the

temporary solution were as follows:

1. The radioactivity content of the bismuth block cooling j water needs to be evaluated.

2. Water -

Bismuth block interaction needs review.

Specifically, (a) has shielding properties of the block i

j been affected?; (b) Are there any chemical reactions between water and bismuth or water and magnesium?

1

' 3. Heat removal with reduced flow should be evaluated.

Estimates of temperature rise without cooling and with

]f 3/4 normal flow of cooling, should be made.

l'-

4. Plan a test run for approximately one hour.

! 5. Permanent correction to problem should be assessed.

1 PERTINENT DATA ABOUT THE BISMUTH BLOCK AND THE COOLING SYSTEM Normal flow condition of cooling water is 1.25 gal / min Maximum temperature rise in cooling water = 28'F (Based on 4.75 MW run for 24 hours on 12/13-14/83.

Water temperature into block was 75*F and out of block j was 103* F) l

) .

Heat deposited in block = flow rate . cp . AT

= 1.25 gal / min x 60 min /hr 8.33 lbs/ gal x 454.54 g/lb x 1 cal /g x 15.55'C

= 4.415 x 10' cal / hour

= 17523 BTU's/ our

. Location of leak in block is at lower right corner near the water outlet pipe. Note that no leak is-observed at inlet or outlet pipes which are also located at lower right corner (see sketch) i

,s' /r

,/O9 ud s Inlet Outlet Leak Pipe Pipe Location

. Fraction of water leaking is about 25%

. It appears that the leak location is at the outlet, j

thus providing full block cooling function. This '

observation is based on the difference in head pressure between inlet and outlet water. '

. The pH of the water which has been circulating in the cooling system for many years is 6.8. j

. The radionuclide analysis of the cooling water showed l the following: '

'H

' ' Zn == 1.8

2. 2xx10**

10' ' pCi/cc pCi/cc Response to questions re.ised by NSC subcommittee:

1. Radioactivity From The Bismuth Block System  !

Approximately 5 5-gallon buckets contained the water that was pumped from the block. A radionuclide analysis was performed on several of these buckets to l determine whether the system contained radioactive  !

i material. The bismuth cooling system is a light water, self-contained system, which is not connected to the primary coolant system of the reactor in any fashion.

I Tritium was found to be present in all containers '

at a concentration of 1.79 x 10*

• pCi/ml. is a low concentration which can be released This from the i

facility to the environment without further dilution (release limit 3 x 10-

• pCi/ml) . A trace quantity of  ;

Zn-65 (2.19 x 10-* pci/ml) was found to be present when analyzed by gamma spectroscopy. As was the case with i tritium, this concentration of En-65 can from~the facility directly to the environment be released without further dilution (release limit 2x 10-* pCi/cc).  !

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j Since all samples were relatively the same, a single

' sample was counted for a total of 54,000 seconds to add validity to the earlier analyses. The presence of En-65 was confirmed at 2.21 x 10-* pCi/ml. The remaining l,

activity was found to be at background levels.

2. Gamma Ray Shielding Provided by Bismuth Block Examination of facility records indicates that the radiation levels in the biomed facility when the i reactor is at power are not well documented. This is l due to a great extent to the decrease j in reactor 4

operating time over the past several years. However, a survey was performed this year with the reactor at a 1

! MW power level. This showed that the general area i

radiation levels averaged approximately 40-50 mR/ hour.

Historical memory of individuals who have been here for a number of years indicates that dose rates in this l

area have remained essentially unchanged.

The above is consistent with the construction of i the biomed facility in that unless some major l deterioration of the innar bismuth block occurred, it is unlikely that changes in the radiation levels in the biomed facility would be noticeable. This is due to j

the fact that in addition to the inner bismuth shield (the leaking block), shielding in the biomed is also i

provided by 12 inches of concrete surrounded by a steel jacket, an outer bismuth block

! outer wall of lead =4 inches). 4Because

(= inches) and an of this i additional shielding,(as stated above, it is highly i improbable that changes in the biomed radiation levels i

would be measurable unless major deterioration of the inner block had occurred. Visual inspectin of the

! inner block indicated that at least on the surface, the block 3 was intact. Lack of residue in the water i collected from the system when the leak began and the i

i slightly acidic pH of this water support the hypothesis that the block itself has not suffered structural

{ damage. -

t

3. The Chemical Reaction Between Water and Bismuth and j Between Water and Magnesium.

[

t Dr. Barefield and Dr. Neumann, faculty members of l the Chemistry Department as well as members of the i Nuclear Safeguards Committee were asked these j gnestions. Their responses are summarized-as follows:

1 1

i Magnesium will normally form a thin layer of oxide on the surface which will then act as a shield to

! prevent further oxidation. The formation of hydroxide i

j of magnesium is possible but not likely at low temperature. Dr. Barefield thought that use of

! /

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i magnesium clad might be connected with magnesium acting as a sacrificial anode to prevent oxidation of the bismuth.

With regard to bismuth, Dr.

Neumann Barefield and Dr.

felt the bismuth-water reaction would be less than one would anticipate with magnesium.

Both, Dr. Barefield and Dr. Neumann, profess any knowledge of what would be did not reactions over a long, long time period = 10 years, or the chemical the tendency for the oxide to flake off. However, over a time span of 10 years or longer the pH of the cooling water remained acidic and the radionuclide analysis showed little activation thus suggesting little reactivity between the water and the metal.

4. Heat Removal With Reduced Flow Dr. Prateen Desai, member of the NSC, performed scoping calculations using extremely conservative assumptions. Heat loss rates were assumed at 80 or 99%. Specifically Dr. Desai solved the following i equation.

oc, or ,, 3r 2

, o

Bt q (,,

Br g where l O'** ,

O*'* =hr 9 (x) 9so

=  !

A attenuation coefficient of bismuth for reactor gammas at average energy of 0.7 MeV p = density of bismuth C, =

specific heat of bismuth T= temperature as a function of position in block x =

thermal conductivity of bismuth y =

fraction of heat source retained in block (0< y<1) g = heat source assumed to be 18,000 BTU's/ hour

.* g.

I J.

! l 1

$ The above equation was normalized as follows: >

i T* = TIx,t) - T.

j T. - Ti (2)

T. = melting point of bismuth T. = initial temperature i

j i

X* = X; t' = t/L' /a (3)

L Where L is the thickness of the block, and a = k o c, with this normalization equation (1) becomes

\

DT*

" 327* L2 o

Bt* 3x*' K (T, - T3 ) 'Yg (x)

Boundary Conditions:

i t ~

t*S o;r*-o i

at 1

t* = 0+t qo q is turned on i

I j The

• results are summarized in Figures 1 and 2.

Figure 1 shows the normalized temperature as a function i.

of distance from the inner to the outer surface of the

block at various time intervals, at one MW power level assuming 80% heat removal rate. Figure 2 shows similar

!. data but with assumption of 994 heat removal

{ one MN power level. rate and i Note that the normalized temperature reaches;the melting point when T* = 1.0.

j. When T*

. is 0.5 for example, T = Ti + 0.5(T.-T4) = 30'C

+ .5(271 - 30'C) = 150.5 C. .

i power Figure 1 shows that 5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> of operation at one MW level, assuming 80% heat removal rate, the temperature of the inner surface of the block would be 150. 5* C. The melting point of bismuth is 271*C.

I The two end walls at Z* = o and X* = 1 are assumed to looseand block heat by convection at the outer surface of the by conduction at the inner.

estimates that heat loss at (Dr. Desai the outer face by

, convection can be up to 1,500 BTU /hr.) I I

i 1 ( -

4 l

5. A Test For One Hour Is Planned With The Temporary Fix To Ascertain The Following  ;

a. Accurate determination of the fraction of water t that leaks from the system. This will be done by measuring the flow rate of the leaking water.

b. Two thermocouples will be installed on the inner bismuth block to measure the temperature at 7 i

inches into the block (i.e., the inner surface temperature), and at the outer face (i.e., the outer surface temperature).  ;

c. Comparison of the performance of the cooling system with the current leak to the performance prior to the leak will be made. This may be ascertained by comparing the temperature. of the return water (hot leg previously for similar ru)ns.as Among measured now and other things such a comparison will help determine whether or not the leak is near the outlet. For a leak near the outlet would not affect the cooling performance of the circulating water and the AT rise would be shn11ar to previously recorded data. ,

d. Should the temperature in the bismuth block as measured by the  :

thermocouples reach 80*C, the reactor will be shutdown and the experbnent terminated.

e. The thermocouples will be calibrated prior to l

making the one megawatt run.

f.

Flow rate setting of bismuth block cooling system hall be lowered from 1 gal / min to 0.75 gal / min.

he flow rate meter is located  !

f the cooling system. on the return leg t Since the leak is at the bottom of block, the return flow rate is decreased (

by about 25%. Consequently the setting for

{

the flow rate needs to be decreased to 0.75 gal / min.

g. The safety blades and the regulating rod shall be calibrated in order prior to the one hour, one megawatt run to meet Technical specifications requirements. The run control

. for the calibration of level.

rods shall be at or below 10 kw power

h. Air sampling in the basement of building be performed before the containment establish a will]ference re point and also the run to during the run near the collection funnel. This will help establish whether or not volatile radioactive

{ - '

substances (not- expected) are released to the air.

1. Surveys to determine the levels of radiation, both l j

neutrons and gammas, will be made in the bio-medical facility. Unfortunately no previous i

record exists for comparison. There is however an approximate " feel" for what these numbers should be.

j. Surveys for Po-210 in the cooling water will made. The pH of be the leaking water shall be determined prior to and during reactor operation.

h  ;

The results for evaluation with of tests and measurements will be submitted to NSC I regard to the efficacy of Assuming that the results justify a request to operate the temporary fix.  ;

the reactor '

with to the temporary fix in place, the management of operate in this mode for a period not to the go NNRC intends beyond the {

l conversion to LEU. A permanent solution to this l currently being investigated and will be reported to problem is soon as-preliminary analysis is completed. the NSC as l

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~Trsnsient Tsmperature Distribution Bismuth Block Due To Heat Generation 0.6

=

3600 see w 0.5 +

Q 7200 sec g 0.4 10800 sec 0.3 :w, ,  ;

18000 sec 0.2 '_ N_

N > Figure la Temperature Distribution withis.

0.1  %. ni,,ueh niocx assu,ing

• a $ 80% heat Removal Rate U %g and One MW Reactor Ng = gi Power.

O I i i 0 5 10 15 20 ,

s,s DISTANCE (cm)

Transient Temperature Distribution In Bismuth Block Due To Heat Generation 0.25

=

3600 SEC y 0.20 m 3 18000 SEC Ltj g 0.15 - - - - ~ -

~

W 36000 SEC b! 0.10 Figure 2: Temperature A viserisation with Bismuth Block Assuming 995 Heat G Removal Rate and One Q MW Reactor Power z 0.05 , m

~ > > > > > > > >

8 3 3 3 3

= 3 3

-m-am -m - -- .-

3 3 as 3

-

3 0.00 i I '

. 0 5 10 15 20 s, DISTANCE (cm)

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