ML20056A104

Responds to NRC 900720 Request for Addl Info Re 900605 Request for Amend to License R-97

ML20056A104
Person / Time
Site:	Neely Research Reactor
Issue date:	07/31/1990
From:	Karam R Neely Research Reactor, ATLANTA, GA
To:	Alexander Adams Office of Nuclear Reactor Regulation
References
NUDOCS 9008030259
Download: ML20056A104 (11)

Text

h Georgia Institute of Technology NEELY NUCLEAR REGEAACH CENTER 900 ATLANTC OAlvE ATLANTA. GEORGIA 30332-0425 July 31, 1990 Mr. Alexander Adams Jr., Project Manager Non-power Reactor, Decommissioning and Environmental Project Directorate Division of Reactor Projects - III, IV, V, and Special Projects Office of Nuclear Reactor Regulation U. S. Nuclear Regulatory Commission Washington, D. C. 20555 i

Subject:

License No. R-97 Amendment Request of June 5, 1990 l

1 This letter contains our responses to the questicns you raised in  !

your letter dated July 20, 1990.

1. Technical Specification 3.1.d Your Question a Please provide wording for the. requested change to Technical Specification 3.1.d and required changes to Table 3.1.

Our Responses No wording change was requested for TS 3.1.d because we believe none is needed. The minimum angle to which each shim-safety blade must be withdrawn so that a free fall from that position to full insertion will result in a scram, will not be changed. Since a scram will take place whenever a negative period of 10 see is achieved, the release of He3 in the fast shutdown system will provide an insertion of -1.5% delta k/k reactivity. This reactivity insertion will definitely result in a scram. A delay of one second before the scram is activated is being sought for the fast shutdown system only.

Consequently, no changes in Table 3.1 are needed. The delay time circuit will only be Osed for the FSS tests. It is not and will not be a permanent feature of the GTRR instruments.

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Mr. Alexander Adams, Jr.

July 31, 1990 Page 2 Your Question 1.b What actual event will trigger the negative period scram time i delay? Setting off the explosive value?

Our. Response:

A switch triggers the detonation of the explosive valve. The same switch also activates the time delay . circuit for. one second. The reactor circuit for the negative period scram or a' the reactor circuit for the positive period scram are not affected. A delay of one second is triggered when the switch is activated and this delay affacts the negative period scram only. -

Your Question 1.c Please add a testing requirement and frequency to the

,. _ Technical Specifications to ensure that the negative period l- scram delay does not exceed one second, l

Our Response:

The delay time circuit will be tested before each use with L calibrated instruments whooe calibrations are traceable to NIST standards. The delay time shall be one second plus or ,

minus 5%.

Your Question 1.d Will this delay system still allow Sou to meet the requirement .

of Technical Specification 3.2.d? Explain'.  !

Our Response:

The delay time from the introduction of a fast scram signal '

into the safety system to the re2 ease of the shim-safety blades is less than 100 milliseconds.

The delay time from the introduct'on of a fast scram signal into the safety system to the release of the shim-safety blades will remain the same (ie., < 100 milliseconds). The actual introduction of a fast scram signal from a negative ll period scram will be delayed.

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Mr. Alexander Adams, Jr.  !

July 31, 1990

• Page 3 t i

3 The surge of He into the FSS tube will of course shutdown the  ;

reactor in 50 milliseconds.  !

Your Question 2.a Your requested change to Technical Specification 3.4.a includes increasing the value of both positive and negative reactivity insertions while your safety analysis considers an initial negative insertion. Either change your requested ,

Technical Specification wording to allow for only initial  ;

, negative insertions or amend your safety analysis to account '

for both positive and negative insertions.

Our Responses  !

The intent for this request is that it applies for the fast shutdown system only. It may be more appropriate to leave Technical Specification 3.4.a as is and simply request permission to allow negative reactivity insertion of up to 1.75% delta k/k for the fast shutdown system tests only. The primary reason for the change remains as was stated in the application of iTune 5, 1990, ie, to allow for error in the calculation.

The wording was revised to state, for the performance of the fast shutdown system tests only the reactivity worth of the experiment shall be limited 'o the insertion of -1.75% delta k/k.

Your Question 2 b The insertion of the gas at power appears to involve an unsecured experiment governed by Technical Specification

3.4.b. The experimental facility itself appears to be a i

secured removable experiment. If the introduction of gas into the experimental facility does not meet the reactivity requirements of Technical Specification 3.4.b, please submit I

a proposed change to this specification along with a safety analysis.

Our Response It is true that by adhering to definitions of " secured experimentsa and " unsecured experiment", as given in Technical

• Specifications 1.21 and 1.22, one would conclude that the introduction of He gas into the experimental fLeility would 3

Mr. Alexander Adams, Jr.

July 31, 1990 Page 4 involve an unsecured experiment which might come under TS 3.4.b. However, TS 1.15a and 1.15b regarding the definition of an experiment when combined with TS 1.21 and 1.22 would also render the calibration of the shim-safety blades as unsecured experiment which would also come under TS 3.4.b.

The movement of a shim-safety blade exceeds the reactivity limit of TS 3.4.b by more than 1000% (5.5% delta k/k for the shim-safety blade to 0.4% delta k/k for the TS 3.4.b limit).

The Technical Specifications are not totally, internally consistent. What we are seeking in our request for permission to perform the fast shutdown facility experiments, is concurrence of the NRC with the Nuclear Safeguard Committee that it is safe to run these experiments in the manner discussed in Appendix A of the application of June 5, 1990.

NRC's approval may be signified by attaching to the license an addendum specifying the conditions under which the experiment shall be performed. A draft of the addendum for your consideration is attached.

Your Question 2.c The insertion of the gas at power appears to involve a rate of reactivity change governed by Technical Specification 3.4.c. If the introduction of gas into the experimental facility does not -meet the rate of reactivity change requirements of Technical Specification 3.4.c, please submit a proposed change to this specification along with a safety i

analysis.

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Our Response It is true that the injection of the He3 at power involves a rate of reactivity change which exceeds the specification in TS 3.4.c. However, if the injection of the He 3 gas is considered as an independent shutdown mechanism and the rate i of reactivity insertion from the He gas is compared with that 3 from the scram of the shim-safety blades, the rates are '

comparable. For example, the scram of the blades inserts about 15% delta k/k in 480 milliseconds for a rate of 15%/.48

= 31.25% delta k/k per sec.

The injection of the He 3 gas yields a reactivity of -1.5%

delta k/k in about 0.05 sec, for a rate of 1.5%/0.05 = 30%

l delta k/k per sec. Consequently, considering the PSS system p

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i Mr. Alexander Adams, Jr.

July 3t, 1990 Page !

as an independent shutdown mechanism, its reactivity insertion rates are not different from those of the control blades of the reactor.

Since ' the FSS experiments are few in number and are to be performed for a limited time and a specific purpose, we prefer not to change the limits imposed by TS 3.4.c. Alternatively, considering the FSS experiments as secured removable experiments, similar to the shim-safety blades in performance and function, then the requirements of TS 3.4.b, TS 3.4.c and TS 3.4.d do not apply. We have taken the latter interpretation as the basis for our application of June 5, 1990.

I Your Question 2.d Can this experiment be conducted within the limitations given in Technical Specification 3.4.d? If no*., please submit a proposed change to this specification along with a safety analysis.

Our Response We believe that under our interpretation that the FSS experiments are a secured experiments", TS 3.4.d does not apply.  !

l Your Question 2.e can this experiment be conducted within the shutdown margin limits established in Technical Specification 3.1.a, 3.1.c and 3.4.k? If not, please submit a proposed change to this '

specification along with a safety analysis. _;

I Our Response:

The current reactivity 'rorth of the shim-safety blades from critical position to fu:ly inserted is 18.1% delta k/k. The reactivity worth of the most reactive shim-safety blade is approximately 6%. The reactivity worth of the injected He 3 gas is -1.5%. The wor *.h of the regulating rod is 0.46%.

Consequently, the shutdown margin as defined in TS 3.1.a for 1

Mr. Alexander Adams, Jr. i July'31, 1990 Page 6 i

the GTRR is (18.1%)-(6%)-(0.46%)-(1.5%) = 10.14% delta k/k I which meets the requirement of TS 3.1.a by a considerable l margin.

The estimated reactivity addition due to flooding the FSS tube is 0.00017 delta k/k (see Analysis in Appendix A of June 5,  ;

1990 submittal) . Consequently the flooding effect on shutdown margin is very, very small.

Your Questions 3.a, 3.b, 3.c and 3.d Proposed Technical Specification 3.4.1 requires wording on  :

! encapsulation to meet the requirements of Technical l Specification 3.4.f.

s Our Response W agrce that proposed Technical Specification 3.4.1 requires wording.on encapsulation to meet the requirements of Technical Specification 3.4. f. To that end, we alter our request on l this issue to as follows:

1. Change TS 3.4.1 to read as follows (same as in proposed l change):

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" Explosive materials in excess of 25 milligrams TNT equivalent shall not be irradiated in the GTRR,"

2. Leave TS 3.4.j as is without change,

3. Leave TS 3.4.k wording as 'is but re-label it as TS 3.4.1, and l

4. Add the following wording for TS 3.4.k:

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" Explosive materials in excess of 25 milligram, but not to exceed 300 milligram TNT equivalent, may be stored within the reactor containment building provided that the explosive is encapsulated in such a manner as to assure compliance with TS 3.4.f.

Your Question 4 Your safety analysis discusses the release of 10 curies of tritium. Please show that your analysis meets the requirements of Technical Specification 3.4.g.

Mr. Alexander Adams, Jr.

July 31, 1990 Page 7 i

Our Response 10 CFR 20 Appendix B Column 1 gives the tritium concentration limit in air to be 5 x .10*' uci/ml. The annual limit is the concentration in air tiraes 2.5 x 10' ml or 1.25 x 10' uCi (10 CFR 20.103).

TS 3.4.g specifies doses less than 10% of the equivalent t annual dose of 10 CFR 20 Appendix B or 1.25 mC1. This value is greater than the one millicurie upper bound estimate given i in the analysis of Appendix A of the June 5, 1990 submittal. t Also 1.25 mei is less than the 2925 uci per see tritium ,

release set point limit. .

The 10 Ci of tritium mentioned in the safety analysis of the application of June 5, 1990 is the maximum possible amount that would be on hand. No more than one millicurie will be present in the containment building at any one time. Thus the '

requirements of TS 3.4.g are met.

1 We hope that the above information answers the questions you raised. Should you have additional questions please let me know.

We would be very pleased if the review process can be completed by the_end of August 1990. We appreciate your help and cooperation. 4 l

l Sincerely, f(4 k(W.---- -

p R. A. Karam, Ph.D., Director l Neely Nuclear Research Center RAK/arr Enclosure 1

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l ADDENDUM l

Proposed GTRR Technical Specification Amendments (Duration Not to Exceed the Conduct of FSS Experiments) l The amendment request for the GTRR operating license of June 5, 1990 was intended to allow the performance of a specific set of experiments on a proposed fast Shutdown System which utilizes the injection of He-3 gas into a confined tube installed in the reactor core. This system is currently planned as an addition to the currently existing reactor safety systems for the Department of Energy Savannah River Site Reactors. Its purpose is to rapidly reduce reactor power to help offset the rapid loss of coolant flow following a hypothetical Double Ended Guillotine Loss of Coolant Event. The tests proposed for the GTRR are intended to demonstrate the efficacy of this system, and are designed specifically as functional tests, i.e. the system would be operated in the GTRR as a shutdown system. The operation of the system is simple.

Pressurized He-3 gas which is a good thermal neutron absorber, is contained in a pressure vessel outside of the reactor. The I pressure vessel is connected to a tube in the core via a valve. l The He-3 is separated from the tubing and rod by a valve. The i proposed tests would involved bringing the reactor to power, connecting the He-3 bottle, actuating the valve (by detonating a small amount of explosive) thus injecting the He-3 into the tube in the core thereby shutting down the reactor. An automatic scram follows no later than one second after the actuation. The He-3 l bottle is deliberately NOT connected to the system prior to the l reactor being at the desired power level to prevent the possibility of the gas being accidentally injected while at power. Also, the

! reactor is delibnately scrammed one second after the event to prevent the posril ility of a gas release affecting the shutdown status of the rea ; tor. The shutdown margin of the Shim-Safety Blades (-10.14% d ita k/k) far exceeds the He-3 reactivity worth, even with the mosc reactive blade and the regulating rod fully withdrawn as stated in the Technical Specifier.tions . This describes the anticipated normal performance of the proposed experiments. Any credible abnormal events which could be anticipated were analyzed and discussed in the safety analysis accompanying the June 5,1990 license amendment request.

On the basis that the Fast Shutdown System (FSS) is an independent shutdown mechanism which functions in a manner similar to the Shim-Safety Blades, it is believed that the FSS meets the definition of a " secured removable experiment" as defined in TS 1.21.

l' Consequently, to test the performance of the FSS system, it is necessary to amend, on a temporary basis, and for the FSS tests only some of the GTRR Technical Specification.

These Technical Specifications are:

1. TS 3.1.d states:

" Prior to criticality each shim-safety blade which is withdrawn above full insertion shall be positioned so that a free fall of the blade towards its full inserted position will result in a reactor scram activated by a negative period scram,"

and Table 3.1 states (paraphrased): ,

"that the period trip shall be equal to or greater than 10 ,

seconds." 4 REQUESTED CHANGE - It is requested that permission be given to delay the actuation signal for the negativo period trip by one second so that the flux as a function or time can be monitored and studied. The one second delay is requested to be in effect during the FSS experiments only.

JUSTIFICATION - The Fast Shutdown System consists of injecting He* -

into a tube located in the core in approximately 50 milliseconds. ,

The magnitude of the reactivity insertion due to the He' has been calculated to be -1.5% delta k/k. The insertion of negative reactivity of this magnitude will cause a scram of the reactor due to the negative period scram set point (-10 sec). It is requested i that the. signal to scram the reactor be delayed one second so that the dynamic change in the flux due to the injection of He' can be  :

measured and studied. The ability to scram the reactor with all four shim safety blades will be unaltered and unaffected. Further, the He* injection itself' will cause reactor shutdown. Delineation of the potential consequences should the He* tube fail as has been discussed previously with the conclusion that a one second delay before initiation of the scram signal to the reactor is not a safety concern.

The one second delay logic is shown in the original application along with the diagram showing how the one second delay unit is incorporated into the GTRR circuit.

The requirements of TS 3.1.d will be met because the negative  !

period scram circuit will stay active during the FSS tests.

The delay of one second will only come into play when the He*

is injected. The scram of the shim-safety blades will take '

place after the one second delay. TS 3.2.d requirement will be met because that portion of the safety circuit is unaffected.

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2. TS SECTION 3.4.a - LIMITATION OF EXPERIMENTS TS 3.4.a states: ,

"The potential reactivity worth of each secured removable experiment shall be limited to 0.015 delta k/k."

REQUESTED CHANGE - It is requested that the above wording be changed to read as follows:

For the performance of the Fast Shutdown System Tests only, the reactivity worth of the experiment shall be limited to the insertion of -1.75% delta-k/k.

JUSTIFICATION - The primary reason for changing this  :

specification is to provide adeguate margin to accommodate the reactivity insertion due the He. The calculated worth of the He' to be injected into the reactor is -0.015 delta k/k, which is the same as the limit specified by TS 3.4.a. To permit t

some margin of error in the calculations, it was felt that it l would be prudent to increase the permissible reactivity worth l of each secured, removable experiment (FSS experiments) from O.015 to 0.0175 delta k/k.

Technical specifications 3.4.b, 3.4.c, 3.4.d do not apply because  ;

the FSS experiments are deemed " secured removable experiments".  !

l The FSS experiments will be conducted within the shutdown. margin limits established in TS 3.1.a, TS 3.1.c, and TS 3.1.k.

3. TS SECTION 3.4.1, 3.4.k, and 3.4.1 i TS 3.4.1 states:

" Explosive materials in excess of 25 milligrams of TNT l equivalent shall not be irradiated or stored within the reactor containment building."

REQUESTED CHANGE FOR TS 3.4.i

! It is requested that the above wording be changed to read as follows:

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" Explosive materials in excess of 25 milligrams of TNT equivalent shall not be irradiated in the GTRR."

TS 3.4.k states:

l " Experiments which could increase reactivity by flooding, shall not remain in or adjacent to the core unless measurements are made to assure that the shut down margin required in Specification 3.1.a would be satisfied after flooding.

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Requested change for TS 3.4.k is that this Technical Specification be designated as Technical Specification TS 3.4.1 with no word change. TS 3.4.k for the FSS tests shall i read as follows: 1

• Explosive materials in excess of 25 milligrams but less than j 300 milligrams TNT equivalent may be stored within the reactor <

containment building provided that such materials are j encapsulated in such a manner to assure compliance with TS )

3.4.f." i i

JUSTIFICATION - Explosive valves will be used in the Fast '

Shutdown System tests to release the He' gas from the high pressure cylinder (~350 psia) through the tubing and into the l tube located in the reactor. The explosive valves will be l located inside a metal box outside of the reactor vessel adjacent to the control room. Each explosive valve contains two primer chambers consisting of 145 milligrams each of l diazodinitrophenol (DDNP) explosive material. Upon firing, the products of combustion are entirely containsd within the body of the val.ve assembly. The structural integrity of the valve body is designed to withstand the forces asrociated with  !

multiple firings. All explosive valve components to be used 4 for tne tests were supplied by Conax Buffalo Corporation under their nuclear quality assurance program which meets the ,

requirements of 10 CFR 50, Appendix B.

It is understood that the above amendment constitutes a temporary  ;

change to GTRR Technical Specification so that the FSS experiments ,

may be carried out. Upon completion of these experiments, the '

changes specified in this amendment shall be null and void, t

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