ML20043D791
| ML20043D791 | |
| Person / Time | |
|---|---|
| Site: | Neely Research Reactor |
| Issue date: | 06/05/1990 |
| From: | Karam R Neely Research Reactor, ATLANTA, GA |
| To: | Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML19298E157 | List: |
| References | |
| NUDOCS 9006110176 | |
| Download: ML20043D791 (6) | |
Text
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4i 6
.k-L Georgia institute of Technologyc i
9,,[g I NEELY NUCLEAR RESEAACH CENTER
' 900 ATLANT4C ORIVE ATLANTA, GEORGIA 3033&o425 -.
1 June 5,~1990 Director, Office of Nuclear Reactor Regulation U.S. Nuclear-Regulatory Commission Washington, D.C. 20555 Re Docket No. 50-160, License No. R-97 Attention Document Control Desk.
Gentlemen On behalf of the Georgia Institute' of Technology,
~
I- hereby-request that thel NucleariRegulatory XCommission amend D Facility- .;
Operating Licenses No. R-97 ~ so , that Fast. Shutdown System (FSS)' '
experiments (described in Appendix A): may ,be conducted at the -
Georgia Tech Research Reactor. .TheEollowing'are.the f applicable-portions of- the Technical Specifications -(TS) that will. require amendment. .
- l. TS SECTION 3.1.D - REACTIVITY IIIMITS TS 3. 2.d states ::
j
- " Prior. to crit $1cality e'ach shim-safety l blade whichE-is'.
withdrawn.above full insertion shall be: positioned so; '
that a frea fall,of the blade towards its full' inserted position vill result 1in alreacter scram activated by a negative ;eriod. scram,'"
j and Table 3.1 which states (paraphrased):.
"that the feriod trip shall be equal to or: greater than
~
i 10 seconns."
REQUESTED CHANGE -'It is. requested that permission.be<given to delay the actuation signal for the negative period trip by-
- one second so that the flux as a function of time 'can be monitored and studied. The one second delay ~1s requested to be in effect during the FSS experiments only. [
JURT2ICATION - The Fast 3Shutdown System _. (see Appendix ' A) -
consists of injecting He into a tube located in the: core in -
approximately 50 milliseconds. The magnitude of the
- - reactivity insertion due'to the He8 has been calculated to be.
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4 U.S. Nuclear Regulatory Commission June 5, 1990 Page 2
-1.5% Ak/k. The insartion 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 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 2 can be measured and studied. The ability to scram the react'r with all four shim safety blades would be unaltered and _ ifected. Further, the He' injoction itself will cause reaci r shutdown. Delineation of the potential consequences should the He' tubo f ail is discussed in Appendix A 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 Figure 1. Figure 2 shows how the one second delay unit is incorporated into the GTRR circuit.
- 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 Ak / k . "
REQUESTED CHANGE - It is requested that the above wording be changed to read as follows:
"The potential reactivity wort h of each secured removable experiment shall be limited to 0.0175 Ak/k provided that j the shutdown margin of the reactor relative to the cold xenon f ree critical condition is at least 0.0275 ok/k with the most reactive shim safety blado and regulating rod fully withdrawn."
JUSTIFICATION -
The primary reason for changing this specification is to provide adequate margin to accommodate the reactivity insertion due to the He'. The calculated worth of the He' to be injected into the reactor is -0.015 Ak/k (see Appendix A), which is the same as the limit specified by TS 3.4.a. To permit some margin of error in the calculations, it was felt that it would be prudent to increase the permissible reactivity worth of each secured, removable experiment (FSS experiments) from 0.015 to 0.0175 Ak/k.
- 3. TS SECTION 3.4.1 AND 3.4.j TS 3.4.1. states:
" Explosive materials in excess of 25 milligrams of TNT l
l
U.S. Nuclear-Regulatory Commission' ,.
June:5, 1990-Page 3 '
equivalentLshall not be irradiated or stored within the reactor containment building."
TS 3.4.j statest. .
" Explosive materials in amounts up to-25 milligrams; TNT equivalent' may be-~ irradiated and stored within the
, _ containment only -if they are encapsulated in such a-
' manner to' assure compliance with Specification 3.4.f in the-event of detonation of.the explosive material."
REQUESTED CHANGE -
TS 3.4.1 be changed to read:
" Explosive materials'in excess of 25 milligrams of TNT
-equivalent shall not be irradiated in the GTRR."
TS 3.4.j be changed to read:
" Explosive materials in excess of 25_ milligrams. TNT equivalent may be stored within the containment building only if they are encapsulated in such a manner to assure full compliance with 10 CFR 50, Appendix B " .
JUSTIFICATION -
Explosive valves will be used - in.--the Fast Shutdown System tests to release the He8 gas from ,the high pressure cylinder (~350 psia) through the tubing and into the-rod located in the reactor. The explosive valves will be 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 diazodinitrophenol (DDNP) explosive material. _ Upon firing, the products of combustion are: entirely contained _within the -
body of the valve assembly. The structural integrity of the-valve body is designed to withstand the forces associated with-multiple firings. All explosive valve components to be used for the tests were supplied by Conax Buf f alo Corporation under-their nuclear quality assurance program which meets the requirements of 10 CFR 50, Appendix.B.
e t
U.S. Nuclear Regulatory Commission--
June 5,-1990 Page 4 W appreciate the cooperation of the USNRC in the review of this license amendment request. We hope that the review process can,be completed by July 31, 1990.
Sincerely, f g. /M --+ ^
R. A. Karam, Ph.D., Director Neely Nuclear Research Center -
RAX/ccg Attachments:
Figures 1 & 2 Modified Technical-Specifications-pages 17 & 18.
Appendix A pc: Mr. A. Adams, NRC Headquarters pc: Mr. Craig Bassett, NRC, Region II
- /' 51U' b Notary Publ c, [kMA County, Oscc/d My Cowhdon brirc May 30,1992
i 4
ONE SECOND ' DEIAY
> Delay.
External Trigger Generator
(
a
. Negative Period OR Function Scram Signal.from Log N Period Driver _
(0 to +12 VDC) Output"to the.
Logic Element
\.
The Negative Period Scram signal'is normally at'+12:-VDC and:near=
ground level for scram condition. The level-of the Scram l signal will ' be . sent to Logic Element except for the time - the - Delay -
Generator output in high; during that. time,the output to the Logic.
Element will be +13 VDC reguardless of = the level of the L Scram. 3 signal. '
Figure 1. One Second Delay Unit. 1 J
y "-
- 3
l i
NEGATIVE PERIOD-SCRAM-l Negative Period Scram vidgnals as wired ,
LOGIC ELEMENT' 5 J1B 6. t Negative 6 TB2 7 Negative Period! Scram -- --
- Pe" lod Scram '
LOG N' PERIOD'#'l LOG N PERIOD #12 ,.
Negative ~ Period Scram Signals.with ONE SECOND DELAY circuits i
LOGIC ELEMENT External )
- 5. J1B 6_ Trigger 0 To Start Delay-(External trigger) (External' trigger) -
ONE SECOND DELAY ONE-SECOND DELAY; 6 .TB2: 7 T T
- LOG N PERIOD #.1 LOG N PERIOD # 2 i
The negative period scram signal is generated by the Log N Period Amplifier. The scram signal is +12 VDC for safe condition and near-ground level for.a scram condition. The One Sercond Delay would be-activated ~by an external trigger and delay any negative-' scram by-1 second from the time.of the trigger. With no trigger, the One Second Delay enables the scram signal to pass through with no delay.
Figure 2. % h4 Delay Icgic to be Incorporated in GTRR Circuit
.