ML103340090
| ML103340090 | |
| Person / Time | |
|---|---|
| Site: | U.S. Geological Survey |
| Issue date: | 11/24/2010 |
| From: | Timothy Debey US Dept of Interior, Geological Survey (USGS) |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| Download: ML103340090 (14) | |
Text
S.USGS science for a changingworld Department of the Interior US Geological Survey PO Box 25046 MS 974 Denver, CO 80225-0046 November 24, 2010 U.S. Nuclear Regulatory Commission Document Control Desk Washington, DC 20555
Reference:
U.S. Geological Survey TRIGA Reactor (GSTR), Docket 50-274, License R-1 13 Request for Additional Information (RAI) dated September 29, 2010
Subject:
Response to the RAI Concerning R-I 13 License Renewal Mr. Wertz:
The Request for Additional Information (RAI) letter dated September 29, 2010 requested responses within 60 days of that date. We have been working diligently to respond to the questions in the RAI; however, there are questions of a very technical nature that will require outside assistance. We have been able to answer some of the questions quickly and have included those answers as an attachment to this cover letter. The questions involving detailed computer code analyses of the reactor are estimated to require an additional 12 months, with outside help, to develop the answers. The reactor staff will continue to develop answers to questions for which they have the required resources, and we will submit those answers to you as they are developed.
We respectfully request an extension of 12 months from November 24, 2010 to deliver our complete responses to you.
Our enclosed responses to RAI questions are Enclosure 1 for Question 4; Enclosure 2 for Question 5.1, for Question 5.2, and Enclosure 4 for Questions 19.1-19.4.
Sincerely, im DeBey U.S. Geological Survey Reactor Supervisor A-Icx,(c
I declare under penalty of perjury that the foregoing is true and correct.
HExecuted on 11/24/10 Copy to:
Tamara Dickinson, Reactor Administrator Reston, VA 22092
Enclosure 1 - USGS November 24, 2010 Response to request for additional information question number 4.
The neutron source used in the GSTR core is a 3.16 Ci Am-241 Be source. It was manufactured by Gammatron Inc, model AN-HP, serial # T- 181. It is a cylindrical double encapsulated source manufactured from ARMCO 17-4. It is housed within a a source holder with an approximate diameter of 0.40 in. and an approximate height of 3.125 in. The source has a half-life equal to the half-life of Am-241, which is 432.7 years. The source yields 6.95* 106 neutrons per second. A measured spectrum of an Am-Be source is shown in Figure 4.1 [1];
however, it should be noted that measured Am-Be spectrums show substantial variation [2].
There is no measurement of the neutron spectrum for the GSTR source. Also, there are no burn-up or regeneration characteristics of the GSTR neutron source.
2 1
0V-L0; n
0 1 2 3 4 5 5 7 8 9 MeV 11 Figure 4.1 Observed neutron specctrm of an Am-Be (o, n) source The source has two allowed positions in the GSTR core. Each storage location is a hole in the top grid plate and the source holder has a shoulder on the upper end which supports the assembly on the top grid plate [3]. The main storage location is in between the F and G rings, between positions G-25, G-26, F-22, and F-21. The other storage location is located on the opposite end of the core between the F and G rings between positions F-5, F-6, G-6, and G-7.
The source stays in its storage location during operations and is removed for training, education, monthly checks, maintenance, and to verify the source interlock.
The source interlock is a safety interlock on the NM- 1000 power monitoring instrument, set at a level of 1* 10-7 % power. It is there to prevent a source-less start up. During the daily checklist pre-start checks, the source is removed from its storage location and the power monitoring instrument, the NM- 1000, is allowed to drop down below the 1*10-7 % power mark to verify the interlock. Next the source is placed next to the NM-1000 detector and a reading above 5 W is verified in order to make sure the NM-1000 is responding correctly. Then the source is returned to its storage position in the core. The source is moved in and out of the core Enclosure 1 - USGS November 24, 2010
Enclosure 1 - USGS November 24, 2010 and within the reactor tank by manipulating a wire attached to the source. The wire may be attached to the top of the reactor tank liner.
[1] H. Kluge, K. Weise, H.W. Zill: Measurement of Spectral Distribution from Radioactive sources and Uranium-235 Fission, and the Resulting Fluence-Dose Convosious Factors.
Neutron Monitoring for Radiation Protection Purposes, IAEA, Wien 1973, Vol. I, p. 13
[2] Neutron Fluence, Neutron Spectra and Kerma, ICRU Report 13, 1969.
[3] Law G.: TRIGA Mark I 1000-KW Pulsing Reactor Mechanical Maintenance and Operating Manual for U.S. Department of the Interior, Geological Survey Denver, Colorado.
February 15, 1969 Enclosure 1 - USGS November 24, 2010
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Enclosure 3 - USGS November 24, 2010 Response to RAI question 5.2:
The core support tripod has been analyzed for stresses during normal operation and design seismic loading. This unit is attached to the reactor tank liner bottom at 3 points. These 3 points each have an attachment pad of aluminum that is welded to the top side of the liner bottom and they are each directly above one of the support ribs that are welded to the bottom side of the liner. The tripod was designed to support the core structure and all associated components. The main structure of the tripod is 2" x 3" rectangular aluminum tubing. The three points of the tripod have 1" thick aluminum plates welded to the tops of the tubing, and an alignment pin and leveling bolt are also located near each of the three tripod points. Each set of alignment pins and leveling bolts mate with a 1" thick aluminum plate that is welded on top of the 1" thick aluminum bottom of the tank liner. Due to the reactor water flow being from natural convection, the resulting hydraulic forces are very small. The leveling bolts are 1" diameter aluminum bolts and they were analyzed to have a direct compressive force of 620 pounds on each bolt. This is well withi'n the strength of the bolts. The bending stress on the bolts was also analyzed, assuming that the bolts were at their maximum extension and a design seismic force occurred.
The design seismic event followed the guidance of American Petroleum Institute (API) 650, appendix E, Zone 1 (Seismic Design of Liquid Storage Tanks). The API guidance was converted to Uniform Building Code (UBC) values so that the requirements of both codes were met. The leveling bolt stress was found to be 13,822 psi during the design seismic event, while the allowable stress on the bolt, without bending, was 21,000 psi. The associated drawings and calculation notes are included in the remaining pages of Enclosure 3.
Enclosure 3 - USGS November 24, 2010
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Enclosure 4 - USGS November 24, 2010 Responses to RAI Questions 19.1 through 19.4 19.1 Added the following definitions to SAR section 14.1; used the accepted definitions from ANSI/ANS-15.1-2007.
Reactor Operator: an individual who is licensed to manipulate the controls of a reactor.
Senior Reactor Operator: An individual who is licensed to direct the activities of reactor operators. Such an individual is also a reactor operator.
Unscheduled shutdown: An unscheduled shutdown is defined as any unplanned shutdown of the reactor caused by actuation of the reactor safety system, operator error, equipment malfunction, or a manual shutdown in response to conditions that could adversely affect safe operation, not including shutdowns that occur during testing or checkout operations.
Reactivity Worth of an Experiment: The reactivity worth of an experiment is the value of the reactivity change that results from the experiment, being inserted into or removed from its intended position.
19.2 No change made: the defined term "Regulating Control Rod" could not be found in ANSI/ANS-15.1-2007 Section 1.3.
19.3 The term "Reactor Operation" in SAR 14.1 was changed to "Reactor Operating."
19.4 The definition of "Reactor Secured" was changed to match the definition of "Reactor Secured" in ANSI/ANS-15.1-2007.
Reactor Secured: A reactor is secured when
- 1. Either there is insufficient moderator available in the reactor to attain criticality or there is insufficient fissile material present in the reactor to attain criticality under optimum available conditions of moderation and reflection;
- 2. Or the following conditions exist:
a) The minimum number of neutron-absorbing control devices is fully inserted or other safety devices are in shutdown position, as required by technical specifications; b) The console key switch is in the off position, and the key is removed from the lock; c) No work is in progress involving core fuel, core structure, installed control rods, or control rod drives unless they are physically decoupled from the control rods; d) No experiments are being moved or serviced that have, on movement, a reactivity worth exceeding the maximum value allowed for a single experiment, or one dollar, whichever is smaller.
Enclosure 4- USGS November 24, 2010